Metocean Glossary

Metocean glossary is a dictionary that is authoritative reference to hydrographic related terms and definitions used in various standards, specifications and other informative referred in Maritime Industry. In Indonesian hydrography, The International Hydrographics Dictionary (S-32) is the main standards of terms and definition used.

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1PointOne thirty-second of a circle, or 11 1/4 degrees. Also called compass point when used in reference to compass directions. The extreme end of a cape; or the outer end of any land area protruding into the water, usually less prominent than a cape. In digital cartography, the 0-dimensional geometric primitive of an object that specifies location. [14]
2TimeThe measurable aspect of duration. The hour of the day reckoned by the position of a celestial reference point relative to a reference celestial meridian. An elapsed interval. [14]
3IceThe solid form of water. [14]
4SurfCollective term for breakers. The wave activity in the area between the shoreline and the outermost limit of breakers. [14]
5RiaA long narrow inlet, with depth gradually diminishing inward; a creek. Any broad river opening into the ocean. [14]
6GatA natural or artificial passage or channel through shoals or steep banks, or across a line of banks lying between two channels. [14]
7WaveA disturbance which moves through or over the surface of the medium with speed dependent upon the properties of the medium. A ridge deformation, or undulation of the surface of a liquid. [14]
8LightA luminous or lighted aid to navigation. For internationally agreed abbreviations of light characteristics see the international chart specifications. [14]
9EarthThe planet which we inhabit. The solid matter of the globe in distinction from water and air. The ground. [14]
10AreaIn united nations law of the sea terminology the seabed and ocean floor and subsoil thereof, beyond the limits of national jurisdiction. [14]
11PlanAn orthographic drawing on a horizontal plane, as of an instrument, a horizontal section, or a layout. A large-scale map or chart of a small area. [14]
12ChartA special-purpose map generally designed for navigation or other purposes. See chart: nautical, paper. [14]
13PhotThe unit of illumination in the cgs system. [14]
14PositionData which define the location of a point with respect to a reference system. The coordinates which define such a location. The place occupied by a point on the surface of the earth, or in space. [14]
15LaneAn established route as an air lane or shipping lane. In an electronic radiolocation lattice, the zone between two lines on which measured values, expressed in terms of the system's electronic unit (wavelength or microsecond), are whole numbers and are one unit apart. See lattice. A lead. [14]
16TideThe periodic rise and fall of the surface of oceans, bays, etc., due principally to the gravitational interactions between the moon, sun, and earth. [14]
17SurveyThe orderly process of determining data relating to the physical or chemical characteristics of the earth. The act or operation of making measurements for determining the relative position of points on, above or beneath the earth's surface. The result of such operations. An organization for making surveys. [14]
18RateIn electronic navigation, the designation of pulse repetition rate for a pair of transmitting stations, their signals, and the resulting lines of position. [14]
19MagnetA body which produces a magnetic field around itself. It has the property of attracting certain materials capable of being magnetized. See heeling magnet. [14]
20DirectionIn surveying and mapping, the angle between a line or plane and an arbitrarily chosen reference line or plane. [14]
21RodA unit of length equal to 5.5 yards or 16.5 feet. Also called perch or pole. A stadia or levelling rod. See also sounding pole. [14]
22HorizonIn general, the apparent or visible junction of the earth and sky, as seen from any specific position. [14]
23Sound(v.i.). To measure the depth of the water. [14]
24SoundA relatively long arm of the sea forming a channel between an island and a mainland or connecting two larger bodies of water, as a sea and the ocean, or two parts of the same body but usually wider and more extensive than a strait. A vibratory disturbance in air or some other elastic medium, capable of being heard by the human ear, and thus of any frequency between about 20 and 20,000 cycles per second. [14]
25Log(v.t.). Said of a ship moving at a specified speed according to the indications given by the log. [14]
26LogAn instrument for measuring the speed or distance or both travelled by a vessel. [14]
27HighSee anticyclone. [14]
28Level(v.t.). To make perfectly horizontal by means of a level. [14]
29LevelA horizontal plane or line; especially, such a plane taken as a basis for the measurement of elevati-on. See sea level, mean sea level, half tide level, still water level. A level tract of land; a stretch of country approximately horizontal and unbroken by elevations. In surveying and levelling, either a spirit level or a levelling instrument. [14]
30PassA break in a mountain range, permitting easier passage from one side of the range to the other; also called a col. A navigable channel leading to a harbor or river. Sometimes called passage. A narrow connecting channel between two bodies of water. [14]
31ColA marked depression in the summit line of a mountain chain, generally affording a pass from one slope to the other. In meteorology, a saddle-backed region of almost uniform pressure which appears between two depressions and two anticyclones arranged alternately in a cross. [14]
32Meter(1) a person who measures. (2) an instrument or apparatus for measuring. (3) a device for measuring a specified thing as in thermometer or barometer. See also metre. [14]
33CurrentWater or other fluid in essentially horizontal motion. In British terminology, a non-periodical movement of water, generally horizontally, due to many causes such as different temperatures and prevalent winds. Some may be temporary, others permanent. [14]
34WindAir motion relative to the earth's surface. Unless it is otherwise specified, only the horizontal component is considered. [14]
35DepthThe vertical distance from a given water level to the bottom. [14]
36StationGenerally, a permanent or temporary location where scientific observations and measurements are made. In surveying, a point whose position has been (or is to be) determined. A station may be a marked station (i.e., a point permanently marked for recovery) or an unmarked station, one which is not recoverable. Also called survey station. [14]
37RamThe underwater projection of ice from an ice front, ice wall, iceberg, or floe. [14]
38PortA place provided with terminal and transfer facilities for loading and discharging cargo or passengers, usually located in a harbor. The left side of a craft, facing forward. The opposite is starboard. [14]
39SphereA curved surface all points of which are equidistant from a fixed point within, called the center. [14]
40LandThe solid portion of the earth's surface, as opposed to sea, water. A part of the earth's surface marked off by natural or political boundaries. [14]
41OceanThe vast body of water on the surface of the globe, which surrounds the land, the main or great sea. One of the main areas into which this body of water is divided geographically. [14]
42RigA temporary, mobile structure, either fixed or floating, used in the exploration stages of oil and gas fields. [14]
43MarkOne of the bits of leather, cloth, etc. Indicating a specified length of a lead line. A charted conspicuous object, structure, or light serving as an indicator for guidance or warning of a craft; a beacon. A definite object, such as an imprinted metal disk, used to designate a survey point and sometimes refers to the entire survey monument. Mark is used with a qualifying term such as station, reference, azimuth, or bench. See also benchmark and reference mark. [14]
44EVAExtreme value analysis (EVA) ; A statistical tool to estimate the likelihood of the occurrence of extreme values based on a few basic assumptions and observed/measured data. [7]
45NavigationThe process of directing the movement of a craft from one point to another. [14]
46Vertical(Adj.). In the direction of gravity; perpendicular to the plane of the horizon. [14]
47Vertical(n.). The direction in which the force of gravity acts. A vertical line, plane, etc. [14]
48CircleIn a surveying instrument, the graduated disk which is perpendicular to and centered about an axis of rotation and is calibrated to read the amount of rotation. [14]
49SignalAs applied to electronics, any transmitted electrical impulse. That which conveys intelligence in any form of communication, such as a time signal, a pip on the scope of electronic equipment, or an object marking the location of a surveying station. [14]
50PhotographA general term for a positive or negative picture made with a camera on sensitized material or prints from such a camera original. [14]
51BaseIn a triangulation, the side of one of a series of connected triangles, the length of which is measured directly and with prescribed accuracy and precision, and from which the lengths of the other triangle sides are obtained by computation. Also called base line or triangulation base line. See also base terminals. [14]
52SunThe luminous celestial body at the center of the solar system, around which other celestial bodies revolve. [14]
53ErgThe unit of energy or work in the cgs system. [14]
54ScaleA series of marks or graduations at definite intervals. The ratio between the linear dimensions of a chart, map, drawing, etc., and the actual dimensions represented. It may be called chart scale or map scale when applied to a chart or a map. In photogrammetry, the ratio of a distance on a photo-graph to a corresponding distance on the ground. The scale of a photograph varies from point-to-point because of displacements caused by tilt and relief; but it is usually taken as f/h where f is the principal distance of the camera and h is the height of the camera above mean ground elevation. [14]
55RangeTwo or more objects in line. Such objects are said to be in range. An observer having them in range is said to be on the range. See also transit. Distance in a single direction or along a great circle. The extreme distance at which an object or light can be seen, or a signal detected or used. The distance a craft can travel without refueling, usually called cruising radius. The difference in extreme values of a variable quantity. [14]
56RadioCommunication by electromagnetic waves, without a connecting wire. A radio receiver. Sometimes called wireless particularly in British terminology. [14]
57MountA large hill or mountain, usually a detached, characteristically conical mass of earth. The term 'mount' is always used instead of mountain when it precedes a proper name. [14]
58Height the vertical distance of the top of an object affixed to the surface of the earth, measured from a specified datum usually a high-water datum. - 2. The vertical dimension of an object. Also called vertical length. [14]
59Map(v.t.). To prepare a map or engage in a mapping operation. [14]
60MapA representation (usually on a flat medium) of all or a portion of the earth or other celestial body, showing the relative size and position of features to some given scale or projection; also, a representation of all or part of the celestial sphere. A map may emphasize, generalize, or omit the representation of certain features to satisfy specific requirements. Maps are frequently categorized and referred to according to the type of information which they are primarily designed to convey, to distinguish them from maps of other types. [14]
61GroundThe bottom of the sea. The solid surface of the earth. [14]
62Ground(v.t.). To touch bottom or run aground. See strand. [14]
63BottomAny ground covered by water. [14]
64MeridianA north-south reference line, particularly a great circle through the geographical poles of the earth, from which longitudes (or departures) and azimuths are reckoned; or a plane normal to the geoid or spheroid defining such a line. The term usually refers to the upper branch. [14]
65Fix(v.t.). In hydrographic surveying, to determine, at regular intervals, the position of ships or boats, while sailing along a line of sounding. The usual method of fixing hydrographic surveys within sight of land is the three-point fix method. [14]
66PeriodThe interval needed to complete a cycle. Any specified duration of time. [14]
67SoundingMeasured or charted depth of water, or the measurement of such a depth. In meteorology, determination of one or several upper air meteorological elements by means of instruments carried up by balloon, aircraft, kite, glider, rocket, satellite, etc. [14]
68Horizontal(adj). Parallel to the plane of the horizon; perpendicular to the direction of gravity. [14]
69FixIn navigation, a relatively accurate position determined without reference to any former position. It may be classed as visual, celestial, electronic, etc., depending upon the means of establishing it. [14]
70BuoyA floating object moored to the bottom in a particular (charted) place, as an aid to navigation or for other specific purposes. Navigational buoys may be classified according to: (a) their shape, appearance, or construction, such as barrel, can, cask, conical, cylindrical, dan, keg, nun, pillar, spar, spherical, or top mark buoy; (b) their colour, such as black, cheque red, green, red buoy; (c) their location, such as bifurcation, fairway, junction, mid-channel, middle-ground, or turning buoy; (d) the various kinds of hazards or dangers to navigation which they mark, such as bar, isolated danger, fish trap, obstruction, spoil ground, telegraph or wreck buoy; (e) their particular purpose or use, such as anchor, anchorage, compass adjustment, dredging, farewell (or landfall), marker, quarantine, station (or watch), or warping buoy. [14]
71DataA representation of facts, concepts, or instructions in a formalized manner suitable for communication, interpretation, or processing. [14]
72AxisThe line, real or imaginary, about which something centers or revolves. [14]
73TemperatureThe intensity or degree of heat. [14]
74TieA survey connection from a point of known position to a point whose position is desired. A tie is made to determine the position of a supplementary point whose position is desired for mapping or reference purposes, or to close a survey on a previously determined point. To tie in is to make such a connection. The point to which the connection is made is termed a tie point. [14]
75ImageThe optical counterpart of an object. [14]
76Mil1. 1/6400 of the circumference of a circle. Approximately 1/1000 radian. 2. 1/1000 of an inch. [14]
77ErrorThe difference between an observed or computed value of a quantity and the ideal or true value of that quantity. [14]
78CompassAn instrument consisting of two legs jointed by a pivot used for describing circles or transferring measurements. Also referred to as pair of compasses. An instrument for indicating a horizontal reference direction relative to the earth. [14]
79TableAn orderly, condensed arrangement of numerical or other information, usually in parallel vertical columns. See conversion table, current tables, tide tables, traverse table. [14]
80ObservationThe act or practice of noting and recording facts and events as for some scientific study. The measure of a quantity whose value is desired. The data so noted and recorded. A single measure, at a single setting of an apparatus. [14]
81ShoreThe narrow strip of land in immediate contact with any body of water including the area between high and low water lines. [14]
82SpeedRate of motion. The terms speed and velocity are often used interchangeably, but speed is a scalar, having magnitude only, while velocity is a vector quantity, having both magnitude and direction. Speed may either be the ship's speed through water, or the speed made good over ground. [14]
83ControlA system of points with established positions or elevations, or both, which are used as fixed references in positioning and correlating map features. Control is generally classified in four orders (with first order denoting highest quality) according to the precision of the methods and instruments used in establishing it, and the accuracy of the resultant positions and elevations. Often called basic control. Regulation or direction of a machine, electronic equipment, etc.; or the dial, knob, switch, etc. For performing this function. The exercise of directing influence over the movements of a craft or missile, with reference to changes in direction and speed. [14]
84EchoReflected radiant energy. [14]
85GravityThat force which tends to pull bodies towards the earth; that is to give bodies weight. Gravity is the resultant of two opposing forces: gravitation and centrifugal force due to the rotation of the earth. [14]
86DownAn area of high, treeless ground, usually undulating and covered with grass. See also dune. [14]
87PlateA thin, metal, plastic, or paper sheet, that carries the printing image and whose surface is treated to make only the image areas ink receptive. [14]
88DiscRotating storage medium composed of one or two usable surfaces or a vertical assembly of such discs with a common axis. Typically, discs combine high storage volumes and short access time allowing fast access to data which is distributed randomly over the medium. [14]
89SextantA double-reflecting instrument for measuring angles, primarily altitudes of celestial bodies. The sextant has an arc of 60°, a sixth of a circle, from which it derives its name, and a range of 120°. In modern practice the term also applies to a similar instrument, regardless of its range. See also octant, quadrant and quintan. [14]
90TransitIn astronomy, the apparent passage of a star or other celestial body across a defined line of the celestial sphere, as a meridian, prime vertical, or almucantar. When no line is specified, a transit across the meridian is usually intended. See meridian transit. The apparent passage of a star or other celestial body across a line in the reticle of a telescope, or some line of sight. The apparent passage of a smaller celestial body across the disk of a larger celestial body. A surveying instrument composed of a horizontal circle graduated in circular measure and an alidade with a telescope which can be reversed in its supports without being lifted therefrom. Also, the act of making such a reversal. A theodolite having a telescope that can be transited in its supports is a transit and is sometimes termed a transit theodolite. All modern theodolites are transits. An astronomical instrument having a telescope which can be so adjusted in position that the line of sight may be made to define a vertical circle. A transit used in astronomical work is usually termed either an astro-nomic(al) transit or a transit instrument. In navigation, the position of two distant, fixed objects when they are in line to an observer; the line passing through them and the observer being a line of position. See also range. [14]
91LockA wet dock in a waterway, permitting a ship to pass from one level to another. See tide lock. [14]
92SecondThe unit of time in the si system. A sixtieth part of a minute, an angle, or an arc. [14]
93TonA unit of weight equal to 1,000 kilograms ('metric ton'), 2,240 pounds ('long ton'), or 2,000 pounds ('short ton'). [14]
94PhaseThe visible aspect of an object. The amount by which a cycle has progressed from a specified origin. In astronomy, any of the stages of variation in the illumination of the moon or a planet. See phase(s) of the moon. In physics, the state of aggregation of a substance, for example, solid (ice), liquid (water), or gas (vapor). [14]
95BeaconA fixed artificial navigation mark that can be recognized by its shape, colour, pattern, top mark or light character, or a combination of these. It may carry various additional aids to navigation. This term is not commonly used when the navigation mark can be classified as a lighthouse. [14]
96RunA brook, or small creek. The distance travelled by a craft during any given time interval, or since leaving a designated place. Complete performance of one programme on a computer. [14]
97CribA permanent marine structure usually designed to support or elevate pipelines; especially a structure enclosing a screening device at the offshore end of a potable water intake pipe. The structure is commonly a heavy timber enclosure that has been sunken with rocks or other debris. [14]
98VentThe orifice through which molten lava reaches the crater of a volcano. Eventually it may become choked as the lava solidifies to form a plug or neck. [14]
99DegreeA unit of angular or circular-arc measurement, equal to 1/360 of a circle. A unit of measurement of temperature in any scale. [14]
100ParallaxAn apparent displacement of the position of a body with respect to a reference point or system, caused by a shift in the point of observation. [14]
101FogSuspension of very small water droplets in the air, generally reducing the horizontal visibility at the earth's surface to less than 1 kilometre. [14]
102CastIn oceanography, a single lowering of a series of water bottles or other oceanographic instruments at an oceanographic station. Also referred to as oceanographic cast. [14]
103FlatA level tract of land, as the bed of a dry lake or an area frequently uncovered at low tide. Usually in plural. [14]
104Track(v.t.). To follow the movements of an object as by radar or an optical system. To navigate by keeping a record, tabular or graphical of the past positions of a craft without regard for future positions. [14]
105TrackThe actual path or route of a craft over the ground or sea bottom, or its graphic representation. In air navigation also called track made good. [14]
106StandardAn exact value (a physical entity or an abstract concept) established and defined by authority, custom, or common consent, to serve as a reference, model, or rule in measuring quantities or qualities, establishing practices or procedures, or evaluating results. In chart construction, a master copy of a chart upon which are marked all corrections affecting the chart between printings. [14]
107EdgeIn topography, the crest of a sharply pointed ridge. [14]
108FrontN meteorology: a) surface of separation of two air masses (frontal surface); b) line of intersection of the surface of separation of two air masses with another surface or with the ground. [14]
109SpheroidAn ellipsoid; a figure resembling a sphere. Also called ellipsoid or ellipsoid of revolution, from the fact that it can be formed by revolving an ellipse about one of its axes. In geodesy, this term is fre-quently used to mean reference spheroid. See also spheroid: oblate and spheroid: prolate. [14]
110NameThe label of a numerical value used particularly to refer to the n (north) or s (south) label of latitude and declination. When latitude and declination are both n or both s, they are said to be of the same name, but if one is n and the others, they are said to be of contrary name. [14]
111ChannelThat part of a body of water (sometimes dredged) deep enough for navigation through an area otherwise not navigable. It is usually marked by a single or double line of buoys and sometimes by ranges. The deepest part of a stream, bay, or strait through which the main current flows. See also strait. [14]
112GridA series of lines, usually straight and parallel, superimposed on a chart or plotting sheet to serve as a directional reference for navigation. See also graticule. Two sets of mutually perpendicular lines dividing a map, chart, or other representation of the earth's surface, into squares or rectangles to permit location of any point by a system of rectangular coordinates. In electronics, an electrode with one or more openings to permit passage of electrons or ions. [14]
113SandLoose material consisting of small but easily distinguishable, separate grains, between 0.0625 and 2.000 millimeters in diameter. [14]
114GroupA term distinguishing a light exhibiting two or more flashes or occultations from one exhibiting a single flash or single occultation. [14]
115LongitudeAngular distance, along a primary great circle, from the adopted reference point. One of coordinates used to describe a position the other being latitude. [14]
116MonthA measure of time based on the motion of the moon in its orbit. [14]
117TapeIn surveying, a ribbon of steel, invar, or other suitable material on which graduations are placed for the measurement of lengths or distances. See also base tape (or wire). [14]
118HoleAn abrupt hollow in the ground or ocean floor. See also passage. [14]
119Clear(v.t.). To make such distance from an object as to have open sea-room. [14]
120ReachA straight section of a river, especially a navigable river between two bends. See also sea reach. An arm of the sea extending into the land. [14]
121Shallow(Adj.). Having little depth. [14]
122Shallow(n.). An area composed of unconsolidated material where the depth of water is relatively slight. It may be a hazard to surface navigation. [14]
123ThunderSharp or rumbling sound which accompanies lightning. [14]
124OrbitThe path of a body or particle under the influence of a gravitational or other force. For instance, the orbit of a celestial body is its path relative to another body around which it revolves. In water waves, the path of a water particle affected by the wave motion. [14]
125DensityIn photography, a measure of the degree of blackening of an exposed film, plate or paper after development, or the direct image (in the case of a print-out material). It is defined strictly as the logarithm of the optical opacity. In oceanography, density is equivalent to specific gravity and represents the ratio, at atmospheric pressure, of the weight of a given volume of sea water to that of an equal volume of distilled water at 4.0°c. [14]
126RotationTurning of a body about an axis within the body, as the daily rotation of the earth. See revolution. [14]
127ComponentSee harmonic constituent. [14]
128Tidal CurrentSee current. [14]
129BeamRadiant energy confined to a particular shape. [14]
130AisSee automatic identification system [14]
131IecInternational electrotechnical commission [14]
132LagThe delay between change of condition and the indication of the change on an instrument. Delay in human reaction. The amount one cyclic motion is behind another, expressed in degrees. The opposite is lead. [14]
133Great CircleSee circle. [14]
134SlopeThe deepening sea floor out from the shelf edge to the upper limit of the continental rise, or the point where there is a general decrease in steepness. [14]
135PlanetA celestial body of the solar system, shining by reflected light and revolving around the sun. [14]
136NegativeA photographic image on film, plate, or paper, in which the subject tones to which the emulsion is sensitive are reversed or complementary. [14]
137DeviationSee deviation: magnetic. [14]
138TelescopeAn optical instrument used as an aid in viewing or photographing distant objects, particularly celestial objects. [14]
139GainThe ration of output voltage, current or power to input voltage, current, or power in electronic instruments. [14]
140HeatA form of energy transferred between systems by virtue of their temperature differences. [1]
141SampleA representative part or single item from a larger whole or group especially produced for inspection or to give evidence of quality. [14]
142AccuracyThe extent to which a measured or enumerated value agrees with the assumed or accepted value. See precision. [14]
143WordAn addressable subdivision of storage memory of a computer system. Usually an integer number of bytes (e.g., 4 bytes = 32 bit) indicating the standard length of number representation in storage. [14]
144CableA unit of distance originally equal to the length of a ship's anchor cable, but now generally considered to be about 600 feet. In the British navy it is 608 feet, or exactly one-tenth of a nautical mile. In the united states navy, it is 720 feet but is infrequently used. Sometimes called cable length. A chain or very strong fibre or wire rope used to anchor or moor vessels or buoys. A stranded conductor or an assembly of two or more electric conductors insulated from each other, but laid up together with a strong, waterproof covering. [14]
145Shoal(Adj.). Shallow. [14]
146Shoal(n.). An offshore hazard to surface navigation with substantially less clearance than the surrounding area and composed of unconsolidated material. [14]
147Shoal(v.i.). To proceed from a greater to a lesser depth. To cause to become less deep. [14]
148SightObservation of the altitude, and sometimes also the azimuth of a celestial body for a line of position, or the data obtained by such observation. Any of various devices used to aid the eyes in lining up an optical instrument on its objective. [14]
149ClimateFluctuating aggregate of atmospheric conditions characterized by the states and developments of the weather of a given area. [14]
150TraverseA method of surveying in which a sequence of lengths and directions of lines between points on the earth are obtained from field measurements and used in determining positions of the points. Also called survey traverse. [14]
151VelocityA vector quantity equal to speed in a given direction. [14]
152RadiationEmission or transfer of energy in the form of electromagnetic waves or particles. The energy itself is also termed radiant energy. [14]
153PathA line of movement; course taken, as the path of a meteor. A line connecting a series of points in space and constituting a proposed or travelled route. [14]
154Celestial BodyAnybody pertaining to the heavens, constituting a unit for astronomical study, such as the sun, the moon, the planets, fixed stars, comets, etc. Also called heavenly body. [14]
155DamA barrier to check or confine anything in motion; particularly one constructed to hold back water and raise its level to form a reservoir, or to prevent flooding. [14]
156DipThe vertical angle, at the eye of an observer between the horizontal and the line of sight to the apparent horizon. Also called dip of the horizon or depression of the horizon. The angle between the horizontal and the lines of forces of the earth's magnetic field at any point. Also called magnetic dip or magnetic inclination. [14]
157MatteConglomerate of sand, mud and seaweed forming a shoal or reef. [14]
158IslandA piece of land surrounded by water. [14]
159DrawingThe graphic representation of data on a non-volatile medium. An impression following the printing of a nautical chart of either its black or its magenta detail on matte finish transparent plastic, used in revising subsequent printings of the chart. [14]
160ContrastIn photography, the actual difference in density between the highlights and the shadows on a negative or positive. Contrast is not concerned with the magnitude of density but only with the difference in densities. Also, the rating of a photographic material corresponding to the relative density difference which it exhibits. [14]
161SedimentParticulate organic and inorganic matter which accumulates in a loose unconsolidated form. It may be chemically precipitated from solution, secreted by organisms, or transported by air, ice, wind, or water and deposited. [14]
162TestThe hard covering or supporting structure of many invertebrates; it may be enclosed within an outer layer of living tissue; a shell. [14]
163ClockInstrument for measuring time and recording hours. [14]
164RadianThe unit of plane angles in the si system. [14]
165AcousticScience of sound, including its production, transmission, and effects. [14]
166MagnetismThe ability to attract magnetic material, notably iron and steel. [14]
167ThermometerInstrument used in the measurement of temperature. [14]
168EbbThe ebb streams. Sometimes the term 'ebb' is also used with reference to vertical tidal movement. The opposite is flood. [14]
169PowerSee magnifying power. [14]
170HeadingThe direction in which a vessel or craft is pointed, usually expressed in degrees from north (true, magnetic, or compass) [14]
171PassageA narrow navigable channel, especially one through reefs or islands. [14]
172SailingA method of solving the various problems involving course, distance, difference of latitude, difference of longitude and departure. The various methods are collectively spoken of as 'the sailings'. [14]
173HarmonicA sinusoidal quantity having a frequency that is an integral multiple of the frequency of a periodic quantity to which it is related. [14]
174PositiveIn photography, an image of the original object which corresponds to the same in the scheme of light and shade. [14]
175CoreThe central or innermost part of anything. See centrosphere. In oceanography, a vertical, cylindrical sample of the bottom sediments from which the nature and stratification of the bottom may be determined. Also, called core sample or sediment core. [14]
176CrestThe highest part of a wave, swell, ridge, etc. [14]
177FloodThe flood streams. Sometimes the term 'flood' is also used with reference to vertical tidal movement. The opposite is ebb. An overflowing of water on land usually dry; inundation. [14]
178MinuteThe sixtieth part of an hour; sixty seconds. The sixtieth part of a degree of arc; sixty seconds. [14]
179ReliefThe elevations or the inequalities, collectively, of a land surface; represented on a map or chart by contours, hypsometric tints, shading, spot elevations, hachures, etc. [14]
180DepositAccumulations of solid material (of any type or from any source) on the sea bottom which eventually may become compacted and consolidated and form sedimentary rock. [14]
181ComputerA person who performs calculations. A device capable of accepting data, processing it according to stored instruction that are followed in automatic sequence, and supplying the results in some form. It usually consists of input and output devices, storage, arithmetic and logical units, and a control unit. [14]
182JunctionPlace of meeting or joining, as that of a tributary with a main river, or of two channels in a waterway. In levelling, the place where two or more lines of levels are connected together. In hydrographic survey, the joining of two adjacent survey sheets. See overlap. [14]
183MountainA natural elevation of the earth's surface rising abruptly from the surrounding level, and attaining an altitude which, relatively to adjacent elevations, is impressive or notable. [14]
184IntersectionIn surveying, the procedure of determining the horizontal position of an unoccupied point (intersec-tion station) by direction observations from two or more known positions. In photogrammetry, the procedure of determining the horizontal position of a point by intersecting lines of direction obtained photogrammetrically. The lines of direction may be obtained directly from vertical photographs or by graphic or mathematical rectification of tilted photographs. [14]
185DialThe face of a watch or clock. The clockwise face of an instrument for indicating, as by a moving pointer, the amount of something; face of a compass, gauge, or meter. A sundial. [14]
186MileA unit of distance. See international nautical mile, sea mile, statute mile. [14]
187PaperFor printing hydrographic charts, heavyweight, single layer paper is used. Such paper is generally made wholly or partly from rags and simulates hand-made paper. It is strong, moisture resistant and manufactured to withstand surface erasure. [14]
188SigniAbbreviation for signalization de navigation instruments. A system of buoyage used in certain inland waters in the Netherlands. [14]
189VectorDirect connection between two points, either given as two sets of coordinates (points), or by direction and distance from one given set of coordinates; or a point in a vector space defined by one set of coordinates relative to the origin of a coordinate system. [14]
190CycloneSee depression. [14]
191Offshore(Adj. And adv.). Away from the shore. [14]
192Offshore(n.). The comparatively flat zone of variable width which extends from the outer margin of the rather steeply sloping shoreface to the edge of the continental shelf. [14]
193Navigational(Adj.). See nautical. [14]
194Bankan elevation of the sea floor over which the depth of water is relatively shallow. [14]
195GyroSee gyroscope. [14]
196SnowPrecipitation of ice crystals, most of which are branched (sometimes starshaped). [14]
197ShelfGeologically an area adjacent to a continent or around an island and extending from the low-water line to the depth at which there is usually a marked increase of slope towards greater depth. See also continental shelf. [14]
198SpringSpring tide. A natural issue of water or other substances from the earth. One on the bottom of the sea is called a submarine spring. [14]
199WeightThe force with which a body is attracted by gravity. Any block or mass of material used for its heaviness. The relative value of an observation, source, or quantity when compared with other observations, sources, or quantities of the same or related quantities. The value determined by the most reliable method is assigned the greatest weight. [14]
200Seaward(Adj. And adv.). Away from the land; toward the sea. [14]
201GradientThe change of any quantity with distance in any given direction. See pressure gradient, temperature lapse rate. The amount of slope, inclination to the horizontal, in road, railway, etc. [14]
202LegEach straight section of a traverse. One part of a craft's track consisting of a single course line. [14]
203HillA small, isolated elevation, smaller than a mountain. See also knoll. [14]
204LakeA large body of water surrounded by land. [14]
205RiftA cleft, fissure, or chasm in the earth. See median valley. [14]
206ZenithThe point where the direction of the plumb line produced above the horizon meets the celestial sphere. [14]
207AstronomyThe science which deals with the size, constitution, motions, relative positions, etc. Of celestial bodies, including the earth. See also astrometry. [14]
208RefractionThe process in which the direction of energy propagation is changed as the result of a change in density within the propagating medium, or as the energy passes through the interface representing a density discontinuity between two media. [14]
209Straight LineMathematically the line of shortest distance between two points in a specified space or on a specified surface. [14]
210BayWide indentation in the coastline generally smaller than a gulf and larger than a cove. For the purposes of the united nations convention on the law of the sea, a bay is a well-marked indentation whose penetration is in such proportion to the width of its mouth as to contain land locked waters and constitute more than a mere curvature of the coast. See also historic bay. [14]
211CardSee compass card. [14]
212LashSee lighter aboard ship. [14]
213Moor(v.t.). To secure a boat or other floating thing to a fixed object or the sea bottom. [14]
214TiltThe angle which anything makes with the horizontal. In photogrammetry, the angle at the perspective center between the photograph perpendicular and the plumb line, or other exterior reference direction; also, the dihedral angle between the plane of the photograph and the horizontal plane. [14]
215NadirThat point on the celestial sphere directly beneath the observer, and directly opposite to the zenith. [14]
216AntennaA conductor or system of conductors for radiating or receiving radio waves. Also called aerial. [14]
217PatternSee lattice. [14]
218SounderA machine or apparatus for sounding. An echo sounder. [14]
219TornadoIn north America, the name for an intense spout of large diameter. [14]
220BoundaryAnything marking a limit; bound; border. [14]
221Sea FloorThe bottom of the ocean and seas where there is a generally smooth gentle gradient. Also referred to as seabed (sometimes seabed or sea-bed), and sea bottom. [14]
222Sea WaterThe water of the seas, distinguished from fresh water by its appreciable salinity. The degree of the salinity greatly affects the water's physical characteristics. [14]
223MagnetometerAn instrument for measuring the intensity and/or the direction of the earth's magnetic field. [14]
224Etch(v.t.). To form an image within the surface of a printing or drawing material by the use of solvents. [14]
225ReefA mass of rock or coral which either reaches close to the sea surface or is exposed at low tide, posing a hazard to navigation. [14]
226RidgeThe linked major mid-oceanic mountain systems of global extent. Also called mid-oceanic ridge. [14]
227MaritimeBordering on, concerned with, or related to the sea. [14]
228OriginalSee reproduction. [14]
229SurroundSee margin. [14]
230ConstituentSee harmonic constituent. [14]
231CodeA method of information representation by mapping it into a machine-readable alphabet, e.g. Textual information may be represented in computer memory by the ascii or the ebcdic alphabet. [14]
232DockThe space between two piers. Also called a slip. [14]
233ListInclination to one side, as of a vessel until she has found equilibrium in an inclined position. Listing is a static condition, as distinguished from heeling which is dynamic. See heel. [14]
234ChainA group of transmitters broadcasting the same programme. In electronic navigation, several related transmitting stations in geographic proximity (decca chain, loran chain, etc.). In digital data, a sequence of one or more-line segments. [14]
235CrustIn geology, the outer layer of the solid earth; the lithosphere. Also called earth's crust. [14]
236Drift(v.i.). To move by action of wind or current without control. [14]
237DriftThe speed of the water due to ocean or tidal currents. A wide, slow-moving current principally caused by winds. The distance a craft is moved by current and wind. Drift angle or leeway. The term is also applied to any superficial deposit caused by a current of water or air. [14]
238StripIn ice terminology, a long narrow area of pack ice, about 1 km or less in width, usually composed of small fragments detached from the main mass of ice, and run together under the influence of wind, swell or current. [14]
239BorderThe district lying along the edge of a country or territory; a frontier. The boundary line which separates one country from another, the frontier line. [14]
240CounterAn indicator on a machine, for keeping count of turns, strokes, etc., of the machine or its parts. [14]
241EclipseThe obscuration of a source of light by the intervention of an object. Whole or partial obscuration of a heavenly body by the interposition of another, or by the passing of one luminous heavenly body into the shadow of another. [14]
242EquinoxOne of the two points of intersection of the ecliptic and the celestial equator, occupied by the sun when its declination is zero. That point occupied on or about March 21, when the sun's declination changes from south to north, is called vernal equinox or first point of aries; that point occupied on or about September 23, when the declination changes from north to south, is called autumnal equinox or first point of libra. Also called equinoctial point. [14]
243ReceiverOne who or that which receives anything, particularly a radio receiver. [14]
244ContinentOne of the main continuous bodies of land on the earth's surface. The mainland, as distinguished from outlying islands, mainland. [14]
245ReductionThe process of substituting for an observed value one derived therefrom. [14]
246ThunderstormOne or more sudden electrical discharges manifested by the flash of light (lightning) and a sharp or rumbling sound (thunder). [14]
247Gal(derived from galileo). The unit of acceleration in the cgs system. See milligal. [14]
248PipSee blip. [14]
249Pile a long heavy timber or section of steel, wood, concrete, etc., forced into the earth or sea floor to serve as a support, as for a pier, or to resist lateral pressure, or as a free standing pole within a marine environment. [14]
250TillUnstratified glacial drift consisting of clay, sand, gravel, and boulders intermingled in any proportions. Also called boulder clay. [14]
251BeachOn a shore, the area on which the waves break and over which shore debris, such as sand, shingle, pebbles accumulate. A beach includes backshore and foreshore. [14]
252GaugeAn instrument for measuring the size or state of anything. [14]
253NeedleShort for magnetic needle. [14]
254SeabedSee sea floor. [14]
255SymbolA character, letter, or similar graphic representation used on a chart, map, hydrographic survey sheet, or diagram to represent some object, quantity, characteristic, etc. [14]
256AnalysisThe drawing and interpretation of the patterns of various weather elements on a surface or upper-air chart. [1]
257ExposureIn photography, the act of exposing a light-sensitive material to a light source. The total quantity of light received per unit area on a sensitized plate or film; may be expressed as the product of the light intensity and the exposure time. [14]
258SalinityA measure of the quantity of dissolved salts in sea water. It is normally defined as the total amount of dissolved solids in sea water in parts per thousand ( °) by weight when all the carbonate has been converted to oxide, the bromide and iodide to chloride, and all organic matter is completely oxidiz-ed. These qualifications result from the chemical difficulty in drying the salts in sea water. In practice, salinity is not determined directly but is computed from chlorinity, electrical conductivity, refractive index, or some other property whose relationship to salinity is well established. Because of the law of constancy of proportions, the amount of chlorinity in a sea water sample is used to establish the sample's salinity. The relationship between chlorinity cl and salinity s as set forth in Knudsen’s tables is s = 0.03 + 1.805 cl. A joint committee of IAPO, UNESCO, ICES, and SCOR proposed the universal adoption of the following equation for determining salinity from chlorinity: s = 1.80655 cl. It was adopted by IAPO in 1963 and ices in 1964. [14]
259Spectrum(pl. Spectra). A series of images formed when a beam of radiant energy is separated into its various wavelength components, as when a beam of white light is refracted and dispersed by a prism. The entire range of electromagnetic radiations, or any part of it used for a specific purpose, as the radio spectrum (10 kilohertz to 300,000 megahertz). [14]
260PrecisionThe degree of refinement of a value not to be confused with accuracy, which is the degree of conformance with the correct value. [14]
261ConjunctionIn astronomy, the situation of two celestial bodies having the same celestial longitude or the same sidereal hour angle. For a superior planet, it occurs when the sun is between the earth and the planet. [14]
262Frequency: RadioAny frequency at which electromagnetic radiation of energy is useful for communication. Radio frequencies are usually classed as very low, below 30 kilohertz; low, 30-300 kilohertz; medium, 300-3,000 kilohertz; high, 3-30 megahertz; very high, 30-300 megahertz; ultra-high, 300-3,000 megahertz; super high, 3,000-30,000 megahertz; extremely high, 30,000-300,000 megahertz. [14]
263MudPelagic or terrigenous detrital material consisting mostly of silt and clay-sized particles (less than 0.06 millimeter) but often containing varying amount of sand and/or organic materials. It is a general term applied to any sticky fine-grained sediment whose exact size classification has not been determined. [14]
264StopSee aperture stop. [14]
265GeoidThe figure of the earth considered as a mean sea level surface extended continuously through the continents. The actual geoid is an equipotential surface to which, at every point, the plumb line (direction in which gravity acts) is perpendicular. It is the geoid which is obtained from observed deflections of the vertical and is the surface of reference for astronomical observations and for geodetic levelling. See reference spheroid. [14]
266WreckThe ruined remains of a stranded or sunken vessel which has been rendered useless. See also dangerous wreck, and derelict. [14]
267RadialA straight line extending outward from a center. In photogrammetry, a line or direction from the radial center to any point on a photograph. The radial center is assumed to be the principal point, unless otherwise designated (e.g., nadir radial). See also isoradial. [14]
268OverlapIn cartography and surveying, the amount by which one chart or survey sheet extends also over an adjoining chart or sheet. The amount by which different sets of survey data, obtained with the same system, cover the same area; customarily expressed as a percentage. [14]
269Sea IceAny form of ice which has originated from sea water. Generally, any ice in the sea. [14]
270AmplitudeIn astronomy, the arc of the horizon, between a celestial body at rising or setting and true east or west point. In tide terminology, the semi-range of the harmonic constituent. In physics, the maximum departure of a wave or other periodic phenomenon from the average or zero position. [14]
271DistortionAn undesired change in waveform. In optics, an aberration affecting the position of the images off the axis, in which objects at different angular distances from the axis undergo different magnifications. Also called lens distortion. In photography, any shift in the position of an image on a photograph which alters the perspective characteristics of the photograph. Causes of image distortion include lens aberration, differential shrinkage of film or paper, and motion of the film or camera. [14]
272InequalityA systematic departure from the mean value of a quantity. See annual inequality, diurnal inequality, lunar inequality, parallax inequality, phase inequality. [14]
273ReflectionThe process whereby a surface of discontinuity turns back a portion of the incident radiation into the medium through which the radiation approached. See surface reflection. [14]
274Sea BottomSee sea floor. [14]
275DeclinationIn astronomy, the angle at the center of the celestial sphere between the radius passing through a celestial body and the plane of the celestial equator. Declination is measured by the arc of the hour circle between the celestial body and the celestial equator. It is plus when the body is north of the equator, and minus when south of it. [14]
276ObstructionIn marine navigation, anything that hinders or prevents movement, particularly anything that endangers or prevents passage of a vessel. The term is usually used to refer to an isolated danger to navigation, such as a sunken rock or pinnacle. [14]
277PrecipitationPhenomenon made up of an aggregate of aqueous particles, liquid or solid, crystallized, or amorphous, which fall from a cloud or group of clouds and reach the ground. [14]
278LeeThat side towards which the wind blows; the sheltered side. [14]
279RaceSwiftly flowing water in a narrow channel or river; also, the channel itself which may be artificial as in a mill-race. Also, a swift rush of water through a narrow channel in tidal waters and caused by the tidal movement of the waters. See tide race. [14]
280ScanSee scope. [14]
281StoneA general term for rock and rock fragments ranging in size from pebbles and gravel to boulders or large rock masses. [14]
282WatchA small timepiece of a size convenient to be carried on the person. [14]
283MirrorAny surface which produces images by reflection of light rays. [14]
284TargetAny object, point, etc., toward which something is directed. An object which reflects a sufficient amount of a radiated signal to produce an echo signal on detection equipment. See radar target, sonar target. The distinctive marking or instrumentation of a ground point to aid in its identification on a photograph. In photogrammetry, target designates a material marking so arranged and placed on the ground as to form a distinctive pattern over a geodetic or other control point marker, on a property corner or line, or at the position of an identifying point above an underground facility or feature. A target is also the image pattern on aerial photographs of the actual mark placed on the ground prior to photography. [14]
285DiagramA graphic representation of certain data. [14]
286HumidityAtmospheric water vapour content, expressed in any of several measures, such as relative humidity. [14]
287BarometerInstrument for measuring atmospheric pressure. [14]
288Submerged(Adj.). Under water; not showing above water. The opposite is uncovered. [14]
289Tidal DayLunar day. The period of the daily cycle of the tides, differing slightly from the lunar day because of priming and lagging of the tide. [14]
290AdjustmentThe determination and application of corrections to observations or measurements, for the purpose of reducing errors or removing internal inconsistencies in observed results. Adjustment may either refer to mathematical procedures or to corrections applied to instruments. [14]
291VisibilityThe extreme horizontal distance at which prominent objects can be seen and identified by the unaided eye. [14]
292BoreA high breaking wave of water, advancing rapidly up an estuary. Bores can occur at the mouths of shallow rivers if the tide range at the mouth is large. They can also be generated in a river when tsunamis enter shallow coastal water and propagate up the river. Also called eager, mascaret, or tidal bore. [14]
293Basina depression of the sea floor more or less equidimensional in plan and of variable extent. [14]
294PlainAny land with a flat or very slightly undulating surface. A flat, gently sloping or nearly level region of the sea floor, for example, abyssal plain. [14]
295PlatformIn geographical literature, a natural or artificial terrace; a flat elevated piece of ground; a tableland, a plateau. In oceanographic terminology, any man-made structure (aircraft, ship, buoy, or tower) from or on which oceanographic instruments are suspended or installed. Structures which are erected on or over the seabed and subsoil for the purpose of exploring for, developing, removing and transporting resources therefrom. [14]
296ParameterA quantity which remains constant within the limits of a given case or situation. [14]
297ReckoningIn navigation, computation by which the position of a ship is found. See dead reckoning. [14]
298ProtractorAn instrument for measuring angles on a surface; an angular scale. In its most usual form, it consists of a circle or part of one (usually a semicircle) graduated in degrees. See protractor: three arm and compass rose. [14]
299Aerial PhotographSee photography. [14]
300SueThe vertical amount which a vessel aground dries due to the fall of the tide. [14]
301DustAny substance comminuted or pulverized, especially earth or other solid matter in a minute and fine state of subdivision, so that the particles are small and light enough to be easily raised and carried in a cloud by the wind. [14]
302InchA unit of length equal to 1/12 of a foot or 2.54 cm. [14]
303NoonThe instant at which a time reference is over the upper branch of the reference meridian. [14]
304SoilThe earth or ground; the face or surface of the earth. The ground with respect to its composition, quality, etc., or as the source of vegetation. [14]
305ScreeA mass of detritus, forming a precipitous, strong slope upon a mountainside. Also, the material composing such a slope. See also talus. [14]
306FixingThe process of rendering a developed photographic image permanent by removing the unaffected light-sensitive material. [14]
307MarginIn cartography, that area of a map or chart lying outside the border. 'Margin' is preferred to the term 'surround'. [14]
308ScreenA device to shield or separate one part of an apparatus from other parts, or to separate the effects of one part on others. In electronic charting, a device connected to a computer displaying information either under computer control, or under user control, e.g. On a cathode-ray tube. Devices allowing for high resolution are capable of displaying also graphics. [14]
309DigitalA method of representing information by combinations of discrete and discontinuous data. [14]
310LightningLuminous manifestations accompanying a sudden electrical discharge which takes place from or inside a cloud or, less often, from high structures on the ground or from mountains. [14]
311Navigable(Adj.). Affording passage to a craft; capable of being navigated. [14]
312DepressionAny hollow or relatively sunken area. In meteorology, a region of the atmosphere in which the pressure is low relative to the surrounding region at the same level. It is represented on a weather chart by a system of isobars at a specified level or of contours at a specified pressure which enclose relatively low values of pressure or level. Also, called low or cyclone. [14]
313Focal PlaneA plane parallel to the plane of a lens or mirror and passing through the focus. In photography, the plane (perpendicular to the axis of the lens) in which images of points in the object field of the lens are focused. [14]
314Water VaporWater in the gaseous phase. [14]
315Lunitidal IntervalThe interval of time between the transit (upper or lower) of the moon over the local or Greenwich meridian and the next high water or low water at a place. The interval is assumed to be local unless otherwise specified. The average of all high-water intervals is called mean high water lunitidal interval, high water interval, or corrected establishment. The average of all low water intervals is called mean low water lunitidal interval, or low water interval. The expressions higher high-water interval, lower high water interval, higher low water interval, and lower low water interval are used when there is considerable diurnal inequality. See establishment. [14]
316LuxUnit of illumination in the si system. [14]
317BergShort for iceberg. [14]
318ConeSee fan. [14]
319KnotA division of the log line, by which the ship's speed is measured. A nautical unit of speed. One knot is one nautical mile per hour. The name is derived from the knots in the log line. [14]
320Focus(pl. Foci). That point at which parallel rays of light meet after being refracted by a lens or reflected by a mirror. Also called focal point. In seismology, the source of a given set of elastic waves. The true center of an earthquake, within which the strain energy is first converted to elastic wave energy. [14]
321Focus(v.t.). The process of adjusting an optical instrument, projector, cathode-ray tube, etc., to produce a clear and well-defined image. [14]
322GlobeThe earth; the world. A spherical structure on whose surface is depicted the geographical configuration of the earth (terrestrial globe). [14]
323PivotA spindle or pin by which a movable part of an instrument is supported so as to be free to turn. The pivot of a compass is usually a fixed point on which the needle hangs by a single jeweled cap. [14]
324RhumbSee rhumb line. [14]
325SonarA system of determining distance of an underwater object by measuring the interval of time between transmission of an underwater sonic or ultrasonic signal and the return of its echo. Direction may also be determined by noting the direction of transmission of the signal. The name sonar is derived from the words sound navigation and ranging. See echo ranging. [14]
326AlidadePivoted sight bar that moves over a graduated arc. The upper part of a theodolite. The alidade used in topographic surveying consists of a straight-edge ruler carrying a telescope or other sighting device and used in recording a direction on the plane table sheet. The term is also used to describe a bearing circle fitted with a telescope to facilitate observation of bearings. If a telescope is used, the instrument is often termed a telescopic alidade. [14]
327DisplayA visual presentation of data. [14]
328Air MassEnsemble of air particles whose paths and physical properties exhibit, in the horizontal, only small, and continuous differences. The mass may extend over an area of several million square miles and over a depth of several kilometers. [14]
329EclipticThe great circle formed by the intersection of the plane of the earth's orbit around the sun (or apparent orbit of the sun around the earth) and the celestial sphere. [14]
330Diurnal InequalityThe difference between the heights of the two high tides (high water inequality) or the two low tides (low water inequality) during a tidal day, or the difference in speed between the two flood or the two ebb currents during a tidal day. The average diurnal inequality is called tropic high-water inequality and tropic low water inequality when referred to the high waters and low waters, respectively, of tropic tides. Mean diurnal high-water inequality is half the average difference between the heights of the two high waters of each tidal day over a 19-year period. Mean diurnal low water inequality is half the average difference between the heights of the two low waters for a similar period. Also called declinational inequality. [14]
331NodeA point that is the start or end point of a line segment. In astronomy, one of the two points of intersection of the orbit of a planet, planetoid, or comet with the ecliptic, or of the orbit of a satellite with the plane of the orbit of its primary. That point at which the body crosses to the north side of the reference plane are called the ascending node; the other, the descending node. The line connecting the nodes is called line of nodes. Also called nodal point. See regression of the nodes. In oceanography, that part of a standing wave where the vertical motion is least, and the horizontal velocities are greatest. See partial node. In optics, a nodal point. [14]
332PipeA hollow metal tube, of varying diameters and lengths, imbedded in the bottom in a manner similar to a pile. Pipes are often used as privately maintained aids to navigation and in the determination of beach or bottom sand migration (deposition or erosion). [14]
333WashThe visible or audible motion of agitated water; especially that caused by the passage of a vessel. [14]
334OtterPlane surface towed forward of its middle length so that it will incline and dive. Used in fishing, minesweeping or surveying. See kite, kite otter, and Oropesa sweep. [14]
335ScendUpward motion of a vessel, either upward motion of the bow and stern associated with pitching or lifting of the entire vessel by waves or swell, when it may be called send. [14]
336ArmingTallow or other substance placed in the recess at the lower end of a sounding lead for obtaining a sample of the bottom. See bottom sample. [14]
337MomentThe tendency or degree of tendency to produce motion about an axis. Numerically it is the quantity obtained by multiplying the force, speed, or mass, by the distance from the point of application or center of gravity to the axis. See magnetic moment. [14]
338MosaicIn photogrammetry, as assembly of aerial photographs whose edges usually have been torn, or cut, and matched to form a continuous photographic representation of a portion of the earth's surface. [14]
339CarrierSee wave: carrier. [14]
340MooringA place where a vessel may be secured. (usually in pl.) The equipment used to secure a vessel. The process of securing a vessel or oceanographic instruments other than anchoring with a single anchor. [14]
341NetworkIn surveying, a pattern or configuration of stations called geodetic network. In geography, a complex system of rivers, canals, etc. In radio, a chain of transmitting radio stations owned and operated as a unit. [14]
342Air BaseIn photogrammetry, the line joining two air stations, or the length of this line; also, the distance (at the scale of the stereoscopic model) between adjacent perspective centers as reconstructed in the plotting instrument. See also photo base. [14]
343Low TideSee low water. [14]
344HurricaneTerm, derived from a Caribbean word, first applied to tropical cyclones of the Caribbean sea. Wind with a speed equal to or greater than 58 knots. (Beaufort scale wind force 12.) [14]
345TransportThe process by which a substance or quantity is carried past a fixed point, or across a fixed plane. In oceanography and meteorology, such quantities are: heat, momentum, mass, dissolved impurities, suspended particles, etc. [14]
346Hour AngleAngular distance west of a celestial meridian, the arc of the celestial equator, or the angle at the celestial pole, between the upper branch of a celestial meridian and the hour circle of a celestial body or the vernal equinox, measured westward through 24 hours (360o). It is usually further designated as local, Greenwich, or sidereal, as the origin of measurement is the local or Greenwich meridian, or the hour circle of the vernal equinox. [14]
347ModulationVariation of some characteristic of a wave, called the carrier wave, in accordance with instantaneous values of another wave, called the modulating wave. Variation of amplitude is amplitude modulation, variation of frequency is frequency modulation, and variation of phase is phase modulation. See modulation: pulse and modulation: space. [14]
348Phenomenon(pl. Phenomena). Any fact, circumstance, or experience that is apparent to the senses and that can be scientifically described or appraised; as, an eclipse is a phenomenon of astronomy. [14]
349Sound WaveSee wave. [14]
350Earth'S Magnetic FieldSee geomagnetic field. [14]
351LimbThe graduated curved part of an instrument for measuring angles, as that part of a marine sextant carrying the altitude scale, or arc. The circular outer edge of a celestial body. The half with the greatest altitude is called the upper limb and the half with the least altitude, the lower limb. [14]
352MoleA massive structure of masonry or large stones serving as a pier or breakwater, or both. Unit of quantity of matter in the si system. [14]
353CliffLand rising abruptly for a considerable distance above the water or surrounding land. [14]
354CoralHard calcareous skeletons of many tribes of marine polyps. [14]
355CorerA device for obtaining a core; a hollow tube that is driven into the ocean floor. Also called coring instrument or coring device. See corer: hydro plastic, corer: piston, piggot gun and vacuum lead. [14]
356InputWhat is put in, as electric current or other power put into a machine. Data to be transferred from an external storage medium, such as punched cards, into the internal storage of a computer. [14]
357ShadeA coloured glass that can be moved into the line of sight of an optical instrument, such as a sextant, to reduce the intensity of light reaching the eye. Also, calledshade glass. See horizon shade, and index shade. [14]
358SwellOcean waves which have travelled out of their generating area. Swell characteristically exhibits a more regular and longer period and has flatter crests than waves within their fetch. Rising of the water of a river above its usual level. Gently rising ground or a rounded hill above the surrounding ground. [14]
359FathomA unit of length equal to 6 feet or 1.83 meters. [14]
360MarkerThat which marks something. A marker beacons. See also radio beacon. [14]
361MasterAn instrument which controls another similar instrument called a repeater. A master station. [14]
362OutputThe amount of power or energy produced by a machine. [14]
363TroughA long depression of the sea floor characteristically flat bottomed and steep sided and normally shallower than a trench. [14]
364ValleyA long depression or hollow in the land lying between hills or stretches of high ground and usually having a river or stream flowing along the bottom. [14]
365BuoyageA system of, or providing with, buoys, serving the purpose of indicating navigable waters. See beaconage. [14]
366ThermalA small, rising parcel of warm air produced when the earth's surface is heated unevenly. [1]
367FreezingSee frost. [14]
368Sidereal(Adj.). Of or pertaining to the stars. [14]
369SolsticeOne of the two points of the ecliptic farthest from the celestial equator; one of the two points on the celestial sphere occupied by the sun at maximum north or south declination. That in the northern hemisphere is called the summer solstice or first point of cancer, and that in the southern hemisphere, the winter solstice or first point of Capricorn. Also called solstitial point. That instant at which the sun reaches one of the solstices, about June 21 (summer solstice) or December 22 (winter solstice). [14]
370AltimeterAn instrument that directly indicates the height above a reference surface. [14]
371AnchorageAn area in which vessels anchor or may anchor. [14]
372High TideSee high water. [14]
373Magnetize(v.t.). To produce magnetic properties. The opposite is demagnetized. [14]
374MagnitudeThe importance, quality, or size of something. In astronomy, relative brightness of a celestial body. According to the accepted classification, a star of the 1st magnitude is a hundred times as bright as a star of the 6th magnitude (the faintest star that can be seen with the unaided eye) and the dis-tribution of magnitudes is logarithmic in terms of brightness. Thus, each reduction in magnitude means an increase of brightness of about 2 1/2. [14]
375MountainsOn the sea floor, a well-delineated subdivision of a large and complex positive feature. See cordillera. [14]
376Solar DaySee day. [14]
377Wind SpeedRatio of the distance covered by the air to the time taken to cover it. The 'instantaneous speed' or, more briefly, the 'speed', corresponds to the case of an infinitely small-time interval. The 'mean speed' corresponds to the case of a finite time interval. [14]
378Compilation in cartography, the selection, assembly, and graphic presentation of all relevant information required for the preparation of a map or chart, or a new edition or part thereof. Such information may be derived from other maps or charts, aerial photographs, surveys, new data, and other sources. In photogrammetry, the production of a map (or portion of a map) from aerial photographs and geodetic control data, by means of photogrammetric instruments. Sometimes called stereo compilation. [14]
379Hour CircleA great circle on the celestial sphere passing through the celestial poles. Also called declination circle, circle of declination, or circle of right ascension. [14]
380ProbabilityThe likelihood of an event measured by the ratio of the favorable cases to the whole number of cases possible. [14]
381Mean Sea LevelThe average height of the surface of the sea at a tide station for all stages of the tide over a 19-year period, usually determined from hourly height readings measured from a fixed predetermined reference level (chart datum). [14]
382AtomThe smallest particle of an element which can enter into a chemical combination. [14]
383Drag(v.t.). To tow a line or object below the surface to determine the least depth in an area or to ensure that a given area is free from navigational dangers to a certain depth. See also sweep. To pull along the bottom, as an anchor. [14]
384FileAn entity of data for a specific task or purpose stored on a mass storage device. [14]
385HornFog signal using compressed air or electricity to vibrate a diaphragm. Horns exist in a variety of types which differ greatly in their sound and power. Further to the recent action taken by the hydrogra-pher of the United Kingdom. Such terms as nautophone, typhon and others are gradually being embraced by the general term 'horn'. [14]
386PullAn impression from an individual printing plate. [14]
387RipsA turbulent agitation of water generally caused by the interaction of currents and wind; in nearshore regions, rips may also be caused by currents flowing swiftly over an irregular bottom. [14]
388GradeRate of slope or degree of inclination, as a 2% grade. See also gradient and grad. [14]
389HeaveThe oscillatory rise and fall of a ship due to the entire hull being lifted by the force of the sea. [14]
390HertzA unit of frequency in the si system. See also cycle per second. [14]
391PatchIn ice terminology, a collection of pack ice, less than 10 km across. [14]
392SurgeA ship's bodily motion forward and backward along the longitudinal axis, caused by the force of the sea acting alternately on the bow and stern. The name applied to wave motion with a period intermediate between that of the ordinary wind wave and that of the tide, from about 1/2 to 60 minutes. Horizontal oscillation of water with comparative short period accompanying a seiche. [14]
393Surge(v.i.). To rise and fall, as a vessel at anchor. To vary abruptly and momentarily in amount, as an electric current in a circuit. [14]
394Ashore(Adj. And adv.). On the shore, on land or aground. [14]
395BreezeA wind of moderate strength. See land and sea (or lake) breeze. [14]
396StadiaA graduated rod used in the determination of distance by observing the intercept on the rod subtending a small known angle at the point of observation. In practice the angle is usually defined by two fixed lines in the reticle of a telescope. Also called stadia rod. [14]
397GeodesyThe science which treats of the determination of the size and figure of the earth (geoid) by such direct measurements as triangulation, levelling and gravimetric observations. [14]
398GlacierA mass of snow and ice continuously moving from higher to lower ground or, if afloat, continuously spreading. The principal forms of glaciers are: ice sheets, ice shelves, ice caps, ice piedmonts, and various types of mountain glaciers. [14]
399LatticeA pattern formed by two or more families of intersecting lines, such as hyperbolic lines of position or parts of circles, drawn on charts, plotting sheets or sounding boards. [14]
400SinkingA downward movement of surface water generally caused by converging currents or when water mass becomes denser than the surrounding water. See upwelling, and convergence. An apparent lowering of distant terrestrial objects by abnormal atmospheric refraction. Because of sinking, objects normally visible at or near the horizon sometimes disappear below the horizon. The opposite is looming. [14]
401Spatial(Adj.). Pertaining to or limited by space. [14]
402ResponseFor a device or system, the motion or other output resulting from an excitation or stimulus under special conditions. [14]
403RouteingA complex of measures concerning routes followed by ships and aiming at reducing the risk of casualties (traffic separation schemes, deep-draught routes, areas to be avoided, etc.). [14]
404TwilightThe periods of incomplete darkness following sunset (evening twilight) or preceding sunrise (morning twilight). Twilight is designated as civil, nautical, or astronomical, as the darker limit occurs when the center of the sun is 6°, 12°, or 18° below the celestial horizon, respectively. [14]
405Base LineThe line from which the outer limits of the territorial sea and certain other outer limits are measured. In radiolocation, the geodesic line between two stations operating in conjunction for the determination of a line of position. Also written as one word. See also base. [14]
406CalibrateV.t.). To fix, check or correct the graduations of a measuring instrument. To determine the calibre of. [14]
407CoastlineThe line where shore and water meet. Shoreline and coastline are generally used synonymously. [14]
408GyroscopeA rapidly rotating mass free to move about one or both axes perpendicular to the axis of rotation and to each other. It is characterized by gyroscopic inertia and precession. Sometimes shortened to gyro. [14]
409ObjectiveSee objective lens. [14]
410StarboardThe right side of a craft facing forward. The opposite is port. [14]
411Fog SignalA warning signal transmitted by a vessel or aid to navigation during period of low visibility. Also, the device producing such a signal. [14]
412PrecessionChange in the direction of the axis of rotation of a spinning body, as a gyroscope, when acted upon by a torque. The direction of motion of the axis is such that it causes the direction of spin of the gyroscope to tend to coincide with that of the impressed torque. [14]
413TopographyThe configuration of the surface of the earth, including its relief, the position of its streams, roads, cities, etc. The earth's natural and physical features collectively. In oceanography, the term is applied to a surface such as the sea bottom or a surface of given characteristics within the water mass. [14]
414TransducerAny device for converting energy from one form to another (electrical, mechanical, or acoustic). [14]
415EquilibriumA state of balance between forces. [14]
416PhotographyThe art or process of producing images on sensitized material through the action of light. [14]
417Plane TableA field device for plotting the lines of a survey directly from the observations. It consists essentially of a drawing board mounted on a tripod, with a ruler on which a telescope or other sighting device is mounted. See alidade. Also written as one word. [14]
418Atmospheric PressureSee pressure. [14]
419FanA relatively smooth, fan-like depositional feature normally sloping away from the outer termination of a canyon or canyon system. Also called cone. [14]
420ClayMineralogically, a hydrous aluminium silicate material with plastic properties and a crystal structure. As a size term, refers to sediment particles ranging from 0.0039 to 0.00024 millimeter, in which case it includes rock flour, calcareous muds, aragonite, etc. [14]
421GustA sudden brief increase in the speed of the wind. [14]
422HeelTransverse inclination of a vessel due to the action of waves, wind, a greater weight on one side, etc. See also list. [14]
423MistSuspension in the air of microscopic water droplets or wet hygroscopic particles, reducing the visi-bility at the earth's surface. [14]
424PierA long, narrow structure extending into the water to afford a berthing place for vessels, to serve as a promenade, etc. See also jetty. [14]
425SendSee scend. [14]
426VaneA device to indicate the direction from which the wind blows. Also called weathervane, wind vane. See anemometer. A sight on an instrument used for observing bearings, as on a pelorus, bearing circle, etc. Also called sight (or sighting) vane. A device to indicate the direction toward which the current flows. [14]
427AheadBearing approximately 000° relative. The term is often used loosely for dead ahead or bearing exactly 000° relative. The opposite is astern. [14]
428BerthPlace in which a ship is moored at wharf. [14]
429EpochA given period of time during which a series of related acts or events takes place. In astronomy, a particular instant for which certain data are given or at which an observation is made, and which then is usable as a reference point. [14]
430Pilot1. A person who directs the movements of a vessel through pilot waters, usually a person who has demonstrated extensive knowledge of channels, aids to navigation, dangers to navigation, etc., in a particular area and is licensed for that area. 2. A book of sailing directions. [14]
431Sweep(v.t. & i.). To tow a line or object below the surface, to determine the least depth in an area or to ensure that a given area is free from navigational dangers to a certain depth; or the removal of such dangers. [14]
432SwingIn photogrammetry, a rotation of a photograph in its own plane about its camera axis. [14]
433WharfA structure serving as a berthing place for vessels. [14]
434AfloatFloating, as opposed to being aground. [14]
435AsternBearing approximately 180° relative. The term is often used loosely for dead astern or bearing exactly 180° relative. The opposite is ahead. [14]
436Bridge1. An elevated structure extending across or over the weather deck of a vessel, or part of such a structure. The term is sometimes modified to indicate the intended use, such as navigating bridge or signal bridge. 2. A structure erected over a depression or an obstacle such as a body of water, railroad, etc., to provide a roadway for vehicles or pedestrians. [14]
437Dredge(v.t.). To remove solid matter from the bottom of a water area. [14]
438DredgeAn apparatus for bringing up solid material from the bottom of a water area, gathering deep water organisms, etc. A dredger. [14]
439AnomalyDeviation from the normal or natural characteristics of a phenomenon. Abnormality. In astronomy, true anomaly is the angle at the sun between lines connecting the sun with a planet and with the planet's perihelion. Mean anomaly and eccentric anomaly are also considered. [14]
440BreakerA wave breaking on the shore, over a reef, etc. Breakers may be roughly classified into three kinds, although the categories may overlap: spilling breakers break gradually over a considerable distance; plunging breakers tend to curl over and break with a crash; and surging breakers peak up, but then instead of spilling or plunging they surge up on the beach face. The french word 'brisant' is also used for the obstacle causing the breaking of the wave. [14]
441EllipseA plane curve constituting the locus of all points the sum of whose distances from two fixed points, called foci, is constant. Also used to characterize errors in positions and measurements. [14]
442Leeward(Adj. And adv.). Toward the lee, or in the general direction toward which the wind is blowing. The opposite is windward. [14]
443ReleaseA device for holding or releasing a mechanism, particularly the device by which the tangent screw of a sextant or surveying instrument is held in place or disengaged from the limb, or circle respectively. In oceanography acoustic releases are used to sever deployed instruments from their anchoring. [14]
444ShutterIn photography, the mechanism of a camera which controls the length of time the emulsion is exposed. [14]
445Infrared(Adj.). Having a frequency immediately beyond the red end of the visible spectrum said of rays of longer wavelength than visible light, but shorter than radio waves. [14]
446Pack IceTerm used in a wide sense to include any area of sea ice, other than fast ice, no matter what form it takes or how it is disposed. Pack ice may be described as very open pack ice (1/10ths-3/10ths), open pack ice (4/10ths-6/10ths), close pack ice (7/10ths-9/10ths), very close pack ice (almost 10/10th with little if any water visible). [14]
447QuadrantA double-reflecting instrument for measuring angles. It is similar to a sextant, but has an arc of 90°. Also a surveying or astronomical instrument composed of a graduated arc about 90° in length, equipped with a sighting device. [14]
448TerminalA number of berths grouped together, providing facilities for handling a particular form of cargo, e.g. Oil terminal, container terminal. [14]
449Windward(Adj. And adv.). In the general direction from which the wind blows; in the wind; on the weather side. The opposite is leeward. [14]
450BroadcastCommunication by radio intended for reception at any point within a specified area. [14]
451DepartureThe distance between two meridians at any given parallel of latitude expressed in linear units, usually nautical miles. The distance to the east or west made good by a vessel in proceeding from one point to another. [14]
452DiaphragmIn a telescope, a thin glass disk on which etched lines forming a reticle are placed. See also reticle, and aperture stop. [14]
453Light RayThe geometrical concept of a single element of light propagated in a straight line and of infinitesimal cross-section; used in analytically tracing the path of light through an optical system. [14]
454StabilityProperty of the state of rest or continuous movement of a system such that any disturbance intro-duced into this state decreases. In meteorology, the term is often used as a synonym of static stability. [14]
455ConvectionIn general, mass motions within a fluid resulting in transport and mixing of the properties of that fluid. In the atmosphere, organized internal motions within a layer of air, leading to vertical transport of heat, momentum, etc. [14]
456OscillatorA device for producing oscillations, especially one of the non-rotating type, as the sound generator of a sonic depth finder or a radio frequency generator. A submarine oscillator is a large, electrically-operated diaphragm horn which produces a sound for transmission through water. [14]
457Rhumb LineA line on the surface of the earth making the same oblique angle with all meridians; a loxodrome spiraling toward the poles in a constant true direction. Parallels and meridians, which also maintain constant true directions, may be considered special cases of the rhumb line. A rhumb line is a straight line on a Mercator projection. Sometimes shortened to rhumb. [14]
458Solar TimeSee time. [14]
459CartographyThe art and science of expressing graphically, by maps and charts, the known physical features of the earth, or of another celestial body. Often includes the works of man and his varied activities. [14]
460Chart DatumSee datum: chart. [14]
461ChronometerA portable timekeeper with a compensated balance, capable of showing time with extreme precision and accuracy. [14]
462Depth CurveA depth curve is a line connecting points of equal water depth which is sometimes significantly displaced outside of soundings, symbols, and other chart detail for clarity as well as generalization. Depth curves therefore often represent an approximate location of the line of equal depth as related to the surveyed line delineated on the source. [14]
463Wave HeightThe vertical distance between a crest and the preceding trough. [9]
464Celestial EquatorSee equator. [14]
465MHWMean High Water (MHW) ; The average of all the high water heights observed. [21]
466MLWMean Low Water (MLW) ; The average of all the low water heights observed. [21]
467BeltIn ice terminology, a long area of pack ice from a few kilometers to more than 100 kilometers in width. [14]
468RimeA white or milky granular deposit of ice formed by the rapid freezing of supercooled water drops as they come in contact with an object in below-freezing air. [1]
469SmogOriginally smog meant a mixture of smoke and fog. Today, smog means air that has restricted visibility due to pollution, or pollution formed in the presence of sunlight/photochemical smog. [1]
470MarshA tract of low-lying land flooded at times and generally swampy. [14]
471PitchThe oscillations of a ship about the transverse axis, due to the bow and stern being raised or lowered on passing through successive crests and troughs of waves. Also called pitching. The distance along the axis of a screw or other helix between consecutive threads or ribs. The distance a propeller would advance longitudinally, in one revolution if there were no slip. [14]
472PoundA unit of mass, equal to 0.45359237 kilograms. [14]
473GnomonAny object the shadow of which serves as an indicator, as the shadow pin of a sun compass. [14]
474PencilIn optics, a set of rays coming to or spreading out from a point. See light pencil. [14]
475Strait(also straits). A passage connecting two larger bodies of water. [14]
476X-RaysElectromagnetic radiation of the same nature as visible radiation but of an extremely short wavelength less than 10-2 micrometers. X-rays are used in radar technology. [14]
477DrizzleFairly uniform precipitation composed exclusively of fine drops of water (diameter less than 0.5 mm), very close to one another. [14]
478DrizzleSmall water drops between 0.2 and 0.5 mm in diameter that fall slowly and reduce visibility more than light rain. [1]
479HummockA natural elevation of the earth's surface resembling a hillock, but smaller and lower. In ice terminology, a mound of ice raised by pressure. May be fresh or weathered. [14]
480OpeningA break in a coastline or a passage through a reef, between shoals, etc. Any break in sea ice which reveals the water. [14]
481PerigeeThat orbital point nearest the earth when the earth is the center of attraction, as opposed to apogee. [14]
482PlotterAn instrument used for plotting straight lines and measuring angles on a chart or plotting sheet. See protractor. In data processing it stands for (a) vector plotter: an electromechanical device for automatically drawing curves. The curves are generated by a sequence of linear incremental pieces ("vectors") depending on the resolution provided by the device. For cartographic purposes, high precision flat-bed plotters (drawing tables) are used. (b) raster or electrostatic plotter: a sophisticated electronic device for producing pictures by means of raster techniques. The picture is generated by lines of pixels drawn sequentially, typically with a resolution of 200-400 pixels per inch. Raster plotters can produce complete pictures in short time irrespective of the complexity of the picture's contents. [14]
483VernierA short, auxiliary scale situated alongside the graduated scale of an instrument, by means of which fractional parts of the smallest division of the primary scale can be measured accurately. [14]
484EyepieceIn an optical device, the lens group which is nearest the eye and with which the image formed by the preceding elements is viewed. [14]
485GeodesicSee geodesic line. [14]
486New MoonSee phases of the moon. [14]
487Open SeaThat part of the ocean not enclosed by headlands, within narrow straits, etc. See high sea. [14]
488PinnacleAny high tower or spire-shaped pillar of rock or coral, alone or cresting a summit. It may extend above the surface of the water. It may or may not be a hazard to surface navigation. [14]
489RepeaterA device for repeating at a distance the indications of an instrument or device. See compass repeater, gyro repeater, steering repeater. [14]
490Lead LineA line, graduated with attached marks and fastened to a sounding lead, used for determining the depth of water when making soundings by hand. Generally used in depths of less than 45 meters (25 fathoms). Lead lines are braided or left-laid. Also called sounding line. [14]
491Mean TimeSee time: mean solar. [14]
492ShorelineThe line where shore and water meet. Although the terminology of coasts and shores is rather confused, shoreline and coastline are generally used as synonymous. [14]
493Soft IronIron or steel which is easily magnetized by induction, but loses its magnetism when the magnetic field is removed. The opposite is hard iron. [14]
494Wire DragAn apparatus for surveying rocky areas where normal sounding methods are insufficient to insure the discovery of all existing obstructions, pinnacles, rocks, etc., above a given depth or for determining the least depth of an area. It consists essentially of a buoyed wire towed at the desired depth by two launches. Often shortened to drag. See drag (v.t.). [14]
495ConversionDetermination of the rhumb line direction of one point from another when the initial great circle direction is known, or vice versa. [14]
496Ebb StreamThe horizontal movement of water associated with falling tide. Ebb streams generally set seaward, or in the opposite direction to the tide progression. Also called ebb, ebb current or outgoing stream. [14]
497Fair Chart(British terminology). The final, carefully made plot of a hydrographic survey. In contrast to the field board (boat sheet in US Terminology) which is a work sheet plotted during field operations from preliminary field data, the fair chart is plotted from corrected data and represents the official permanent record of that particular survey. Also called fair sheet. It is called smooth sheet in US Terminology. [14]
498GraduationThe placing of marks on an instrument or device to represent standard values thereon. Also, the marks so placed. The division and subdivision of latitude and longitude shown on the borders of a chart. See also scale. [14]
499Grid NorthSee north. [14]
500ParametricCharacterizing a quantity which is influenced by the behavior of one or more parameters. [14]
501CalibrationThe act or process of determining certain specific measurements in an instrument or device by comparison with a standard, for the purpose of correcting or compensating errors or for purposes of record. [14]
502ConvergenceIn oceanography, a situation whereby waters of different origins come together at a point or, more commonly, along a line known as a convergence line. Along such a line the denser water from one side sinks under the lighter water from the other side. See sinking. [14]
503EvaporationThe process by which a liquid changes into a gas. [1]
504Least DepthThe shoalest sounding value obtained on a feature. [14]
505Storm SurgeA rise above normal water level on the open coast due only to the action of wind stress on the water surface. Storm surge resulting from a hurricane or other intense storm also includes the rise in level due to atmospheric pressure reduction as well as that due to wind stress. A storm surge is more severe when it occurs in conjunction with a high tide. Also called storm tide, storm wave, tidal wave. [14]
506ThermoclineA vertical negative temperature gradient in some layer of a body of water, which is appreciably greater than the gradients above and below it; also a layer, in which such a gradient occurs. The principal thermoclines in the ocean are either seasonal, due to heating of the surface water in summer, or permanent. Also called discontinuity layer, or thermal layer. [14]
507Projection: StereographicA perspective projection having the point of projection at the opposite end of the diameter of the sphere from the point of tangency of the plane of projection. It is conformal and is the only azimuthal projection having that quality. When the center of the projection is located at a pole of the sphere, it is called a stereographic polar projection; when on the equator, a stereographic meridional projection; and when on some other selected parallel of latitude, a stereographic horizon projection. Also called azimuthal orthomorphic projection. [14]
508DewDeposit of water drops on objects at or near the ground, produced by the condensation of water vapor from the surrounding clear air. [14]
509AlgaA plant of simple structure which grows chiefly in water, such as the various forms of seaweed. [14]
510HailPrecipitation of small balls or pieces of ice (hailstones) with a diameter ranging from 5 to 50 mm (0.2 to 2.0 in) or sometimes more, falling either separately or agglomerated into irregular lumps. [14]
511KiteA mechanical contrivance towed beneath the surface to warn of arrival in water of a certain depth. See submarine sentry. A contrivance for holding the inner end of an Oropesa sweep to the required depth. [14]
512LoopIn oceanography, that part of a standing wave where the vertical motion is greatest and the horizon-tal velocities are least. Loops (sometimes called antinodes) are associated with clapotis and with seiche action resultant from resonant wave reflecting in a harbor or bay. [14]
513PeakA prominent elevation either pointed or of very limited extent across the summit. Also called pike. [14]
514PostA small beacon, more substantial than a perch, used for marking channels. See also pile. [14]
515CanalAn artificial waterway with no flow, or a controlled flow, used for navigation or for draining or irrigating land (ditch). [14]
516MouthThe place of discharge of a stream into the ocean or entrance to a bay from the ocean. [14]
517ProofIn cartography, an advanced copy of a map produced to check the design, register and/or to enable errors to be detected and corrected before final printing. [14]
518StakeAn elongated wood or metal pole embedded in the bottom to serve as a marker or support for fish nets. [14]
519AuroraLuminous phenomenon which appears in the high atmosphere, mainly in high latitudes, in the form of rays, arcs, bands, draperies, or corona. Also called polar aurora. [14]
520DebrisSee detritus. [14]
521IsobarLine joining points of equal pressure on a given surface (level surface, vertical cross section, etc.). [14]
522MirageOptical phenomenon consisting essentially of steady or wavering, single or multiple, upright or inverted, vertically enlarged or reduced, images of distant objects. [14]
523QuartzCrystalline silica. In its most common form it is colourless and transparent, but it takes a large variety of forms of varying degrees of opaqueness and colour. It is the most common solid mineral. Part of the ocean bed is composed of quartz. [14]
524ShowerPrecipitation, often short-lived and heavy, falling from convective clouds; the drops or solid particles in showers are usually bigger than the corresponding elements in other types of precipitation. Showers are characterized by their sudden beginning and ending, generally by large and rapid changes of intensity, and, most frequently, by the appearance of the sky; namely, rapid alternations of dark, menacing clouds (cumulonimbus) and of clearances of short duration. [14]
525SummitThe highest point, part or elevation; top or apex. [14]
526AbyssalBelonging to the lowest depths of the ocean, generally below 3,700 meters (2,000 fathoms). [14]
527AlmanacA periodical publication of astronomical data useful to a navigator. It contains less information than an ephemeris, and values are generally given to less precision. If information is given in a form and to a precision suitable for air navigation, it is called an air almanac. [14]
528GeologyThe science which has for its object the investigation of the earth's crust, of the strata which enter into its composition with their mutual relations, and of the successive changes to which their present condition and position are due. [14]
529Ice CapSee ice sheet. [14]
530Sea-BedSee sea floor [14]
531ShadingGradations of light, colour, or thickness of lines; or indications of shadows. Shading of lines is sometimes used on charts to produce the effect of height or depth. See also hill shading. [14]
532BuoyancyForce resulting from the upward pressure of water, acting upon the immersed volume of a body, set against the total weight of such body. If the volume immersed is such that the upward pressure counterbalances the weight of the body, the buoyancy is said to be positive and the body floats on the surface; if the volume immersed is insufficient, the weight of the body is greater than the upward pressure, the buoyancy is negative, and the body sinks. [14]
533CoverageThe actual area covered (by charts, photographs, etc.). The area controlled by a radiolocation system. [14]
534EntranceThe seaward end of a channel, harbor, dock, etc. [14]
535PendulumA body so suspended from a fixed point as to swing freely to and from under the combined forces of gravity and momentum. A vertical bar so supported from below by a stiff spring as to vibrate to and for under the combined action of gravity and the restoring force of the spring. [14]
536RecorderThe man on a survey party who records the observational data. A recording instrument. The part of an instrument or machine that records. [14]
537ResidualSee error: residual. [14]
538SamplingThe process of taking samples. [14]
539SoftwareAll programs which can be used on a computer system. In particular the system software (i.e. The operating system) consists of all programs which are necessary for the proper functioning of the computer. The application software consists of all programs developed for special user applications. [14]
540SweepingThe process of towing a line or object below the surface, to determine whether an area is free from isolated submerged dangers to vessels and to determine the position of any dangers that exist, or to determine the least depth of an area. [14]
541Temporal(Adj.). Pertaining to or limited by time. [14]
542GraticuleThe network of lines representing meridians and parallels on a map, chart, or plotting sheet. See also grid. A scale at the focal plane of an optical instrument to aid in the measurement of objects. See also reticle. [14]
543ReflectorA device capable of or intended for reflecting particles or radiant energy. See radar reflector. [14]
544Sea StateNumerical scale of the average surface wave height as defined by the WMO code. Also called state of the sea. [14]
545Boat Sheet(US Terminology). The work sheet used by the hydrographer in the field for plotting the details of a hydrographic survey as it progresses. See also field board. [14]
546Dip CircleAn instrument for measuring magnetic dip. It consists essentially of a dip needle or magnetic needle, suspended in such manner as to be free to rotate about a horizontal axis. Also called inclinometer, or dipping compass. See also earth inductor. [14]
547Lapse RateThe rate at which an atmospheric variable (usually temperature) decreases with height. (see environmental lapse rate.) [1]
548PollutantsAny gaseous, chemical, or organic matter that contaminates the atmosphere, soil, or water. [1]
549True NorthSee north. [14]
550Wave CrestThe highest part of a wave. [14]
551Air StationN photogrammetry, the point in space occupied by the camera lens at the moment of exposure. Also called exposure station or camera station. [14]
552Camera AxisSee axis of camera. [14]
553Datum PlaneA vertical control datum. Although a level surface is not a plane, the vertical control datum is frequently referred to as the datum plane. [14]
554GravitationIn general, the mutual attraction between masses of matter (bodies). Gravitation is the component of gravity which acts towards the earth. [14]
555Large ScaleSee scale. [14]
556PhotometeorOptical phenomenon of the atmosphere. [14]
557Electromagnetic WavesEnergy propagated in the form of electromagnetic waves. These waves do not need molecules to propagate them, and in a vacuum they travel at nearly 300,000 km per sec (186,000 mi per sec). See radiant energy. [1]
558CalmWind with a speed zero or less than 2 knots (beaufort scale wind force 0). The state of sea when there are no waves. [14]
559CapeA piece of land projecting into a body of water. [14]
560GageSee gauge: tide. [14]
561RoseName given to a compass card, or other diagram, having radiating lines. [14]
562ScarA lofty, steep face of rock upon a mountain-side; a precipice; cliff. [14]
563SillA sea floor barrier of relatively shallow depth restricting water movement between basins. [14]
564SiltAn unconsolidated sediment whose particles range in size from 0.0039 to 0.0625 millimeters in diameter (between clay and sand size). [14]
565AwashAdj. And adv.). Flush with, or washed by the waves. [14]
566FetchAn area of the sea surface over which seas are generated by a wind having a constant direction and speed. The length of the generating area, measured in the direction of the wind in which the seas are generated. [14]
567Locus(pl. Loci). All possible positions of a point or curve satisfying stated conditions. [14]
568NoiseAny undesired sound. By extension, noise is any unwanted disturbance within a useful frequency band, such as undesired electric waves in a transmission channel or device. [14]
569ScarpThe steep face of a hill. See also escarpment. [14]
570ShellThe hard outside covering of an animal. Part of the ocean bed is composed of numerous shells of marine animals. [14]
571SlaveA slave station. [14]
572TitleIn cartography, an inscription, on the chart or fair chart, including any useful information and details concerning the hydrographic survey, the natural scale, and geodetic, magnetic and tidal data. [14]
573CursorA device used with an instrument, to provide a movable reference, as the runner of a slide rule, or the rotatable bearing indicator on a radar scope. In computer systems, a highlighted point on the display which indicates the actual working position. For graphical editing special cursors (e.g. Crosses, cross-hairs) can be selected. On output the cursor is moved automatically by the computer; on input it is under user control by means of a manual controlling device. A cursor may also be a manually positionable device, sometimes magnifying lens and a reticula to be used in connection with a digitizer. [14]
574FreezeA condition occurring over a widespread area when the surface air temperature remains below freezing for a sufficient time to damage certain agricultural crops. A freeze most often occurs as cold air is advected into a region, causing freezing conditions to exist in a deep layer of surface air. Also called advection frost. [1]
575LagoonAn enclosed area of salt or brackish water separated from the open sea by some more or less effec-tive, but not complete, obstacle such as low sand bank. The name most commonly used for the area of water enclosed by a barrier reef or atoll. [14]
576PascalThe unit of pressure in the si system. [14]
577PilingA group of piles set in a row. [14]
578RocketIn hydrography or navigation, a pyrotechnic projectile used for signaling, or for life-saving purposes. [14]
579DraughtSee draft. [14]
580ErosionThe general process of the wearing away of rocks and soil at the earth's surface by natural agencies. [14]
581IcebergA large mass of floating or stranded ice broken away from a glacier or from an ice shelf. Often of considerable height (in any case more than 5 m above the level of the sea). [14]
582Inshore(Adj. And adv.). Near or towards the shore. [14]
583LandingA place where boats receive or discharge passengers, freight, etc. [14]
584ProfileA graph or curve showing elevation or distribution of some property vs. Distance along a line. The vertical scale may be greatly exaggerated with respect to the horizontal scale. An example of a profi-le is the graphic record made by a recording echo sounder operating while a vessel is underway. A vertical section of the surface of the ground, or of underlying strata, or both, along any fixed line. [14]
585SnapperA bottom sampling device used to collect a small amount (less than 1 pint) of material from the ocean floor. It has metal jaws that snap shut when the device touches the bottom. Also called clam shell snapper. [14]
586StorageIn a computer, a device in which data can be inserted and preserved, and from which data can be retrieved. Common storage devices are magnetic tapes, drums, disks and cores. [14]
587TerrainStanding ground. A tract of country considered with regard to its natural features, configuration, etc. [14]
588EmulsionIn photography, a suspension of a salt of silver in gelatine or collodion, used to coat plates, films, or papers. [14]
589Fast IceSea ice which remains fast, generally in the position where originally formed, and which may attain a considerable thickness. It is found along coasts, where it is attached to the shore, or over shoals, where it may be held in position by islands, grounded icebergs or grounded polar ice. [14]
590MillibarA unit of pressure equal to 1/1,000 of a bar. The millibar is much used in meteorology. [14]
591MomentumQuantity of motion. That property of a particle which is given by the product of its mass with its velocity. [14]
592Monument(US Terminology). In surveying, a structure used or erected to mark the position of a station; permanence is implied. [14]
593ResurveyA retracing on the ground of the lines of an earlier survey, in which all points of the earlier survey that are recovered are held fixed and used as a control. If too few points of the earlier survey are recovered to satisfy the control requirements of the resurvey, a new survey may be made. A resurvey is related directly to an original survey although several resurveys may interpose between them. [14]
594Swath(E)The strip or lane on the ground or sea floor scanned by the swath(e) sounding system when the survey platform proceeds along its course. [14]
595ClearanceIn navigation, a safe distance off a danger. In meteorology: a) decrease of total cloud amount when the latter is large; b) time at which this decrease takes place; c) gap in a cloud layer covering the entire sky. Also called clearing. [14]
596EphemerisA statement presenting positions and related data for a celestial body for given epochs (dates) at uniform intervals of time. Also a publication containing such data for a number of celestial bodies. See also almanac: air and almanac: nautical. [14]
597Gas FieldAn area in which natural gas occurs in quantities worthy of exploitation. [14]
598Hand LeadSee lead. [14]
599HyperbolaAn open curve with two parts, all points of which have a constant difference in distance from two fixed points called foci. [14]
600Ice SheetA continuous mass of ice and snow of considerable thickness and large area. Ice sheets may be resting on rock (see inland ice sheet) or floating (see ice shelf). Ice sheets of less than 40,000 sq. Km resting on rock are called ice caps. [14]
601IndicatorThat part of electronic equipment in which the data obtained by the receiver is presented for visual observation. This is usually in the form of a scope or dial. [14]
602InterceptThe name given in marcq St. Hilaire method to the difference between the calculated altitude and the true altitude of a celestial body. Also called altitude difference. [14]
603IsocentreThe unique point common to the plane of a photograph, its principal plane, and the plane of an assumed truly vertical photograph taken from the same camera station and having an equal principal distance. The point of intersection on a photograph of the true principal line and the isometric parallel. The point on a photograph intersected by the bisector of the angle between the plumb line and the photograph perpendicular. The isocenter is significant because it is the center of radiation for displacements of images caused by tilt. [14]
604MessengerIn oceanographic terminology, a cylindrical metal weight, usually hinged and with a latch so that it can be fastened around a wire, and sent down to actuate water bottles and current meters after they have been lowered to the desired depth. [14]
605Neat LineLine, usually grid or graticule, bounding the detail of a map. Also referred to as inner neat line to differentiate from border drawn outside of neat line. Also written as one word. [14]
606OmnirangeA radio aid to navigation providing direct indication of the magnetic bearing (omnibearing) of that station from any direction. Also called omnidirectional range or omnidirectional beacon. [14]
607ProjectorAn optical instrument which throws the image of a negative or print upon a screen or other viewing surface, usually at a larger scale. An underwater acoustic transmitter. See underwater sound projector. [14]
608Si SystemSee systems international. [14]
609Sound RayA line perpendicular at each of its points to the fronts of a sound wave. [14]
610Sub-PointThat point on the surface of the earth at which a particular celestial body is in the zenith at a specified time. Also called 'geographical position of a celestial body'. Called sub-celestial point in canadian terminology. See sublunar point, subsolar point, substellar point. [14]
611VibrationPeriodic motion of an elastic body or medium in alternately opposite directions from equilibrium; oscillation. The motion of a vibrating body during one complete cycle; two oscillations. [14]
612Anchor IceCe which is attached to the bottom, irrespective of the nature of its formation. Also called bottom ice, depth ice, ground ice, lappened ice and underwater ice. [14]
613CollimatorAn optical device for artificially creating a target at infinite distance (a beam of parallel rays of light) used in testing and adjusting certain optical instruments. It usually consists of a converging lens and a target (a system or arrangement of cross hairs) placed at the principal focus of the lens. [14]
614HydrophoneAn electroacoustic transducer that responds to water-borne sound waves and delivers essentially equivalent electric waves. See also pressure hydrophone. [14]
615Plumb LineThe line of force in the geopotential field. The continuous curve to which the direction of the normal gravity is everywhere tangential. [14]
616QuadratureAn elongation of 90° usually specified as east or west in accordance with the direction of the body from the sun. The moon is at quadrature at first and last quarters. See phases of the moon. The situation of two periodic quantities differing by a quarter of a cycle. [14]
617Scale: BarA graduated line on a map, plan, photograph, or mosaic, by means of which actual ground distances may be determined. Also called graphic scale or linear scale. [14]
618ScatteringIn physics, the change in direction of a particle or wave, because of a collision with another particle or system. In electromagnetism, diffusion of electromagnetic waves in a random manner by air masses in the upper atmosphere. See also: tropospheric scattering. [14]
619Tide GaugeSee gauge. [14]
620TurbulenceA state of fluid flow in which the instantaneous velocities exhibit irregular and apparently random fluctuations, so that in practice only statistical properties can be recognized and submitted to analysis. Superimposed on the mean motion of the air, an agitation composed of air motions which are uncoordinated and in a state of continuous change. [14]
621Wave FrontThe leading side of a wave. [14]
622Bathymetric(Adj.). Of or pertaining to bathymetry. [14]
623Field Board(British terminology). Wooden board, or zinc or plastic sheet, used by hydrographers and land surveyors for plotting and recording the details of the survey in the field. Separate boards are usually prepared for topography and sounding respectively. The former are referred to as topography boards; the latter as sounding boards. See also boat sheet, and plane table. [14]
624Image PointIn photogrammetry, the image on a photograph corresponding to a definite object on the ground. [14]
625InclinationThe angle which a line or surface makes with the vertical, horizontal or with another line or surface. [14]
626InstabilityProperty of the state of rest or continuous movement of a system such that any disturbance intro-duced into this state grows. In meteorology, the term is often used as a synonym of static instability. [14]
627Slack WaterThe interval when the speed of the tidal current is very weak or zero; usually refers to the period of reversal between ebb and flood currents. Also called slack tide. [14]
628Tidal DatumSee datum. [14]
629Trade WindsPersistent winds, mainly in the lower atmosphere, which blow over vast regions from a subtropical anticyclone toward the equatorial regions. The predominant directions of the trade winds are from ne in the northern hemisphere and from se in the southern hemisphere. [14]
630True CourseSee course. [14]
631Celestial CoordinatesSee coordinates. [14]
632ApexThe top, peak, or highest point of something, as of a mountain. See also vertex. [14]
633BermA narrow, raised path or embankment along a stream, canal, or beach. On a beach it may be formed by the deposit of material by waves and marks the limit of high tides. [14]
634BoomA floating barrier used to protect a river or harbor mouth or to create a sheltered area for storage purposes. [14]
635ByteA unit consisting of 8 bits, frequently used for measuring the capacity of storage devices. 1 Kbyte = 210 byte = 1.024 byte (kilo-byte); 1 Mbyte = 220 byte = 1.048.576 byte (mega-byte); 1 Gbyte = 230 byte = 1.073.741.824 byte (giga-byte). [14]
636DrumA rotating cylinder on which is set a registering card or paper for recording purposes. Cylinder around which cable is wound in a winch. [14]
637EddyA circular movement of water usually formed, where currents pass obstructions, between two adjacent currents flowing counter to each other, or along the edge of a permanent current. [14]
638Foul(1) to entangle or become entangled; e.g. As a propeller becoming entangled in cables, nets, or seaweed. (2) to attach or come to lie on the surface of submerged objects, usually in large numbers or amounts as barnacles on the hull of a ship. [14]
639IsleAn island. Now more usually applied to an island of smaller size, except in established appellation, as the 'British isles'. [14]
640KelpOne of an order of usually large blade-shaped or vinelike brown algae. [14]
641LavaThe fluid or semi-fluid matter flowing from a volcano. The substance that results from the cooling of the molten rock. Part of the ocean bed is composed of lava. [14]
642LoomThe glow of a light which is below the horizon, caused by reflection by solid particles in the air. Vague first appearance of land at sea. [14]
643PoolA small body of still or standing water, permanent or temporary; chiefly one of natural formation. A deep or still place in a river or stream. In ice terminology, any enclosed relatively small area in pack ice, drift ice, other than a lead. See polynia. [14]
644RuinA ruin is a structure in a decayed or deteriorated condition resulting from neglect or disuse, or a damaged structure in need of repair. A ruin is considered hazardous if it extends over or into navigable waters and thus represents a danger to surface navigation. [14]
645SlipSee dock. [14]
646Beset(Adj.). Of a ship when surrounded so closely by sea ice that steering control is lost. The term does not imply pressure. See also icebound, nipped. [14]
647BrookA small stream; a rivulet. Also called run. [14]
648CometA heavenly body having a starlike nucleus with a luminous foggy envelope (see coma), and usually developing a long luminous tail when near the sun. [14]
649DiverA person skilled in the practice of diving. [14]
650FaultIn geology, a break of shear in the earth's crust with an observable displacement between the two sides of the break, and parallel to the plane of the break. [14]
651GaussThe cgs unit of magnetic induction. [14]
652HavenAn enclosed and protected harbor. [14]
653InsetIn cartography: a) a small area outside the neat lines of a map or chart included within the neat lines or borders to avoid publishing a separate graphic of the small area alone; b) a representation of a small area on a larger scale (e.g., town-plan inset), or of a large area at a smaller scale (e.g., orientati-on inset); c) any information, not normally appearing within the geographic limits of a map, which has been enclosed by border lines and included within the map neat lines. Insets are always placed in areas where important features will not be obscured. [14]
654InvarAn alloy of nickel and steel which has a low coefficient of expansion. [14]
655LedgeA shelf-like projection, on the side of a rock or mountain. A rocky formation continuous with and fringing the shore. [14]
656MagmaThe molten material in a state of fusion under the crust of the earth from which igneous rocks are formed. [14]
657PixelContraction for "picture element". The smallest element resolvable by electronic raster devices such as scanner, display, and plotter. See remote sensing. [14]
658RaconA radar beacon which returns a coded signal which provides identification of the beacon as well as range and bearing. The range and bearing are indicated by the location of the first character received on the radar ppi scope. The name 'racon' is derived from the words radar beacon. [14]
659SlushAn accumulation of ice crystals which remain separate or only slightly frozen together. It forms a thin layer and gives the sea surface a greyish or leaden-tinted colour. With light winds no ripples appear on the surface. [14]
660SpireA pointed structure extending above a building. The spire is seldom less than two‘ thirds of the entire height and its lines are rarely broken by stages or other features. The term is not applied to short pyramid-shaped structures rising from a tower or belfry. [14]
661SpoutPhenomenon consisting of an often violent whirlwind, revealed by the presence of a cloud column or inverted cloud cone (funnel cloud), protruding from the base of a cumulonimbus and of a 'bush' composed of water drops raised from the surface of the sea or of dust, sand, or litter, raised from the ground. [14]
662SwampAn area of spongy land saturated with water. It may have a shallow covering of water, usually with a considerable amount of vegetation appearing above the surface. [14]
663ApogeeThat orbital point farthest from the earth when the earth is the center of attraction, as opposed to perigee. [14]
664BinaryThe number system using 2 as the base for number representation. Binary numbers are composed of bits. Generally any element capable of only two mutually exclusive states is called binary. [14]
665ComberA deep water wave whose crest is pushed forward by a strong wind and is much larger than a whitecap. Also called beach comber. A long-period spilling breaker. See also roller. [14]
666FilterIn optics, any transparent material which, by absorption, selectively modifies the light transmitted through an optical system. In ocean-wave forecasting, a set of formulas that define the particular wave frequencies and directions in the fetch area which are of significance at the point of forecast. [14]
667HollowTrough or depression between crests of sea-waves. A cavity or hole. [14]
668LaunchLarge open or half decked boat. [14]
669RippleThe ruffling of the surface of water, hence a little curling wave or undulation. A wave controlled to a significant degree by both surface tension and gravity. [14]
670RollerAn indefinite term, sometimes considered to denote one of a series of long-crested, large waves which roll in upon a coast, as after a storm. Large breakers on exposed coasts formed by swell coming from a great distance. See comber. [14]
671RunwayA defined rectangular area, on a land aerodrome, prepared for the landing and take-off run of aircraft along its length. [14]
672SludgeSpongy whitish ice lumps, a few centimeters across; they consist of slush, of snow slush and some-times of spongy ice lumps formed on the bottom of the sea and emerging on the surface. [14]
673SquallAtmospheric phenomenon characterized by a very large variation of wind speed: it begins suddenly, has a duration of the order of minutes, and decreases rather suddenly in speed. It is often accom-panied by a shower or thunderstorm. (WMO classification squall requires wind speed to increase by at least 8m/s, top speed of at least 11m/s, and lasting at least 1 minute in duration) [14]
674Strand(v.t. & i.). To run aground. The term strand usually refers to a serious grounding, while the term ground refers to any grounding, however slight. [14]
675TripodA three-legged stand for theodolite, camera, signals, etc. [14]
676UprushThe rush of water up onto the beach following the breaking of a wave. See run-up. [14]
677ZodiacThe band of the sky extending 8.5° either side of the ecliptic. The sun, moon, and navigational planets are always within this band, with the occasional exception of Venus. The zodiac is divided into 12 equal parts, called 'signs', each part being named for the principal constellation originally within it. [14]
678AgroundTouching, resting or lodged on the bottom of shallow water. The opposite is afloat. [14]
679BlunderSee error: gross. [14]
680CaissonA steel structure used for closing the entrance of locks, wet and dry docks. See also lock gate. [14]
681CultureAll features constructed on the surface of the earth by man, such as cities, railways, canals, etc. [14]
682CumulusA cloud in the form of individual, detached domes or towers that are usually dense and well defined. It has a flat base with a bulging upper part that often resembles cauliflower. Cumulus clouds of fair weather are called cumulus humilis. Those that exhibit much vertical growth are called cumulus congestus or towering cumulus. [1]
683FairwayThat part of a river, harbor etc. Where the main navigable channel for vessels of larger size lies. It is also the usual course followed by vessels entering or leaving harbors and sometimes called ship channel . [14]
684LoomingAn apparent elevation of distant terrestrial objects by abnormal atmospheric refraction. Because of looming, objects below the horizon are sometimes visible. The opposite is sinking. The appearance indistinctly of an object during a period of low visibility. [14]
685NavareaThe short title for a geographical sea area (may include inland seas, lakes and waterways navigable by sea-going ships) established for the purpose of coordinating the broadcast of navigational warnings. The term navarea followed by a roman numeral may be used to identify a particular sea area. The delimitation of such areas is not related to and shall not prejudice the delimitation of any boundaries between states. [14]
686OutflowThe flow of water from the river or its estuary to the sea. Total volume for any given period of time. [14]
687PelorusA compass card in the form of a metal plate mounted in gimbals to maintain a horizontal position and fitted with sight-vanes for observing bearings where direct use of the compass for this purpose is impracticable. Also called dumb compass or bearing plate. See also alidade. [14]
688PlateauA flat or nearly flat elevation of considerable areal extent, dropping off abruptly on one or more sides; a tableland. [14]
689PlummetA sounding lead. A plumb bob. [14]
690SubsoilAll naturally occurring matter lying beneath the sea-bed or deep ocean floor. [14]
691TsunamiA long-period sea wave produced by a submarine earthquake or volcanic eruption. It may travel unnoticed across the ocean for thousands of miles from its point of origin. It builds up to great heights over shoal water. Also called tsunami, tidal wave, seismic sea wave. [14]
692AerosolsTiny suspended solid particles (dust, smoke, etc.) Or liquid droplets that enter the atmosphere from either natural or human (anthropogenic) sources, such as the burning of fossil fuels. Sulfur-containing fossil fuels, such as coal, produce sulfate aerosols. [1]
693AsteroidOne of the many small planets revolving around the sun, most of the orbits being between those of mars and jupiter. Also called planetoid or minor planet. [14]
694Dry DockSee dock. [14]
695EnvelopeIn electronics, a graph defining the variations in amplitude of successive oscillations in an amplitude-modulated wave. [14]
696GuidanceThe exercise of directing influence over the movements of a craft or missile with particular refe-rence to the selection of a flight path. [14]
697Ice EdgeThe boundary at any given time between the open sea and sea ice of any kind, whether drifting or fast. [14]
698InmarsatA company providing mobile satellite communications. The only company (2011) providing services within the gmdss. [14]
699Land IceSee glacier ice. [14]
700Log LineA graduated line used to measure the speed of a vessel through the water or to measure the speed of a current from a vessel at anchor. The line secured to a log. See current pole. [14]
701Obscured(Adj.). Said of the arc of a light sector designated by its limiting bearings in which the light is not visible from seaward. [14]
702PipelineA string of interconnected pipes used for the transport of matter, nowadays mainly oil or gas . [14]
703ScribingA method of preparing a map by cutting the lines into a prepared coating. [14]
704StreamerA string of hydrophones towed behind a ship. [14]
705TrackingThe process of observing the sequential changes in the position of a target to establish its motion. [14]
706UncoversSee covers and uncovers. [14]
707AccretionThe gradual building up of land over a long period of time, solely by the action of the forces of nature, on a beach by deposition of water or air-borne material. Artificial accretion is a similar build-up of land by reason of an act of man. Also called aggradation. [14]
708AlignmentThe placing of objects along a straight line. In navigation, the bringing into line of two or more conspicuous objects, such as lights, beacons, etc. Also their bearing as seen by an observer from seaward. [14]
709AstrolabeAn instrument formerly used for measuring altitudes of celestial bodies. See astrolabe: prismatic. [14]
710Date LineThe line coinciding approximately with the 180th meridian, at which each calendar day first begins, the boundary between the -12 and +12 time zones. The date on each side of this line differs by one day, but the time is the same in these two zones. Sometimes called calendar line or international date line. [14]
711Full MoonSee phases of the moon. [14]
712HeliostatAn instrument composed of one or more plane mirrors, so mounted and arranged that a beam of sunlight may be reflected by it in any desired direction and kept there by continuous adjustment. It is used in geodetic surveying for reflecting a beam of sunlight from a station towards another distant station, where it can be observed with a theodolite. Also called heliotrope, or Galton’s sun signal. [14]
713High SeasThe open sea beyond the exclusive economic zone, the territorial sea or the archipelagic waters of an archipelagic state. [14]
714Ice CoverSee ice concentration. [14]
715InterfaceA surface, usually plane, forming the boundary between adjacent solids, spaces or immiscible liquids. In data processing it describes all information (signals, data) and the specifications ("protocol") required for exchanging data between two units of a system. Interfaces exist between hardware and software units but also between computer and human user. [14]
716LightshipA distinctively marked vessel anchored or moored at a charted point, to serve as an aid to navigation. By night it displays a characteristic light(s), and is usually equipped with other devices, such as a fog signal, submarine sound signal, and radio beacon, to assist navigation. Also called light vessel. [14]
717MicrowaveA very short radio wave, usually 30 cm to 0.3 mm. [14]
718Polar LowDepression that forms in polar air, often near a boundary between ice and sea. [15]
719ResectionThe graphical or analytical determination of a position as the intersection of at least three lines of known relative direction to corresponding points of known position. In photogrammetry, the determination of the position and/or attitude of a camera, or the photograph taken with that camera, with respect to the exterior coordinate system. [14]
720RoadsteadAn area near the shore, where vessels can anchor in safety; usually a shallow indentation in the coast. Also called road or roads. See open roadstead. [14]
721Wave: SkyAn indirect radio wave which travels from the transmitting antenna into the sky, where the ionosphere bends it back toward the earth. Also called ionospheric wave. See wave: ground. [14]
722Zone TimeSee time. [14]
723Cold FrontAny non-occluded front which moves in such a way that colder air replaces warmer air. [14]
724Coral ReefA reef, often of large extent, composed chiefly of coral and its derivatives. [14]
725DegaussingNeutralization of the strength of the magnetic field of a vessel, by means of suitably arranged electric coils permanently installed in the vessel. See also cable: degaussing. [14]
726EarthquakeA shaking or trembling of the crust of the earth caused by underground volcanic forces or by breaking and shifting of rock beneath the surface. [14]
727ElongationThe angular distance of a body of the solar system from the sun. The angle at the earth between lines to the sun and another celestial body of the solar system. The term is usually used in connection with inferior planets. The greatest elongation of such a body is its maximum angular distance from the sun, as observed from the earth. The position of a star when its azimuth east or west of the meridian is greatest. [14]
728Fish HavenAreas established by private interests, usually sport fishermen, to simulate natural reefs and wrecks that attract fish. The reefs are constructed by dumping assorted junk in areas which may be of very small extent or may stretch a considerable distance along a depth contour. Fish havens are outlined and labeled on charts. Also called fishery reefs. [14]
729Fixed StarA star. The expression is used particularly to distinguish stars from other heavenly bodies; so called by ancients to distinguish stars from the wandering planets. [14]
730IonosphereThat part of the atmosphere, extending from about 70 to 500 km, in which ions and free electrons exist in sufficient quantities to reflect electromagnetic waves. [14]
731Jet StreamRelatively strong winds concentrated within a narrow band in the atmosphere. [1]
732Local TimeSee time. [14]
733Neap RangeThe mean semidiurnal range of tide when neap tides are occurring; the mean difference in height between neap high water and neap low water. Sometimes called mean neap range. [14]
734Neap TidesTides of decreased range or tidal currents of decreased speed occurring semimonthly as the result of the Moon being in quadrature. The neap range (Np) of the tide is the average range occurring at the time of neap tides and is most conveniently computed from the harmonic constants. It is smaller than the mean range where the type of tide is either semi diurnal or mixed and is of no practical significance where the type of tide is predominantly diurnal. The average height of the high waters of the neap tide is called neap high water or high water neaps (MHWN) and the average height of the corresponding low waters is called neap low water or low water neaps (MLWN). [22]
735OppositionThe situation of two periodic quantities differing by half a cycle. In astronomy, the situation of two celestial bodies having either celestial longitudes or sidereal hour angles differing by 180°. The term is usually used only in relation to the position of a superior planet or the moon with reference to the sun. [14]
736Polar AxisSee axis. [14]
737ResolutionThe separation by an optical system of parts of an object or of two or more objects close together. The degree of ability to make such a separation, called resolving power, is expressed as the minimum distance between two objects that can be separated. The degree of ability of a radar set to indicate separately the echoes of two targets in range and bearing. [14]
738SaturationThe condition existing when the greatest possible amount of anything has been reached, as a magnetic substance which cannot be further magnetized, or an electronic aid to navigation which is being used by all the craft it can handle. At given temperature and pressure, state of moist air whose mixing ratio is such that the moist air can co-exist in neutral equilibrium with an associated condensed phase (liquid or solid) at the same temperature and pressure, the surface of separation being plane. [14]
739Small HaloSee halo. [14]
740Wire AngleThe angle measured between the sounding wire, or the oceanographic wire, and the vertical. [14]
741ConspicuousAdj.). Term applied to an object either natural or artificial which is distinctly and notably visible from seaward. [14]
742Core BarrelThe tubular section of a core sampling device. Bottom sediment samples are collected either directly in the core barrel or in a plastic liner placed inside it. Also called coring (or core) tube. [14]
743CulminationThe position of a heavenly body when at highest apparent altitude. Also, for a heavenly body which is continually above the horizon, the position of lowest apparent altitude. Culmination occurs when the body transits the local meridian. See meridian transit. [14]
744Drift AngleThe difference between course steered and course made good when due to action of current and wind. The angle between the tangent to the turning circle and the centerline of the ship. [14]
745Fathom LineA depth curve with depth expressed in fathoms. Also called fathom curve, isobath. [14]
746HydrographyHydrography is the branch of applied sciences which deals with the measurement and description of the physical features of oceans, seas, coastal areas, lakes and rivers, as well as with the prediction of their change over time, for the primary purpose of safety of navigation and in support of all other marine activities, including economic development, security and defence, scientific research, and environmental protection. [14]
747Lens SystemThe combination of two or more lenses placed in series on the same principal axis. [14]
748Lunar MonthSee month: synodical. [14]
749MaintenanceAll procedures and activities required to keep equipment operational. [14]
750MeteorologyScience of the atmosphere. [14]
751Nadir PointSee nadir: photograph. [14]
752RetardationIn electronic navigation, the amount of delay in time or phase angle introduced by the resistivity of the ground over which the signal is passing. In tide terminology, daily retardation. [14]
753ThermographThermometer used to give a graphical record of the time variations of temperature. [14]
754Tide TablesTables listing daily predictions, usually a year in advance, of the times and heights of the tide. These predictions are usually supplemented by tidal differences and tidal constants by means of which additional predictions can be obtained for numerous other places. See tide prediction. [14]
755TroposphereLower part of the terrestrial atmosphere, extending from the surface up to a height varying from about 9 km at the poles to about 17 km at the equator, in which temperature decreases fairly regularly with height. From an analogy with the atmosphere, the term is sometimes applied in oceanography to the upper ocean layer of relatively high temperature that is found in middle and lower latitudes and within which strong currents are present. See stratosphere. [14]
756Ultraviolet(Adj.). Having a frequency immediately beyond the violet end of the visible spectrum. Said of rays of shorter wavelength than visible light but longer than x-rays. [14]
757Environmental Lapse RateThe rate of decrease of air temperature with elevation. It is most often measured with a radiosonde. [1]
758GapA narrow break in a ridge or rise. [14]
759KeySee cay. [14]
760MSLMean Sea Level (MSL) ; The arithmetic mean of hourly heights observed. Shorter series are specified in the name; e.g. monthly mean sea level and yearly mean sea level. [21]
761SacAn indentation in the contours on a chart showing submarine relief which is analogous to a gulf on the surface. The opposite term is submarine peninsula. [14]
762DyneThe unit of force in the cgs system. [14]
763GulfA part of the sea extending into the land, usually larger than a bay. [14]
764MenuA list of commands and/or options. The user selects the desired command by moving the cursor to the respective position on the menu or by entering an appropriate code at the command entry line of the display. [14]
765MHWNMean High Water Neaps (MHWN) ; The height of mean high water neaps is the average throughout the year (when the average maximum declination of the moon is 23.5°) of two successive high waters during those periods of 24 hours when the range of the tide is at its least. The values of MHWN vary from year to year with a cycle of approximately 18.6 years. [24]
766MHWSMean High Water Springs (MHWS) ; The height of mean high water springs is the average throughout the year (when the average maximum declination of the moon is 23.5°) of two successive high waters during those periods of 24 hours when the range of the tide is at its greatest. The values of MHWS vary from year to year with a cycle of approximately 18.6 years. [24]
767MLWNMean Low Water Neaps (MLWN) ; The height of the mean low water neaps is the average height obtained by the two successive low waters during periods of 24 hours when the range of the tide is at its least. The values of MLWN vary from year to year with a cycle of approximately 18.6 years. [24]
768MLWSMean Low Water Springs (MLWS) ; The height of mean low water springs is the average throughout the year (when the average maximum declination of the moon is 23.5°) of two successive high waters during those periods of 24 hours when the range of the tide is at its greatest. The values of MLWS vary from year to year with a cycle of approximately 18.6 years. [24]
769QuayA wharf approximately parallel to the shoreline and accommodating ships on one side only, the other side being attached to the shore. It is usually of solid construction, as contrasted with the open pile construction usually used for piers. [14]
770TankA fixed structure for storing liquids. [14]
771TuffA rock formed of fragments of volcanic origin, dust, ashes, etc., thrown out of a volcano during an eruption, frequently hardened to a rock. Hence tuff-cone, a volcanic cone built up of such material. [14]
772YardA unit of length equal to 3 feet, 36 inches, or 0.9144 metre. [14]
773AbeamIn a line approximately at right angles to the ship's keel; also: the waist or middle part of the ship. [14]
774AggerSee tide: double. [14]
775DeltaAn area of alluvial deposit, usually triangular in outline, near the mouth of a river. [14]
776InletA narrow opening by which the water penetrates into the land. [14]
777IsletA small island. [14]
778JettyIn US Terminology, a structure, such as a wharf or pier, so located as to influence current or protect the entrance to a harbor or river. In British terminology, a pier, usually of solid construction, intended as a berthing place for vessels. See dock, landing, wharf. [14]
779LaserLight amplification by stimulated emission of radiation. A device that produces an intense beam of monochromatic, spatially coherent light. [14]
780LeveeA depositional natural embankment bordering a canyon, valley or sea channel on the ocean floor. [14]
781Lidar(light detection and ranging) an instrument that measures distance to a reflecting object by emitting timed pulses of laser light and measuring the time between emission and reception of reflected pulses. The measured time interval is converted to distance. In survey use, the lidar system usually scans the light pulses across the track of the survey platform (usually an aircraft) so that successive pulses cover a swath(e) either side of the platform's track. Infra-red lasers will reflect off land and water and are normally used for topographic lidar surveys. Blue-green lasers will penetrate water and are used in hydrographic lidar surveys. [14]
782ProbeAny device inserted in an environment for the purpose of obtaining information about the environ-ment. [14]
783SirenA type of fog signal apparatus which produces sound by virtue of the passage of air through slots or holes in a revolving disk. [14]
784SpoilMud, sand, silt or other deposit obtained from the bottom of a channel or harbor by dredging. [14]
785SwashA narrow channel or sound within a sand bank, or between a sand bank and the shore. Also called swash way. A bar over which the sea washes. The rush of water up onto a beach following the brea-king of a wave. [14]
786TrendThe general direction of something, such as a coastline. [14]
787CanyonA relatively narrow, deep depression with steep sides, the bottom of which generally has a continuous slope. [14]
788CareenCausing a vessel to lie over on one side. [14]
789DrogueA current measuring assembly consisting of a weighted parachute and an attached surface buoy. Also called parachute drogue. [14]
790IsogonLine which is the locus of points at which the direction of wind is the same. [14]
791IsoporSee isoporic line. [14]
792LegendA description, explanation, table of symbols, and other information, printed on a map or chart to provide a better understanding and interpretation of it. The title of a map or chart formerly was considered part of the legend, but this usage is obsolete. [14]
793MatrixIn oceanography, rock or sediment in which larger grains are embedded in a mass of smaller grains. In printing, a metal plate, usually of copper, for moulding the face of a type. In graphic arts, a mold in which type characters are cast in line-casting machines and foundry type. [14]
794MedusaSee coelenterate and jellyfish. [14]
795Nebula(pl. Nebulae). An aggregation of matter outside the solar system, large enough to occupy a perceptible area but which has not been resolved into individual stars. [14]
796Occupy(v.t.). In surveying, to observe with a surveying instrument at a station; also, to set a surveying instrument over a point for the purpose of making observations. In oceanography, to stop a ship at a selected location, an oceanographic station, for the purpose of gathering oceanographic observations. [14]
797OffsetIn surveying, a short line perpendicular to a surveyed line, measured to a line or point for which data are desired, thus locating the second line or point with reference to the first or surveyed line. An offset is also a jog in a survey or other line, the line having approximately the same direction both before and after passing the jog. Offsets are measured from a surveyed line or lines to the edges of an irregular-shaped body of water, or to any irregular line which it is desired to locate. [14]
798P-CodeThe precise (or protected) gps code; a very long (about 1014 bit) sequence of pseudo-random binary biphase modulations on the gps carrier at a chip rate of 10.23 MHz which does not repeat itself for about 267 days. Each one-week segment of the p-code is unique to one gps satellite and is reset each week. See also c/a code. [14]
799RamarkA radar marker beacon which continuously transmits a signal appearing as a radial line on the ppi, the line indicating the direction of the beacon. Ramarks are intended primarily for marine use. The name 'ramark' is derived from the words radar marker. [14]
800RegimeIn climatology, term used to characterize the seasonal distribution of one or more elements at a given place. [14]
801RulingA mechanically produced series of equally spaced parallel lines at a predetermined 'angle of ruling'. Used to distinguish particular areas of a map by providing a paler shade of the full printing colour. [14]
802Run-UpThe rush of water up a structure on the breaking of a wave. The amount of run-up is the vertical height above still water level that the rush of water reaches. See uprush. [14]
803SeawayA moderately rough sea. Used chiefly in the expression 'in a seaway'. Headway of a vessel. The sea as a route of travel from one place to another; a shipping lane. [14]
804SinkerWeight used to sink fishing line or sounding line. [14]
805StrandThe portion of the seashore between high and low water line. [14]
806TapingThe operation of measuring a distance on the ground using a tape or ribbon of metal or other material. Also called chaining. [14]
807TracerForeign substance introduced into the water by natural or artificial means which enables determination of water movement through measurement of distribution and location of the substance at the same time. [14]
808Y-AxisA vertical axis in a system of rectangular coordinates; that line on which distances above or below (north or south of) a reference line are marked, especially on a map, chart, or graph. The line which is perpendicular to the x-axis and passes through the origin. [14]
809Bay IceLevel fast ice of more than one winter's growth, which may be nourished by surface layers of snow. Thickness of ice and snow up to about 2 m above sea level. When bay ice becomes thicker than this, it is called an ice shelf. [14]
810BedrockAny solid rock underlying soil or unconsolidated sediments. [14]
811CalorieA unit of quantity of heat, originally defined as the amount of heat required to raise the temperature of one gram of water through one degree c. The 15-degree gram-calorie is the amount of heat required to raise the temperature of one gram of water from 14°.5 c to 15°.5 c and is equal to 4.1855 joules. [14]
812CandelaThe unit of luminous intensity in the si system. [14]
813Daymark1. The identifying characteristics of an aid to navigation which serve to facilitate its recognition against a daylight viewing background. On those structures that do not by themselves present an adequate viewing area to be seen at the required distance, the aid is made more visible by affixing a daymark to the structure. A daymark so affixed has a distinctive colour and shape depending upon the purpose of the aid. 2. An unlighted navigational mark. [14]
814DolphinA post or group of posts, used for mooring or warping a vessel, or as an aid to navigation. The dolphin may be in the water, on a wharf or on the beach. [14]
815El NiñoAn extensive ocean warming that begins along the coast of peru and ecuador and extends westward over the tropical pacific. Major el niño events, or strong el niños, occur once every 2 to 7 years as a current of nutrient-poor tropical water moves southward along the west coast of south america. [1]
816GimbalsA device consisting of two rings pivoted at right angles to each other, for supporting anything, such as an instrument, in such a manner that it will remain essentially horizontal when the support tilts. Also called cardanic suspension. [14]
817GlonassA space-based, radio-positioning, navigation and time-transfer system operated by the government of the russian federation. Glonass to which differential corrections have been applied is known as differential glonass (dglonass). See also global navigation satellite system. [14]
818ImpulseSee pulse. [14]
819IsobathSee depth curve, fathom line. [14]
820RaftingPressure process whereby one piece of ice overrides another. Most common in new and young ice. [14]
821SeaweedAny macroscopic marine alga or seagrass. [14]
822SunspotAny of the dark spots sometimes seen at the surface of the sun; they are believed to have some connection with magnetic disturbances on earth. [14]
823TerraceA relatively flat horizontal or gently inclined surface, sometimes long and narrow, which is bounded by a steeper ascending slope on one side and by a steeper descending slope on the opposite side. [14]
824TropicsSee torrid zone. [14]
825AbscissaSee coordinates: plane rectangular. [14]
826AchromatSee achromatic lens. [14]
827Acid FogCloud droplets or raindrops combining with gaseous pollutants, such as oxides of sulfur and nitrogen, to make falling rain (or snow) acidic pH less than 5.0. If fog droplets combine with such pollutants, it becomes acid fog. [1]
828AnaglyphA stereogram in which the two views are printed or projected superimposed in complementary colors, usually red and green. By viewing through filter spectacles of corresponding complementary colors a stereoscopic image is formed. [14]
829AnalogueThe way of representing information by continuous data. [14]
830AphelionThat orbital point farthest from the sun when the sun is the center of attraction, as opposed to perihelion. [14]
831BackrushThe seaward return of water following uprush of waves on a beach. [14]
832BinnacleThe stand in which a compass is mounted and in which lighting and compensatory units are carried. [14]
833BulkheadOn land, a structure or partition built to retain or prevent sliding of the land. A secondary purpose is to protect the upland against damage from wave action. Bulkheads are frequently backfilled thereby increasing the utility of the adjacent land area. [14]
834CatenaryThe curve formed by a uniform cable, chain, or tape supported only at its ends. [14]
835ChartletA small auxiliary chart giving new details on a particular area, to be added to the chart after publication. Also, called block correction or chart amendment patch. A small chart, such as one showing the coverage area of electronic navigational systems, with the distribution of its lines of position, corrections to be applied to readings, location and identification of transmitters, etc. [14]
836DetritusIn geology, material removed by disintegration and other processes from the surface of rocks. There is a general tendence to use debris. In marine biology, suspended matter of organic origin permanently incapable of reproduction organic detritus may often 'collect' a considerable amount of inorganic material. [14]
837Downwind(Adj. And adv.). In the direction toward which the wind is blowing. The opposite is upwind. [14]
838DraftingThe art of drawing from given specifications. [14]
839GridironSee careening grid. [14]
840HardwareAll physical material components of a computer system as e.g. Central processing unit (cpu), peripheral devices etc. May also include individual chips. [14]
841Ice CakeA floe smaller than 10 m across. If less than 2 m, it is termed brash ice or small ice cake. [14]
842Ice RiseA mass of ice resting on rock and surrounded either by an ice shelf or partly by an ice shelf and partly by sea. No rock is exposed and there may be none above sea level. Ice rises often have a dome-shaped surface. The largest known is about 100 km across. [14]
843Ice WallAn ice cliff forming the seaward margin of an inland ice sheet, ice piedmont or ice rise. The rock basement may be at or below sea level. See ice front. [14]
844LandmarkAny fixed object used to mark a boundary on the ground. - 2. Any prominent object at a fixed location on land which can be used in determining a location or a direction. [14]
845LeadsmanA person using a sounding lead to determine depth of water. [14]
846MangroveOne of several genera of tropical trees or shrubs which produce many prop roots and grow along low-lying coasts into shallow water. [14]
847Mean SunSee sun. [14]
848MidnightTwelve hours from noon, or the instant the time reference crosses the lower branch of the refe-rence celestial meridian. [14]
849PlanktonThe passively drifting or weakly swimming organisms in marine and fresh waters. [14]
850ScanningDirecting a beam of radiant energy successively over all points of a given region. [14]
851SeaboardA general term for the rather extensive coastal region bordering the sea. [14]
852Sky WaveSee wave. [14]
853SurveyorA person engaged in surveying. [14]
854TaffrailThe after rail at the stern of a vessel. [14]
855Upstream(Adj. & adv.). Toward the source of a stream. The opposite is downstream. [14]
856WaterwayA line of water (river, channel, etc.) Which can be utilized for communication or transport. [14]
857WreckageGoods or parts of a wrecked vessel washed ashore or afloat; remains of a wreck. [14]
858AnthelionPure white, rounded spot, but sometimes iridescent or surrounded by coloured rings or arcs, which appears on very rare occasions opposite the sun and at the same height above the horizon. [14]
859BacksightIn nautical astronomy, an observation of a celestial body made by facing 180° from the azimuth of the body. In levelling, a reading on a levelling rod held on a point whose elevation has been previously determined and which is not the closing sight of a level circuit. Also written as two words. See also foresight. [14]
860Civil DaySee day. [14]
861Data BaseAn organized collection of data stored so as to be capable of use by relevant applications with the data being accessed by different logical paths. It should be application independent. [14]
862EngravingThe act, process or art of cutting or etching designs or letters on metal plates, wooden blocks, etc. For printing. Any printed impression made from an engraved surface. [14]
863FootscrewSee levelling screw. [14]
864Free WaveSee wave. [14]
865Index ArmA slender bar carrying an index; particularly that bar which pivots at the center of curvature of the arc of a marine sextant and carries the index and the vernier or micrometer. Also called index bar. [14]
866IsoclinalN.). See isoclinal line. [14]
867Isopycnic(Adj.). Of or pertaining to equal density. [14]
868Isopycnic(n.). See isopycnic line. [14]
869LandspoutRelatively weak non supercell tornado that originates with a cumuliform cloud in its growth stage and with a cloud that does not contain a mid-level mesocyclone. Its spin originates near the surface. Landspouts often look like waterspouts over land. [1]
870Level IceSea ice with a flat surface which has never been hummocked. [14]
871LimestoneA rock which consists chiefly of calcium carbonate. [14]
872Neap RiseSee mean neap rise. [14]
873Oil FieldAn area in which oil occurs in quantities worthy of exploitation. [14]
874Planetary(Adj.). Of a planet or the planets. Like a planet. Terrestrial. [14]
875Polar IceSea ice that is more than one year old (in contrast to winter ice). The WMO code defines polar ice as any sea ice more than one year old and more than 3 meters thick. [14]
876PollutionThe direct or indirect alteration of the physical, chemical, thermal, biological or radioactive properties of any part of the environment in such a way as to create a hazard or potential hazard to the health, safety or welfare of any living species. [14]
877ReservoirA place where anything is collected and stored, generally in large quantity; especially a pond, lake or basin, either natural or artificial, for the storage, regulation and control of water. [14]
878ResponsorA radio receiver which receives a reply from a transponder and produces an output suitable for feeding to a display system. A responsor is usually combined in a single unit with an interrogator which sends out the pulse that triggers a transponder, the combined unit being called an inter-rogator-responsor. [14]
879Surf ZoneThe area between the outermost breaker and the limit of wave uprush. [14]
880Tide WaveA long-period wave associated with the tide-producing forces of the moon and sun; identified with the rising and falling of the tide. Also called tide bulge. See tide, tidal movement, stand of tide. [14]
881TitrationA chemical method for determining the concentration of a substance in solution. In oceanography, the most common titration is that for chlorinity. [14]
882UpwellingThe process by which water rises from a lower to a higher depth, usually as a result of divergence and offshore currents. See sinking. [14]
883Wind WaveSee wave. [14]
884Young IceNewly formed level ice in the transition stage of development from ice rind or pancake ice to winter ice. Thickness from 5 to 15 cm. [14]
885AnemographAn instrument which records wind speed and direction. See also anemometer. [14]
886BathymetryThe determination of ocean depths. The general configuration of sea floor as determined by profile analysis of depth data. [14]
887ChlorinityThe total amount in grams of chlorine, bromine and iodine contained in one kilogram of sea water, assuming that the bromine and the iodine had been replaced by chlorine. See salinity. [14]
888Day: SolarThe duration of one rotation of the earth on its axis, with respect to the sun. This may be either a mean solar day, or an apparent solar day, as the reference is the mean or apparent sun, respectively. The duration of one apparent rotation of the sun. [14]
889DivergenceIn oceanography, a horizontal flow of water, in different directions, from a common center or zone; often associated with upwelling. [14]
890Driver RodA device employed together with a sinker to obtain bottom samples when wire sounding. It consists, essentially, of a galvanized iron tube the lower part of which contains a flap valve for retaining a bottom specimen. The tube releases the sinker when it strikes the bottom. Also called driver tube. [14]
891Field StopThe physical element (such as an aperture stop, diaphragm or lens periphery) of an optical system which limits the field of view covered by the system. [14]
892Gust FrontA boundary that separates a cold downdraft of a thunderstorm from warm, humid surface air. On the surface its passage resembles that of a cold front. [1]
893Gyro: FreeA two-degree-of-freedom gyro or a gyro the spin axis of which may be oriented in any specified attitude. Also called free gyroscope. [14]
894Ice IslandA form of tabular berg found in the arctic ocean, with a thickness of 30 to 50 m and from a few thousand square meters to 500 sq. Km in area. Ice islands are characterized by a regularly undulating surface, which gives them a ribbed appearance from the air. [14]
895Index MarkIn photogrammetry, a real mark (such as a cross or dot) lying in the plane or the object space of a photograph and used singly as a reference mark in certain types of monocular instruments, or as one of a pair to form a floating mark (as in certain types of stereoscopes). [14]
896Inmarsat-CThe digital satellite communications system for store-and-forward text or data messaging using mobile terminals with omni-directional antennas. Inmarsat-c is the only system (2011) that allows ships to meet the majority of the satellite communication requirements of the gmdss including distress alerting, reception of maritime safety information and general communications. [14]
897Light ListSee list of lights. [14]
898LighthouseA distinctive structure on or off a coast exhibiting a major light designed to serve as an aid to navigation. [14]
899On The BowBearing approximately 045° relative (on the starboard bow) or 315° relative (on the port bow). The expression is often used loosely for broad on the bow, or bearing exactly 045° or 315° relative. See also broad on the bow. [14]
900PerihelionThat orbital point nearest the sun, when the sun is the center of attraction, as opposed to aphelion. [14]
901Rain Gaugesee gauge. [14]
902Rock AwashA rock awash at chart datum. [14]
903RoundaboutA routing measure comprising a separation point or circular separation zone and a circular traffic lane within defined limits. Traffic within the roundabout is separated by moving in a counter-clockwise direction around the separation point or zone. [14]
904Sea BreezeA coastal local wind that blows from the ocean onto the land. The leading edge of the breeze is termed a sea-breeze front. [1]
905StreamlineA line of flow. In meteorology, line envelope in space of the tangents to the instantaneous wind directions at a given time. Also written as two words. See also trajectory. [14]
906Tidal WaveSee wave. [14]
907Tide CycleSee tidal cycle. [14]
908Tide RangeSee range of tide. [14]
909Tide StaffA tide gauge consisting of a vertical graduated pole from which the height of tide at any time can be read directly. Also called tide pole. [14]
910Time: MeanSee time: mean solar. [14]
911TropopauseUpper limit of the troposphere. [14]
912Ultrasonic(Adj.). Having a frequency above the audible range. [14]
913Undulating(Adj.). Having the form of waves or swells, as undulating land. [14]
914UndulationA continuously propagated motion to and from, in any fluid or elastic medium, with no permanent translation of the particles themselves. [14]
915Wave TrainA series of waves moving in the same direction. See wave: solitary. [14]
916Wind ForceNumber on a progressive scale (beaufort wind scale) corresponding to the effects produced by winds within a range of speeds. Force exerted by the wind on a construction, object, etc. [14]
917Wind ShearThe rate of change of wind speed or wind direction over a given distance. [1]
918Y-ParallaxSee parallax. [14]
919ArchipelagoA group of islands. [14]
920Circumpolar(Adj.). Revolving about the elevated pole without setting. A celestial body is circumpolar when its polar distance is approximately equal to or less than the latitude of the observer. The actual limit is extended somewhat by the combined effect of refraction, semidiameter, parallax, and the height of the observer's eye above the horizon. [14]
921CoastliningThe process of obtaining data from which the coastline can be drawn on a chart. [14]
922Course LineA line of position approximately parallel to the course. [14]
923Danger AreaAn area designated by a proper authority, in which a danger to craft exists. Also called danger zone. [14]
924Datum LevelSee datum: vertical control and datum: chart. [14]
925Dumpy LevelSee levelling instrument: dumpy level. [14]
926Ebb CurrentSee ebb stream. [14]
927EquinoctialSee equator: celestial. [14]
928Gauge: TideA device for measuring the height of tide. A graduated staff in a sheltered area where visual observations can be made; or it may consist of an elaborate recording instrument making a continuous graphic record of tide height against time. Such an instrument is usually actuated by a float in a pipe communicating with the sea through a small hole which filters out shorter waves. [14]
929Ground WaveSee wave. [14]
930Index ErrorSee error. [14]
931LithographyThe art or process of printing from a flat stone or metal plate by a method based on the repulsion between grease and water. The original lithographic material was bavarian limestone; but zinc and aluminium are now used. [14]
932Median LineA line every point of which is equidistant from the nearest points on the baselines of two or more states between which it lies. [14]
933MesocycloneA vertical column of cyclonically rotating air within a supercell thunderstorm. [1]
934On The BeamBearing approximately 090° relative (on the starboard beam) or 270° relative (on the port beam). The expression is often used loosely for broad on the beam, or bearing exactly 090° or 270° relative. Also called abeam. See also broad on the beam. [14]
935Outer LimitThe extent to which a coastal state claims or may claim a specific jurisdiction in accordance with the provisions of international law. [14]
936Phase AngleThe phase difference of two periodically recurring phenomena of the same frequency, expressed in angular measure. The angle at a celestial body between the sun and earth. [14]
937Polar FrontQuasi-permanent front of great extent, of middle latitudes, which separates relatively cold polar air and relatively warm tropical air, and on which waves are produced. [14]
938Rising TideSee tide. [14]
939Sedimentary(Adj.). Formed by the deposition of sediment. [14]
940Signal LampSee lamp. [14]
941Slant RangeSee slant distance. [14]
942Spring RiseSee mean spring rise. [14]
943StereoscopeA binocular optical instrument for helping an observer to view photographs, or diagrams, to obtain the mental impression of a three-dimensional model. [14]
944StereoscopyThe science and art which deals with the use of binocular vision for observation of a pair of overlapping photographs or other perspective views, and with the methods by which such viewing is produced. [14]
945Tidal RangeSee range of tide. [14]
946Projection: Transverse MercatorA projection of the cylindrical type, being in principle equivalent to the regular Mercator projection turned (transverse) 90° in azimuth. In this projection, the central meridian is represented by a straight line, corresponding to the line which represents the equator on the regular Mercator projection. Neither the geographical meridians, except the central meridian, nor the geodetic paral-lels, except the equator (if shown), are represented by straight lines. It is a conformal projection. Also called transverse cylindrical orthomorphic projection. [14]
947BogWet spongy ground consisting of decaying vegetation, which retains stagnant water, too soft to bear the weight of any heavy body. [14]
948MWLMean water level (MWL) ; The average of all hourly water levels over the available period of record. [12]
949BeatThe periodic variation that results from the superposition of two oscillations whose frequencies differ by a small amount. [14]
950ComaAn aberration affecting the sharpness of images off the axis, in which rays from a point object off the axis passing through a given circular zone of the lens, come to a focus in a circle rather than a point, and the circles formed by rays through different zones are of different sizes and are located at different distances from the axis. Therefore, the image of a point object is comet-shaped. The foggy envelope surrounding the nucleus of a comet. [14]
951CrabThe condition caused by failure to orient a camera with respect to the track of the airplane. In vertical photography, crab is indicated by the edges of the photographs not being parallel to the airbase lines. [14]
952DgpsSee differential gps [14]
953DuneA mound, ridge or hill of drifted sand on the seacoast or in a desert. See sand dune and down. [14]
954GaleWind with a speed between 32 and 37 knots (beaufort scale wind force 8). [14]
955GnssSee global navigation satellite system [14]
956GrabA kind of closing scoop or bucket used in dredging or for bringing up bottom samples. [14]
957HHWLHighest High Water Level (HHWL) [-]
958HookA sharp bend or angle in the course or length of anything; especially a bend in a river. A projecting corner, point or spit of land. [14]
959LLWLLower Low Water Line (LLWL) ; The intersection of the land (shore) with the water surface at the elevation of mean lower low water. [23]
960LochThe Scottish term for (1) a lake, and (2) a fiord. [14]
961MarlA crumbling, earthy deposit, particularly one of clay mixed with sand, lime, decomposed shells, etc. Sometimes a layer of marl becomes quite compact. Part of the ocean bed is composed of marl. [14]
962MesaA high tableland (s.w. And w. United states). [14]
963MHWLMean High Water Line (MHWL); The line on a chart or map which represents the intersection of the land with the water surface at the elevation of mean high water. [22]
964MireA piece of wet swampy ground. [14]
965MLWLMean Low Water Line (MLWL); The intersection of the land (shore) with the water surface at the elevation of water level. [23]
966NeckIn oceanography, the narrow band of water flowing swiftly seaward through the surf. See current: rip. In geography, a narrow piece of land with water on each side; an isthmus. [14]
967RampA sloping structure that can either be used, as a landing place, at variable water levels, for small vessels, landing ships, or a ferry boat, or for hauling a cradle carrying a vessel. An accumulation of snow that forms an inclined plane between land or land ice elements and sea ice or ice shelf. Also called drift ice foot. [14]
968SbesSee single beam echo sounder [14]
969SpurA subordinate elevation, ridge or rise projecting outward from a larger feature. [14]
970VeinA narrow lead or lane in pack ice. In mineralogy, a crack or fissure in the rocks of the earth's crust in which highly heated waters from below have deposited from solution crystalline minerals (especially vein quartz) and, under certain circumstances, metallic minerals of economic importance. [14]
971VoltThe unit of potential difference or electromotive force in the si system. [14]
972WeirA dam erected across a river to raise the level of the water. A fence of stakes set in a river or along the shore as a trap for fish. The word is now restricted to smaller works, the larger are called dams. [14]
973ZoomA method of enlarging graphics on a graphical display, usually a function provided by the hardware of the screen. Either a selected window may be enlarged to cover the entire screen or by repeatedly pressing a key, a stepwise or continuous enlargement of the screen contents can be invoked, keeping the graphics centered at the screen's center. [14]
974AtlasA collection of charts or maps to be kept (loose or bound) in a volume. [14]
975AtollA coral island consisting of a ring-shaped reef nearly or entirely surrounding a central lagoon. [14]
976BayouA minor sluggish waterway or estuarial creek, generally tidal or characterized by a slow current, with a course generally through lowlands or swamps, tributary to or connecting with other bodies of water. Various specific meanings have been implied in different parts of the southern united states. Sometimes called slough. [14]
977BenchSee terrace. [14]
978Clean(Adj.). Free from obstructions, unevenness, imperfections, as a clean anchorage. [14]
979FucusSee rockweed. [14]
980GorgeA narrow opening, between hills, usually with precipitous sides. [14]
981GuyotSee table mount. [14]
982HalosRings or arcs that encircle the sun or moon when seen through an ice crystal cloud or a sky filled with falling ice crystals. Halos are produced by refraction of light. [1]
983JouleThe unit of work or energy in the si system. [14]
984LaganSee jettison. [14]
985PanelIn cartography, the completed assembly of pieces of film positives onto a grid or projection which is used as a base for compilation. In photogrammetry, an element of a target used for control station identification on aerial photography. [14]
986PerchA staff placed on top of a buoy, rock, or shoal as a mark for navigators. A ball or cage is sometimes placed at the top of the perch, as an identifying mark. A unit of length equal to 5.5 yards or 16.5 feet. Also called rod, pole. [14]
987PingoSmall conical hills having a large central core of ice formed from the encroachment of permafrost and the resulting hydrostatic pressure. [14]
988SarosThe eclipse cycle of about 18 years, almost the same length as 223 synodical months. At the end of each saros the sun, moon, and line of nodes return to approximately the same relative positions, and another series of eclipses begins, closely resembling the series just completed. [14]
989ScourThe action of a current or flow of water in clearing away mud or other deposit; in civil engineering an artificial current or flow produced for this purpose. [14]
990Shoot(v.t.). To observe the altitude of (a celestial body). [14]
991SprayEnsemble of water droplets torn by the wind from the surface of an extensive body of water, gene-rally from the crests of waves, and carried up a short distance into the air. [14]
992TyfonSee typhon. [14]
993VigiaA pinnacle, rock, or shoal the existence or position of which is doubtful, or a warning note to this effect on a chart. [14]
994WrackSee rockweed. [14]
995AlbedoThe ratio of radiant energy reflected to that received by a surface, usually expressed as a percentage. [14]
996AmpereThe unit of density of electric current in the si system. [14]
997BoomerSeismic instrument for shallow penetration work. The boomer transducer produces acoustic pulses by the motion of a metal plate in the water. [14]
998CirrusA high cloud composed of ice crystals in the form of thin, white, featherlike clouds in patches, filaments, or narrow bands. [1]
999DefileA narrow pass or gorge between mountains. [14]
1000F-StopSee aperture: relative. [14]
1001FurrowOn the sea floor, a closed, linear, narrow, shallow depression. [14]
1002GravelLoose detrital material ranging in size from 2 to 256 mm. [14]
1003IntakeThe place where water is taken into a channel or pipe from a river or other body of water, to drive a mill, or supply a canal, waterworks, etc. [14]
1004JetsamSee jettison. [14]
1005LeaperSee lipper. [14]
1006MantleThe relatively plastic region between the crust and core of the earth. Also called asthenosphere. [14]
1007MicronOne millionth of a metre; one thousandth of a millimeter. [14]
1008NavtexThe system for the broadcast and automatic reception of maritime safety information by means of narrow-band direct-printing telegraphy. [14]
1009NeapedSee beneaped. [14]
1010NektonThose animals of the pelagic division that are active swimmers, such as most of the adult squids, fishes, and marine mammals. [14]
1011NexradAn acronym for next generation weather radar. The main component of nexrad is the wsr 88-d, doppler radar. [1]
1012OctantA double-reflecting instrument for measuring angles. It is similar to a sextant but has an arc of only 45°. [14]
1013PebbleA small stone worn smooth and rounded by the action of water, sand, ice, etc. Ranging in diameter between 4 and 64 millimeters. [14]
1014PingerA battery powered acoustic device equipped with a transducer that transmits sound waves. When the pinger is attached to a wire and lowered into the water, the direct and bottom reflected sound can be monitored with a listening device. The difference between the arrival time of the direct and reflected waves is used to compute the distance of the pinger from the ocean bottom. [14]
1015SaddleA broad pass or col, resembling in shape a riding saddle in a ridge or between contiguous elevations. [14]
1016SchistA foliated metamorphic rock which can be split into thin flakes or flat lenticles. Schists are usually named from the dominant mineral, e.g. Mica schist. [14]
1017Scoria(pl. Scoriae). Volcanic rock fragments usually of basic composition, characterized by marked vascularity, dark colour, high density, and a partly crystalline texture. [14]
1018SeicheA standing wave oscillation of an enclosed or semi-enclosed water body that continues, pendulum fashion, after the cessation of the originating force, which may have been either seismic, atmospheric, or wave induced. [14]
1019StraysIn echo sounding, false indications occasionally appearing on the dial or fathogram of an echo sounder. They may be caused by the motion of the vessel through the water, by acoustic or electric noises in the ship, or by electric noises in the echo sounding equipment. Strays may be mistaken for the true echo or may be of such a nature as to prevent the identification of the true echo. [14]
1020SunsetThe crossing of the apparent horizon by the upper limb of the descending sun. [14]
1021SyzygyIn astronomy, either of two opposing points in the orbit of a planet or satellite, especially of the moon, at which it is in conjunction with or in opposition to the sun. [14]
1022TrenchA long narrow, characteristically very deep and asymmetrical depression of the sea floor with relatively steep sides. [14]
1023UplandThe higher ground of a region contrasted with the valleys and plains. Used in contrast to lowland. [14]
1024Upwind(Adj. & adv.). In the direction from which the wind is blowing. The opposite is downwind. [14]
1025WindowIn computer applications, a rectangular subdivision of the screen showing information without affec-ting other parts of the screen; a method allowing to view different items of information (e.g. Different data sets or graphics) at the same time. On graphical displays a window may be selected with the cursor and subsequently be enlarged (zoom). [14]
1026X-AxisA horizontal axis in a system of rectangular coordinates; that line on which distances to the right or left (east or west) of the reference line are marked, especially on a map, chart, or graph. [14]
1027BenthosThe category of marine organisms that live on, in, or close to the bottom of the oceans. [14]
1028BollardSmall, shaped post, mounted on a wharf or dolphin used to secure ship's lines. Also see mooring. [14]
1029CeilingSee height of cloud base. [14]
1030CindersFragments formed when magma is blown into the air; larger in size than volcanic ash. Cinders are a constituent of certain marine sediments. [14]
1031EastingThe distance a craft makes good to the east. The opposite is westing. In a cartesian reference system the value of one coordinate, usually expressed in meters, measured from the central meridian in east-west direction; used e.g. In the UTM system. [14]
1032EcologyThe science of the economy of animals and plants dealing with the relations of living organism to their surroundings. [14]
1033EstuaryThat portion of a stream influenced by the tide of the body of water into which it flows. A bay, as the mouth of a river, where the tide meets the river current. [14]
1034EyewallA wall of dense thunderstorms that surrounds the eye of a hurricane. [1]
1035FlotsamSee jettison. [14]
1036FoulingThe mass of living and non-living bodies and particles attached to or lying on the surface of a submerged man-made or introduced object; more commonly considered to be only the living or attached bodies. [14]
1037GibbousAdj.). See phases of the moon. [14]
1038HeadwayMotion in a forward direction. Also called seaway. [14]
1039HillockA small hill. [14]
1040Ice AgeThe most recent period of extensive continental glaciation that saw large portions of north America and Europe covered with ice. It began about 2 million years ago and ended about 10,000 years ago. See pleistocene epoch. [1]
1041Ice FogSee fog. [14]
1042IcefootA narrow strip of ice attached to the coast, unmoved by tides and remaining after the fast ice has broken free. [14]
1043ImageryTechniques to obtain, process or interpret images created by different types of radiation, e.g. Light, infrared, x-rays. [14]
1044InsularOf or pertaining to an island or islands. [14]
1045IsogramThat line on a chart or diagram connecting points having equal values of same phenomenon. [14]
1046IsolineA line representing the intersection of the plane of a vertical photograph with the plane of an overlapping oblique photograph. If the vertical photograph were tilt-free, the isoline would be the isometric parallel of the oblique photograph. [14]
1047MoonbowRainbow whose formation is the same as that of the ordinary rainbow, but whose light comes from the moon and not from the sun. Also called lunar rainbow. [14]
1048New IceA general term which includes frazil ice, slush, sludge, pancake ice and ice rind. [14]
1049OverlayIn mapping, a record on a transparent medium to be superimposed on another record. [14]
1050PolygonA non-self-intersecting, closed chain defining the boundary of an area. [14]
1051PolyniaA water area enclosed in ice, generally fast; this water area remains constant and usually has an oblong shape; sometimes limited to one side by the coast. Any enclosed sea water area in pack ice other than a lead, not large enough to be called open water. If a polynia is found in the same region every year, for example, off the mouths of big rivers, it is called a recurring polynia. A temporary small clearing in pack ice which consists of small ice floes and brash ice in continuous local movement is called an unstable polynia; an opening which is flanked by large floes and therefore appears to be relatively stable is called a stable polynia. When frozen over, a polynia becomes an ice skylight from the point of view of the submariner. [14]
1052Rip-RapSee groin. [14]
1053ScannerA device for directing a beam of radiant energy successively over all points of a given region. In data processing a photo-electronic device for digital reproduction of pictures. The picture is scanned line wise and decomposed into a matrix-like raster of individual pixels. In contrast to vectorial digitizers, the information to coherent elements of the picture (lines, symbols) is lost by this rasterization process. To retrieve these elements the rasterized picture has to be vectorized by pattern recognition methods and manual post-processing. [14]
1054SlipwayThe prepared and usually reinforced inclined surface on which keel- and bilge-blocks are laid for supporting a vessel under construction. [14]
1055SpiculeA minute needlelike or multiradiate calcareous or siliceous body in sponges, radiolarians, primitive chitons, and echinoderms. They frequently are identified in marine sediment samples. [14]
1056StratusA low, gray cloud layer with a rather uniform base whose precipitation is most commonly drizzle. [1]
1057SunriseThe crossing of the apparent horizon by the upper limb of the ascending sun. [14]
1058SwingerSee fix: circular. [14]
1059TaglineA line, either marked at equal intervals or run over a registered sheave, used in large-scale surveys to take equally spaced soundings at predetermined distances from the control stations. [14]
1060Tie NetSee triangulation net. [14]
1061TopmarkA characteristic shape secured at the top of a buoy or beacon to aid in its identification. [14]
1062TorrentRushing stream of water; great downpour of rain. [14]
1063TyphoonName given to tropical cyclones of the china sea and, more generally, of the north-west pacific. [14]
1064VariateA variate is a quantity that may take on any of the values of a specified set with a specified relative frequency or probability often known as random variable. It is to be regarded as defined not merely by a set of permissible values, but by an associated frequency (probability) function expressing how often those values appear in a given situation. [14]
1065AbrasionThe wearing away or rounding of surfaces by friction. [14]
1066AeronomyTerm proposed for the study of the chemistry and physics of the high atmosphere. [14]
1067AliasingAn occurrence in tidal analysis when the sea level varies with a period that is less than the sampling period. Due to the varying position of the samples on the curve, a spurious tidal frequency appears in the analysis. It is usually only possible when there is a seiche at the observation site or observations are taken at intervals greater than one hour. [14]
1068Base NetSee base extension triangulation. [14]
1069Bow EchoA line of thunderstorms on a radar screen that appears in the shape of a bow. Bow echoes are often associated with damaging straight-line winds and small tornadoes. [1]
1070BridgingSee stereo triangulation. [14]
1071Can BuoyA buoy the above-water part of which is in the shape of a cylinder. Sometimes called cylindrical buoy. [14]
1072C-Factor(US Terminology). In photogrammetry, an empirical value which expresses the vertical measuring capability of a given stereoscopic system; generally defined as the ratio of the flight height to the smallest contour interval accurately plottable. The c-factor is not a fixed constant but varies over a considerable range, according to the elements and conditions of the photogrammetric system. In planning for aerial photography, the c-factor is used to determine the flight height required for a specified contour interval, camera, and instrument system. [14]
1073ClearingSee clearance. [14]
1074CompilerA program that translates programs from one programming language (source program) into another programming language (object program). Typically, the compiler translates from a higher, user understandable language to a lower, machine interpretable language. [14]
1075CrescentAdj.). See phases of the moon. [14]
1076Dan BuoyA buoy consisting of a ballasted float carrying a staff which supports a flag or light. [14]
1077DerelictAny property abandoned at sea, often of sufficient size as to constitute a menace to navigation, especially an abandoned vessel. See wreck. [14]
1078Ebb TideSee tide: falling. [14]
1079EchogramA graphic record of depth measurements obtained by an echo sounder. See fathogram. [14]
1080EelgrassSee seagrass. [14]
1081EpipolesIn the perspective set-up of two photographs, (two perspective projections), the points on the planes of the photographs where they are cut by the air base. [14]
1082EvectionA perturbation of the moon in its orbit due to the attraction of the sun. See also lunar inequality. [14]
1083Eye BaseSee interpupillary distance. [14]
1084F-NumberSee aperture: relative. [14]
1085GustnadoA relatively weak tornado associated with a thunderstorm's outflow. It most often forms along the gust front. [1]
1086HachuresShort lines drawn on a chart or map for representing relief. These lines are drawn in the direction of the slope and intensified on the shaded side of the feature assuming the area is illuminated from the north-west. Unlike the contour lines, they give no indication of the actual height of land above sea level. See also hill shading. [14]
1087HeadlandA high steep promontory. Usually called head when coupled with a specific name. [14]
1088Ice FloeSee floe. [14]
1089Ice RindA thin, elastic, shining crust of ice, formed by the freezing of sludge on a quiet sea surface. Thickness less than 5 cm. [14]
1090Icebound(Adj.). Said of a harbor, inlet, etc. When navigation by ships is prevented due to ice, except possibly with the assistance of an icebreaker. Of a ship, surrounded so closely by ice as to be incapable of proceeding. [14]
1091IsoplethAn isogram of equal or constant value of a given quantity, with respect to either time or space. [14]
1092IsothermIn meteorology, the line which is the locus of points which have the same value of air temperature. [14]
1093JettisonThe throwing overboard of objects, especially to lighten a craft in distress. Jettisoned objects that float are termed flotsam; those that sink, jetsam; and heavy articles that are buoyed for future recovery, lagan. See derelict. [14]
1094LandfallThe first sighting of land when approached from seaward. By extension, the term is sometimes used to refer to the first contact with land by any means, as by radar. [14]
1095LayeringA method of emphasizing on a chart differences in height or depth by use of varying tints. Also referred to as layer tinting. [14]
1096Log ChipThe wooden quadrant forming part of a chip log. Also called log ship. [14]
1097LunationSee month: synodical. [14]
1098MainlandThe principal land or largest part of a continent, as distinguished from a relatively small island or peninsula. [14]
1099MarigramSee tide curve. [14]
1100MastheadThe top of a mast. [14]
1101NorthingThe distance a craft makes good to the north. The opposite is southing. In a cartesian reference system the value of one coordinate, usually expressed in meters, measured from the origin in north-south direction; used e.g. In the UTM system. [14]
1102NutationIrregularities in the precessional motion of the equinoxes because of varying positions of the moon, and, to a lesser extent, of other celestial bodies, with respect to the ecliptic. Because of nutation the earth's axis nods like a top, describing an irregular circle about the mean pole in a period of about 19 years. [14]
1103OdographA mechanical instrument containing a distance-measuring element which is moved or turned by an amount proportional to the actual distance travelled; a compass element which provides a fixed-reference direction, and an integrator which provides for the resolution of the direction of motion into components and for the summation or integration of the distance components. Also, an instrument for recording the distance travelled by a vehicle or pedestrian. [14]
1104OvertideA shallow water harmonic tide constituent with a speed that is a multiple of the speed of one of the basic constituents of the tide-producing force. See harmonic constituent, and shallow water constituent. [14]
1105PhotomapA photomosaic of a specified land area, which also contains marginal information, descriptive data, and a reference grid and/or projection. See also mosaic. [14]
1106Piedmont(Adj.). Situated or formed at the base of mountains. [14]
1107PigmentsA colouring matter used as paint or dye or a natural colouring matter of a tissue. [14]
1108ProvinceIn oceanography and in a morphological sense, a region composed of a group of similar physiographic features whose characteristics are markedly in contrast with surrounding areas (rarely used in marine cartography). [14]
1109Red TideA red or reddish-brown discoloration of surface waters, most frequently in coastal regions, caused by concentration of certain microscopic organisms, particularly dinoflagellates. Toxins produced by the dinoflagellates can cause mass kills of fishes and other marine animals. [14]
1110RevolverSee fix: circular. [14]
1111Sea BuoySee farewell buoy. [14]
1112Sea MileThe length of one minute of arc, measured along the meridian in the latitude of the position; its length varies both with the latitude and with the figure of the earth in use. Used in navigation to measure distances on sea charts using the Mercator projection. Not to be confused with nautical mile or international nautical mile. [14]
1113Sea WallAn embankment or wall for protection against waves or tidal action along a shore or water front. [14]
1114SeagrassAny grass like marine alga. Eelgrass is one of the best known seagrasses. [14]
1115ShallowsAn indefinite term applied to expanses of shoal or shallow water. [14]
1116StelliteA trade name for an alloy of chromium, cobalt and tungsten. Stellate mirrors, free of imperfection and practically indestructible, are frequently used in hydrographic sextants. See sextant: sounding. [14]
1117Stranded(1) the terms "stranded" and "sunken" apply exclusively to items that once were afloat but which are now resting on the bottom. Stranded items project above the sounding datum while sunken items do not project above the sounding datum. These terms apply most often to wrecks. Masts, funnels, and other extensions of wreck superstructure should be disregarded when applying the above definition; i.e., such features may project above the sounding datum and still have the wreck classified as sunken. (2) the grounding of a vessel so that it is not soon refloated; a serious grounding. [14]
1118TidelandLand which is under water at high tide and uncovered at low tide. [14]
1119Time TagReference assigned to each measurement input from a sensor to identify the time (either cpu, gps, or utc) when a measurement was actually made by that particular sensor; time tags allow adjustment of data from different sensors to a common time reference. [14]
1120True SunSee sun: apparent. [14]
1121WaveformThe graphical representation of a wave, showing variation of amplitude with time. Also written as two words. [14]
1122WetlandsThe term "wetlands" means those areas that are inundated or saturated by surface or ground water at a frequency and duration sufficient to support, and that under normal circumstances do support, a prevalence of vegetation typically adapted for life in saturated soil conditions. Wetlands generally include swamps, marshes, bogs and similar areas. [14]
1123AcclivityAn upward slope of ground; as opposed to declivity. [14]
1124Acid RainCloud droplets or raindrops combining with gaseous pollutants, such as oxides of sulfur and nitrogen, to make falling rain (or snow) acidic pH less than 5.0. If fog droplets combine with such pollutants it becomes acid fog. [1]
1125Air SpeedThe speed of an aircraft relative to the surrounding atmosphere. As opposed to ground speed. [14]
1126BackbeachAlso written as two words. See backshore. [14]
1127Bar ScaleSee scale. [14]
1128BasepointA basepoint is any point on a baseline. [14]
1129BlackbodyA hypothetical object that absorbs all of the radiation that strikes it. It also emits radiation at a maximum rate for its given temperature. [1]
1130Box GaugeSee gauge: float. [14]
1131CapacitorSee condenser. [14]
1132Data BankA collection of data in a common location, relating to a given set of subjects. Usually comprised of several data bases considered as an entity. [14]
1133DaybeaconAn unlighted beacon. A day beacon is identified by its colour, shape, and number of its daymark. The simplest form of day beacon consists of a single pile with a daymark affixed at or near its top. [14]
1134DecimetreOne-tenth of a metre. [14]
1135DeclivityA downward slope or sloping of a hill; as opposed to acclivity. [14]
1136Depth IceSee anchor ice. [14]
1137Dock: DryAn artificial basin fitted with a gate or caisson, into which vessels can be floated and the water pumped out to expose the vessel's bottom. Also called graving dock. [14]
1138DownburstA severe localized downdraft that can be experienced beneath a severe thunderstorm. (compare microburst and macroburst.) [1]
1139Draft AftSee draft. [14]
1140Echometer(France). An ultrasonic echo sounder with a visual depth-indicating device. The signals are produced and received by quartz-crystal transmitting and receiving units. Its range is from 6 to 660 meters. [14]
1141Echoscope(France). An ultrasonic echo sounder similar to echometer. The echoscope is portable, intended for shoal-water sounding from small boats. Its range is from 1 to 60 meters. [14]
1142FacsimileAn exact reproduction or copy. [14]
1143FathogramA graphic record of depth measurements obtained by a fathometer (erroneously applied to any echogram). [14]
1144Fish FarmAn assemblage of cages, nets, rafts and floats or posts where fish, including shellfish, are artificially cultivated. [14]
1145ForeshoreThat part of shore which lies between high and low water mark at ordinary tide. [14]
1146ForesightIn levelling, a reading on a levelling rod held on a point whose elevation is to be determined. See also backsight. [14]
1147GrivationSee variation: grid. [14]
1148HailstoneGlobule or piece of ice, with a diameter varying between 5 and 50 mm or even more, the fall of which constitutes hail. Hailstones consist almost entirely of transparent ice, or of a series of layers of transparent ice with a thickness of at least 1 mm, alternating with translucent layers. [14]
1149Half TideSee tide. [14]
1150Hard IronIron or steel which is not readily magnetized by induction, but which retains a high percentage of the magnetism acquired. The opposite is soft iron. [14]
1151High NoonSee noon: local apparent. [14]
1152HoarfrostDeposit of ice, having a crystalline appearance, generally assuming the form of scales, needles, feathers or fans. Hoarfrost is produced in a manner similar to dew but at a temperature below 0°c. Also written as two words. [14]
1153HodographUsed in oceanography. The tidal current vector hodograph is the figure traced out by the tip of a vector representing the current over the tidal cycle. [14]
1154HydrologyThe scientific study of the waters of the earth, especially with relation to the effects of precipitation and evaporation upon the occurrence and character of water in streams, lakes, and on or below the land surfaces. [14]
1155Ice FrontThe vertical cliff forming the seaward face of an ice shelf. See ice wall. [14]
1156Ice ShelfA floating ice sheet of considerable thickness. Ice shelves are usually of great horizontal extent and have a level or gently undulating surface. They are nourished by local snow accumulation and often also by the seaward extension of land glaciers. Limited areas may be aground. The initial stage is called bay ice until the surface is more than about 2 m above sea level. The seaward edge is termed an ice front. [14]
1157Isometric(Adj.). Of or pertaining to equal measure. [14]
1158JellyfishAny of various free-swimming coelenterates having a disc- or bell-shaped body of jellylike consistency. Many have long tentacles with nematocysts (stinging cells). Some are capable of producing glowing ball luminescence. Any jellylike free-floating organism. The term 'jellyfish' often is applied to the ctenophores and may be applied to certain tunicates. Also called medusa. [14]
1159Land MileSee statute mile. [14]
1160Lee ShoreShore that is to leeward of a vessel. See weather shore. [14]
1161Lens AxisSee axis of lens. [14]
1162Level NetLines of spirit levelling connected together to form a system of loops and circuits extending over an area. Also called survey net. [14]
1163LimnologyThe scientific study of the biological, chemical, geographical, and physical features of fresh waters, especially of lakes and ponds. [14]
1164LoxodromeA curve, on the surface of a sphere, intersecting all great circles of the sphere at a constant oblique angle, theoretically never reaching the pole while closely approaching it. See rhumb line. [14]
1165Lunar DaySee day. [14]
1166MegahertzOne million hertz; one thousand kilohertz. The term is used as the equivalent of one million cycles per second. [14]
1167Milky WayA broad, faintly luminous band seen across the sky at night, consisting of innumerable stars and nebulae, so distant as to be indistinguishable without a telescope. [14]
1168NearshoreClose to the shore. [14]
1169NoctilucaA genus of usually pale pink luminescent dinoflagellates large enough to be seen by the unaided eye. This particular organism is responsible for much of the sheet-type luminescence noted in coastal waters of various parts of the world ocean. [14]
1170OcclusionProcess of progressive decrease of area of warm sector at the earth's surface, and its ultimate disappearance, by the junction of the cold air masses which initially precede the warm front and follow the cold front. Front between these two cold air masses, after their junction (also termed occluded front). [14]
1171PedometerA pocket-size instrument which registers in linear units the distance traversed by the pedestrian carrying it. See passometer. [14]
1172PeninsulaA piece of land that is almost an island, being nearly surrounded by water; by extension any piece of land projecting into the sea, so that the greater part of its boundary is coastline. [14]
1173Phase LagAngular retardation of the maximum of a constituent of the observed tide behind the correspon-ding maximum of the same constituent of the hypothetical equilibrium tide. Also called tidal epoch. [14]
1174PlanetoidSee asteroid. [14]
1175ProcessorSee microprocessor. [14]
1176Range RodA simple surveyor's rod, fitted with a sharp-pointed steel shoe. It is usually painted red and white alternately, and used to line up points of a survey. [14]
1177Reef FlatA flat expanse of dead reef rock which is partly or entirely dry at low tide. [14]
1178RemanenceSee magnetic retentivity. [14]
1179ResonanceRe-enforcement or prolongation of any wave motion, such as sound, radio waves, etc., resulting when the natural frequency of the body or system in vibration is equal to that of an impressed vibration. In tides, the water movement resulting from the natural period of oscillation of a body of water which approximates the period of one of the tide-producing forces. [14]
1180ResponderA transmitter, fitted to a submersible or on the seabed, which can be triggered by a hardwired external control signal to transmit an interrogation signal which is received by a transducer or hydrophone. [14]
1181RevetmentFacing of stone or other material, either permanent or temporary, placed along the edge of a stream to stabilize the bank and to protect it from the erosive action of the stream. [14]
1182Sea ReachThe straight part of a river between the last bend and the sea. [14]
1183Side ShotA reading or measurement from a survey station to locate a point which is not intended to be used as a base for the extension of the survey. A side shot is usually made for the purpose of determining the position of some object which is to be shown on the map. [14]
1184SnowstormStorm of blowing snow. [14]
1185TelemeterAn instrument for determining the distance from one point to another. Some such instruments employ a telescope and measure the angle subtended by a short base of known length. The complete equipment for measuring any quantity, transmitting the results electrically to a distance point, and there recording the values measured. [14]
1186ThresholdIn aeronautical terminology, the beginning of that portion of the runway usable for landing. [14]
1187Tide LockA lock situated between a basin or canal and tidewater to maintain the water at a desired level as the height of the tide changes. Also called guard lock. [14]
1188Tide PoleSee tide staff. [14]
1189TidewaterWater affected by tides or sometimes that part of it which covers the tideland. The term is sometimes used broadly to designate the seaboard. See tidal waves. [14]
1190TimepieceAn instrument for measuring time. See chronometer, clock, watch. [14]
1191TributaryA river which joins a larger one. [14]
1192Tunny NetA net built at sea for catching tunnies. [14]
1193WashoversSmall deltas formed on the lagoon side of a bar separating the lagoon from the open sea. Storm waves breaking over the bar deposit sediment on the lagoon side in the form of deltas. Also called wave deltas. [14]
1194WatershedWater-parting. The whole region or area contributing to the supply of a river or lake; drainage area; catchment area or basin. [14]
1195Wind RoseFor a given station and period of time, a star-shaped diagram indicating the relative frequencies of different directions of wind, sometimes also the frequencies of groups of wind speeds in different directions. [14]
1196Wind TideSee wind set-up. [14]
1197AlmucantarAny small circle on the celestial sphere parallel to the horizon. Also called parallel of altitude. [14]
1198BarysphereSee centrosphere. [14]
1199Blind SeasSee blind rollers. [14]
1200Blind ZoneAn area within or from which little or no radio signal is received. Also called zone of silence. [14]
1201BreakwaterA structure protecting a shore area, harbor, anchorage, or basin from waves. See also floating breakwater. [14]
1202ChallengerSee interrogator. [14]
1203ChromatismSee aberration of light. [14]
1204ClinometerAn instrument for indicating the degree of slope or the angle of roll or pitch of a vessel, according to the plane in which it is mounted. [14]
1205Cocked HatTriangle on chart, formed by three position lines that do not cross at one point. Also called triangle of error. Note. This expression is seldom used by american navigators. [14]
1206CompactingPieces of sea ice are said to be compacting when they are subjected to a converging motion, which increases ice concentration and/or produces stresses which may result in ice deformations. [14]
1207Compensate(v.t.). To counteract an error, as in an instrument; to counterbalance. [14]
1208Daily RateSee chronometer rate. [14]
1209Datum LineSee reference line. [14]
1210Day NumberThe sequentially numbered day of the year, usually starting with day number 1 on 1st January. [14]
1211DefinitionIn photography, and electronic equipment, the degree of clarity and sharpness of an image. See resolution and resolving power. [14]
1212Dove PrismA prism which reverts the image but does not deviate nor displace the beam. A given angular rotation of the prism about its longitudinal axis causes the image to rotate through twice the angle. Also called a rotating prism. [14]
1213Downstream(Adj. and Adv.). In the direction of flow of a current or stream. The opposite is upstream. [14]
1214EarthshineSee earth light. Also written as two words. [14]
1215EmbankmentAn artificial elevation composed of earth, stone, etc. To hold back water. [14]
1216EscarpmentAn elongated, characteristically linear, steep slope, separating horizontal or gently sloping sectors of the sea floor in non-shelf areas. Also abbreviated to scarp. [14]
1217False EchoSee echo. [14]
1218Field WorkAll activities in the field required for a hydrographic survey. [14]
1219Flood TideSee tide: rising. [14]
1220Frazil IceFine spicules or plates of ice in suspension in water. [14]
1221Grease IceA later stage of freezing than frazil ice when the crystals have coagulated to form a soupy layer on the surface. Grease ice reflects little light, giving the sea a matt appearance. [14]
1222Hack WatchSee watch. [14]
1223Heat BurstA sudden increase in surface air temperature often accompanied by extreme drying. A heat burst is associated with the downdraft of a thunderstorm, or a cluster of thunderstorms. [1]
1224HeliographA device for reflecting the sun's rays from one point to another for sending messages. In meteorology, instrument which records the time interval during which solar radiation reaches sufficient intensity to cast distinct shadows. Also called sunshine recorder. [14]
1225HeliotropeSee heliostat. [14]
1226HygrographHygrometer which includes an arrangement for the time recording of atmosphere humidity. [14]
1227HypsographA circular instrument of the slide-rule type used to compute elevations from vertical angles and horizontal distances. [14]
1228HypsometerA device for measuring heights of land surfaces by the boiling point of water. [14]
1229Julian DayThe number of each day, as reckoned consecutively since the beginning of the present Julian period on January 1, 4713 BC. The Julian day begins at noon, 12 hours later than the corresponding civil day. [14]
1230Landlocked(Adj.). Almost or quite enclosed by land. Said of an area of water, as a bay, harbor, etc., entirely protected from the sea. [14]
1231Large HaloSee halo. [14]
1232Level AxisSee axis of spirit level. [14]
1233Light BeamA group of pencils of light, as those originating at the many points of an illuminated surface. A beam of parallel light rays is a special case in which each pencil is of such small cross-section that it may be regarded as a ray. [14]
1234Log FactorThe ratio represented by the true distance divided by the log distance. [14]
1235Lower LimbSee limb. [14]
1236Mean DraftSee draft. [14]
1237MesosphereThe atmospheric layer between the stratosphere and the thermosphere. Located at an average elevation between 50 and 80 km above the earth's surface. [1]
1238OceanologySee oceanography. [14]
1239Open CoastA coast that is not sheltered from the sea. [14]
1240OrthodromeAny line on a chart representing a great circle track between two points. [14]
1241Orthogonal(Adj.). At right angles; rectangularly meeting, crossing, or lying at right angles. [14]
1242Patent LogSee log. [14]
1243PermafrostA layer of soil or bedrock at a variable depth beneath the surface of the earth in which the temperature has been below freezing continuously from a few to several thousands of years. Permafrost exists where the summer heating fails to descend to the base of the layer of frozen ground. [14]
1244RadiosondeInstrument carried through the atmosphere, equipped with devices permitting one or several meteorological elements (pressure, temperature, humidity, etc.) To be determined, and provided with a radio transmitter for sending this information. [14]
1245Rafted IceType of pressure ice formed by one floe overriding another. [14]
1246Rear LightSee light(s): range. [14]
1247Red SectorA sector of the circle of visibility of a navigational light in which a red light is exhibited. Such sectors are designated by their limiting bearings, as observed at some point other than the light. Red sectors are often located so that they warn of danger to vessels. [14]
1248Roof PrismA type of prism in which the image is reverted by a roof, that is, two surfaces inclined at 90° to each other. [14]
1249SeismologyThe science and study of earthquakes, and their causes and effects and related phenomena. [14]
1250SettlementThe general lowering in level of a moving vessel, relative to what its level would be were it motionless. Settlement is due to the regional depression of the surface of the water in which the ship moves. It is not an increase in displacement. Settlement is a factor to be reckoned in echo sounding. [14]
1251Sight LineSee collimation: line of. [14]
1252Slack TideSee slack water. [14]
1253Solar YearSee year: tropical. [14]
1254Sonic WaveSee wave: sound. [14]
1255Sound BuoySee buoy. [14]
1256Speed LineA line of position approximately perpendicular to the course. [14]
1257Stadia RodSee stadia. [14]
1258Star GlobeA small globe representing the celestial sphere, on which the apparent positions of the stars are indicated. It is usually provided with graduated arcs and a suitable mount for determining the approximate altitude and azimuth of the stars, to serve as a star finder. Also called celestial globe. [14]
1259Steel TapeSee tape. [14]
1260StereopairSee stereoscopic pair. [14]
1261Stop WatchSee watch. [14]
1262Storm TideSee storm surge. [14]
1263Storm WaveSee wave. [14]
1264Sugar LoafA descriptive term for a conical hill. [14]
1265Survey NetSee level net, triangulation net. [14]
1266TachymetryA method of surveying for the rapid determination of distance, direction, and relative elevation of a point with respect to the instrument station by a single observation on a rod or other object at the point. The stadia method of surveying is an example of tachymetry. [14]
1267Tented IcePressure ice in which two ice floes have been pushed into the air, leaving an air space underneath. [14]
1268Tidal RiseSee rise of tide. [14]
1269VariometerAn instrument for comparing magnetic forces, especially of the earth's magnetic field. [14]
1270Wall CloudAn area of rotating clouds that extends beneath a supercell thunderstorm and from which a funnel cloud may appear. Also called a collar cloud and pedestal cloud. [1]
1271Warm FrontAny non-occluded front which moves in such a way that warmer air replaces colder air. [14]
1272Watch BuoySee station buoy. [14]
1273Wave GroupA series of waves in which the wave direction, wavelength, and wave height vary only slightly. [14]
1274WesterliesOne, lying between the approximate latitudes 35oand 65o in each hemisphere, in which the air motion is mainly from west to east, especially in the high troposphere and low stratosphere. Near the earth's surface, the zone is particularly well marked in the southern hemisphere. [14]
1275WesterliesThe dominant westerly winds that blow in the middle latitudes on the poleward side of the subtropical high- pressure areas. [1]
1276X-ParallaxSee parallax: absolute stereoscopic. [14]
1277Age Of TideSee age of phase inequality. [14]
1278Aiming LineSee collimation: line of. [14]
1279Air DensityThe ratio of the mass of a substance to the volume occupied by it. Air density is usually expressed as g/cm3 or kg/m3. Also see density. [1]
1280Air SextantSee sextant. [14]
1281AltocumulusA middle cloud, usually white or gray. Often occurs in layers or patches with wavy, rounded masses or rolls. [1]
1282AltostratusA middle cloud composed of gray or bluish sheets or layers of uniform appearance. In the thinner regions, the sun or moon usually appears dimly visible. [1]
1283AnticycloneRegion of the atmosphere where the pressure is high relative to the surrounding region at the same level. It is represented on a synoptic chart by a system of isobars at a specified level or of contours at a specified pressure which enclose relatively high values of pressure or level. Also called high. [14]
1284Area SurveyA method of bottom relief survey consisting of surveying overlapping strips which allow soundings to be obtained with a specified accuracy at any position of the area under survey. [14]
1285AstigmatismAn aberration affecting the sharpness of images for objects off the axis, in which the rays passing through different meridians of the lens come to focus in different planes. [14]
1286AttenuationA lessening in amount, particularly the reduction of the amplitude of a wave or the intensity of light or sound with distance from the origin. [14]
1287Basal PlaneSee epipolar plane. [14]
1288BifurcationA division into two branches. [14]
1289Box CompassSee declinatoire. [14]
1290Buoy: SoundA buoy equipped with a characteristic sound signal. Sound buoys may be further classified according to the manner in which the sound is produced, such as bell, gong, horn, trumpet, or whistle buoy. [14]
1291Buoy: SuperA very large buoy designed to carry a signal light of high luminous intensity at a high elevation. See also large automatic navigation buoy (lanby). [14]
1292Check AngleA third angle taken to a fourth point as a check to a three-point fix. [14]
1293Coast Pilot(US Terminology). A descriptive book for the use of mariners, containing detailed information of coastal waters, harbor facilities, etc., of an area. Such books are prepared by the national ocean service for waters of the US. And its possessions. See also sailing directions. [14]
1294CorrelationThe removal of discrepancies that may exist among survey data, so that all parts are interrelated without apparent error. [14]
1295Cross HairsSee cross wires. [14]
1296Danger ZoneSee danger area. [14]
1297Datum PointSee reference point. [14]
1298DelineationIn cartography, the visual selection and distinguishing of map worthy features on various possible source materials by outlining the features on the source material, or on a map manuscript (as when operating a stereoscopic plotting instrument); also a preliminary step in compilation. [14]
1299Dipsey LeadSee lead: deep sea. [14]
1300Diurnal ArcSee arc: astronomical. [14]
1301Drying ReefA reef or part thereof which dries at low water. [14]
1302Forel ScaleA colour scale employed as a means of determining the colour of sea water. [14]
1303Front LightSee light(s): range. [14]
1304Frost PointThe temperature to which atmospheric moisture must be cooled to reach the point of saturation with respect to ice. [14]
1305Grid MethodIn photogrammetry, a method of plotting detail from oblique photographs by superimposing a perspective of a map grid on a photograph and transferring the detail by eye, that is, by using the corresponding lines of the map grid and its perspective as placement guides. See also grid: per-spective. [14]
1306HydrosphereThe waters of the earth's surface collectively. The 'water sphere' in comparison and contrast with lithosphere and atmosphere. [14]
1307Index GlassSee index mirror. [14]
1308Isomagnetic(Adj.). Of or pertaining to lines connecting points of equality in some magnetic element. [14]
1309Isomagnetic(n.). See isomagnetic line. [14]
1310Land BreezeWind of coastal regions blowing at night from the land towards a large water surface as a result of nocturnal cooling of the land surface. [14]
1311Land SurveySee survey: cadastral. [14]
1312Layer DepthIn oceanography, the thickness of the mixed layer; or the depth to the top of the thermocline. [14]
1313Marker BuoyA temporary buoy used in surveying to mark a location of particular interest such as a shoal or reef. See also station buoy. [14]
1314OccultationThe concealment or extinguishment of the light of an aid to navigation during the dark periods of its cycle. In astronomy, the concealment of a celestial body by another which crosses the line of view. Thus, the moon occults a star when it passes between the observer and the star. [14]
1315Ocean WaterWater having the physical-chemical characteristics of the open sea, where continental influences are at a minimum. [14]
1316PlanisphereA map or chart that is the projection of all or part of a sphere on a plane. A representation, on a plane, of the celestial sphere, especially one on a polar projection, with means provided for making certain measurements such as altitude and azimuth. See star finder. [14]
1317Plumb PointSee nadir: photograph. [14]
1318Radial PlotSee radial triangulation. [14]
1319Radio RangeA radio facility the emissions of which are intended to provide a definite course guidance. [14]
1320Radio StarsSources of radio waves existing in the universe. The position of many of the radio stars have been plotted but their signals are generally very weak. [14]
1321RestitutionThe process of determining the true planimetric position of objects whose images appear on photographs. Restitution corrects for distortion resulting from both tilt and relief displacement. [14]
1322Rip CurrentSee current. [14]
1323Safety ZoneThe area around an offshore installation within which vessels are prohibited from entering without permission. Special regulations protect installations within a safety zone and vessels of all nationalities are required to respect the zone. [14]
1324Scale ErrorThe difference between the principal scale and the particular scale resulting from projection distortion. [14]
1325Secchi DiscA white, black, or varicolored disc, 30 centimeters in diameter, used to measure water transparency (clarity). The disc is lowered in the water and the depth (in meters) at which it disappears from sight is averaged with the depth at which it reappears. This average value is used to represent sea water transparency. [14]
1326SelenotropeA device used in geodetic surveying for reflecting the moon's rays to a distant point, to aid in long-distance observations. [14]
1327Slope AngleThe angle between a slope and the horizontal. [14]
1328SpeedometerAn odometer recording the speed of a craft by a process of differentiation. [14]
1329Spot HeightSee spot elevation. [14]
1330Squaring UpSee squares: method of. [14]
1331Star FinderA device to facilitate the identification of stars. Sometimes called a star identifier. See planisphere. [14]
1332StereomodelSee stereoscopic image. [14]
1333StratopauseTop of the inversion layer in the upper stratosphere, at about 50-55 km. [14]
1334Summer TimeSee time: daylight saving. [14]
1335Sumner LineA celestial line of position, particularly one established by the Sumner method. Named after captain Thomas h. Sumner, the discoverer of the line of position by celestial observation. [14]
1336Sunken RockA rock potentially dangerous to surface navigation, the summit of which is below the lower limit of the zone for rock awash. [14]
1337Tape: InvarAny survey tape made of invar. [14]
1338Tape: SteelAny survey tape made of steel. [14]
1339Tidal LevelDepth or height contours defined by the rise and fall of the astronomical tide. [13]
1340Time: CivilSolar time in a day (civil day) that begins at midnight. [14]
1341TransceiverA combination transmitter and receiver in a single housing, with some components being used by both parts. See transponder. [14]
1342Valley LineSee talweg. [14]
1343W/T StationSee radio station. [14]
1344Waning MoonSee phases of the moon. [14]
1345Wave TroughSee trough. [14]
1346Wave: SoundA mechanical disturbance advancing with finite velocity through an elastic medium and consisting of longitudinal displacements of the ultimate particles of the medium, that is, consisting of compressional and rare-factional displacements parallel to the direction of advance of the disturbance; a longitudinal wave. Also called sonic wave, or acoustic wave. [14]
1347Waxing MoonSee phases of the moon. [14]
1348Wet CompassSee compass: liquid. [14]
1349Wind Set-UpThe vertical rise in the still water level on the leeward side of a body of water caused by wind stresses on the surface of the water. The difference in still water levels on the windward and the leeward sides of a body of water caused by wind stresses on the surface of water. Synonymous with wind tide. Wind tide is usually reserved for use on the ocean and large bodies of water. Wind set-up is usually reserved for use on reservoirs and smaller bodies of water. See tide: meteorological. [14]
1350Wire: InvarA wire made of invar metal used in measurement of geodetic bases. [14]
1351Grid: Universal Transverse Mercator (Utm)A grid system in which a grid network is applied to transverse Mercator projections of zones of the earth's surface extending to 80° n. And s. Latitudes. [14]
1352d50One of the sediment characteristic which is in the median grain size. ; The portions of particles with diameters smaller and larger than this value are 50%. Also known as the median diameter. [24]
1353GutA narrow passage such as a strait or inlet. A channel in otherwise less deep water, generally formed by water in motion. [14]
1354KaySee cay. [14]
1355OhmThe unit of electrical resistance in the si system. [14]
1356VoeAn inlet, bay, or creek. [14]
1357ArpaSee automatic radar plotting aid. [14]
1358BiasThe distortion of a result through negligence of a factor usually introducing a systematic error of unchanging magnitude and sign throughout a given series of observations. [14]
1359BlipIndication of a signal on the scope of an electronic instrument, produced by a short sharply-peaked pulse of voltage. [14]
1360CragA steep or precipitous rugged rock. [14]
1361DykeSee dike. [14]
1362FirnOld snow which has become granular and dense under the action of various processes of melting and refreezing, also including sublimation. [14]
1363FontComplete assortment of all the different characters of a particular size and style of type. [14]
1364GlenA narrow, secluded valley. [14]
1365GyreA closed circulatory system, but larger than a whirlpool or eddy. [14]
1366HazeSuspension in the atmosphere of extremely small, dry particles which are invisible to the naked eye but are numerous enough to give the sky an appearance of opalescence. [14]
1367Hulk the hull of a wrecked or condemned ship, from which the fittings and superstructure have usually been removed, which is moored in a permanent position or grounded. [14]
1368Int1 the compendium of symbols, abbreviations and terms to be used on paper and raster nautical charts, for use principally as a reference by mariners, as derived from the "regulations of the IHO for international (int) charts and chart specifications of the IHO" (IHO s-4). [14]
1369LullA momentary decrease in the speed of the wind. [14]
1370OozeA soft mud or slime. A fine-grained pelagic sediment containing undissolved sand- or silt-sized, calcareous or siliceous skeletal remains of small marine organisms in proportion of 30 percent or more, the remainder being amorphous clay-sized material. [14]
1371SnagA tree or branch embedded in a river or lake bottom and not visible on the surface, forming thereby a hazard to boats. [14]
1372SpitA small point of land or narrow shoal projecting into a body of water from the shore. [14]
1373SwayThe side-to-side bodily motion of a ship, independent of rolling, caused by uniform pressure being exerted all along one side of the hull. [14]
1374ThawMelting of snow and/or ice, at the earth's surface, following a temperature rise above 0°c. [14]
1375TrimThe way in which a ship floats on the water, in relation to her fore-and-aft line, whether on an even keel or down by the bow or by the stern. [14]
1376TufaA chemical sedimentary rock composed of calcium carbonate or silica, precipitated from percolating ground water or from a spring. [14]
1377WadiA watercourse that is permanently dry or dry except for the rainy season. [14]
1378WakeThe path of disturbed water or air behind a craft in motion. [14]
1379WattThe unit of power in the si system. [14]
1380Apron1. A gently dipping featureless surface, underlain primarily by sediment, at the base of any steeper slope. 2. The area of wharf or quay for handling cargo. 3. A sloping underwater extension of an iceberg. 4. An outwash plain along the front of a glacier. [14]
1381Apsis(pl. Apsides) see line of apsides. [14]
1382AwipsAcronym for advanced weather interactive processing system. New computerized system that integrates and processes data received at a weather forecasting office from nexrad, asos, and analysis and guidance products prepared by nmc. [1]
1383BaryePressure unit in the cgs system. [14]
1384BightA bend or curve in the coastline, a bend in a river, etc. In ice terminology, an extensive crescent-shaped indentation in the ice edge formed either by wind or current. [14]
1385BluffA cliff or headland with an almost perpendicular face. [14]
1386ButteAn isolated flat-topped hill, similar to, but smaller than a mesa. [14]
1387CairnA mound of stones, usually conical or pyramidal, raised as a landmark or to designate a point of importance in surveying. [14]
1388ChaosThe property describing a system that exhibits erratic behavior in that very small changes in the initial state of the system rapidly lead to large and apparently unpredictable changes sometime in the future. [1]
1389CrackAny fracture or rift in sea ice not sufficiently wide to be described as a lead. [14]
1390CreekA comparatively narrow inlet, of fresh or salt water, which is tidal throughout its whole course. A small tributary. A small, narrow bay which extends farther inland than a cove. [14]
1391ElbowA sudden turn in a channel, river, or shoreline. [14]
1392FaradThe unit of electrical capacitance, in the si system. [14]
1393FirthA Scottish word: an arm of the sea; an estuary of a river. [14]
1394FjordSee fiord. [14]
1395FlumeAn inclined channel for conveying water from a distance to be utilized for power, transportation, irrigation, etc. [14]
1396GammaPhotographic term for negative contrast resulting from development, and not the contrast of the subject itself; a numerical measure of contrast in the development of a negative. A small unit of magnetic field intensity generally used in describing the earth's magnetic field. It is defined as being equal to 10-5 oersted. [14]
1397GullySmall valley cut into soft sediments on the continental shelf or continental slope. [14]
1398HenryThe unit of electrical inductance in the si system. [14]
1399KnollA relatively small isolated elevation of a rounded shape. On the sea floor, an elevation somewhat smaller than a seamount and of rounded profile characteristically isolated or as a cluster. Also called hill. [14]
1400LoughIrish equivalent of the Scottish loch. [14]
1401LumenThe unit of luminous flux in the si system. [14]
1402LurchA sudden roll to one side. See list. [14]
1403MoireUndesirable patterns occurring when reproductions are made from halftone proofs or steel engravings, caused by conflict between the ruling of the halftone screen and the dots or lines of the original; a similar pattern occurring in multicolor halftone reproductions and usually due either to incorrect screen angles or misregister of the colour impressions during printing. [14]
1404MouseIn computer systems, a pointing device operated by moving on a flat surface. See also cursor, joy-stick. [14]
1405ShugaAn accumulation of spongy white ice lumps, a few centimeters across; the lumps are formed from grease ice or slush and sometimes from anchor ice rising to the surface. [14]
1406SleetA type of precipitation consisting of transparent pellets of ice 5 mm or less in diameter. Same as ice pellets. [1]
1407SlimeSoft, fine, oozy mud or other substance of similar consistency. [14]
1408SquatFor a ship underway, the change of level of the bow and stern from the still water condition in re-sponse to the elevation and depression of the water level about the hull resulting from the bow and stern wave systems. [14]
1409TalusA slope. A sloping mass of detritus lying at the base of a cliff or the like, and consisting of material which has fallen from its face; also the slope or inclination of the surface of such a mass. [14]
1410TeslaThe unit of magnetic flux density in the si system. [14]
1411VarveA sedimentary deposit, bed, or lamination deposited in one season. It is usually distinguished by colour or composition and used as an index to changes in the depositional environment. [14]
1412VirgaPrecipitation that falls from a cloud but evaporates before reaching the ground. (see fall streaks.) [1]
1413WeberThe unit of magnetic flux in the si system. [14]
1414WedgeIn optics, a refracting prism of very small deviation such as those used in the eyepiece of some stereoscopes. In meteorology, term synonymous with ridge, though usually applied to a fast-moving ridge between two depressions or troughs. [14]
1415BillowA great wave. [14]
1416BoringForcing a vessel under power through ice. [14]
1417CamberA small basin, usually with a narrow entrance, situated inside a harbor. [14]
1418Choppy(adj). Of the sea, having short, abrupt, breaking waves dashing against each other. [14]
1419CobbleA naturally rounded stone larger than a pebble. [14]
1420CoronaPhotometeor formed by one or more sequences (seldom more than three) of coloured rings of relatively small radius, centered on the sun or moon. [14]
1421CraterBowl-shaped cavity, at the summit or on the side of a volcano. [14]
1422CupolaA small dome-shaped tower or turret rising from a building. [14]
1423CutterA boat belonging to a warship. [14]
1424Dries'see covers and uncovers. [14]
1425DuplexA method in which telecommunication between two stations can take place in both directions simultaneously. [14]
1426FadingLoss of strength in received signals due to temporary variations in the conditions of propagation. [14]
1427FenderA device let down between the side of a ship or a wharf or other ship to protect from chafing when ships are lying alongside or to take the shock of a bump when going alongside. [14]
1428HaboobA dust or sandstorm that forms as cold downdrafts from a thunderstorm turbulently lift dust and sand into the air. [1]
1429HomingNavigation toward a point by maintaining constant some navigational coordinate(s), usually bearing. The procedure of using the direction-finding equipment of one radio station with the emission of another radio station, where at least one of the stations is mobile, and whereby the mobile station proceeds continuously towards the other station. [14]
1430KlaxonA small power fog signal sometimes operated by hand. [14]
1431LeagueA varying measure of distance, usually about three miles. [14]
1432LeewayThe leeward motion of a vessel due to wind. It may be expressed as distance, speed, or angular difference between course steered and course through the water. Drift angle. Also called drift. [14]
1433LipperSlight ruffling or roughness on a water surface. Light spray from small waves. Also called leaper. [14]
1434MarinaA harbor facility for small boats, yachts, etc., where supplies, repairs, and various services are available. [14]
1435MassifA large mountain-mass; the central mass of a mountain; a compact and more or less independent portion of a range. [14]
1436NewtonThe unit of force in the si system. [14]
1437Nipped(Adj. And adv.). Said of a ship which is beset when ice forcibly presses against it. See beset, icebound. [14]
1438OffingThat part of the visible sea a considerable distance from the shore, or that part just beyond the limits of the area in which a pilot is needed. [14]
1439Photic(Adj.). Of sea water, that is penetrated or influenced by sunlight. [14]
1440PhotonA discrete quantity of energy that can be thought of as a packet of electromagnetic radiation traveling at the speed of light. [1]
1441PolderLand reclaimed from the sea or other body of water by the construction of an embankment to restrain the water. See dike. [14]
1442PuddleAn accumulation on the ice of melt water, mainly due to melting snow, but in the more advanced stages also to the melting of ice. Initial stage consists of patches of melted snow. [14]
1443PulsarA rotating neutron star emitting electromagnetic radiation in regular pulses related to its rotational period. [14]
1444PumiceAn excessively cellular, glassy lava. It is very light and can float on water until it becomes waterlogged and sinks. [14]
1445Q-WaveSee wave: love. [14]
1446RadomeA dome, usually of glass reinforced plastic, housing a radar aerial. These domes are often prominent. The term is also used for domes or pods housing similar equipment in ships or on aircraft. [14]
1447RavineIn general, any steep-sided valley. [14]
1448RefugeA place of safety for a vessel in danger. [14]
1449ReseauA network. In photography, a glass plate on which is etched a network of fine lines. Sometimes used as a focal-plane plate to provide a means of calibrating film distortion. [14]
1450RodmanA person using a surveying rod. [14]
1451RotorsTurbulent eddies that form downwind of a mountain chain, creating hazardous flying conditions. [1]
1452RubbleFragments of hard sea ice, roughly spherical and up to 1,5 meters (5 feet) in diameter, resulting from the disintegration of larger ice formations. When afloat, commonly called brash ice. Loose angular rock fragment. [14]
1453RunnelThe smallest of natural streams; a brook or run. A trough or corrugation formed in the foreshore or in the bottom, immediately offshore, formed by waves or tidal currents. [14]
1454SalinaA salt marsh or salt pond separated from the sea but flooded by high tides. [14]
1455SchoolSee shoal. [14]
1456SloughA minor marshland or tidal waterway which usually connects other tidal areas; often more or less equivalent to a bayou. Quagmire, swamp, miry place. [14]
1457SluiceSliding gate or other contrivance for changing the level of a body of water by controlling flow into or out of it. [14]
1458SteppeAn area of grass-covered, treeless plains that has a semiarid climate. [1]
1459StrathA broad elongated depression with relatively steep walls located on a continental shelf. The longi-tudinal profile of the floor is gently undulating with greatest depths often found in the inshore portion. [14]
1460StylusA pointer that is operated by placing it in a display space or a tablet. [14]
1461SundogA colored luminous spot produced by refraction of light through ice crystals that appears on either side of the sun. Also called parhelia. [1]
1462Tie In(v.i.). See tie. [14]
1463TongueA projection of the ice edge up to several kilometers in length, caused by wind and current. A relatively narrow strip of land. An inlet. A narrow, rapid current. A protrusion of water into a region of different temperature. [14]
1464TrivetA low support for a surveying instrument which is used where a tripod cannot be used. [14]
1465TyphonA diaphragm horn which operates under the influence of compressed air or steam. Called siren in Canadian terminology. Also called Tyfon. [14]
1466VarsolAn oil used as the liquid in some modern magnetic compasses. [14]
1467VeneerA thin layer of sediment covering a rocky surface. [14]
1468Vertex(pl. Vertices). The highest point; the vertices of a great circle are the points nearest the pole. See apex. [14]
1469Aphotic(Adj.). Without light. [14]
1470Blow UpEnlarge photographically. [14]
1471BoulderA rounded rock with a diameter of 256 millimeters (about 10 inches) or larger. [14]
1472CalvingThe breaking away of a mass of ice from a glacier, ice front, or iceberg. [14]
1473ClutterConfused unwanted echoes on a radar display. [14]
1474ConsoleThe housing of the main operating unit of electronic equipment, in which indicators and general controls are located. A portion of a computer used to control the machine manually. [14]
1475CoulombThe unit of electric charge in the si system. [14]
1476DampingThe dissipation of energy with time or distance. The progressive reduction of amplitude of oscillations, waves, etc. [14]
1477DecibarOne-tenth of a bar. [14]
1478DecibelSee bel. [14]
1479DerechoStrong, damaging, straight-line winds associated with a cluster of severe thunderstorms that most often form in the evening or at night. [1]
1480DerrickA tall pyramid of latticed steel mounted over a borehole. [14]
1481DiopterA unit of refractive power of an optical system in the si system. [14]
1482Dog LegA leg which does not lead directly to the destination or way point. [14]
1483DredgerA vessel or floating structure equipped with machinery for excavating ditches or canals, deepening channels and harbors, and removing solid matter from the bottom of a water area. Also called a dredge. [14]
1484End LapSee overlap. [14]
1485Fog GunA gun used as a fog signal. [14]
1486FreshetAn area of comparatively fresh water at or near the mouth of a stream flowing into the sea. A flood or overflowing of a river caused by heavy rains or melted snow. [14]
1487GlitterThe spots of light reflected from a point source by the surface of the sea. [14]
1488GraniteLight-coloured, acidic igneous rock mineralogically composed primarily of quartz and potassium-sodium rich feldspars in which the mineral grains are visible to the naked eye (phaneritic texture). [14]
1489GrowlerA piece of ice almost awash, smaller than a bergy bit. [14]
1490HolidayAn unintentional unsurveyed area within a given hydrographic survey where the spacing between sounding lines or surveys exceeds the maximum allowable limits. [14]
1491HuntingFluctuation about a midpoint due to instability, as oscillations of the needle of an instrument about the zero point, or alternate lead and lag of a synchronous motor with respect to the alternating current. [14]
1492IndeltaInland area where a river subdivides (now in common use, especially in Australia). [14]
1493IsogrivA line connecting points of equal grid variation. [14]
1494IsotopeTwo or more nuclides having the same atomic number, hence constituting the same element, but differing in mass number. [14]
1495IsthmusA narrow strip of land connecting two larger bodies of land. [14]
1496KedgingMoving a vessel by laying out an anchor and then hauling the vessel up to the anchor. [14]
1497La NiñaA condition where the central and eastern tropical pacific ocean turns cooler than normal. [1]
1498LockingIn electronic navigation, a term describing the condition of two transmitters when their signals maintain a stable phase relationship. One station is then said to be locked to the other. [14]
1499Logging1. Gauging ship's speed with a log. 2. Record events. [14]
1500LowlandLow and relatively level land at a lower elevation than adjoining districts. [14]
1501MagentaAdj.). A mixture of red and blue in equal parts. [14]
1502Meander(often in plural). A winding, convolution or winding course, as of a stream. A deviation of the flow pattern of a current. [14]
1503Mock-UpA model of something to be used for testing or study. [14]
1504MonsoonWind of the general circulation of the atmosphere, typified by the seasonal persistence of a given wind direction and by a pronounced change in this direction from one season to another. The term is generally confined to those cases in which the primary cause is the differential heating (changing in nature from summer to winter) of a continent relative to a neighbouring ocean. [14]
1505MontageA series of related pieces of copy appearing as one to tell a complete story. [14]
1506NarrowsA navigable narrow part of a bay, strait, river, etc. [14]
1507NippingThe closing of ice around a ship so that the ship is beset and subjected to pressure from the ice. [14]
1508NodulesIn oceanography, concretionary lumps of manganese, cobalt, iron, and nickel found widely scattered on the ocean floor. Rocks of various sizes and shapes often are encrusted with these metals. [14]
1509NowcastShort-term weather forecasts varying from minutes up to a few hours. [1]
1510NunatakAn isolated hill or mountain peak of rock projecting above an inland ice sheet. [14]
1511OerstedThe cgs unit of magnetic field intensity in the si system. [14]
1512Old IceAny sea ice more than 1 year old. [14]
1513OutcropNaturally protruding, or erosional exposed or uncovered part of a rock, most of which is covered by overlying material. [14]
1514PontoonFloating structure, usually rectangular in shape which serves as landing, pierhead or bridge support. [14]
1515PrickerA pointed tool used instead of a pencil for laying off finer and more accurate lines on a plotting sheet. [14]
1516QuayageA comprehensive term embracing all the structures in a port alongside which vessels can lie. [14]
1517RainbowGroups of concentric arcs with colors ranging from violet to red, produced on a "screen" of water drops (raindrops, droplets of drizzle or fog) in the atmosphere by light from the sun or moon. [14]
1518Red MudSee mud. [14]
1519RivuletA small river. [14]
1520Road(S)See roadstead. [14]
1521SandingAn irregular dot pattern used on some of the early hydrographic surveys to accentuate the area between the high- and low-water lines. [14]
1522SavannaA tropical or subtropical region of grassland and drought-resistant vegetation. Typically found in tropical wet- and-dry climates. [1]
1523Sea FogSee fog. [14]
1524SeamarkAn aid to navigation located with the express purpose of being visible from a distance to seaward. Often erected in shoal water rather than on land. [14]
1525SeaportA port on or near the sea and readily accessible to seagoing vessels. [14]
1526ShimmerApparent fluttering of objects at the earth's surface, when they are viewed in an almost horizontal direction above strongly heated surfaces. [14]
1527ShingleRounded, often flat waterworn rock fragments larger than approximately 16 millimeters. [14]
1528SiemensThe unit of conductance in the si system. [14]
1529Sigma-TSymbol ïƒ t). A conveniently abbreviated value of the density of a sea water sample of temperature t and salinity s: ïƒt = (rho(s,t)-1) * 1000 , where rho(s,t) is the value of the sea water density in cgs units at standard atmospheric pressure. If, for example, rho(s,t) = 1.02648, then ïƒt = 26.48. [14]
1530SimplexA method in which telecommunication between two stations takes place in one direction at a time. [14]
1531SparkerAn echo sounder which uses an electrical spark discharge as the sound source. A recorder produces a chart which represents a vertical cross section of the geological structure beneath the water bottom. [14]
1532SpindleA spar serving as a beacon. A slender pin or rod, as one constituting part of a machine. [14]
1533SplinesFlexible rulers or interpolation algorithm used to draw smooth curves between points when constructing e.g. Hyperbolic lattices. [14]
1534Stratum(pl. Strata). A single sedimentary bed or layer of generally homogenous rock, independent of thickness. [14]
1535SubplanAn inset on a survey sheet used to extend the survey coverage shown on the sheet, or to show small congested areas at enlarged scales. [14]
1536SundialAn instrument that indicates time by the position of the shadow of a pointer or gnomon cast by the sun on the face of a dial marked in hours. [14]
1537SyntonyThe situation of two or more oscillating circuits having the same resonant frequency. [14]
1538ThalwegSee talweg. [14]
1539TidewayA channel through which a tidal current runs. [14]
1540TilliteRock formed of consolidated or lithified till and generally a record of a glacial epoch, older than that of the quaternary. [14]
1541TonnageThe carrying capacity of ships. [14]
1542TriptonCollectively, all of the dead suspended particulate matter in aquatic habitats. [14]
1543ViaductA structure consisting of a series of arches or towers supporting a roadway, waterway, etc., across a depression, etc. [14]
1544WestingThe distance a craft makes good to the west. The opposite is easting. [14]
1545Wet FogSee fog. [14]
1546Y-LevelSee levelling instrument: y level. [14]
1547AerologyStudy of the free atmosphere. [14]
1548AerovaneA wind instrument that indicates or records both wind speed and wind direction. Also called a skyvane. [1]
1549AffluentA stream flowing into a larger stream or lake; a tributary. [14]
1550AnalemmaA scale of the sun's daily declination drawn from tropic of cancer to tropic of Capricorn on terrestrial globes. An orthographical projection of the sphere made on the plane of the meridian, the eye being supposed to be an infinite distance and in the east or west point of the horizon. [14]
1551Array(S)The order in which equipment (antenna, oceanographic equipment) or mathematical quantities are ordered. [14]
1552AvulsionRapid erosion of shoreland by waves during a storm. [14]
1553BackwashWater or waves thrown back by an obstruction such as a ship, breakwater, cliff, etc. [14]
1554Bar BuoyA buoy marking the location of a bar. [14]
1555BarogramRecord made by a barograph. [14]
1556Base MapSee map. [14]
1557Beam SeaWaves moving in a direction approximately 90° from the heading. [14]
1558BlizzardViolent and very cold wind which is laden with snow, some part, at least, of which has been raised from snow-covered ground. This term originated in north America but has been extended to include similar winds in other countries. [14]
1559C/A CodeThe standard (coarse/acquisition, or clear/access) gps code; a sequence of 1023 pseudo-random binary biphase modulations on the gps carrier at a chip rate of 1.023 MHz, thus having a code repetition period of one millisecond. See also p-code. [14]
1560CadastreA public record of the extent, value, and ownership of land for purposes of taxation. [14]
1561CausewayA raised way across low or wet ground or water. [14]
1562ChainingSee taping. [14]
1563ClapotisThe french equivalent for a type of standing wave. [14]
1564Co-Phasesee. CO-TIDAL [14]
1565Co-RangeLines on a cotidal chart joining places which have the same tidal range or amplitude. Usually drawn for a particular constituent or tidal condition (e.g. spring tides). [16]
1566Co-TidalLines on a cotidal chart joining places where tide has the same phase, for example where high water occurs at the same time. Usually drawn for a particular constituent or tidal condition. [16]
1567Data SetA logical entity of data consisting of several elements (fields) grouped under one criterion. [14]
1568Deadbeat(Adj.). Aperiodic, or without a period. [14]
1569Deadhead(1) a block of wood used as anchor buoy. (2) a bollard. [14]
1570DiaphoneA device operated by compressed air for producing a distinctive fog signal. [14]
1571DoldrumsThe region near the equator that is characterized by low pressure and light, shifting winds. [1]
1572DoldrumsZone of calm or light variable winds, in the lower atmospheric layers, situated near the thermal equator; the zone follows, with slight time lag, the annual meridional fluctuation of the thermal equator. [14]
1573DuplexerA switching device used to connect a transmitter and a receiver to the same antenna. [14]
1574Fog BankFog, generally caused by local conditions, which extends over a small area some hundreds of meters wide. [14]
1575Fog BellA bell used as a fog signal. [14]
1576Fog GongA gong used as a fog signal. [14]
1577Fog HornA horn used as a fog signal. [14]
1578Fog: IceSuspension of numerous minute ice crystals in the air, reducing the visibility at the earth's surface. [14]
1579Fog: SeaAdvection fog which forms over the sea. [14]
1580Fog: WetFog formed of droplets sufficiently large to deposit water on objects. [14]
1581ForelandA cape or promontory. [14]
1582Gram(Me)A cgs unit of mass equal to one one-thousandth of a kilogram. [14]
1583HalationIn photography, a spreading of a photographic image beyond its proper boundaries, due especially to reflection from the side of the film or plate support opposite to that on which the emulsion is coated. Particularly noticeable in photographs of bright objects against a darker background. [14]
1584HalftoneIn photography or printing, a technique in which the solid image is broken up by the use of a screen into evenly spaced dots of equal density but of varying size. This gives an illusion of continuous tone. [14]
1585HatchingThe drawing or engraving of fine, parallel or crossed lines to show shading. [14]
1586Head SeaA sea in which the waves move in a direction approximately opposite to the heading. [14]
1587Heli PadA site on which helicopters may land and take off. [14]
1588Ice FreeWater surface completely free of ice. [14]
1589IsobrontLine joining, on a chart, places on the earth's surface where, on a given day, the first clap of thunder has been heard simultaneously. In climatology, line drawn on a chart through places which have the same average number of days on which thunder is heard in a given period. [14]
1590IsostasyA condition of approximate equilibrium in the outer part of the earth, such that the gravitational effect of masses extending above the surface of the geoid in continental areas is approximately counterbalanced by a deficiency of density in the material beneath those masses while the effect of deficiency of density in the ocean waters is counterbalanced by an excess of density in the material under the oceans. [14]
1591JoystickIn computer systems, a pointing device operated by pressing a stick in a desired direction. [14]
1592Keg BuoyA buoy consisting of a keg to which is attached a small pole with a flag, used by fishermen to mark the position of a trawl line. See dan buoy. [14]
1593Lake IceIce formed in lakes. [14]
1594LateriteA soil formed under tropical conditions where heavy rainfall leaches soluble minerals from the soil. This leaching leaves the soil hard and poor for growing crops. [1]
1595Lee TideSee tide: leeward. [14]
1596Level: YSee levelling instrument: y level. [14]
1597Littoral(Adj.). Of or pertaining to a shore, especially of the sea. [14]
1598Littoral(n.). A coastal region. Intertidal zone. [14]
1599Log BookBook in which events connected with the ship are entered. Also written as one word. [14]
1600Log BoomHeavy logs chained or lashed together and moored or anchored so as to enclose and contain rafted logs. See also boom. [14]
1601Log ShipSee log chip. Also written as one word. [14]
1602Make WayTo progress through the water. [14]
1603MilligalA unit of acceleration equal to 1/1,000 of a gal, or 1/1,000 centimeter per second, per second. This unit is used in gravity measurement, being approximately one-millionth of the average gravity at the earth's surface. [14]
1604Mud: RedA reddish-brown terrigenous deep-sea mud which accumulates on the sea floor in the neighbour-hood of deserts and off the mouths of great rivers; contains calcium carbonate up to 25 per cent. [14]
1605Nun BuoyA buoy the above water part of which is in the shape of a cone or a truncated cone. [14]
1606ParabolaAn open curve all points of which are equidistant from a fixed point, called the focus, and a straight line. [14]
1607PictomapA map supplement on which the photographic imagery of a standard photomosaic has been con-verted into interpretable colors and symbols by means of tonal masking techniques. [14]
1608PierheadThe outer end of a pier. Also called wharfhead. [14]
1609Pinpoint(v.t. And i.). To establish (position) with great accuracy. [14]
1610PitchingSee pitch. [14]
1611PlanformThe outline or shape of a body of water as determined by the still water level. [14]
1612PorosityThe ratio of the aggregate volume of pore space in a rock or sediment to its total volume, usually expressed as a percentage. [14]
1613PsephyteA coarse fragmental rock (conglomerate) or deposit composed of rounded pebbles. [14]
1614Q-FactorThe pressure coefficient of the unprotected thermometer expressed in °c. [14]
1615QuintantA double-reflecting instrument for measuring angles. It is similar to a sextant, but has an arc of 72°. [14]
1616Rapid(S)Portions of a stream with accelerated current where it descends rapidly but without a break in the slope of the bed sufficient to form a waterfall. Usually used in the plural. [14]
1617RepromatReproduction material, generally in the form of positive or negative copies on film or glass for each colour plate, from which a map or chart may be reproduced without redrafting. [14]
1618RockweedOne of a group of marine plants, principally of an order (fucales) of the brown algae, mostly multi-branched and leathery, which grow attached to rocks in the intertidal zone by means of an organ called a holdfast. Also called wrack or fucus. [14]
1619Sandwavea large wavelike sediment feature in very shallow water and composed of sand. The wavelength may reach 100 meters; the amplitude may be up to 20 meters. Also sand-wave or sand wave. Sometimes called a mega-ripple. [14]
1620Sea MoatSee moat. [14]
1621SeashoreThe shore of a sea or ocean. [14]
1622ShelvingA gently sloping area. [14]
1623ShipyardA place where ships are built or repaired. [14]
1624Side LapSee overlap. [14]
1625SolenoidA coil of wire, often helical in form, which becomes an electromagnet when an electric current is passed through it. [14]
1626SouthingThe distance a craft makes good to the south. The opposite is northing. [14]
1627Steep-To(Adj.). Precipitous. The term is applied particularly to a shore, bank or shoal that descends steeply to a lower level. [14]
1628SternwayMaking way through the water in a direction opposite to the heading. [14]
1629StoopingApparent decrease in the vertical dimension of an object near the horizon, due to large inequality of atmospheric refraction in the line of sight to the top and bottom of the object. The opposite is towe-ring. [14]
1630Subsonic(Adj.). Designating or of speeds that are less than that of sound. [14]
1631SwashwaySee swash. [14]
1632TidemarkA high water mark left by tidal water. The highest point reached by a high tide. A mark placed to indicate the highest point reached by a high tide, or, occasionally, any specified state of tide. [14]
1633ToponymyThe place names or the study of place names of a country or district. [14]
1634ToweringApparent increase in the vertical dimension of an object near the horizon, due to large inequality of atmospheric refraction in the line of sight to the top and bottom of the object. The opposite is stoo-ping. [14]
1635UndertowA seaward flow near the bottom of a sloping beach. The subsurface return by gravity flow of the water carried up on shore by waves or breakers. See also backrush. [14]
1636Wave AgeThe state of development of a wind-generated sea surface wave, conveniently expressed by the ratio of wave speed to wind speed. Wind speed is usually measured at about 8 meters above still water level. [14]
1637Wet DockSee dock. [14]
1638WhitecapA crest of a wave which becomes unstable in deep water, toppling over or breaking. See breaking of waves. [14]
1639WirelessSee radio. [14]
1640AdvectionThe horizontal transfer of any atmospheric property by the wind. [1]
1641AltimetryThe process of determining the difference of elevation by the use of altimeters. [14]
1642AmbiguityUncertainty of value or meaning because of the possibility of two or more interpretations. The condition when navigational coordinates define more than one position, direction, line of position, or surface of position. [14]
1643AmidshipsAt, near, or toward the middle of a ship. [14]
1644AnemogramRecord of the anemograph. [14]
1645AngstroemA unit of length, used especially in expressing the length of light waves, equal to one ten-thousandth of a micron or one hundred-millionth of a centimeter (1 x 10-8 cm). [14]
1646AnticlineAn arch of stratified rock in which the layers bend downward in opposite directions from the crest. [14]
1647BackshoreThat part of a beach which is usually dry, being reached only by the highest tides. Also called back beach. See also foreshore. [14]
1648BackwaterWater turned back by an obstruction, opposing current, etc. Water held back from the main flow. [14]
1649BandwidthThe number of units (hertz, kilohertz, etc.) Of frequency required for transmission. [14]
1650Bar CheckAn on-site calibration method for echo sounders. [14]
1651BarographRecording barometer. [14]
1652BarotropyThe condition and type of motion in which pressure is constant on surfaces of constant density, e.g. Surface tides. [14]
1653Base TiltSee tilt. [14]
1654BeaconageA system of beacons. See buoyage. [14]
1655Beam WindWind blowing in a direction approximately 90° from the heading. [14]
1656Bell BuoySee buoy: sound. [14]
1657Bergy BitA massive piece of sea ice or disrupted hummocked ice; also medium-sized piece of floating glacier ice. Generally less than 5 m above sea level, and not more than about 10 m across. [14]
1658Berm LineIn cartography, the outer edge of vegetation shown as shoreline on charts in marsh or mangrove areas. [14]
1659BiosphereSpherical terrestrial layer comprising the lower part of the atmosphere, the seas and the upper layers of the soil within which living organisms can exist naturally. [14]
1660Black IceA thin sheet of ice that appears relatively dark and may form as supercooled droplets, drizzle, or light rain come in contact with a road surface that is below freezing. Also, thin dark-appearing ice that forms on freshwater or saltwater ponds, or lakes. [1]
1661Boat GridSee careening grid or gridiron. [14]
1662Boat SlipA slipway designed specifically for boats. [14]
1663Brash IceAccumulation of floating ice made up of small fragments not more than 2 meters across; the wreckage of other forms of ice. [14]
1664CartogramA map showing geographical statistics by means of lines, dots, shaded areas, etc. [14]
1665CartoucheA panel on a map, often with decoration, enclosing the title or other legends, the scale, etc. [14]
1666Cold WaveMarked cooling of the air, or the invasion of very cold air, over a large area. [14]
1667Collimate(v.t.). In physics and astronomy, to render parallel to a certain line or direction; to render parallel, as rays of light; to adjust the line of sight of an optical instrument so that it is in the proper position relative to the other parts of the instruments. In photogrammetry, to adjust the fiducial marks of a camera so that they define the principal point. [14]
1668CondenserIn optics, a lens or lens system designed to concentrate the illumination from a light source on a limited area. In electricity, a device for receiving and storing an electric charge. Also called a capacitor. [14]
1669Cross SeaA series of waves or swell crossing another wave system at an angle. [14]
1670Ctd ProbeInstrument for measuring electrical conductivity, temperature and depth of the sea water. See probe. [14]
1671DeflectorAn instrument for measuring the directive force acting on a magnetic compass on different headings, for use in compass adjustment. [14]
1672DepressorA device to maintain a towfish at a given depth. [14]
1673Detail(S)In cartography, the items or particulars of information (shown on a map by lines, symbols, and lettering) which, when considered as a whole, furnish the comprehensive representation of the physical and cultural features of the earth's surface. [14]
1674Dew-PointThe temperature to which air must be cooled at constant pressure and constant water vapor content to reach saturation. [14]
1675DigitizerA computer aided device equipped with a digitizing table and a cursor for digitally capturing graphical data (pictures, charts), usually based on vector-techniques (as opposed to a scanner). The digitizing table consists of a gridded electrical network under the table's surface which allows an automatic computation of the planar x/y coordinates of a cursor's position. Lines are sequentially scanned by moving the cursor along the position and identifying the appropriate symbol on a menu. [14]
1676Dock SillThe foundation at the bottom of the entrance to a dry dock or lock against which the caisson or gates close. The depth of water controlling the use of the dock or lock is measured from the sill to the surface. [14]
1677Dock: WetA dock in which water can be maintained at any level by closing a gate when the water is at the desired level. [14]
1678Dry ProofAn impression of a chart pulled from the engraved plate onto a dry sheet of paper. This impression is fainter than a damp-pulled copy and unsuitable for ordinary use but is free from distortion. [14]
1679DuststormEnsemble of particles of dust or sand energetically lifted to great heights by a strong and turbulent wind. Also called sandstorm. Also written as two words. [14]
1680DynameterAn instrument for measuring the magnifying power of a telescope. [14]
1681Edge WaveSee wave. [14]
1682EmbaymentAn indentation in a shoreline forming an open bay. [14]
1683ExtrusionIn cartography, the extension of detail outside the neat line. [14]
1684FilteringThe process of selecting specific data from a specific source in accordance with certain rules, formulae, or algorithms. [14]
1685Fish LeadSee lead. [14]
1686Fish WeirSee fish trap. [14]
1687Float-Off(British terminology). The paper of a field board when detached from the board on completion of the work for which the field board was prepared. [14]
1688Foam LineThe front of a wave as it advances shoreward, after it has broken. [14]
1689Fog SirenA siren used as a fog signal. [14]
1690Foul AreaAn area of numerous uncharted dangers to navigation. The area charted serves as a warning to the mariner that all dangers are not charted individually and that navigation through the area may be hazardous. The term "foul" should not be applied to a soft continuum with indefinite boundaries such as mud or sand; to areas congested with marine vegetation such as kelp or grass in water; or to materials not likely to cause damage to a vessel. [14]
1691Free PortA port where certain import and export duties are waived (unless goods pass into the country) to facilitate re-shipment to other countries. [14]
1692FrostbiteThe partial freezing of exposed parts of the body, causing injury to the skin and sometimes to deeper tissues. [1]
1693Gamma RaySee x-rays. [14]
1694GelbstoffYellowish organic material suspended in sea water which causes greenish colour of the sea water in coastal areas; usually transported into the sea by rivers. [14]
1695GeomaticsThe science and technology of spatial information management, including the acquisition, storage, analysis and processing, display and dissemination of geo-referenced information. [14]
1696GeosphereThe solid and liquid portions of the earth; the lithosphere plus the hydrosphere. [14]
1697Gong BuoySee buoy: sound. [14]
1698Half Byte4 bits of a 8 bit byte; usually used to encode the figures 0....9. [14]
1699HaloclineA vertical gradient of salinity (which is usually positive) in some layer of the body of water, which is appreciably greater than the gradients above and below it. [14]
1700Head WindWind which blows in a direction opposite to that in which an object is moving, with respect to the earth's surface. [14]
1701Heat WaveMarked warming of the air, or the invasion of very warm air, over a large area. [14]
1702HodometerSee odometer. [14]
1703Hook EchoThe shape of a hook on a doppler radar screen that indicates the possible presence of a tornado. [1]
1704Horn BuoySee buoy: sound. [14]
1705Ice BlinkA typical whitish glare on low clouds above an accumulation of distant ice. It is especially glowing when observed on the horizon. [14]
1706Ice FieldArea of pack ice consisting of any size floes, which is greater than 10 km across. [14]
1707Ice LimitThe average position of the ice edge in any given month or period based on observations over a number of years. [14]
1708Ice StormIntense formation of ice on objects by the freezing, on impact, of drops of rain or drizzle. [14]
1709ImpedanceThe total opposition offered to an alternating current. It may consist of any combination of resistance, inductive reactance, or capacitive reactance. [14]
1710Index BarSee index arm. [14]
1711Index MapSee map. [14]
1712Ironbound(Adj.). Said of a rugged, rocky coast which affords no anchorage. [14]
1713IsoradialA radial from the isocenter. [14]
1714Leap YearSee year: civil. [14]
1715Left BankOf a river, the bank of the left-hand side as one proceeds downstream. [14]
1716Life BuoySee buoy. [14]
1717LithologyThe scientific study of rocks. Literally, the science of stones. [14]
1718LocalizerA radio facility which provides signals for lateral guidance of aircraft with respect to a runway center line. [14]
1719Log: ChipA log consisting essentially of a weighted wooden quadrant attached to a bridle in such a manner that it will float in a vertical position, and a log line, speed being measured by casting the quadrant overboard and counting the knots in the line paid out in unit time. [14]
1720L-Z GraphA graph used to determine 'in situ' depths of oceanographic observations by the wire depths minus thermometric depth method. [14]
1721MadreporeA branching or stag-horn coral, also any perforated stone coral. [14]
1722MagnetronAn electron tube for converting direct-current energy into radio-frequency energy by means of a magnetic field. [14]
1723ManoeuvrePlanned and controlled movement of a vehicle. [14]
1724ManometerAn instrument for measuring pressure of gases and vapors. [14]
1725Map NadirSee nadir. [14]
1726Map ScaleSee scale. [14]
1727Map: BaseA map showing certain fundamental information, used as a base upon which additional data of specialized nature are compiled. Also, a map containing all the information from which maps showing specialized information can be prepared; a source map. [14]
1728MarigraphA recording tide gauge. [14]
1729Mark BoatA temporary sounding mark consisting of a whaler moored head and stern, with a signal on board. [14]
1730Mean NoonSee noon. [14]
1731MegacycleOne million cycles; one thousand kilocycles. The term is often used incorrectly as the equivalent of one million cycles per second. [14]
1732MesoscaleThe scale of meteorological phenomena that range in size from a few km to about 100 km. It includes local winds, thunderstorms, and tornadoes. [1]
1733MeteogramA chart that shows how one or more weather variables has changed at a station over a given period of time or how the variables are likely to change with time. [1]
1734MeteoriteA meteor that reaches the surface of the earth as a solid particle. [14]
1735MetrologyThe science of weights and measures. [14]
1736Mock SunsName often given to parhelia, paranthelia and anthelia when they are particularly bright. [14]
1737MultiplexIn photogrammetry, an instrument for making a topographic map from aerial photographs. A three-dimensional optical model of the terrain to be mapped is produced, in miniature, by direct optical projection from a pair of overlapping photographs. This instrument uses the anaglyph principle. [14]
1738New ChartSee chart. [14]
1739Open PortA port which is not icebound during winter. [14]
1740Open WaveThe stage of development of a wave cyclone (midlatitude cyclonic storm) where a cold front and a warm front exist, but no occluded front. The center of lowest pressure in the wave is located at the junction of the two fronts. [1]
1741OrographyThe branch of physical geography which deals with the formation and features of mountains; the description of mountains. [14]
1742OverfallsShort, breaking waves occurring when a strong current passes over a shoal or other submarine obstruction or meets a contrary current or wind. See rips. [14]
1743OverprintIn cartography, an additional plate, generally in a distinctive colour, printed down on a map or chart which is already complete in itself. Overprints may be used to reproduce specialized information (e.g., to add aeronautical information to a topographic map) or to incorporate revision data without the amendment of existing plates. [14]
1744Pie GraphCircular symbol divided into sectors to indicate proportions of a total value. [14]
1745Plumb BobA conical device, usually of brass and suspended by a cord, by means of which a point can be projec-ted vertically into space over relative short distances. Also referred to as plummet. [14]
1746QuadripodA four-legged stand for triangulation, signals, etc. [14]
1747QuenchingThe great reduction in underwater sound transmission or reception resulting from absorption and scattering of sound energy by air bubbles entrapped around the sonar dome. See attenuation. [14]
1748QuicksandA loose mixture of sand and water that yields to the pressure of heavy objects. Such objects are difficult to extract once they begin sinking. [14]
1749Reed HornA horn that produces sound by means of a steel reed vibrated by air under pressure. [14]
1750Rill MarkA small groove, furrow or channel made in mud or sand on a beach by tiny streams following an outflowing tide. [14]
1751SafetynetThe international service for the broadcast and automatic reception of maritime safety information via the inmarsat egc system in waters where an international navtex service is not provided. [14]
1752Salt PansShallow pools of brackish water used for the natural evaporation of sea water to obtain salt. [14]
1753Sand DuneA ridge of sand piled up by the action of wind on sea coasts or in deserts. [14]
1754Sea ScarpSee escarpment. [14]
1755SemaphoreAny apparatus for signaling. [14]
1756ShorefaceThe narrow zone seaward from the low tide shoreline, permanently covered by water, over which the beach sands and gravels actively oscillate with changing wave conditions. [14]
1757SiltationThe deposition or accumulation of silt that is suspended in a body of water. [14]
1758SmoothingAveraging of data in space or time, designed to compensate for random errors or fluctuations of a scale smaller than that presumed significant to a specific problem. [14]
1759SonargramThe analog echo record produced by the side scan sonar recording device on special chemically-treated paper. [14]
1760Sono-BuoyA buoy with equipment for automatically transmitting a radio signal when triggered by an underwater sound signal. [14]
1761Spar BuoyA buoy made of a tapered log or metal shaped like a tapered log, and secured so as to float in an approximately vertical position. [14]
1762Split FixSee fix. [14]
1763StandpipeA tall cylindrical structure in a waterworks system, whose height is several times greater than its diameter. It extends from the ground and may be supported by a skeleton-type framework. [14]
1764SteradianThe unit of a solid angle in the si system. [14]
1765StipplingGraduation of shading by numerous separate touches. Shallow areas on charts, for instance, are sometimes indicated by numerous dots decreasing in density as the depth increases. [14]
1766Sun: MeanA fictitious sun conceived to move eastward along the celestial equator at a rate that provides a uniform measure of time equal to the average apparent time. It is used as a reference for reckoning mean time, zone time, etc. [14]
1767Sun: TrueSee sun: apparent. [14]
1768TablelandAn elevated region of land with a generally level surface of large or considerable extent; a lofty plain; a plateau. [14]
1769Tail WindWind which blows in the same direction as that in which an object is moving, with respect to the earth's surface. [14]
1770TectonicsThe study of origin and development of the broad structural features of the earth. [14]
1771TelemetryThe study and technique involved in measuring a quantity or quantities in place, transmitting this value to a station, and there interpreting, indicating, or recording the quantities; and transmitting commands from the station to control the measurement device. [14]
1772TelemotorA hydraulic or electrical device controlling the action of power at a distance, specifically, a device which controls the steering gear of a ship. [14]
1773Tide GateA restricted passage through which water runs with great speed due to tidal action. [14]
1774Tide RaceA strong tidal current or a channel in which such a current flows. [14]
1775Tide: EbbSee tide: falling. [14]
1776Tide: LowSee low water. [14]
1777Tie PointPoint of closure of a survey either on itself or on another survey. [14]
1778Time BallA visual time signal in the form of a ball. [14]
1779Time ZoneSee zone. [14]
1780ToleranceThe maximum allowable variation from a standard or from specified conditions. [14]
1781True WindWind vector in relation to the earth's surface. For a moving object it is the vector sum of the relative wind and the velocity of the object. [14]
1782Tuff-ConeSee tuff. [14]
1783TurbiditeTurbidity current deposits, characterized by both vertically and horizontally graded bedding. [14]
1784TurbidityReduced water clarity resulting from the presence of suspended matter. Water is considered turbid when its load of suspended matter is visibly conspicuous, but all waters contain some suspended matter and therefore are turbid. Reduced transparency of the atmosphere, caused by absorption and scattering of radiation by solid or liquid particles, other than clouds, held there in suspension. [14]
1785Type FaceA type of print, such as roman, egyptian, caslon, etc. [14]
1786Uncovered(Adj.). Above water. The opposite is submerged. [14]
1787Warm PoolA body of warm water entirely surrounded by cold water. [14]
1788Water SkyTypical dark patches and strips on low clouds over a water area enclosed in ice or behind its edge. [14]
1789WaterlineThe line marking the junction of land and water. The line along which the surface of the water touches a vessel's hull. Also written as two words. [14]
1790Wave BaseThe greatest depth at which sediment on the sea floor can just be stirred by the oscillating water. [14]
1791WavemeterAn instrument for measuring waves. One used for ocean waves usually measures height and period; one used for electromagnetic or sound waves usually measures length. Also written as two words. [14]
1792WhirlpoolWater in rapid rotary motion. See eddy. [14]
1793WhirlwindGeneral term for a small-scale rotating column of air. [14]
1794Wind Farma collection of wind turbines that are collocated and are organized as a single power generation unit. [14]
1795Wind VaneAn instrument used to indicate wind direction. [1]
1796Air CameraA camera specially designed for use in flying craft. [14]
1797AlkalinityThe number of milliequivalents of hydrogen ions that are neutralized by 1 kilogram of sea water at 20°c when a large excess of acid is added. [14]
1798AnemometerInstrument used in the measurement of wind speed or of wind speed and direction. See also anemograph. [14]
1799AnnotationAny marking on illustrative material for the purpose of clarification, such as numbers, letters, symbols, and signs. [14]
1800AntiselenaLuminous phenomenon analogous to anthelion, the luminary being the moon. [14]
1801Anti-TradeAir current with a westerly component which in various subtropical regions of either hemisphere sometimes blows above the trade wind. [14]
1802AstrometryThat branch of astronomy dealing with the determination of positions and motions of celestial bodies, including the earth. [14]
1803AutomationThe technique of improving human productivity in the processing of materials, energy and information, by utilizing in various degrees elements of automatic control, and of automatically executed product programming. [14]
1804BathymeterAn instrument primarily designed for measuring depth of water. [14]
1805Beam WidthThe angular measure of the transverse section of a beam (usually in the main lobe) lying within directions corresponding to specified values of field strength relative to the maximum. [14]
1806Bold CoastA prominent land mass that rises steeply from the sea. [14]
1807BorderlandA region adjacent to a continent, normally occupied by or bordering a shelf and sometimes emerging as islands, that is irregular or blocky in plan or profile, with depths well in excess of those typical of a shelf. [14]
1808Bottom IceSee anchor ice. [14]
1809Buoy: LifeA buoy intended to keep persons afloat. Also called life jacket. [14]
1810Cable BuoySee buoy. [14]
1811Cable SignA sign on a post marking the point from which a cable runs under water. [14]
1812Calcareous(adj). Composed of or containing calcium or calcium carbonate. [14]
1813CalculatorA machine for performing arithmetical operations usually more complex than that done by an adding machine; a calculating machine, which may be mechanical, electrical, electronic or a combination of all three. A person who calculates. [14]
1814CavitationThe turbulent formation, generally mechanically induced, including growth and collapse of bubbles in a fluid, and occurring when the static pressure at any point in fluid flow is less than fluid vapor pressure. [14]
1815Cgs SystemSee centimeter-gram-second (cgs) system. [14]
1816Chart: NewThe first publication of a chart. [14]
1817ChlorosityThe property of sea water corresponding to the chlorinity expressed as grams per litre at 20°. [14]
1818Choppy SeaThe state of the sea caused by interaction of waves running in different directions. [14]
1819Civil TimeSee time. [14]
1820Civil YearSee year. [14]
1821ColatitudeThe complement of the latitude, or 90° minus the latitude. [14]
1822ComparatorAn instrument for measuring a dimension in terms of a standard. An optical instrument for measuring rectangular or polar coordinates of points on any plane surface, such as a photographic plate. [14]
1823ConductionThe transfer of heat by molecular activity from one substance to another, or through a substance. Transfer is always from warmer to colder regions. [1]
1824ConfluenceFlowing together. The place where two or more rivers, streams, etc. Unite. In meteorology, progressive drawing together of the streamlines in the direction of flow. [14]
1825ContouringThe process of establishing lines representing equal values of a quantity on a map or chart. [14]
1826Coral HeadA massive mushroom or pillar shaped coral growth. [14]
1827CordilleraA range or system of mountains. [14]
1828CovarianceThe arithmetic mean or expected value of the product of the deviations of corresponding values of two variables from their respective mean values. [14]
1829Cross WindWind which blows in a direction perpendicular to that of the motion of a moving object, relative to the earth's surface. [14]
1830CrosslinesSounding lines that cross the main system of lines at either right angles or at an oblique angle to serve as a check on the accuracy of the work. [14]
1831Dark SlideSee slide: dark. [14]
1832Day: CivilA mean solar day beginning at midnight. [14]
1833Day: LunarThe duration of one rotation of the earth on its axis, with respect to the moon. Its average length is about 24h50m of mean solar time. Also called tidal day. The duration of one rotation of the moon on its axis, with respect to the sun. [14]
1834Day: TidalSee day: lunar and tidal day. [14]
1835Dead AheadBearing 000° relative. If the bearing is approximate, the term ahead should be used. [14]
1836Dead WaterThe phenomenon which occurs when a ship of low propulsive power negotiates water which has a thin layer of fresher water over a deeper layer of more saline water. As the ship moves, part of its energy goes into generation of an internal wave which causes a noticeable drop in efficiency of propulsion. [14]
1837DiagenesisThe chemical and physical changes that sediments undergo after their deposition, by lithification. [14]
1838DispersionThe separation of radiant energy into its various components. In optics, the separation of light into its component colors by its passage through a diffraction grating or by refraction such as that provided by a prism. In oceanography, the separation of a complex surface gravity wave disturbance into its component parts. [14]
1839Divider(S)Measuring compasses having both legs pointed, used principally for measuring distances and coordinates. [14]
1840Drift BuoyA data collection buoy which is not moored to the sea bottom, but drifting freely in response to currents, tides, and wind. [14]
1841Drift LeadSee lead. [14]
1842Earth TideSee tide. [14]
1843Exit PupilThe image of aperture stop formed by all the lens elements on the image side of the aperture stop. [14]
1844Fair SheetSee fair chart. [14]
1845Fix: SplitA fix obtained by measuring two angles to four objects whose positions are known, i.e. With no common center object. [14]
1846Float WellA vertical pipe or box with a relatively small opening in the bottom, used to enclose the float of a tide gauge so the float will be little affected by nontidal motions of the water. Synonymous with stilling well. [14]
1847Form LinesLines drawn to represent the shape of terrain; unlike contour lines, these are drawn without regard to a true vertical datum or regular vertical interval. [14]
1848Foul BerthA berth in which a vessel cannot swing to her anchor or moorings without fouling another vessel or striking an obstruction. [14]
1849GeophysicsThe study of the physical characteristics and properties of the earth. [14]
1850GlaciologyThe study of snow and ice on the earth's surface, with specific concentration on the regime of active glaciers. [14]
1851Gold SlideAn adjustable attachment to a mercurial barometer for giving resultant of corrections for index error, height of instrument above sea level, variation in gravity due to latitude, temperature. Invented by col. E. Gold. [14]
1852GoniometerAn instrument for measuring angles. A pick-up coil which eliminates the necessity of having to rotate a radio direction finder antenna to determine direction. [14]
1853GravimeterA weighing device or instrument of sufficient sensitivity to register variations in the weight of a constant mass when the mass is moved from place to place on the earth and thereby subjected to the influence of gravity at those places. Also called gravity meter. [14]
1854Grid TicksShort lines indicating where selected grid lines intersect the neat line. [14]
1855Ground IceSee anchor ice. [14]
1856Ground LogSee log. [14]
1857Guard LockSee tide lock. [14]
1858Gyro PilotAn automatic pilot controlled by gyroscopes. An automatic device for steering a vessel by means of control signals from a gyroscopic compass. [14]
1859HinterlandThe district behind that lying along the coast; the back country. [14]
1860HummockingPressure process by which level ice becomes broken up into hummocks. [14]
1861HydrometerAn instrument for determining the specific gravity of liquids. [14]
1862HygrometerAn instrument for measuring the humidity of the air. See also psychrometer. [14]
1863HypsometryThe determination of elevations above sea level. Generally applied to the determination of eleva-tions through the measurement of air pressure by observing the boiling point of a liquid. [14]
1864HysteresisRetardation or lag in the effect of changing forces, as in ship's magnetism induced by the earth's magnetic field. [14]
1865Ice NucleiParticles that act as nuclei for the formation of ice crystals in the atmosphere. [1]
1866Infrasonic(Adj.). Having a frequency below the audible range. [14]
1867InsolationAmount of direct solar radiation incident per unit horizontal area at a given level. Downward-directed solar radiation (global radiation). [14]
1868Invar TapeSee tape. [14]
1869Invar WireSee wire. [14]
1870Isodynamic(Adj.). Of or pertaining to equality of force. [14]
1871IsohalsineSee isohaline. [14]
1872Jet StreakA region of high wind speed that moves through the axis of a jet stream. Also called jet maximum. [1]
1873Kite OtterA multi-plane device which can be used either as a kite or as an otter depending on the way it is slung. See oropesa sweep. [14]
1874KymatologyThe science of waves and wave motion. [14]
1875Lead (Led)A navigable passage through ice. The amount one cyclic motion is ahead of another, expressed in degrees. [14]
1876Lead: FishA fish-shaped sounding lead which reduces to a minimum the inclination of the wire when trailed, making unnecessary its removal from the water between soundings. [14]
1877Lead: HandA light sounding lead (3 to 5 kilos) having usually a line of not more than 40 to 50 meters. [14]
1878Light-YearA unit of length equal to the distance light travels in one year. This unit is used as a measure of stellar distance. [14]
1879Lunar TideSee under tide. [14]
1880MacroscaleThe normal meteorological synoptic scale for obtaining weather information. It can cover an area ranging from the size of a continent to the entire globe. [1]
1881Making WayProgressing through the water. [14]
1882Map: IndexIn aerial photography, a map showing the location and numbers of flight strips and photographs. [14]
1883MicroburstA strong localized downdraft (downburst) less than 4 km wide that occurs beneath thunderstorms. A strong downburst greater than 4 km across is called a macroburst. [1]
1884MicrophoneAn electroacoustic device containing a transducer which is actuated by sound waves and delivers essentially equivalent electric waves. [14]
1885MicroscaleThe smallest scale of atmospheric motions. [1]
1886Mixed SeasThe state of the sea resulting from the interaction of wind, waves, and swell. [14]
1887Mixed TideSee tide. [14]
1888Mobile RigSee rig. [14]
1889Mock MoonsName given sometimes to paraselenae, parantiselenae and antiselenae when they are bright. [14]
1890MonitoringChecking of the operation and performance of an electronic system through reception of its signals. [14]
1891Nadir: MapThe map position for the ground nadir. [14]
1892NanosecondA thousand millionth of a second. [14]
1893NautophoneA horn having a diaphragm oscillated by electricity. [14]
1894New SurveySee resurvey. [14]
1895NiggerheadLarge blocks of coral torn loose from the outer face of a reef and tossed on to the reef flat by storm waves or tsunamis. The blocks are blackened by a crust of lichens after detachment from the reef. [14]
1896Noon: MeanTwelve o'clock mean time. [14]
1897Ocean EddyA moving or stationary local rotating formation where water predominantly moves along circular paths. [14]
1898Open SoundA bay similar to a lagoon but with large openings between the protecting islands. [14]
1899Open WaterA relatively large area of free navigable water in an ice-encumbered sea. In US Terminology, an area of sea with less than one-tenth ice concentration. [14]
1900OpisometerA recording device designed to measure by revolutions of a small wheel, continuous linear distances on a map. Used in measuring the length of shoreline by closely following all the indentations and sinuosity’s of the shore. [14]
1901OutgassingThe release of gases dissolved in hot, molten rock. [1]
1902Ozone (O3)An almost colorless gaseous form of oxygen with an odor similar to weak chlorine. The highest natural concentration is found in the stratosphere where it is known as stratospheric ozone. It also forms in polluted air near the surface where it is the main ingredient of photochemical smog. Here, it is called tropospheric ozone. [1]
1903Ozone (O3)An almost colorless gaseous form of oxygen with an odor similar to weak chlorine. The highest natural concentration is found in the stratosphere where it is known as stratospheric ozone. It also forms in polluted air near the surface where it is the main ingredient of photochemical smog. Here, it is called tropospheric ozone. [1]
1904Ozone HoleA sharp drop in stratospheric ozone concentration observed over the Antarctic during the spring. [1]
1905PantographAn instrument for copying a chart, drawing, etc., to any desired scale within the limits of the instrument. [14]
1906ParaseleneOptical phenomenon of the halo family, similar to but less brilliant than the parhelion, the luminary being the moon. [14]
1907Pass PointIn photogrammetry, a point whose horizontal and/or vertical position is determined from photo-graphs by photogrammetrically methods and which is intended for use (as in the manner of a supplemental control point) in the orientation of other photographs. [14]
1908PassometerA pocket-size instrument which registers the number of steps taken by the pedestrian carrying it. See pedometer. [14]
1909PhonometerAn instrument for measuring the intensity or frequency of sounds. [14]
1910Photo BaseThe length of the air base as represented on a photograph. [14]
1911PhotoindexA mosaic made by assembling individual photographs, with accompanying designations, into their proper relative positions and copying the assembly photographically at a reduced scale. [14]
1912PhotometerAn instrument used in measuring the intensity of light, especially in determining the relative intensity of different lights. [14]
1913Piggot GunA coring instrument for obtaining deep-sea bottom samples. This instrument uses an explosive charge to drive a metal bit into the bottom at the instant the sharp end of the bit strikes the bottom. [14]
1914PlanimeterA mechanical integrator for measuring the area of a plane surface. [14]
1915PlanimetryThe measurement of plane surfaces. The plan details of a map. [14]
1916PromontoryA high point of land extending into a body of water. A cape. [14]
1917PycnoclineA vertical positive density gradient in some layer of a body of water, which is appreciably greater than gradients above and below it. [14]
1918Radar BuoySee buoy. [14]
1919Radar DomeA dome shaped structure used to protect the antenna of a radar installation. [14]
1920Radar LineSee radar guided track. [14]
1921Radar ViewA depiction (photographic reproduction or drawing) of appearance of landmarks on the ppi scope of a radar set at a particular geographic location, intended to facilitate the identification of the coast. This can aid the navigator to identify or match his own radar image of these same landmarks. [14]
1922RadarsondeEquipment used for determining high-level winds, by means of radar aimed at a target carried by a free balloon. [14]
1923Radio AidsAn aid to navigation transmitting information by radio waves. [14]
1924Radio MastA tower, pole, or other structure for elevating an antenna. [14]
1925RadiometerAn instrument for measuring the intensity of radiant energy. [14]
1926Real ImageSee image. [14]
1927Region A,BWithin the iala maritime buoyage system there are two international buoyage regions, designated as region a and region b, where lateral marks differ only in the colors of port and starboard hand marks. [14]
1928Relief MapSee map. [14]
1929Right BankOf a river, the bank on the right-hand side as one proceeds downstream. [14]
1930Rock BorerA member of any of several families of bivalves that live in cavities they bore in soft rock, concrete and other material. [14]
1931Rock FlourFinely ground rock particles, chiefly silt size, resulting from glacial abrasion. A component of marine deposits off glacial stream mouths. [14]
1932Rocky AreaAn area with a rocky bottom. [14]
1933Rod: RangeSee range rod. [14]
1934Roll CloudA dense, roll-shaped, elongated cloud that appears to slowly spin about a horizontal axis behind the leading edge of a thunderstorm's gust front. [1]
1935Rotten IceSea ice which has become honeycombed in the course of melting, and which is in an advanced state of disintegration. [14]
1936Salt MarshFlat, poorly drained coastal swamps which are flooded by most high tides. [14]
1937Sea ValleySee valley. [14]
1938SeamanshipA general term for the art by which vessels are handled. [14]
1939Shadow PinA small rod or pin used to cast a shadow on an instrument, such as a magnetic compass or sun com-pass, to determine the direction of the luminary; a gnomon. [14]
1940Shore LeadA lead between pack ice and the shore, or between pack ice and a narrow fringe of fast ice. [14]
1941Sill DepthThe greatest depth over a sill. [14]
1942Sketch MapSee map. [14]
1943Solar ApexSee apex. [14]
1944Solar CellA cell using the solar light or other light energy for conversion into electric energy. [14]
1945Solar TideSee tide. [14]
1946Sonic BoomA loud explosive-like sound caused by a shock wave emanating from an aircraft (or any object) traveling at or above the speed of sound. [1]
1947StadimeterAn instrument used to measure the distance from the observer to a more-or-less distant object, such as a vessel, when the height of a specified part of the latter (e.g. The mast) is known. It is in effect a hand-held range finder. [14]
1948Star ChartSee chart. [14]
1949StatoscopeA highly sensitive barometer or altimeter for measuring slight variations in pressure or altitude. [14]
1950StereogramA stereoscopic pair of photographs or drawings correctly oriented and mounted or projected for stereoscopic viewing. [14]
1951Sun PillarA vertical streak of light extending above (or below) the sun. It is produced by the reflection of sunlight off ice crystals. [1]
1952Supersonic(Adj.). Designating or of a speed greater than the speed of sound. [14]
1953Swash MarkThe thin wavy line of fine sand, mica scales, bits of seaweed, etc., left by the uprush when it recedes from its upward limit of movement on the beach. [14]
1954Swept AreaAn area that has been determined to be clear of navigational dangers to a specified depth [14]
1955TablemountA seamount having a comparatively smooth flat top. Also called guyot. [14]
1956TabulationOrderly arrangement as in a table. [14]
1957TachometerA device that indicates or measures the revolutions per minute of a revolving shaft or the velocity of a machine. [14]
1958Tape: BaseSee base tape (or wire). [14]
1959ThermogramRecord made by a thermograph. [14]
1960Tidal BoreSee bore. [14]
1961Tidal FlatA marsh or sandy or muddy coastal flatland which is covered and uncovered by the rise and fall of the tide. [14]
1962Tide BulgeSee tide wave. [14]
1963Tide CrackThe fissure at the line of junction between an immovable icefoot or ice wall and fast ice, the latter being subject to the rise and fall of the tide. [14]
1964Tide CurveAny graphic representation of the rise and fall of the tide. Time is generally represented by the abscissae and the height of the tide by ordinates. For normal tides the curve so produced approximates a sine curve. Also called marigram. [14]
1965Tide: HalfThe condition or time of the tide when at the level midway between any given high tide and the following or preceding low tide. [14]
1966Tide: HighSee high water. [14]
1967Tide-Bound(Adj.). Unable to proceed because of insufficient depth of water due to tidal action. [14]
1968Tilt: BaseIn photogrammetry, the inclination of the air base with respect to the horizontal. [14]
1969Time: ZoneThe local mean time of a reference or zone meridian, whose time is kept throughout a designated zone. The zone meridian is usually the nearest meridian whose longitude is exactly divisible by 15°. [14]
1970TrajectoryThe curved path of something hurtling through space. In meteorology, curve traced by the successive positions of a moving particle of air. Curve traced by the successive positions of the center of a selected synoptic system, such as a depression. In oceanography, the path followed by moving water particles. In electronics the path followed by electrons emanating from the cathode as in an electron tube. [14]
1971UndercliffA terrace or lower cliff formed by a landslide. Also written as two words. [14]
1972Upper LimbSee limb. [14]
1973VectographA stereoscopic photograph composed of two superimposed images which polarize light in planes 90° apart. When these images are viewed through polaroid spectacles with the polarization axes at right angles, an impression of depth is obtained. [14]
1974VignettingIn photography, a gradual reduction in density of parts of a photographic image due to the stopping of some of the rays entering the lens. [14]
1975WaterspoutA column of rotating wind over water that has characteristics of a dust devil and a tornado. [1]
1976Wave SetupThe result of 'sets' of waves transporting water shoreward and raising the sea level. [16]
1977Wave: EdgeAn ocean wave travelling parallel to a coast, with crests normal to the coastline. Such a wave has a height that diminishes rapidly seaward and is negligible at a distance of one wavelength offshore. [14]
1978Wave: FreeA wave that continues to exist after the generating force has ceased to act, in contrast with a forced wave that is generated and maintained by a continuous force. A free wave on a water surface is one created by a sudden impulse, thereafter influenced only by friction, the dimensions of the basin, and the dispersive character of the water medium it moves in. Most ocean surface waves except tidal waves are free waves. See oscillation. [14]
1979Wave: TideSee tide. [14]
1980Wave: WindA wave resulting from the action of wind on a water surface. See fetch. [14]
1981Winter IceMore or less unbroken, level sea ice of not more than one winter's growth originating from young ice. Thickness from 15 cm to 2 m. [14]
1982Wire: BaseSee base tape (or wire). [14]
1983Wreck BuoyA buoy marking the location of a wreck. [14]
1984XerographyA process of electrostatic printing which employs a special selenium-coated plate, useable many times over. [14]
1985XerophytesDrought-resistant vegetation. [1]
1986Abyssal GapA gap in a sill, ridge, or rise that lies between two abyssal plains. [14]
1987AggradationSee accretion. [14]
1988Agonic LineThe line through all points on the earth's surface at which the magnetic variation is zero. [14]
1989Air AlmanacSee under almanac. [14]
1990Amici PrismA prism which deviates the rays of light through 90° and because of its shape inverts the image. See roof prism. [14]
1991Anchor BuoyA buoy marking the position of an anchor. [14]
1992Angle: HourSee hour angle. [14]
1993Antipode(S)Place(s) on the surface of the earth directly opposite to each other. [14]
1994Apex: SolarThe point of the celestial sphere towards which the solar system as a whole is moving. It lies in the constellation of Hercules. [14]
1995AquacultureThe cultivation of aquatic fauna and flora. [14]
1996Axis: PolarIn a system of polar or spherical coordinates, the primary axis of direction. [14]
1997BaroclinityThe condition and type of motion in which pressure is not constant on surfaces of constant density, e.g. Internal waves. [14]
1998Barrel BuoySee buoy. [14]
1999BathysphereA diving sphere for deep-sea observations. [14]
2000Box SextantA small portable instrument used for approximate measurement of angles. [14]
2001Buoy: CableA buoy used to indicate the run of a submarine cable. [14]
2002Buoy: RadarA buoy with a cluster of radar reflectors. [14]
2003CandlepowerLuminous intensity expressed in candelas. Also written as two words. [14]
2004Chart ScaleSee scale. [14]
2005Chart: FairSee fair chart. [14]
2006Chart: GridA chart only showing a cartographic grid on its inner border. [14]
2007Chart: StarA representation, on a flat surface, of the celestial sphere or a part of it, showing the positions of the stars and sometimes other features of the celestial sphere. [14]
2008ChlorophyllThe green pigment contained in the leaves of plants. See photosynthesis. [14]
2009ChronographAn instrument for measuring and recording time or time intervals. [14]
2010Circle: DipSee dip circle. [14]
2011ClimatologyStudy of climates (causes, variations, distributions, types, etc.). [14]
2012CoalescenceThe merging of cloud droplets into a single larger droplet. [1]
2013Coast ChartSee chart. [14]
2014Contour MapSee map. [14]
2015Core SampleSee core. [14]
2016Cosmic DustVery fine particles of solid matter in any part of the universe, including meteoric dust and zodiacal light particles in the solar system, interstellar matter of uncertain origin in the milky way galaxy, and accumulation of dark matter in other galaxies. [14]
2017CustomhouseThe office, especially in harbors, at which customs are collected. [14]
2018Danger BuoySee isolated danger mark. [14]
2019Danger LineA line drawn on a chart, to indicate the limits of safe navigation for a vessel of specific draft. A dotted line on a chart to emphasize the presence of an obstruction. [14]
2020Dart LeaderThe discharge of electrons that proceeds intermittently toward the ground along the same ionized channel taken by the initial lightning stroke. [1]
2021Dead AsternBearing 180° relative. If the bearing is approximate, the term astern should be used. Also called right astern. [14]
2022Demagnetize(v.t.). To remove magnetism. The opposite is magnetize. [14]
2023Depth GaugeSee gauge. [14]
2024Design WaveDeterministic wave used for the design of an offshore structure. [14]
2025DiapositiveA positive photograph on a transparent medium. One which has a right reading image when viewed through the base support. [14]
2026DiffractionThe bending of the rays of radiant energy around the edges of an obstacle, or when passing near the edges of an opening, or through a small hole or slit, resulting in the formation of a spectrum, or arrangement by wavelength of component waves, producing, for visible wavelengths, the chromatic spectrum. The bending of a wave as it passes an obstruction. [14]
2027Direct WaveSee wave. [14]
2028DiscrepancyA difference between results of duplicate or comparable measures of a quantity. The difference in computed values of a quantity obtained by different processes using data from the same survey. [14]
2029Dish AerialA parabolic aerial for the receipt and transmission of high frequency radio signals. [14]
2030Dixie AlleyRegion in the southern united states, typically over mississippi and alabama, where tornadoes often form. [1]
2031Double TideSee tide. [14]
2032Draft MarksNumerals at the bow and stern of a vessel that indicate the depth to which the vessel is submerged. [14]
2033DraughtsmanSee draftsman. [14]
2034Driver TubeSee driver rod. [14]
2035Drying LineThe line marking the transit from water to land; usually the low-water line. [14]
2036Duck BlindsNon floating structures used for concealing waterfowl hunters. They usually consist of a wooden framework covered with brush. They are essentially unreported to any charting authority when built. They are unlighted and often constructed in navigable water without regard to the possible hazard they pose, especially to the small craft operator. Many are substantial structures built on piles. Even after they are eventually reduced to ruins the pilings may persist for years. [14]
2037Dx90-FormatFormat for supply or interchange of digital cartographic data. Dx90 provides two modes: the sequential, and the chain mode. [14]
2038DynamometerAn apparatus for measuring force or energy. [14]
2039Earth LightFeeble light of the dark part of the moon's disc produced by the solar light reflected by the earth including the atmosphere. Also written as one word. Also called earthshine. [14]
2040ElectrotapeA trade name for a precise electronic distance measuring device operating on the same principle as the tellurometer. Originally designated as micro-dist. [14]
2041Erect ImageSee image. [14]
2042Exit WindowThe image of the field stop formed by all the lens elements on the image side of the field stop. [14]
2043Field ChartSee chart. [14]
2044Field SheetThe hydrographer's or topographer's work sheet; it presents a graphic display of all surface and subsurface features in the area being surveyed. See also boat sheet. [14]
2045Flare StackA tall structure used for burning-off waste oil or gas. [14]
2046Flash FloodA flood that rises and falls quite rapidly with little or no advance warning, usually as the result of intense rainfall over a relatively small area. [1]
2047Float GaugeSee gauge. [14]
2048Focal PointSee focus. [14]
2049Fog PatchesFog in banks irregularly distributed. [14]
2050Fog TrumpetA trumpet used as a fog signal. [14]
2051Fog WhistleA whistle used as a fog signal. [14]
2052Forced WaveSee wave. [14]
2053Forward LapSee overlap. [14]
2054Foul BottomA hard, uneven, rocky or obstructed bottom having poor holding qualities for anchors, or one having rocks or wreckage that would endanger an anchored vessel. [14]
2055Foul GroundAn area over which it is safe to navigate but which should be avoided for anchoring, taking the ground or ground fishing. [14]
2056Frost SmokeFog-like clouds, due to the contact of cold air with relatively warm sea water, which appear over newly formed leads and pools, or leeward, of the ice edge, and which may persist while slush or sludge and young ice are forming. [14]
2057Gauge: RainInstrument for measuring the depth of water from precipitation supposed distributed over a hori-zontal impervious surface and not subject to evaporation. Also written as one word. [14]
2058Glacier IceAny ice floating on the sea as an iceberg, which originates from a land glacier. Also called land ice. [14]
2059Green FlashA small green color that occasionally appears on the upper part of the sun as it rises or sets. [1]
2060Grid CourseSee course. [14]
2061Gross ErrorSee error. [14]
2062Gulf StreamA warm, swift, narrow ocean current flowing along the east coast of the united states. [1]
2063Hadley CellA thermal circulation proposed by George Hadley to explain the movement of the trade winds. It consists of rising air near the equator and sinking air near 30° latitude. [1]
2064Hard BottomThe sea floor not covered by unconsolidated sediment. [14]
2065Heat StrokeA physical condition induced by a person's overexposure to high air temperatures, especially when accompanied by high humidity. [1]
2066HindcastingMethod of simulating historical (metocean) data for a region through numerical modelling [14]
2067HydrometeorMeteor consisting of an ensemble of liquid or solid water particles falling through or suspended in the atmosphere, blown by the wind from the earth's surface or deposited on objects on the ground or in the free air. [14]
2068HypothermiaThe deterioration in one's mental and physical condition brought on by a rapid lowering of human body temperature. [1]
2069Ice ClusterA concentration of sea ice covering hundreds of square kilometers, which is found in the same region every summer. [14]
2070Image: RealAn image actually produced and capable of being shown on a surface, as in a camera. [14]
2071IndentationA recess in a coastline. [14]
2072Index ChartSee chart. [14]
2073Index ShadeOn a sextant, one of the pivoting coloured glasses which can be swung before the index mirror for reducing the glare of the sun. [14]
2074IridescenceBrilliant spots or borders of colors, most often red and green, observed in clouds up to about 30° from the sun. [1]
2075Jack-Up RigA rig which provides a stable drilling structure in shallow waters by extending supporting legs onto the seabed. The legs are retracted when the rig is under tow. [14]
2076Kelvin WaveA long ocean wave whose amplitude decreases from right to left along the wave crest when viewed in the direction of travel in the northern hemisphere and from left to right in the southern hemisphere. The component of gravity acting down the slope is exactly balanced by the deflecting force of the earth's rotation, the Coriolis force. [14]
2077Lake BreezeSee sea breeze. [14]
2078Latent HeatThe heat that is either released or absorbed by a unit mass of a substance when it undergoes a change of state, such as during evaporation, condensation, or sublimation. [1]
2079Lead (Lã¨D)A heavy, soft, malleable, bluish-grey metallic chemical element. Anything made of this metal, such as a weight for sounding depths of water. [14]
2080Lead: DriftSounding lead dropped to bottom, to indicate movement of a vessel. [14]
2081Least CountThe finest reading that can be made directly (without estimation) from a vernier or micrometer. [14]
2082Light FloatA boat-like structure used instead of a light buoy in waters where strong streams or currents are experienced, or when a greater elevation than that of a light buoy is necessary. [14]
2083Light: RearSee light(s): range. [14]
2084Line SquallSquall which occurs along a squall line. [14]
2085LithosphereThe solid, rocky part of the earth; earth's crust distinguished from atmosphere, hydrosphere. [14]
2086Log: GroundA device for determining the course and speed made good over the ground in shallow water, consisting of a lead attached to a line. The lead is thrown overboard and allowed to rest on the bottom. The course being made good is indicated by the direction the line tends and the speed by the amount of line paid out in unit time. [14]
2087Log: PatentFormer name for a towed log. Any mechanical log, particularly a taffrail log. [14]
2088MagnetogramAn analogue time record of the temporal variations in a magnetic element measured at a magnetic observatory. [14]
2089Map: ReliefA map emphasizing relief or relative elevations. See relief model. [14]
2090Map: SketchA map drawn freehand and greatly simplified which, although preserving the essential space relationships, does not truly preserve scale or orientation. [14]
2091Marine FarmSee fish farm. [14]
2092MesoclimateThe climate of an area ranging in size from a few acres to several square kilometers. [1]
2093Meter WheelA special block used to measure paid out sampling line at oceanographic stations. [14]
2094MicrosecondOne millionth of a second. [14]
2095MicroseismsMore or less persistent feeble earth tremors caused by natural sources such as atmospheric pressure systems or waves. [14]
2096Mixed LayerIn oceanography, the surface layer of virtually isothermal water, which frequently exists above the thermocline. The thickness of the layer is dependent on the temperature gradient. [14]
2097Mud SnapperSee snapper. [14]
2098North: GridAn arbitrary reference direction used with grid navigation. The northerly or zero direction indicated by the grid datum of directional reference. [14]
2099North: TrueThe direction of the north geographic pole. [14]
2100OmnibearingThe magnetic bearing of an omnirange. [14]
2101OpalescenceWhitish colour of the atmosphere and a slight change of the apparent colour of objects with respect to normal (for example, bluish colour of an object normally black or dark) produced by the scattering of light by small particles held in suspension in the atmosphere. [14]
2102OverrunningA condition that occurs when air moves up and over another layer of air. [1]
2103Oxygen (O2)A colorless and odorless gas that occupies about 21 percent of dry air in the lower atmosphere. [1]
2104Pacific AirCool, moist air that originates over the Pacific Ocean, moves eastward, then descends the rocky mountains and moves over the plains as dry, stable, relatively cool air. [1]
2105Pancake IcePieces of new ice, usually approximately circular, about 30 cm to 3 m across, and with raised rims, due to the pieces striking against each other as the result of wind and swell. [14]
2106Pecked LineIn cartography, a symbol consisting of a line broken at regular intervals. [14]
2107Pencil BeamA beam in which the radiant energy is concentrated in an approximately conical or cylindrical portion of space of relatively small diameter. This type beam is used for many revolving navigational lights. [14]
2108PercolationThe process by which water is forced by wave action through the interstices of the bottom sediment and has a tendency to reduce wave heights. [14]
2109PhotosphereThe visible surface of the sun and direct source of almost all its radiation. It is a gaseous layer some 400 km thick, below which the sun becomes opaque. [14]
2110Pillar BuoyA buoy composed of a tall central structure on a broad flat base. [14]
2111Pilot ChartSee chart. [14]
2112Pivot PointAfter a ship has assumed its drift angle in a turn, the point on the centerline between the bow and the center of gravity at which the resultant of the velocities of rotation and transaction is directed along the centerline. To an observer on board, the ship appears to rotate about this point. [14]
2113Plate LevelSee level. [14]
2114PluviographRain gauge which includes an arrangement for the time recording of the depth of water from precipitation. [14]
2115Polar ChartSee chart. [14]
2116Press ProofA lithographed impression taken from among the first copies run on the press and used for checking purposes. Also called press pull. [14]
2117Print: BlueA nonreproducible blue image or outline usually printed photographically on paper. [14]
2118PseudorangeThe time shift required to align (correlate) a replica of the gps code generated in the receiver with the received gps code, scaled into distance by the speed of light. This time shift is the difference between the time of signal reception (measured in the receiver time frame) and the time of emission (measured in the satellite time frame). [14]
2119Qtg StationA radio station which is prepared to provide qtg service, that is to say, to transmit upon request from a ship, a radio signal, the bearing of which can be taken by that ship. [14]
2120Radar ChainAn arrangement of radar sets in a chain usually used for vessel traffic control. [14]
2121Radar ChartSee chart. [14]
2122Rain ShadowThe region on the leeside of a mountain where the precipitation is noticeably less than on the windward side. [1]
2123Ratio PrintSee print. [14]
2124ReflectanceThe ratio of light given off by an object to the amount of light striking the object, expressed as percentage. [14]
2125Rift ValleySee median valley. [14]
2126Ripple MarkUndulating surface features of various shapes produced in unconsolidated sediments by wave or current action. [14]
2127River MouthThe exit or point of discharge of a river into the sea, a lake, or another river. [14]
2128Running FixSee fix. [14]
2129Safety AidsSee aid to navigation. [14]
2130SalinometerAny device or instrument for determining salinity, especially one based on electrical conductivity methods. [14]
2131Sea ChannelA continuously sloping elongated discrete depression commonly found in fans or abyssal plains and customarily bordered by levees on one or both sides. [14]
2132SeismographAn instrument that records the direction, intensity and time of earthquakes. [14]
2133SelectivityThe degree of decrease in the response of a resonant device with departure from resonance. Selec-tivity determines the ability of a radio receiver to differentiate between signals of different carrier frequency. [14]
2134SexagesimalAn angular division whereby a circle is divided in 360 equal parts called degrees. A degree is divided in 60 minutes and one minute in 60 seconds. [14]
2135Shade GlassSee shade. [14]
2136Shadow ZoneA region into which very little sound energy penetrates. [14]
2137Shelf BreakSee shelf edge. [14]
2138Shelf CloudA dense, arch-shaped, ominous-looking cloud that often forms along the leading edge of a thunderstorm's gust front, especially when stable air rises up and over cooler air at the surface. Also called an arcus cloud. [1]
2139Signal: FogSee fog signal. [14]
2140Sky CompassSee compass. [14]
2141Slide: DarkA thin plate (usually metal or fibre, rigid or flexible) which, after insertion in a camera magazine, renders it light-tight. [14]
2142Snow GrainsPrecipitation in the form of very small, opaque grains of ice. The solid equivalent of drizzle. [1]
2143Speed ScaleSee scale. [14]
2144Spoil BanksSubmerged accumulations of dumped material dredged from channels or harbors. [14]
2145Squall LineFictitious moving line, sometimes of considerable extent, along which squall phenomena occur. [14]
2146SteeragewayThe condition wherein the ship has sufficient way on that it will respond to rudder movements to maintain desired course. [14]
2147StereometerA measuring device comprising a micrometer movement by means of which the separation of two index marks can be changed to measure parallax difference on a stereoscopic pair of photographs. Also called parallax bar. [14]
2148Stream: EbbSee ebb stream. [14]
2149Strong GaleWind with a speed between 41 and 47 knots (beaufort scale wind force 9). [14]
2150Sun CompassSee compass. [14]
2151Surface MapA map that shows the distribution of sea-level pressure with isobars and weather phenomena. Also called a surface chart. [1]
2152Survey BoatA boat used for hydrographic surveys. [14]
2153Survey BuoySee buoy. [14]
2154Survey MarkAn object placed at the site of a station to identify the surveyed location of that station. In particular, an object whose coordinates are used for control in a geodetic network. Also called marker, geodetic marker, and monument. [14]
2155Survey: NewSee resurvey. [14]
2156Swirl ErrorSee error. [14]
2157Tangent ArcAn arc of light tangent to a halo. It forms by refraction of light through ice crystals. [1]
2158Terrigenous(Adj.). Derived from the land. Applied to marine deposits, originating from the erosion of the land as opposed to pelagic deposits. [14]
2159Texas TowerA fixed tower mounted on the continental shelf or on a shoal, used to drill and operate gas or petroleum wells, and to provide a platform for aids to navigation and meteorological or oceanographic instrumentation. [14]
2160ThermoprobeA transducer used to measure temperature 'in situ' of ocean bottom sediments at depths beneath the bottom. Such measurements when combined with heat conductivity information provide a measurement of heat flow through the ocean bottom. [14]
2161Tidal BasinSee basin. [14]
2162Tidal EpochSee phase lag. [14]
2163Tidal WaterAny water the level of which changes periodically due to tidal action. See tidewater. [14]
2164Tide Rip(S)Small waves formed on the surface of water by the meeting of opposing tidal currents or by a tidal current crossing an irregular bottom. Vertical oscillation, rather than progressive waves, is charac-teristic of tide rips. [14]
2165Tide SignalSee signal. [14]
2166Tide: EarthPeriodic movement of the earth's crust caused by the tide-producing forces of the moon and sun. [14]
2167Tide: FloodSee tide: rising. [14]
2168Tide: LunarThat part of the tide due solely to the tide-producing forces of the moon, as distinguished from that part caused by the forces of the sun. See tide: solar. [14]
2169Tide: MixedThe type of tide in which a diurnal wave produces large inequalities in heights and/or durations of successive high and/or low waters. This term applies to the tides intermediate to those predomi-nantly semidiurnal and those predominantly diurnal. [14]
2170Tide: SlackSee slack water. [14]
2171Tide: SolarThat part of the tide due solely to the tide-producing forces of the sun, as distinguished from that part caused by the forces of the moon. [14]
2172Tide: StormSee storm surge. [14]
2173Time: LocalTime based upon the local meridian as reference, as contrasted with that based upon a zone meridian, or the meridian of Greenwich. Any time kept locally. [14]
2174Time: SolarTime based upon the rotation of the earth relative to the sun. See time: apparent solar, time: astronomical, time: civil, time: mean solar. [14]
2175Torrid ZoneThat part of the earth between the tropic of cancer and the tropic of Capricorn. Also called the tropics. [14]
2176Track ChartA chart showing recommended, required, or established tracks, and usually indicating turning points, courses, and distances. [14]
2177TriangulateThe process of triangulation. [14]
2178TrilaterateThe process of trilateration. [14]
2179UltrasonicsThe science and technology relating to sound waves of frequencies above the audible range. [14]
2180Upslope FogFog formed as moist, stable air flows upward over a topographic barrier. [1]
2181Vacuum LeadA corer which makes use of hydrostatic pressure to force a tube into the bottom sediment. [14]
2182VelocimeterAn instrument used for the 'in situ' measurement of the speed of sound in the sea and other natural waters. [14]
2183Watch: HackA watch used for timing observations of celestial bodies regulating ship's clocks, etc. [14]
2184Watch: StopA watch that can be started, stopped, and reset at will, to indicate elapsed time. [14]
2185Water FrontLand at the end of a stream, harbor, etc. The part of a city or town on such land; wharf or dock area. [14]
2186WatercourseA stream of water, a river or a brook; also an artificial channel for the conveyance of water. [14]
2187Wave DeltasSee washovers. [14]
2188Wave: ShortA radio wave shorter than those of the standard broadcasting band. In oceanography, waves under conditions where the relative depth (water depth/wavelength) is greater than 0.5 and where the phase velocity is independent of water depth, but dependent upon wavelength. [14]
2189Wave: StormA wind-generated sea surface wave of great height. See storm surge. [14]
2190Wave: TidalThe wave motion of the tides. In popular usage, any unusually high (and therefore destructive) water level along a shore. It usually refers to either a storm surge or tsunami. [14]
2191International Commission For The Scientific Exploration Of The Mediterranean Sea (Icsem)serves as liaison for research in Mediterranean laboratories; promotes international activities on behalf of countries bordering the Mediterranean. [14]
2192LATLowest astronomical tide (LAT); The lowest level astronomical tide that can be expected to occur under average meteorological conditions and under any combination of astronomical conditions. [24]
2193HATHighest astronomical tide (HAT); The highest level astronomical tide that can be expected to occur under average meteorological conditions and under any combination of astronomical conditions. [24]
2194EraIn geology, any of the main divisions of geological time. [14]
2195LowSee depression. [14]
2196SeaThe great body of salt water in general, as opposed to land; ocean. One of the smaller divisions of the oceans. The state of the surface of the ocean with regard to wave or swell, as a calm sea. See cross sea, head sea, beam sea, following sea, quartering sea, sugar loaf sea. [14]
2197SurveyingSpecifically, the science or art of making such measurements as are necessary to determine the relative position of points above, on, or beneath the surface of the earth, or to establish such points. Generally, the art of making a survey. [14]
2198AerialSee antenna. [14]
2199Magnetic FieldThe space in which a magnetic influence exists. [14]
2200SatelliteA relatively small celestial body revolving around a planet. Name sometimes given to the fictitious bodies assumed in the harmonic analysis of tides. [14]
2201Tidal CurrentAn alternating, horizontal movement of water associated with the rise and fall of the tide, these movements being caused by gravitational forces due to the relative motions of Moon, Sun, and Earth. [20]
2202Sea LevelThe height of the sea surface uninfluenced by wind waves and swell, which is frequently measured relative to a reference horizon. Observations of the sea level over a certain period are often evaluated to render minimum, maximum, and mean sea level. [14]
2203OrientationThe act of establishing the correct relationship in direction with reference to the points of the compass. The state of being in correct relationship in direction with reference to the points of the compass. A map is in orientation when the map symbols are parallel with their corresponding ground features. A photograph is in orientation when it correctly presents the perspective view of the ground or when images on the photograph appear in the same direction from the point of observation as do the corresponding map symbols. See orientation of plane table, orientation of surveying instrument, orientation: photogrammetric. [14]
2204Nodal PointIn optics, one of the two points on the optical axis of a lens (or a system of lenses) such that a ray emergent from the second point is parallel to the ray incident at the first. The first nodal point is referred to as the front nodal point or incident nodal point, and the second nodal point as the rear nodal point or emergent nodal point. An amphidromic point. In astronomy, a node. [14]
2205PositioningThe process of determination of a position. [14]
2206OscillationThe variation, usually with time, of the magnitude of a quantity with respect to a specified reference when the magnitude is alternately greater and smaller than the reference. Half an oscillatory cycle, consisting of a fluctuation or vibration in one direction; half a vibration. [14]
2207Spirit LevelSee level. [14]
2208Celestial SphereAn imaginary sphere of infinite radius, concentric with the earth, on which celestial bodies are imagined to be projected. Also called celestial concave. [14]
2209Magnetic CompassSee compass. [14]
2210OceanographyThe study of the sea, embracing and integrating all knowledge pertaining to the sea's physical boundaries, the chemistry and physics of sea water, marine biology, and submarine geology. In strict usage oceanography is the description of the marine environment, whereas oceanology is the study of the oceans and related sciences. [14]
2211Shallow WaterCommonly, water of such a depth that surface waves are noticeably affected by bottom topog-raphy. It is customary to consider water of depths less than half the surface wavelength as shallow water. [14]
2212Water BottleA device for collecting water samples from varying depths. They are lowered in an 'open' state to the required depth and can be closed before being hauled up by means of a messenger. Water bottles can be operated in series that is with more than one bottle on the wire rope so that water samples can be taken at a number of depths on the same cast. Also called water specimen cup. [14]
2213Nautical ChartA chart specifically designed to meet the requirements of marine navigation, showing depths of water, nature of bottom, elevations, configuration and characteristics of coast, dangers and aids to navigation. May be a paper chart, electronic navigational chart (enc) or a raster navigational chart (rnc). Also called marine chart, hydrographic chart, or simply chart. - 2. (from solas chapter v) a special-purpose map or a specially compiled database from which a map is derived, that is issued officially by or on the authority of a government, authorized hydrographic office or other relevant government institution and is designed to meet the requirements of marine navigation. [14]
2214Line Of PositionA line indicating a series of possible positions of a craft, determined by observation or measurement. Also called position line. See celestial line of position, circle of position, course line, electronic line of position, fix, hyperbolic line of position, latitude line, leading line, longitude line, retired line of position, sonic line of position, speed line, sumner line, surface of position, visual line of position. [14]
2215Hydrographic SurveySee survey. [14]
2216TransponderA combined receiver and transmitter whose function is to transmit signals automatically when triggered by an interrogator. See transceiver. [14]
2217Level: SpiritA small closed vessel of glass (vial), having the inside surface of its upper part curved in form; the vessel is nearly filled with a fluid of low viscosity (alcohol or ether), enough free space being left for the formation of a bubble of air and gas, which will always assume a position at the top of the vessel. There are two types of spirit levels used in surveying: one has the curved surface spherical in form, producing a bubble of circular outline; and is properly called a circular level (also universal level or bull's eye level). The other and much more generally used type has a vessel in the form of circular tube, the longitudinal axis of which is also circular in form. It is the type usually referred to when the term 'spirit level' is used. The spirit level is also called spirit bubble or sensitive bubble. [14]
2218Line Of SightThe straight line between two points. This line is in the direction of a great circle, but does not follow the curvature of the earth. See also collimation: line of. [14]
2219Nautical MileA unit of length used principally in navigation. See international nautical mile. [14]
2220DisplacementIn radiolocation, the half of the band of uncertainty having as its center line an electronic line of position. In photogrammetry, any shift in the position of an image on a photograph which does not alter the perspective characteristics of the photograph (i.e. Shift due to tilt of the photograph, scale change in the photograph, and relief of the objects photographed). [14]
2221Echo SoundingDetermination of the depth of water by measuring the time interval between emission of a sonic or ultrasonic signal and return of its echo from the bottom. Also called acoustic sounding. See also echo sounder. [14]
2222Dead ReckoningA method of navigation utilizing only the speed and heading of the craft, without reference to external aids. In air navigation, the best estimate of course and speed over the ground is used, i.e., dead reckoning incorporates wind vector. [14]
2223Vertical PlaneSee plane. [14]
2224Angular DistanceThe angular difference between two directions, numerically equal to the angle between two lines extending in the given directions. The arc of the great circle joining two points, expressed in angular units. [14]
2225Focal LengthThe distance from the rear nodal point of a lens to the focal plane for an object at infinity. The distance from the surface of a mirror to its focus. Also called focal distance. [14]
2226Control PointA point on the ground whose position (horizontal and vertical) is used as a base for a dependent survey. Also referred to as control station.- 2. In photogrammetry, any point in a horizontal and vertical control system that is identified on a photograph and used for correlating the data shown on that photograph. More specific terms are photo-control point, picture control point and ground control point. [14]
2227Current MeterAn instrument for the measurement of either speed alone or of both direction and speed of a current. See current pole, Ekman current meter, price-gurley current meter, roberts radio current meter, swallow float, savonius rotor current meter, wollaston current meter. [14]
2228EstablishmentThe interval of time between the transit (upper or lower) of the moon and the next high water at a place. The average establishment at the time of full or new moon is called vulgar or common establishment, or high water full and change. Also called high water lunitidal interval, or establishment of the port. See lunitidal interval. [14]
2229Sounding LineA line of sounding. A lead line. [14]
2230Celestial PoleSee pole. [14]
2231Line Of SoundingA series of soundings along a predetermined line, and at stated intervals, when surveying. Also referred to as sounding line. See check lines, cross lines, cross-section lines, inter line, split line, starred lines, track line of sounding, systems of sounding lines. [14]
2232Tropical CycloneCyclone of tropical origin of small diameter (some hundreds of kilometers). It is characterized by violent wind and torrential rain. Sometimes accompanied by a thunderstorm. [14]
2233Water SampleA portion of water brought up from a certain depth to determine its composition, or physical properties viz: temperature, salinity and density. [14]
2234Magnetic PoleEither of the two places on the surface of the earth where the magnetic dip is 90°, that in the northern hemisphere being designated north magnetic pole, and that in the southern hemisphere being designated south magnetic pole. The magnetic poles are not fixed and do not coincide with the geographical poles. Either of those two points of a magnet where the magnetic force is greatest. [14]
2235Map ProjectionSee projection. [14]
2236Mean Solar DaySee day: solar. [14]
2237Principal LineIn photogrammetry, the trace of the principal plane upon the photograph, (e.g., the line through the principal point and the photograph nadir). [14]
2238Vertical CircleSee circle. [14]
2239Sextant AltitudeSee under altitude. [14]
2240Weather ForecastStatement of the expected meteorological conditions for a specified period, and for specified area or portion of air space. [14]
2241Relative PositionSee position. [14]
2242Perspective CentreThe point of origin or termination of bundles of perspective rays. The two such points usually associated with a survey photograph are the interior perspective center and the exterior perspective center. In a perfect lens-camera system, perspective rays from the interior perspective center to the photographic images enclose the same angles as the corresponding rays from the exterior perspective center to the objects photographed. In a lens having distortion this is true only for a particular zone of the photograph. In a perfectly adjusted lens-camera system the exterior and interior perspective centers correspond, respectively, to the front and rear nodal points of the camera lens. [14]
2243Survey SheetSee hydrographic survey sheet. [14]
2244Levelling RodA straight rod or bar, designed for use in measuring a vertical distance between a point on the ground and the line of collimation of a levelling instrument which has been adjusted to horizontal position. Also called levelling staff. [14]
2245Scale: NaturalThe ratio between the linear dimensions of a chart, drawing, etc., and the actual linear dimensions represented, expressed as a proportion. Occasionally called representative fraction, fractional scale or numerical scale. [14]
2246Horizontal AxisSee axis. [14]
2247Principal PointIn photogrammetry, the foot of the perpendicular from the interior perspective center to the plane of the photograph (i.e. The foot of the photograph perpendicular). [14]
2248Territorial SeaA belt of water of a defined breadth but not exceeding 12 nautical miles measured seaward from the territorial sea baseline. [14]
2249Zenith DistanceThe vertical angle between the zenith and the object which is observed or defined. Zenith distance is the complement of the altitude. See zenith distance: double. [14]
2250Meridian TransitThe apparent passage of a celestial body across a celestial meridian. Upper or superior transit is the passage across the upper branch of the celestial meridian. Lower or inferior transit is the passage across the lower branch. The lower transit may take place either above the horizon as is the case of circumpolar celestial bodies, or across that branch of the meridian lying below the observer's horizon. Also called transit, meridian passage, culmination. [14]
2251Coordinate SystemA fixed system of lines used to define the position of a point, line, or plane. [14]
2252Pressure GradientVector, perpendicular to the isobaric line or surface, directed towards low pressure and of intensity equal to the rate of variation of the pressure with distance. Also called barometric gradient. [14]
2253Sextant: Sounding(British terminology). A simplified and more robustly constructed version of the marine sextant intended primarily for use in hydrographic survey. It has no shades, a wide angle low magnification telescope and is generally graduated in minutes of arc. It may be fitted with either a vernier or a micrometer reading device. Both mirrors are silvered all over to enable angles up to 180° to be measured. Some sounding sextants have a 90° prism attachment which reflects the normal direct line of sight 90° to the left. Called surveying sextant, or hydrographic sextant in US Terminology. [14]
2254Primary Great CircleA great circle used as the origin of measurement of a coordinate; particularly such a circle 90° from the poles of a system of spherical coordinates, as the equator. Also called primary circle, fundamental circle. [14]
2255Water ColumnA vertical continuum of water from sea surface to sea-bed. [14]
2256Depth ContourSee depth curve. [14]
2257Ground SurveySee survey. [14]
2258Level SurfaceA surface which, at every point, is perpendicular to the direction of gravity. A level surface is an equipotential surface. The geoid or, in general, any surface parallel to it, is a level surface. If changes in elevation due to tides, winds, etc. Are neglected, the surface of the sea is a level surface. A level surface is not a plane surface, but it is sometimes so regarded in surveys of limited areas. [14]
2259Range Of TideThe difference in height between consecutive high and low tides at a place. Also called tidal (or tide) range. [14]
2260Coriolis ForceComposite centrifugal force, due to the rotation of the earth, which acts on moving particles, whose motion is considered relative to that of the earth. [14]
2261Height Of TideThe vertical distance from the chart datum to the level of the water at any time. [14]
2262Mercator ChartSee chart. [14]
2263Objective LensIn telescopes and microscopes, the optical component which receives light from the object and forms the first or primary image. In a camera, the image formed by the objective lens is the final image. In a telescope or microscope used visually, the image formed by the objective lens is magnified by the eyepiece. Also called objective or object-glass. [14]
2264ReconnaissanceIn surveying, a general examination or survey of the main features, or certain specific features, of a region, usually as a preliminary to a more detailed survey. An examination of an area to gain specific information, as the weather conditions, extent and nature of ice, etc. [14]
2265Sounding DatumSee datum. [14]
2266Magnetic NeedleA small, slender magnetized bar which tends to align itself with magnetic lines of force. [14]
2267Navigation MarkAn artificial or natural object of easily recognizable shape or colour, or both, situated in such a position that it may be identified on a chart or related to a known navigational instruction. Alternative term for visual aid to navigation. Includes both buoys and beacons (fixed artificial navigation mark). [14]
2268Collimation AxisThe line through the optical center of the objective lens perpendicular to the axis of rotation of the telescope. Also called axis of collimation. [14]
2269Error Of ClosureThe amount by which a quantity obtained by a series of related measurements differs from the true or fixed value of the same quantity. Also called closing error. [14]
2270Geodetic EquatorSee equator. [14]
2271Horizontal PlaneSee plane. [14]
2272Vertical ControlSee control. [14]
2273Eccentric StationA survey point over which an instrument is centered and observations are made, which is not in the same vertical line with the station it represents, and to which the observations will be reduced before being combined with observations at other stations. Also called false station or satellite station. See eccentric reduction. [14]
2274Greenhouse EffectThe warming of an atmosphere by its absorbing and emitting infrared radiation while allowing shortwave radiation to pass on through. The gases mainly responsible for the earth's atmospheric greenhouse effect are water vapor and carbon dioxide. See atmospheric greenhouse effect. [1]
2275Celestial MeridianSee meridian. [14]
2276Current: ReversingA tidal current which flows alternately in approximately opposite directions, with slack water at each reversal. Such currents occur principally in areas where motion is largely restricted to relatively narrow channels. Also called rectilinear current or rectilinear stream. [14]
2277Oblique PhotographSee photograph. [14]
2278Harmonic ConstituentOne of the harmonic elements in a mathematical expression for the tide-producing force, and in corresponding formulae for the tide or tidal current. Each constituent represents a periodic change or variation in the relative positions of the earth, sun and moon. Also called tidal constituent or component. [14]
2279True HorizonSee horizon. [14]
2280Acoustic WaveSee wave: sound. [14]
2281Apparent TimeSee time: apparent solar. [14]
2282Earth'S CrustSee crust. [14]
2283Fixed StationA radiolocation station which is situated in one particular spot throughout the period of its operation. As opposed to mobile station. Also called shore oceanography, a platform from which repeated observations are taken. These include coastal and island stations, light vessels, weather ships, automatic floating stations and ice islands. Also called fixed platform. [14]
2284Geodesic LineThe shortest line on a mathematically derived surface, between two points on that surface. A geodesic line on a reference spheroid is called a geodetic line. Also termed a geodesic. [14]
2285Least SquaresA method of adjusting observations in which the sum of the squares of all the deviations or residuals derived in fitting the observations to a mathematical model, is made a minimum. Least squares have also been designated as minimum squares. [14]
2286Nansen BottleA device used by oceanographers to obtain subsurface samples of sea water. The bottle is lowered by wire; its valves are open at both ends. It is then closed 'in situ' by allowing a weight (called a messenger) to slide down the wire and strike the reversing mechanism. This causes the bottle to turn upside down, closing the valves and reversing the reversing thermometers which are mounted in a special thermometer case on it. If, as is usually done, a series of bottles is lowered, then the reversal of each bottle releases another messenger to actuate the bottle beneath it. [14]
2287Nodical MonthSee month. [14]
2288Ocean CurrentSee current. [14]
2289Radial CentreIn photogrammetry, the selected point on a photograph from which radials (directions) to various image points are drawn or measured (i.e., the origin of radials). The radial center is either the principal point, the nadir point, the isocenter, or a substitute center. [14]
2290Radio StationA place equipped to transmit radio waves. Such a station may be either stationary or mobile, and may also be provided with a radio receiver. In British terminology, also called w/t station. [14]
2291Radius VectorA straight line connecting a fixed reference point or center with a second point, which may be moving. In astronomy, the expression is usually used to refer to the straight line connecting a cele-stial body with another which revolves around it, as a radius vector of the earth and moon. See coordinates: plane polar and coordinates: polar. [14]
2292Stand Of TideThe condition at high tide or low tide when there is no change in the height of the water. It may be called high water stand if it occurs at the time of high tide, and low water stand if it occurs at low tide. Also called stand. [14]
2293Station: TideA place where tidal observations are obtained. It is a primary tide station when continuous observations are available for a sufficient number of years to determine the characteristic tide features for the locality. A secondary tide station is operated during a short period of time to obtain data for a specific purpose. [14]
2294Swinging ShipThe process of placing a vessel on various headings and comparing magnetic compass readings with the corresponding magnetic directions, to determine deviation. This usually follows compass compensation (or adjustment), and is done to obtain information for making a deviation table. Also called compass calibration, or calibration of compass. See compensation of magnetic compass. [14]
2295Air NavigationSee navigation. [14]
2296Diurnal MotionThe apparent daily motion of a celestial body. [14]
2297Frequency BandSee band of frequency. [14]
2298Geodetic DatumSee datum. [14]
2299Gradient TintsSee hypsometric tints. [14]
2300Ground ControlSee control. [14]
2301On The QuarterBearing approximately 135° relative (on the starboard quarter) or 225° relative (on the port quarter). The expression is often used loosely for broad on the quarter, or bearing exactly 135° or 225° relative. See also broad on the quarter. [14]
2302Personal ErrorSee error. [14]
2303Prime VerticalSee prime vertical circle. [14]
2304Time: ApparentSee time: apparent solar. [14]
2305Wind DirectionThe direction from which the wind is blowing. [1]
2306Control Stationsee control point . [14]
2307Lens DistortionSee distortion. [14]
2308Modulating WaveSee wave. [14]
2309Parhelic CirclePhotometeor of the halo family, consisting of a white, horizontal circle, situated at the same angular height as the sun. [14]
2310Plane SurveyingSee surveying. [14]
2311Principal PlaneIn photogrammetry, the vertical plane through the internal perspective center containing the photograph perpendicular of a tilted photograph. [14]
2312Relative MotionMotion of one object or body relative to another. The expression is usually used in connection with problems involving motion of one craft, torpedo, or missile relative to another, the direction of such motion being called direction of relative movement, and the speed of such motion being called speed of relative movement or relative speed. Usually called apparent motion when applied to the change of position of a celestial body as observed from the earth. Also called relative movement. [14]
2313Station Pointer(British terminology). A metal instrument with three legs, a circle graduated in degrees and 1/2 degrees, and a vernier or micrometer for setting the angles. See also protractor: three arm. [14]
2314Axis Of HomologyIn photogrammetry, the intersection of the plane of the photograph with the horizontal plane of the map or the plane of reference of the ground. Corresponding lines in the photograph and map planes intersect on the axis of homology. Also called the axis of perspective, or map parallel. [14]
2315Central MeridianSee meridian: initial. [14]
2316Compass: HangingA compass having its binnacle overhead and its graduated card facing downward. Also referred to as overhead compass, or inverted compass. [14]
2317Direction FinderSee radio direction finder. [14]
2318Mean Water LevelThe average surface level of a body of water. [14]
2319Oscillatory WaveSee wave. [14]
2320Parallax: AnnualThe angle subtended at a celestial body by the radius of earth's orbit. Also called heliocentric parallax, or stellar parallax. [14]
2321Aid To NavigationA visual, acoustical, or radio device, external to a ship, designed to assist in determining a safe course or a vessel ™s position, or to warn of dangers and/or obstructions. Aids to navigation usually include buoys, beacons, fog signals, lights, radio beacons, leading marks, radio position fixing systems and gnss which are chart-related and assist safe navigation. [14]
2322Bottom: Nature OfThe feature of the bottom including the material of which it is composed and its physical characteristics. Also called character (or characteristics) of the bottom, or quality of the bottom. [14]
2323Geodetic MeridianSee meridian. [14]
2324Horizontal CircleSee circle. [14]
2325Parallactic AngleThat angle of the astronomical triangle at the celestial body; the angle between a body's hour circle and its vertical circle. Also called position photogrammetry, the angle subtended by the eye of the observer at the object viewed. Also called angle of convergence or angular parallax. [14]
2326Personal EquationThe time interval between the sensory perception of a phenomenon and the motor reaction thereto. Personal equation may be either positive or negative, as an observer may anticipate the occurrence of an event, or wait until he actually sees it occur before making a record. This is a syste-matic error, treated as of the constant type. It is a personal error, for which the term personal equation is reserved. It is of special significance in observations of time, made to determine chronometer correction. [14]
2327Reference StationSee station. [14]
2328Stereoscopic PairIn photogrammetry, two photographs of the same area taken from different air stations so as to afford stereoscopic vision. Frequently called a stereopair. [14]
2329Altitude: ApparentThe sextant altitude of a celestial body corrected for index error, dip (height of eye), and (for sun or moon only) semidiameter. Also called rectified altitude. [14]
2330Angle Of IncidenceThe angle between the line of motion of a ray and the perpendicular to a surface at the point of impingement. [14]
2331Geodetic LongitudeSee longitude. [14]
2332Greenwich MeridianSee meridian. [14]
2333Low Water IntervalSee lunitidal interval. [14]
2334PhototriangulationThe process for the extension of horizontal and/or vertical control whereby the measurements of angles and/or distances on overlapping photographs are related into a spatial solution using the perspective principles of the photographs. Generally, this process involves using aerial photographs, and is called aero triangulation, aerial triangulation, or photogrammetric extension. [14]
2335Temporal VariationSee magnetic temporal variation. [14]
2336Aberration Of LightAstronomy, the apparent displacement in position of a heavenly body caused by the combination of the velocity of light and that of an observer on the surface of the earth. Aberration of light due to the rotation of the earth on its axis is termeddiurnal aberration. That due to the revolution of the earth around the sun is termedannual aberration. In optics, failure of an optical system to bring all light rays received from a point object to a single image point or to a prescribed geometric position. Spherical aberration is caused by rays from various zones of a lens or mirror coming to focus at different distances from the lens or mirror. Chromatic aberration(orchromatism) is due to the differences in refraction of the coloured rays of the spectrum; those of each colour having a different focus. [14]
2337Closure Of TriangleSee error of closure of triangle. [14]
2338Radial TriangulationThe aero triangulation procedure, either graphical or analytical, in which directions from the radial center, or approximate radial center, of each overlapping photograph are used for horizontal-control extension by the successive intersection and resection of these direction lines. A radial triangulation also is correctly called a radial plot or a minor-control plot. If made by analytical methods, it is called an analytical radial triangulation. A radial triangulation is assumed to be graphical unless prefixed by the word analytical. [14]
2339Tape: Sag CorrectionThe difference between the effective length of a tape (or part of a tape) when supported continuously throughout its length and when supported at a limited number of independent points. Also called catenary correction. [14]
2340Electronic NavigationSee navigation. [14]
2341Spheroid Of ReferenceSee reference spheroid. [14]
2342Flattening Of The EarthThe ratio of the difference between the equatorial and polar radii of the earth (major and minor semi-axes of the spheroid) and its equatorial radius (major semi-axis). The flattening of the earth is the ellipticity of the spheroid. Also called compression. [14]
2343Weather ShipSee ocean station vessel. [14]
2344Aerial CameraSee camera. [14]
2345Aerial SurveySee survey. [14]
2346Annual ChangeSee magnetic annual change. [14]
2347Azimuth AngleAzimuth measured from 0° at the north or south reference direction clockwise or counter-clockwise through 90° or 180°. It is labelled with the reference direction as a prefix and the direction of measurement from the reference direction as a suffix. [14]
2348Azimuth: BackAn azimuth 180° from a given azimuth. In geodesy, the direction of the line ba as distinguished from the forward azimuth ab. The two differ by 180° plus the amount of convergence of the meridians between points a and b. Also called reverse azimuth. See azimuth: geodetic. [14]
2349Bottom SampleA portion of the sea bottom material brought to the surface for examination. See also core. [14]
2350Drift CurrentSee current. [14]
2351Floating MarkIn photogrammetry, a mark seen as occupying a position in the three-dimensional space formed by the stereoscopic fusion of a pair of photographs and used as a reference mark in examining or measuring the stereoscopic model. [14]
2352Heavenly BodySee celestial body. [14]
2353Horizon GlassThat glass of a marine sextant, attached to the frame, through which the horizon is observed. That half of this glass nearer the frame is silvered to form the horizon mirror for reflecting the image of a celestial body; the other half is clear. [14]
2354Initial PointThe origin of a system in the rectangular system of surveys of which a principal meridian and a base line constitute the axes for a given area. Also called fundamental point. [14]
2355Inner HarbourSee under harbor. [14]
2356Leading Marks(British terminology). Aids to navigation or other indicators so located as to indicate the path to be followed. Leading marks identify a leading line when they are in transit. See also range. [14]
2357Luminous FluxSee flux. [14]
2358MagnetizationThe degree to which a body is magnetized. The magnetic moment per unit volume. Also called intensity of magnetization. [14]
2359Plane SailingSee sailing. [14]
2360Position LineSee line of position. [14]
2361RadiolocationDetermination of position or of a line of position by means of radio equipment. See navigation: electronic. [14]
2362RectificationThe process of projecting a tilted or oblique photograph onto an horizontal reference plane, the angular relationship between the photograph and the plane being determined by ground methods. [14]
2363Regular ErrorSee error: systematic. [14]
2364Sidereal TimeSee time. [14]
2365Standing WaveSee wave. [14]
2366Survey SignalSee signal. [14]
2367Tide: DiurnalA tide in which the tidal cycle consists of one high water and one low water each tidal day. In British terminology also called single day tide. [14]
2368Tilting LevelSee levelling instrument: tilting level. [14]
2369Tropical YearSee year. [14]
2370True AltitudeSee altitude. [14]
2371Turning PointIn levelling, a point on which both a minus sight (foresight) and a plus sight (backsight) are taken on a line of direct levelling. In topographic surveys, any point on which the rod is held while the instrument (plane table) is moved to another station. In a traverse, any point of junction of two legs. Also called traverse point. [14]
2372Valley BreezeA local wind system of a mountain valley that blows downhill (mountain breeze) at night and uphill (valley breeze) during the day. See mountain breeze. [1]
2373Wave SpectrumIn ocean wave studies, a graph showing the distribution of wave heights with respect to frequency in a wave record. [14]
2374Wind SpectrumMeasure of the variance associated with the fluctuating wind speed per unit frequency band. NOTE 1 The wind spectrum is an expression of the dynamic properties of the wind (turbulence). It reflects the fluctuations about and in the same direction as a certain mean wind speed, usually the 1 h sustained wind speed. There is hence no direction variable associated with the wind spectrum within this document. NOTE 2 As the sustained wind speed varies with elevation, the wind spectrum is a function of elevation. [15]
2375Bearing: SonicA bearing determined by measuring the direction from which a sound wave is coming. Also called acoustic bearing. [14]
2376Climate ChangeA change in the long-term statistical average of weather elements such as temperature or precipitation sustained over several decades or longer. Climate change is also called climatic change. [1]
2377Current TablesTables listing predictions of the times and speeds of tidal currents at various places, and other pertinent information. Also called tidal current tables. [14]
2378Land TerritoryContinental or insular land masses that are above water at high tide. [14]
2379Low Water LineSee low water mark. [14]
2380Magnetic NorthSee north. [14]
2381Optical CentreThe point of intersection of lines which represent within the lens those rays whose emergent directions are parallel to their respective incident directions. This point lies on the optical axis. [14]
2382Optical SystemA series of lenses, apertures, prisms, mirrors, etc., so arranged as to perform a definite optical function. [14]
2383Phantom BottomA false bottom indicated by an echo sounder, some distance above the actual bottom. Such an indication, quite common in the deeper parts of the ocean, is due to large quantities of small organisms. Also called deep scattering layer (DSL) or false bottom. [14]
2384Plotting SheetA blank chart, usually on the Mercator projection, showing only the graticule and a compass rose, so that the plotting sheet can be used for any longitude. In hydrographic surveying, a working sheet on which the main stations of the survey are plotted. It forms the framework of the survey and provides the basis for accurately locating and plotting all the detail of the survey. See also lattice. [14]
2385Radar: PrimaryRadar which transmits a signal and receives the incident energy reflected from an object to detect the object in contrast to secondary radar which receives pulses from a transponder triggered by pulses transmitted from the radar. [14]
2386Reference LineAny line which can serve as a reference or base for the measurement of other quantities. Also called datum line. [14]
2387Secular ChangeAn increase or decrease of intensity and/or change of direction of the total magnetic field over a period of many years. [14]
2388Sound PressureSee pressure. [14]
2389Sound VelocityThe rate of motion at which sound energy moves through a medium. The velocity of sound in sea water is a function of temperature, salinity, and the changes in pressure associated with changes in depth. An increase in any of these factors tends to increase the velocity. [14]
2390Tropical StormOrganized thunderstorms with a cyclonic wind circulation between 35 and 64 knots. [1]
2391Vernal EquinoxThe equinox at which the sun approaches the northern hemisphere and passes directly over the equator. Occurs around march 20. [1]
2392Year: TropicalThe period of one revolution of the earth around the sun, with respect to the vernal equinox. Because of precession of the equinoxes, this is not 360° with respect to the stars, but 50".3 less. A tropical year is about 20 minutes shorter than a sidereal year, averaging 365 days, 5 hours, 48 minutes, and 46 seconds in 1900 and is decreasing at the rate of 0.00530 second annually. Also called astronomical, equinoctial, natural, or solar year. [14]
2393Bouguer AnomalyA difference between an observed value of gravity and a theoretical value at the point of observation, which has been corrected for the effect of the topography and elevation only, the topography being considered as resting on a plane of indefinite extent. [14]
2394Cardinal PointsThe four points of the horizon at the intersections of the horizon with the meridian and the prime vertical; the north, south, east and west points. [14]
2395Chart: GnomonicA chart on the gnomonic projection. Also called great circle chart. [14]
2396Chart: NauticalA chart specifically designed to meet the requirements of marine navigation, showing depths of water, nature of bottom, elevations, configuration and characteristics of coast, dangers and aids to navigation. Also called marine chart, hydrographic chart, or simply chart. [14]
2397Compass: LiquidA magnetic compass having a bowl completely filled with liquid in order to damp the swinging of the card. Sometimes called spirit compass, or wet compass. [14]
2398Coordinate AxesSee coordinates: plane rectangular. [14]
2399Current StationThe geographic location at which current observations are conducted. Also, the facilities used to make current observations. These may include a buoy, ground tackle, current meters, recording mechanism, and radio transmitter. See control current station and subordinate current station. [14]
2400Data ProcessingAny operation carried out with data usually with the help of a computer. [14]
2401Error: StandardThe square root of the arithmetic mean of squared deviations from the mean. Also called standard deviation, when the deviations do not represent errors, or root mean square error. [14]
2402Flight AltitudeSee altitude. [14]
2403Gust Wind SpeedMaximum value of the wind speed of a gust averaged over a short (3 s to 60 s) specified duration within a longer (1 min to 1 h) specified duration. NOTE 1 For design purposes, the specified duration depends on the dimensions and natural period of the (part of the) structure being designed such that the structure is designed for the most onerous conditions; thus, a small part of a structure is designed for a shorter gust wind speed duration (and hence a higher gust wind speed) than a larger (part of a) structure. NOTE 2 In practice, for design purposes, the gust wind speeds for different durations (e.g. 3 s, 5 s, 15 s, 60 s) are derived from the wind spectrum. [15]
2404High Water LineSee high water mark. [14]
2405Mean Solar TimeSee time. [14]
2406Navigation: AirThe navigation of aircraft. Occasionally called aerial navigation or navigation. See navigation: surface. [14]
2407Oblate SpheroidSee spheroid. [14]
2408OrthophotographA photographic copy, prepared from a perspective photograph, in which the displacements of images due to tilt and relief have been removed. [14]
2409Point Of OriginSee coordinates: origin of. [14]
2410Pole: CelestialEither of the two points of intersection of the celestial sphere and the extended axis of the earth, labelled n or s to indicate either the north celestial pole or the south celestial pole. [14]
2411Reference LevelSee datum: chart and datum: vertical control. [14]
2412Repetition RateThe rate at which recurrent signals are transmitted. Also called recurrence rate. [14]
2413Scatter DiagramJoint probability of two or more (metocean) parameters. NOTE A scatter diagram is especially used with wave parameters in the metocean context. The wave scatter diagram is commonly understood to be the probability of the joint occurrence of the significant wave height (Hs) and a representative period (Tz or Tp). [15]
2414Side Scan SonarA form of active sonar in which fixed acoustic beams are directed into the water perpendicularly to the direction of travel to scan the bottom and generate a record of the bottom configuration. [14]
2415Synodical MonthSee month. [14]
2416Time: GreenwichTime based upon the Greenwich meridian as reference. [14]
2417Topographic MapSee map. [14]
2418Transit PassageIn straits used for international navigation, all ships and aircraft enjoy the unimpeded right of transit passage. This means the freedom of navigation and overflight solely for the purpose of continuous and expeditious transit of the strait between one part of the high seas or an exclusive economic zone and another part of the high seas or an exclusive economic zone. See also innocent passage. [14]
2419Vectorial AngleSee coordinates: plane polar. [14]
2420Wire Drag SweepSee survey: wire drag. [14]
2421Altimeter: RadioAny instrument used for determining an aircraft's flight altitude by the measurement of time intervals between the emission and return of electromagnetic pulses. Also called pulse radio altimeter or radar altimeter. See altitude: flight. [14]
2422Annual VariationSee magnetic annual variation. [14]
2423Apparent HorizonSee horizon. [14]
2424Differential GpsDifferential gps is implemented by placing a gps monitor receiver at a precisely known location. Instead of computing a navigation fix, the monitor determines the range error to every gps satellite it can track. These ranging errors are then transmitted to local users where they are applied as corrections before computing the navigation result. [14]
2425Eccentric SignalA signal which is not in the same vertical line with the station it represents. [14]
2426Equilibrium TideSee tide. [14]
2427Greenhouse GasesGases in the earth's atmosphere, such as water vapor and carbon dioxide, that allow much of the sunlight to pass through but are strong absorbers of infrared energy emitted by the earth and the atmosphere. Other greenhouse gases include methane, nitrous oxide, fluorocarbons, and ozone. [1]
2428Magnetic ElementVariation, dip, or magnetic intensity. [14]
2429Micrometer ScrewA finely threaded screw of definite pitch, with a head graduated to show how much the screw has been moved in or out; used in micrometers. [14]
2430Radio NavigationSee navigation: electronic. [14]
2431Rear Nodal PointSee nodal point. [14]
2432Semidiurnal TideSee tide. [14]
2433Spring Low WaterSee mean low water springs. [14]
2434Systematic ErrorSee error. [14]
2435Weather AnalysisOperation of studying the general state of the atmosphere over a region, with respect to synoptic charts. Also called synoptic analysis. [14]
2436AerotriangulationSee phototriangulation. [14]
2437Bathymetric ChartSee chart. [14]
2438Celestial HorizonSee horizon. [14]
2439Centre Of GravitySee gravity. [14]
2440Geodetic LatitudeSee latitude. [14]
2441Geomagnetic FieldThe magnetic field of the earth. Also called terrestrial magnetic field or earth's magnetic field. [14]
2442Marine NavigationSee navigation. [14]
2443Navigation: SonicAvigation by means of sound waves whether or not they are within the audible range. Also called acoustic navigation. [14]
2444Parallax: DiurnalThe difference in the apparent direction or position of a celestial body as observed from the center of the earth and a point on its surface. This varies with the body's altitude and distance from the earth. Also called geocentric parallax. [14]
2445Stability: StaticState of hydrostatic equilibrium of the atmosphere in which a particle of air moved from its initial level undergoes a hydrostatic force which tends to restore it to this level. Also called hydrostatic stability. [14]
2446Strip CoordinatesSee coordinates. [14]
2447TelecommunicationAny transmission, emission, or reception of signs, signals, writing, images and sounds or intelligence of any nature by wire, radio, visual or other electromagnetic systems. [14]
2448Triangulation NetArcs of triangulation, sometimes with lines of traverse, connected together to form a system of loops or circuits extending over an area. Sometimes called tie net when used to tie small islands together. Also called traverse net or survey net. [14]
2449Aerial PhotographySee photography. [14]
2450Circle Of LatitudeA great circle of the celestial sphere through the ecliptic poles, and hence perpendicular to the plane of the ecliptic. [14]
2451Condition EquationSee equation. [14]
2452Continental MarginThe zone, generally consisting of shelf, slope and continental rise, separating the continent from the abyssal plain or deep sea floor. [14]
2453Dry Adiabatic RateThe rate of change of temperature in a rising or descending unsaturated air parcel. The rate of adiabatic cooling or warming is about 10°c per 1000 m (5.5°f per 1000 ft). [1]
2454Hayford'S SpheroidThe spheroid based upon an investigation made in 1909 by hayford, a geodesist of US Coast & geodetic survey, using the large triangulation net then existing in the US A., and taking into account the inequal density of the earth's crust. The geodetic and geophysical union (now the international union of geodesy and geophysics) adopted in 1924 the hayford's spheroid (with some slight modifications) as the international ellipsoid of reference. [14]
2455Infrared RadiationElectromagnetic radiation with wavelengths between about 0.7 and 1000 mm. This radiation is longer than visible radiation but shorter than microwave radiation. [1]
2456Luminous IntensitySee intensity. [14]
2457Photochemical SmogOriginally smog meant a mixture of smoke and fog. Today, smog means air that has restricted visibility due to pollution, or pollution formed in the presence of sunlight, photochemical smog. Also see smog. [1]
2458Thermometric DepthSee depth. [14]
2459Topographic SurveySee survey. [14]
2460Angle Of RefractionThe angle between a refracted ray and the perpendicular to the refraction surface. [14]
2461Figure Of The EarthThe defining elements of the mathematical surface which approximates the surface of the geoid. The figure of the earth has been proved to be approximately an oblate spheroid. See also geoid and spheroid. [14]
2462Geocentric ParallaxSee parallax: diurnal. [14]
2463Horizontal ParallaxSee parallax. [14]
2464Line Of CollimationSee collimation. [14]
2465Mercator ProjectionSee projection. [14]
2466Micrometer: TransitA form of registering micrometer with its movable wire placed in the focal plane of an astronomic transit and at right angles to the direction of motion of the image of a star which is observed at or near culmination. The transit micrometer is also termed an impersonal micrometer, because it almost completely eliminates the effect of the personal equation on time observations made with it. [14]
2467Reference DirectionA direction used as a basis for comparison of other directions. [14]
2468Topographic FeatureA single feature of the surface of the earth such as a mountain or valley. [14]
2469Coastwise NavigationSee navigation. [14]
2470Course: Great CircleThe direction of the great circle through the point of departure and the destination, expressed as the angular distance from a reference direction, usually north, to the direction of the great circle. The angle varies from point to point along the great circle. At the point of departure it is called initial great-circle course; at the destination it is called final great-circle course. [14]
2471Density Of SoundingsIntervals between lines of sounding and soundings in the same line. Density of soundings mostly depends on the scale and nature of the survey. Also called frequency of soundings. [14]
2472Hydrostatic PressureSee pressure. [14]
2473Interior OrientationSee orientation. [14]
2474Levelling InstrumentAn instrument designed for the accurate measurement of height differences by the process of levelling. Its essential parts are a telescope and a spirit level. Also called a level. [14]
2475Magnetism: PermanentMagnetism which is retained for long periods without appreciable reduction, unless the magnet is subjected to a demagnetizing force. Because of the slow dissipation of such magnetism, it is sometimes called subpermanent magnetism. [14]
2476Moist Adiabatic RateThe rate of change of temperature in a rising or descending saturated air parcel. The rate of cooling or warming varies but a common value of 6°c per 1000 m (3.3°f per 1000 ft) is used. [1]
2477Multiple Lens CameraSee camera. [14]
2478Nature Of The BottomSee bottom: nature of. [14]
2479Navigational WarningA message containing urgent information relevant to safe navigation broadcast to ships in accordance with the provisions of the international convention for the safety of life at sea, 1974, as amended. See coastal warning, local warning, navarea warning. [14]
2480Oceanographic SurveySee survey. [14]
2481Micrometer MicroscopeA filar micrometer so placed that its wire moves in the focal plane of a microscope. [14]
2482Projection: ConformalA projection in which all angles around any point are correctly represented. In such a projection the scale is the same in all directions about any point. Very small shapes are correctly represented, resulting in an orthomorphic projection. Hence, the terms of 'conformal' and 'orthomorphic' are used synonymously since neither characteristic can exist independently of the other. [14]
2483Reversing ThermometerSee thermometer. [14]
2484Triangulation StationSee station. [14]
2485Radio Direction FinderRadio receiving equipment which determines the direction of arrival of a signal by measuring the orientation of the wave front or of the magnetic or electric vector. Radio direction finders may be either manual or automatic. Also called direction finder. Formerly called radio compass. [14]
2486Reduction Of SoundingsThe correction of the observed depths, for the height of tide above or below the plane of reference at the time of sounding. Usually the term reduction of soundings does not cover corrections other than those due to tide. See correction of soundings, lead line correction and tide reducer. [14]
2487Tape: Grade CorrectionA correction applied to a distance measured on a slope to reduce it to a horizontal distance between the vertical lines through its end points. Also termed slope correction or correction for inclination of tape. [14]
2488Chart (Or Map): WeatherGeographical map on which meteorological conditions or elements are represented by figures, symbols, or isopleths. Also called synoptic chart (or map). [14]
2489Orthomorphic ProjectionSee projection: conformal. [14]
2490Mean Zero-Crossing PeriodAverage period of the (up or down) zero-crossing waves in a sea state. NOTE In practice the mean zero-crossing period is often estimated from the zeroth and second moments of the wave spectrum as T_z= T_2= √(m_0 (f)/m_2 (f) )=2π√(m_0 (ω)/m_2 (ω) ) [15]
2491Weather TideSee tide: windward. [14]
2492Abyssal PlainAn extensive, flat, gently sloping or nearly level region at abyssal depths. [14]
2493AccommodationThe faculty of the human eye to adjust itself to give sharp images for different object distances. In stereoscopy, the ability of the eyes to bring two images into superimposition for stereoscopic viewing. [14]
2494Aperture StopThe physical element (such as a diaphragm, or lens periphery) of an optical system which limits the size of the pencil of rays traversing the system. Also called thestop. Diameter of that part of the lens actually used. [14]
2495Apparent NoonSee noon. [14]
2496Apparent WindSee relative wind. [14]
2497Azimuth: GridThe angle in the plane of projection between a straight line and the y-axis of a plane-rectangular coordinate system. See bearing: grid. [14]
2498Blind RollersLong, high swells which have increased in height, almost to the breaking point, as they pass over shoals or run in shoaling water. Called blind seas in some localities. [14]
2499Boundary WaveSee wave: internal. [14]
2500Cadastral MapSee map. [14]
2501Closing ErrorSee error of closure. [14]
2502Codeclination90° minus the declination. See polar distance. [14]
2503Compound TideSee tide. [14]
2504Contact GlassSee focal plane plate. [14]
2505Contact PlateSee focal plane plate. [14]
2506Contact PrintSee print. [14]
2507Current CycleA complete set of tidal current conditions, as those occurring during a tidal day, lunar month, or metonic cycle. [14]
2508Diurnal RangeSee range. [14]
2509Doppler RadarA radar that determines the velocity of falling precipitation either toward or away from the radar unit by taking into account the doppler shift. [1]
2510Draft ForwardSee draft. [14]
2511Earth CurrentSee current(s): telluric. [14]
2512Elevated PoleSee pole. [14]
2513Exercise AreaAn area shown on charts within which naval, military or aerial exercises are carried out. Also called military practice area. [14]
2514False StationSee eccentric station. [14]
2515Farewell BuoyThe outermost buoy marking the entrance to a channel or harbor. Also called sea buoy. Known as landfall buoy in British terminology. [14]
2516Fiducial AxesIn photogrammetry, the lines joining opposite fiducial marks on a photograph. Also called photograph axes. [14]
2517First QuarterSee phases of the moon. [14]
2518Flood CurrentSee flood stream. [14]
2519Geodetic LineSee geodesic line. [14]
2520Grid MeridianSee meridian. [14]
2521Gyro RepeaterAn electrically operated dial repeating at a distance the indications of the master gyro compass. [14]
2522Harbour WorksPermanent man-made structures built along the coast which form an integral part of the harbor system such as jetties, moles, quays or other port facilities, coastal terminals, wharves, breakwaters, sea walls, etc. [14]
2523Heeling ErrorSee error. [14]
2524Horizon TraceIn photogrammetry, an imaginary line, in the plane of a photograph, which represents the image of the true horizon; it corresponds to the intersection of the plane of a photograph and the horizontal plane containing the internal perspective center or rear nodal point of the lens. Also called horizon line. [14]
2525Hummocked IceSea ice piled haphazardly one piece over another, and which may be weathered. [14]
2526Internal WaveSee wave. [14]
2527InterpolationThe process of determining intermediate values between given values in accordance with some known or assumed rate or system of variation. [14]
2528IsobathythermA line or surface showing the depths in oceans or lakes at which points have the same temperature. Isobathytherms are usually drawn to show cross sections of the water mass. [14]
2529Isogonic LineA line connecting points of equal magnetic variation. Also called isogonal (or isogonic). [14]
2530Junction BuoyA buoy marking the inner end of a middle ground. Usually called a middle ground buoy in British terminology, without regard to direction of travel. [14]
2531Latitude LineA line of position extending in a generally east-west direction. [14]
2532Local Warning a navigational warning which covers inshore waters, often within the limits of jurisdiction of a harbor or port authority. [14]
2533Lookout TowerAny tower surmounted by a small house in which a watch is habitually kept, as distinguished from an observation tower in which no watch is kept. [14]
2534Lost' Stationsee station: unrecoverable. [14]
2535Lower TransitSee meridian transit. [14]
2536Lunar EclipseSee eclipse. [14]
2537MagnificationThe apparent enlargement of anything. In optics, the term relates to the properties of lenses and lens systems to produce an image which differs in dimension from the related object. [14]
2538Marker BeaconA radio beacon which radiates a signal to define an area, as an aid to navigation. Usually called marker radio beacon or marker. [14]
2539Median ValleyThe axial depression of the mid-oceanic ridge system. See rift. [14]
2540Metonic CycleA period of 19 years, after which the various phases of the moon fall on approximately the same days of the year as in the previous cycle. [14]
2541Metric SystemA system of weights and measures, based upon the metre. [14]
2542Minor ControlSee control: photogrammetric. [14]
2543Mother VesselThe lead vessel when surveying with several vessels. [14]
2544Nocturnal ArcSee arc: astronomical. [14]
2545Observed TideThose data from tide observing equipment such as tide gauges, staffs, etc. "actual tides" is an expression often used in referring to "observed tides". [14]
2546Ocean StationAs defined by the international civil aviation organization, a specifically located area of ocean surface, roughly square and 200 nautical miles on a side. An ocean station vessel on patrol is said to be 'on station' when it is within the perimeter of the area. [14]
2547Offshore WindWind blowing from the land toward the sea. See land breeze. [14]
2548Outer HarbourSee harbor. [14]
2549Picture PlaneA plane upon which a system of lines or rays from an object to form an image or picture can be projected. In perspective drawing, the system of rays is understood to converge to a single point. In photogrammetry, the photograph is the picture plane. [14]
2550Pointing LineSee collimation: line of. [14]
2551Pressure WaveA short-period oscillation of pressure such as that associated with the propagation of sound through the atmosphere; a type of longitudinal wave. [14]
2552Radio BearingSee bearing. [14]
2553Radio CompassSee radio direction finder. [14]
2554Relative TiltSee tilt. [14]
2555Return Period(Also called recurrence interval.) The average time until the next occurrence of a defined event. When the time to the next occurrence has a geometric distribution, the return period is equal to the inverse of probability of the event occurring in the next time period, that is, T = 1/P, where T is the return period, in number of time intervals, and P is the probability of the next event's occurrence in a given time interval. [4]
2556ReverberationContinuation of radiant energy, particularly sound by multiple reflection. Sound scattered towards the source, principally from the ocean surface (surface reverberation) or bottom (bottom reverberation), and from small scattering sources in the medium such as bubbles of air and sus-pended solid matter (volume reverberation). [14]
2557Rotary StreamSee current: rotary. [14]
2558Shaded ReliefSee illuminated relief. [14]
2559Shore StationSee fixed station. [14]
2560Shoreline MapShoreline maps are the graphic representation of plane table and photogrammetric surveys. The maps contain graphic data relating to the shoreline, alongshore natural and manmade features, and a narrow zone of natural and manmade features inland from the shoreline. The original sources of a shoreline map are ground survey data and photographs. Utilizing these sources, photogrammetric map compilation techniques, and instruments, cartographers generate shoreline maps, overlays, and associated data. The data are primarily generated to support nautical chart maintenance, new nautical chart construction, and hydrographic survey operations. [14]
2561Side Echo(Es)See echo(es): false. [14]
2562Sidereal YearSee year. [14]
2563Slave StationIn a radio navigation system, the transmitting station controlled or triggered by the signal received from the master station. Often shortened to slave. [14]
2564Solar EclipseSee eclipse. [14]
2565Sound ChannelThe region in the water column where sound velocity first decreases to a minimum value with depth and then increases in value as a result of pressure. Above the minimum value sound rays are bent downward, and below the minimum value sound rays are bent upward; the rays are thus trapped in this channel. Sound travelling in a deep channel can be detected thousands of miles from the sound source. [14]
2566Sounding BookSee sounding record. [14]
2567Sounding LeadA lead used for determining depth of water. Also referred to as plummet. [14]
2568Sounding Mark(British terminology). A mark erected for control of sounding; its position is determined by plotting using intersections from sextant fixes. [14]
2569Sounding WireA wire used with a sounding machine in determining depth. [14]
2570Speed Of LensSee aperture: relative. [14]
2571Squaring DownSee squares: method of. [14]
2572Station ErrorSee deflection of the vertical. [14]
2573Swinging BuoySee compass adjustment buoy. [14]
2574Synoptic HourHour, expressed in terms of ut, at which, by international agreement, meteorological observations are made simultaneously throughout the globe. [14]
2575Tracing ClothA fine semitransparent linen or cotton cloth sized on one side and dull on the other. [14]
2576Tropical WaveA migratory wavelike disturbance in the tropical easterlies. Tropical waves occasionally intensify into tropical cyclones. They are also called easterly waves. [1]
2577Trunnion AxisSee axis: horizontal. [14]
2578Two-Way RouteA route within defined limits inside which two-way traffic is established, aimed at providing safe passage of ships through waters where navigation is difficult or dangerous. [14]
2579Upper TransitSee meridian transit. [14]
2580Vertical AxisSee axis. [14]
2581Virtual ImageSee image. [14]
2582Wind VelocitySee wind vector. [14]
2583Wire SoundingSee sounding. [14]
2584Air PhotographSee photograph: aerial. [14]
2585Air PollutantsSolid, liquid, or gaseous airborne substances that occur in concentrations high enough to threaten the health of people and animals, to harm vegetation and structures, or to toxify a given environment. [1]
2586Arm Of The SeaA narrow portion of the sea projecting from the main body. The expression is often shortened to 'arm'. [14]
2587AudiofrequencyA frequency within the audible range, about 20 to 20.000 cycles per second. Also called sonic frequency. [14]
2588Azimuth CircleSee bearing circle. [14]
2589Base ApparatusAny apparatus designed for use in measuring with accuracy and precision the length of a base in triangulation, or the length of a line in traverse. [14]
2590Bearing: RhumbThe direction of a rhumb line through two terrestrial points expressed as angular distance from a reference direction. Also called Mercatorial (or Mercator) bearing. [14]
2591Brackish WaterWater in which salinity values range from approximately 0.50 to 17.00 parts per thousand. [14]
2592Camera StationSee air station. [14]
2593Change Of TideA reversal of the direction of motion (rising or falling) of a tide. The expression is also sometimes applied to a reversal in the set of a tidal current. Also called turn of the tide. See also stand of tide. [14]
2594Coplane: BasalIn photogrammetry, the condition of exposure of a pair of photographs in which the two photographs lie in a common plane parallel to the air base. If the air base is horizontal, the photographs are said to be exposed in horizontal coplane. [14]
2595Dip CorrectionThat correction to sextant altitude due to the dip of the horizon. Also called height of eye correction. [14]
2596Drying HeightsHeights above sounding datum, of any areas (banks, foreshores, rocks, etc.) Which dry at low water. [14]
2597Eddy ViscosityThe turbulent transfer of momentum by eddies giving rise to an internal fluid friction, in a manner analogous to the action of molecular viscosity in laminar flow, but taking place on a much larger scale. The value of the coefficient of eddy viscosity is of the order 104 square centimeters per second. [14]
2598Entrance PupilThe image of the aperture stop formed by all the lens elements on the object side of the aperture stop. [14]
2599Error EquationSee equation. [14]
2600External ErrorSee error: theoretical. [14]
2601Fiducial MarksIn photogrammetry, index marks, usually four, which are rigidly connected with the camera lens through the camera body and which form images on the negative and usually define the principal point of the photograph. Also marks, usually four in number, in any instrument, which define the axes whose intersection fixes the principal point of a photograph and fulfills the requirements of interior orientation. In surveying, an index line or point. A line or point used as a basis of reference. [14]
2602Fishing GroundA water area in which fishing is frequently carried on. Also called fishing area or fishing zone. [14]
2603Fixed PlatformSee fixed station. [14]
2604Floating PointIn computer systems the type of numeric data approximately representing real numbers. A floating point number is composed of an exponent and a mantissa specifying the numerical value relative to the exponent. Owing to the limited length of a computer word, the floating point representation may cause a loss of precision. [14]
2605Freezing PointTemperature of solidification of a liquid in given conditions. [14]
2606Friction LayerAtmospheric layer extending from the earth's surface and of depth about 600 to 800 m, within which air motion is affected significantly by surface friction. Above this layer lies the 'free atmosphere'. [14]
2607Global WarmingIncreasing global surface air temperatures that show up in the climate record. The term global warming is usually attributed to human activities, such as increasing concentrations of greenhouse gases from automobiles and industrial processes, for example. [1]
2608Greenwich TimeSee time. [14]
2609Heeling MagnetA permanent magnet placed vertically in a tube under the center of a marine magnetic compass, to correct for heeling error. [14]
2610Hertzian WavesSee wave(s): radio. [14]
2611Holding GroundAn expression usually used with a modifying adjective to indicate the quality of the holding power of the material constituting the bottom of an anchorage; e.g., of good (or poor) holding ground. [14]
2612Index ContoursCertain contour lines (usually every fifth) accentuated by use of a line heavier than the intervening ones. [14]
2613List Of LightsA publication tabulating navigational lights, with their locations, candle powers, characteristics, etc. To assist in their identification, and details of any accompanying fog signal. A list of lights may contain other information useful to a navigator. Also called light list. [14]
2614Local MeridianSee meridian. [14]
2615Longitude LineA line of position extending in a generally north-south direction. [14]
2616Luminous RangeSee range. [14]
2617Marine SextantSee sextant. [14]
2618Mass TransportIn oceanography, the voluminous transfer of water from one region to another. [14]
2619Master CompassSee compass. [14]
2620Masthead AngleThe vertical angle subtended by a ship's mast. [14]
2621Modulated WaveSee wave. [14]
2622Month: NodicalThe interval of time between two successive passages of the moon through the same node of its orbit. The length of the nodical month averages 27.21222 mean solar days. Also called draconic month. [14]
2623Mountain RangeA line of mountains. Also referred to as range of mountains. [14]
2624Neap Low WaterSee mean low water neaps. [14]
2625PhotosynthesisThe formation of carbohydrates in living plants from water and carbon dioxide, by the action of sunlight on the chlorophyll. [14]
2626Polar DistanceAngular distance from a celestial pole; the arc of an hour circle between a celestial pole, usually the elevated pole, and a point on the celestial sphere, measured from the celestial pole through 180°. When the declination and latitude are of the same name, codeclination is the same as polar distance measured from the elevated pole. [14]
2627Position AngleSee parallactic angle. [14]
2628Prime MeridianSee meridian. [14]
2629Probable ErrorSee error. [14]
2630Range: DiurnalThe difference in height between mean higher high water and mean lower low water. Also called great diurnal range. [14]
2631Reference MarkIn surveying, a supplementary mark of permanent character close to a station or to a base terminal, to which it is related by an accurately measured distance and direction, and/or a difference in elevation. [14]
2632Reference TapeA base tape employed solely for use as a standard of comparison. Also called standard tape. [14]
2633Relative SpeedSee relative movement. [14]
2634Remote SensingThe measurement or acquisition of information of some property of an object or phenomenon by a recording device that is not in physical or infinite contact with the object or phenomenon under study. Sometimes restricted to the practice of data collection in the wavelengths from ultraviolet to radio regions. [14]
2635Residual ErrorSee error. [14]
2636Safety FairwayAn area within which permits are not granted for the erection of oil or gas related structures. The use of a safety fairway is not usually mandatory, but is recommended. [14]
2637Satellite BoatA subsidiary boat used in parallel sounding. [14]
2638Scale ParallelUsed in Mercator projection charts to indicate the parallel at which the noted scale of the chart is exact. The scale parallel itself need not necessarily be depicted within the chart. [14]
2639Secondary PortSee station: subordinate. [14]
2640Semimajor AxisOne-half of the longest diameter of an ellipse. [14]
2641Semiminor AxisOne-half of the shortest diameter of an ellipse. [14]
2642Sidereal MonthSee month. [14]
2643Slant DistanceThe straight-line distance from one point to another, as contrasted with ground distance. This expression is customarily used only when the straight line connecting the two points lies above the surface of the earth. Also called slant range. [14]
2644Solar ConstantThe rate at which solar energy is received on a surface at the outer edge of the atmosphere perpendicular to the sun's rays when the earth is at a mean distance from the sun. The value of the solar constant is about two calories per square centimeter per minute or about 1376 w/m2 in the si system of measurement. [1]
2645Sounding BoardSee field board. [14]
2646Source DiagramA small scale map or index placed on a chart to indicate the coverage area, and textual description, of the source data, used in construction of the chart. Also called compilation diagram. [14]
2647Speed: AngularChange of direction per unit time. Also called angular rate or angular velocity. [14]
2648Spirit CompassSee compass: liquid. [14]
2649Spot ElevationA point on a map or chart whose elevation is noted. It is usually indicated by a dot accompanied by a number indicating the vertical distance of the point from the reference datum. Spot elevations are used principally to indicate points higher than their surroundings. Also called spot height. [14]
2650TransformationIn photogrammetry, the process of projecting a photograph (mathematically, graphically, or photographically) from its plane onto another plane by translation, rotation, and/or scale change. The projection is made onto a plane determined by the angular relations of the camera axes and not necessarily onto a horizontal plane. See also rectification. [14]
2651Tropical MonthSee month. [14]
2652Vanishing TideSee tide. [14]
2653Wave: StandingA type of wave in which the surface of the water oscillates vertically between fixed points, called nodes, without progression. The points of maximum vertical rise and fall are called antinodes or loops. At the nodes, the underlying water particles exhibit no vertical motion but maximum horizontal motion. At the antinodes the underlying water particles have no horizontal motion and maximum vertical motion. They may be the result of two equal progressive wave trains travelling through each other in opposite directions. Also called stationary wave. [14]
2654Well: OffshoreA borehole that produces or is capable of producing oil or natural gas. [14]
2655Acid DepositionThe depositing of acidic particles (usually sulfuric acid and nitric acid) at the earth's surface. Acid deposition occurs in dry form (dry deposition) or wet form (wet deposition). Acid rain and acid precipitation often denote wet deposition. (see acid rain.) [1]
2656Age Of The MoonThe elapsed time since the last new moon; usually expressed in days and fractions of a day. See phases of the moon. [14]
2657Aneroid CapsuleMetallic capsule, of thin sides, partially evacuated by a fixed amount, carrying an arrangement to prevent its collapsing under atmospheric pressure, and whose shape changes in accordance with changes of this pressure. [14]
2658Apparent MotionSee relative motion. [14]
2659Bathymetric MapA topographic map of the ocean floor, or the bed of a lake. A topographic chart of the bed of a body of water, or a part of it. Generally, bathymetric maps show depths by contour lines and gradient tints. [14]
2660Coastal WarningA navigational warning, or in-force bulletin, promulgated as part of a numbered series by a national coordinator. [14]
2661Compass BearingSee bearing. [14]
2662Contiguous ZoneA zone contiguous to a coastal state's territorial sea, which may not extend beyond 24 nautical miles from the baselines from which the breadth of the territorial sea is measured. The coastal state may exercise certain control in this zone subject to the provisions of international law. [14]
2663Course RecorderA device which makes an automatic record of the headings of a vessel. See dead reckoning tracer. [14]
2664Cust ProtractorSee protractor. [14]
2665Datum: GeodeticA set of parameters specifying the reference surface or the reference coordinate system used for geodetic control in the calculation of coordinates of points on the earth. Commonly datums are defined as horizontal and vertical datums separately. For a local geodetic datum the reference surface is defined by five parameters: the latitude and longitude of an initial point, the azimuth of a line from this point, and the parameters of the reference spheroid. Absolute datums specify the initial point of the reference ellipsoid to be (ideally) located at the earth's center of mass. For modern reference systems using datum information given by satellites additional parameters are defined, e.g. Gravity models. See also horizontal control datum. [14]
2666Datum: SoundingThe horizontal plane or tidal datum to which the soundings on a hydrographic survey are reduced. Also called datum for sounding reduction. [14]
2667Diurnal CurrentSee current. [14]
2668Eccentric AngleSee latitude: parametric. [14]
2669Elevation TintsSee hypsometric tints. [14]
2670Equal AltitudesTwo altitudes of the same celestial body observed east and then west of the meridian, when it has reached the same value. The expression also applies to the practice, essentially obsolete, of determining the instant of local apparent noon by observing equal altitudes of the sun. [14]
2671Equisignal ZoneSee zone. [14]
2672Forward AzimuthSee azimuth: geodetic. [14]
2673Geodetic SurveySee survey. [14]
2674Gravity AnomalyThe difference between the observed gravity value properly reduced to sea level and the theoretical gravity obtained from gravity formula. See bouguer anomaly, free-air anomaly, isostatic anomaly. [14]
2675Half Tide LevelThe level midway between mean high water and mean low water. It may differ slightly from mean sea level. Also called mean tide level. [14]
2676Hurricane WatchA hurricane watch indicates that a hurricane poses a threat to an area (often within several days) and residents of the watch area should be prepared. [1]
2677Inferior MirageSee mirage. [14]
2678Internal WatersWaters on the landward side of the baseline of the territorial sea and landlocked waters within the state. [14]
2679Inversion LayerAtmospheric layer, horizontal or approximately so, in which the temperature increases with increasing height. See temperature inversion. [14]
2680Irregular ErrorSee error: accidental. [14]
2681Laplace AzimuthSee azimuth. [14]
2682Laplace StationSee station. [14]
2683Light: RhythmicA signal light that shows intermittently, in any given direction, with a regular periodicity. Also referred to as intermittent light. [14]
2684Linear ParallaxSee parallax: absolute stereoscopic. [14]
2685Local Mean TimeSee time. [14]
2686Luminous SignalSee signal. [14]
2687Mean Wind SpeedTime-averaged wind speed, averaged over a specified time interval. NOTE The mean wind speed varies with elevation above mean sea level and the averaging time interval; a standard reference elevation is 10 m and a standard time interval is 1 h. See also Sustained Wind Speed and Gust Wind Speed. [15]
2688Micrometer CombA notched scale placed at right angles to the movable wire of a micrometer and so designed that one turn of the micrometer screw will move the micrometer wire across one notch of the comb; the central notch of the comb in conjunction with the zero of the micrometer head furnishes a fiducial point from which all micrometer readings are reckoned. The comb is used for keeping count of whole turns of the micrometer screw, parts of turns being read on the graduated micrometer head. [14]
2689Minus SoundingsSee sounding. [14]
2690Navarea WarningA navigational warning or in-force bulletin promulgated as part of a numbered series by a navarea co-ordinator. [14]
2691Neap High WaterSee mean high water neaps. [14]
2692Normal EquationSee equation. [14]
2693Numerical ScaleSee scale: natural. [14]
2694Perspective RayA line joining a perspective center and a point object. [14]
2695PhototheodoliteA ground-survey instrument combining a theodolite and a surveying camera in which the relation-ship between the camera axis and the line of collimation of the theodolite can be measured. [14]
2696Polyvinyl CorerSee corer: hydroplastic. [14]
2697Position CircleSee circle of position. [14]
2698Progress SketchA map or sketch showing work accomplished. In triangulation and traverse, each point established is shown on the progress sketch as well as lines observed over and bases measured. In a levelling survey, the progress sketch shows the route followed and the towns passed through, but not necessarily the locations of the bench marks. [14]
2699Radar AltimeterSee altimeter: radio. [14]
2700Radio AltimeterSee altimeter. [14]
2701Rainfall AmountThickness of the layer of water which accumulates on a horizontal surface, as the result of one or more falls of precipitation, in the absence of infiltration or evaporation, and if any part of the precipitation falling as snow or ice were melted. Also called amount of precipitation. [14]
2702Range: LuminousThe greatest distance at which a light can be seen merely as a function of its luminous intensity, the meteorological visibility, and the sensitivity of the observer's eye. [14]
2703Recurrence RateSee repetition rate. [14]
2704Reference PlaneSee datum: chart, and datum: vertical control. [14]
2705Reference PointAny point which can serve as a reference or base for the measurement of other quantities. Also called datum point. [14]
2706Reflected LightThe process whereby a surface turns back a portion of the radiation that strikes it. When the radiation that is turned back (reflected) from the surface is visible light, the radiation is referred to as reflected light. See reflection. [1]
2707Reported DangerAn object dangerous to navigation which is shown on a chart but the existence of which has not been confirmed. Sometimes called vigia. [14]
2708Restricted AreaA specified area designated by appropriate authority within which access or navigation is restricted in accordance with certain specified conditions. [14]
2709Right AscensionAngular distance east of the vernal equinox; the arc of the celestial equator, or the angle at the celestial pole, between the hour circle of the vernal equinox and the hour circle of a point on the celestial sphere, measured eastward from the hour circle of the vernal equinox through 24 hours. [14]
2710Routeing SystemAny system of one or more routes or routing measures aimed at reducing the risk of casualties; it includes traffic separation schemes, two-way routes, recommended tracks, areas to be avoided, inshore traffic zones, roundabouts, precautionary areas and deep-water routes. [14]
2711Sea Level DatumA determination of mean sea level that has been adopted as a standard datum of heights although it may differ from a later determination over a longer period of time. [14]
2712Subastral PointSee substellar point. [14]
2713Subsurface MarkSee underground mark. [14]
2714Supercell StormA severe thunderstorm that consists primarily of a single rotating updraft. Its organized internal structure allows the storm to maintain itself for several hours. Supercell storms can produce large hail and dangerous tornadoes. [1]
2715Superior MirageA refraction phenomenon that makes an object appear to be displaced from its true position. When an object appears higher than it actually is, it is called a superior mirage. When an object appears lower than it actually is, it is an inferior mirage. See mirage. [1]
2716Three-Point FixSee fix. [14]
2717Tidal ConstantsTidal relations that remain essentially constant for any particular locality. Tidal constants are classed as harmonic and non-harmonic, the harmonic constants consisting of the amplitudes and epochs, and the non-harmonic constants including those values determined directly from observations, such as tidal ranges and intervals. [14]
2718Track Made GoodSee track. [14]
2719Tracking CameraSee camera: ballistic. [14]
2720Transition ZoneThe water area between two opposing currents manifested by eddies, upwelling, rips, and similar turbulent conditions occurring either vertically or horizontally; or a zone between two water masses of differing physical characteristics such as temperature and/or salinity. [14]
2721Transverse WaveSee wave. [14]
2722Travelling WaveSee wave: progressive. [14]
2723Trochoidal WaveSee wave. [14]
2724True Solar TimeSee time: apparent solar. [14]
2725Variation: GridAngular difference in direction between grid north and magnetic north. It is measured east or west from grid north. Also called grivation, or grid magnetic angle. [14]
2726Wave RefractionSee refraction of water waves. [14]
2727Wave: ModulatedA wave which varies in some characteristic in accordance with the variations of a modulating wave. See wave: continuous. [14]
2728Winter SolsticeApproximately December 21 in the northern hemisphere when the sun is lowest in the sky and directly overhead at latitude 231d2°s, the tropic of Capricorn. [1]
2729Angular ParallaxSee parallactic angle. [14]
2730Angular VelocitySee speed: angular. [14]
2731Assumed PositionSee position. [14]
2732Astro-NavigationSee navigation: celestial. [14]
2733Benthic DivisionIn the classification of the marine environment and its inhabitants, a primary division of the sea which includes all of the ocean floor. The other primary division of the sea is the pelagic division. [14]
2734Binocular VisionSimultaneous vision with both eyes. [14]
2735Compass MeridianSee meridian. [14]
2736Compass RepeaterA device for repeating at a distance the indications of the master compass. [14]
2737Continental Risea gentle slope rising from the oceanic depths towards the foot of a continental slope. [14]
2738Conversion AngleSee arc to chord correction. [14]
2739Conversion ScaleA scale for the conversion of units of one measurement to equivalent units of another measurement. See nomogram. [14]
2740Conversion TableA table for the conversion of units of one measurement to equivalent units of another measurement. See nomogram. [14]
2741Corrector MagnetSee compensator: magnetic. [14]
2742Course Made GoodThe actual track made good over the ground (seabed); the direction of the point of arrival from the point of departure. Course made good is the direction component of the resultant ship's velocity and the water current. Course made good should not be confused with heading, or ship's head. [14]
2743Deep Ocean FloorThe surface lying at the bottom of the deep ocean. [14]
2744Depth Of The SeaThe vertical distance from the water surface to the sea bottom. [14]
2745Digital ComputerSee computer. [14]
2746Diurnal ParallaxSee parallax. [14]
2747Duration Of FallSee duration of rise and fall. [14]
2748Electronic ChartA very broad term to describe the data, the software, and sometimes the electronic system, capable of displaying chart information. [14]
2749Exposure StationSee air station. [14]
2750Fixed Angle Plot(British terminology). Plot prepared in advance for use in normal sounding in lieu of a station pointer. The arcs of equal angle subtended by selected marks are drawn on the sounding board at convenient intervals depending on the scale. The observed sextant angles can then be plotted in the field by visual inspection. See also circle sheet, and sounding: fixed angle. [14]
2751Geodetic AzimuthSee azimuth. [14]
2752Geodetic ControlSee control. [14]
2753Graduation ErrorSee error of graduation. [14]
2754Grid CoordinatesSee coordinates. [14]
2755Half ConvergencySee arc to chord correction. [14]
2756HygrothermographInstrument resulting from the combination of a thermograph and a hygrograph and furnishing, on the same diagram, simultaneous time recording of atmospheric temperature and humidity. Also called thermohygrograph. [14]
2757Inferior TransitSee meridian transit. [14]
2758Initial MeridianSee meridian. [14]
2759Inland Ice SheetAn ice sheet of considerable thickness and more than about 50,000 sq. Km in area, resting on rock. Inland ice sheets near sea level may merge into ice shelves. [14]
2760Intercept MethodSee marcq st. Hilaire method. [14]
2761Local AttractionLocal magnetic disturbance. Also deflection of the plumb line due to a mountain or other irregularity in earth's crust. [14]
2762Magnetic AnomalySee local magnetic disturbance. [14]
2763Magnetic BearingSee bearing. [14]
2764MagnetostrictionThe phenomenon wherein ferromagnetic material experience an elastic strain when subjected to an external magnetic field. Also, the converse phenomenon in which mechanical stresses cause a change in the magnetic induction of a ferromagnetic material. [14]
2765Meridian PassageSee meridian transit. [14]
2766Meridional PartsThe length of the arc of a meridian between the equator and a given parallel on a Mercator chart, expressed in units of 1 minute of longitude at the equator. [14]
2767Nautical AlmanacSee almanac. [14]
2768Navigation: LandNavigation of vehicles across land or ice. The expression is generally used in connection with the crossing of a region devoid of roads or landmarks, so that methods similar to those employed in air or marine navigation must be employed. [14]
2769Navigational Aid(US Terminology). An instrument, device, chart, method, etc., intended to assist in the navigation of a craft. An aid to navigation is a navigational aid but the latter expression should not be confused with the former which refers only to devices external to a craft. [14]
2770Neritic ProvinceSee pelagic division. [14]
2771Oceanic ProvinceSee pelagic division. [14]
2772Optical ParallaxSee parallax: instrumental. [14]
2773Photograph NadirSee nadir. [14]
2774Rational HorizonSee horizon: celestial. [14]
2775Residual CurrentPart of the total current that is not constituted from harmonic tidal components (i.e. the tidal stream). NOTE Residual currents are caused by a variety of physical mechanisms and comprise a large range of natural frequencies and magnitudes in different parts of the world. [15]
2776Responder BeaconSee transponder beacon. [14]
2777Small Correction(British terminology). Minor corrections made to the chart plates. They have been discontinued since 1954. [14]
2778Spherical ExcessThe amount by which the sum of the three angles of a spherical triangle exceeds 180°. [14]
2779Spheroid: OblateAn ellipsoid of revolution, the minor axis of which is the axis of revolution. The earth is approximately an oblate spheroid. [14]
2780Spirit LevellingSee levelling. [14]
2781Static StabilitySee stability. [14]
2782Subpolar ClimateA climate observed in the northern hemisphere that borders the polar climate. It is characterized by severely cold winters and short, cool summers. Also known as taiga climate and boreal climate. [1]
2783Subtropical HighA semipermanent high in the subtropical high-pressure belt centered near 30° latitude. The Bermuda high is located over the Atlantic Ocean off the east coast of north america. The pacific high is located off the west coast of north america. [1]
2784Sulfate AerosolsTiny suspended solid particles (dust, smoke, etc.) Or liquid droplets that enter the atmosphere from either natural or human (anthropogenic) sources, such as the burning of fossil fuels. Sulfur-containing fossil fuels, such as coal, produce sulfate aerosols. See aerosols. [1]
2785Survey: GeodeticA survey in which the figure and size of the earth is considered. It is applicable for large areas and long lines and is used for the precise location of basic points suitable for controlling other surveys. [14]
2786Tidal DifferenceDifference in time or height of a high or low water at a subordinate station and at a reference station for which predictions are given in the tide tables. The difference, when applied according to sign to the prediction at the reference station, gives the corresponding time or height for the subordinate station. [14]
2787Vibrating NeedleA magnetic needle used in compass adjustment to find the relative intensity of the horizontal components of the earth's magnetic field and the magnetic field at the compass location. Also called horizontal force instrument. See compensation of magnetic compass. [14]
2788Water EquivalentThe depth of water that would result from the melting of a snow sample. Typically about 10 inches of snow will melt to 1 inch of water, producing a water equivalent of 10 to 1. [1]
2789Wave: ContinuousA series of waves of like amplitude and frequency. See wave: modulated, pulse. [14]
2790Weather ElementsThe elements of air temperature, air pressure, humidity, clouds, precipitation, visibility, and wind that determine the present state of the atmosphere, the weather. [1]
2791Well: ProductionA borehole, producing oil or natural gas, which is covered by a seabed installation of valves and pipelines for the controlled removal of the product. See also sub-sea completion. [14]
2792Wind CirculationThe flow of air through a given area. [14]
2793Adiabatic ProcessA thermodynamic change of state of a system in which there is no transfer of heat or mass across the boundaries of the system. In an adiabatic process, compression always results in warming, expansion in cooling. [14]
2794Aneroid BarometerAn instrument designed to measure atmospheric pressure. It contains no liquid. [1]
2795Annual AberrationSee aberration of light. [14]
2796Anomalistic MonthSee month. [14]
2797Bilby Steel TowerA demountable and transportable triangulation tower for elevating a theodolite and luminous signals above the ground, designed by j.s. Bilby, usc&gs. [14]
2798Centrifugal ForceThe force with which a body moving under constraint along a curved path reacts to the constraint. Equal and opposite to the centripetal force. [14]
2799Collimation ErrorSee error of collimation. [14]
2800Compass CorrectorSee compensator: magnetic. [14]
2801Compass: SteeringThe compass placed next to the steering wheel, by which the course is steered. See also steering repeater. [14]
2802Computer GraphicsAll methods and techniques used in computer sciences to represent data in graphical form and to process images. [14]
2803Controlled MosaicSee mosaic. [14]
2804Current DirectionSee direction of current. [14]
2805Daily RetardationThe amount of time by which corresponding tidal phases grow later day by day (averages approximately 50 minutes). [14]
2806Datum For HeightsSee datum: vertical control. [14]
2807Discoloured WaterUnnatural coloured areas in the sea due to the existence of shoals. Sea water having a colour other than the blues and greens normally seen. Variations of the colors red, yellow, green and brown, as well as black and white, have been reported. Discolorations may appear in patches, streaks, or large areas and may be caused by concentrations of inorganic or organic particles or plankton. See red tide. [14]
2808False CoordinatesSee coordinates. [14]
2809Field ExaminationA special purpose hydrographic, wire drag, or side scan sonar survey of very limited area; i.e., usually an investigation of one or more individual and scattered items. [14]
2810Geodetic ParallelSee parallel. [14]
2811Ground PhotographSee photograph: terrestrial. [14]
2812Horizon: ApparentThe irregular line along which rays from the point of observation are tangent to the surface of the earth. Also called visible (or local) horizon. [14]
2813Hyperbolic SystemRadiolocation system supplying hyperbolic lines of position. [14]
2814Indian Tide PlaneSee indian spring low water. [14]
2815Induced MagnetismSee magnetism. [14]
2816Intersected PointSee station: intersection. [14]
2817Logarithmic ScaleSee scale. [14]
2818Longshore CurrentA current paralleling the shore largely within the surf zone. It is caused by the excess water brought to the zone by the small net mass transport of wind waves. Longshore currents feed into rip currents. [14]
2819Magnetic MeridianSee meridian. [14]
2820Meridian AltitudeSee altitude. [14]
2821Meridian DistanceIn astronomy, the hour angle of a celestial body when close to but not exactly on the astronomical meridian. In plane surveying, the perpendicular distance in a horizontal plane of a point from a meridian of reference. [14]
2822Negative AltitudeSee angle of depression. [14]
2823No Anchoring AreaA routing measure comprising an area within defined limits where anchoring is hazardous or could result in unacceptable damage to the marine environment. Anchoring in a no anchoring area should be avoided by all ships or certain classes of ships, except in case of immediate danger to the ship or the persons on board. [14]
2824Nyquist FrequencyThe highest frequency that may be uniquely resolved in a time series from a given sampling interval. The nyquist frequency is equal to twice the sampling interval. Analyzing frequencies for which the nyquist criterion is not met leads to aliasing. [14]
2825Observed AltitudeSee altitude. [14]
2826Personal ParallaxSee parallax: instrumental. [14]
2827Perspective PlaneAny plane containing the perspective center. The intersection of a perspective plane and the ground will always appear as a straight line on an aerial photograph. [14]
2828Plane CoordinatesSee coordinates: plane rectangular. [14]
2829Point Of SymmetryThe point in the focal plane of a camera about which all lens distortions are symmetrical. If the lens were perfectly mounted, the point of symmetry would coincide with the principal point. [14]
2830Polar CoordinatesSee coordinates. [14]
2831Positive AltitudeSee angle of elevation. [14]
2832Radiative ForcingAn increase (positive) or a decrease (negative) in net radiant energy observed over an area at the tropopause. An increase in radiative forcing may induce surface warming, whereas a decrease may induce surface cooling. [1]
2833Recommended TrackA route which has been specially examined to ensure so far as possible that it is free of dangers and along which, ships are advised to navigate. [14]
2834Relative HumidityThe ratio of the actual vapor pressure to the vapor pressure corresponding to saturation at the prevailing temperature. [14]
2835Run Of MicrometerSee error of run. [14]
2836Spheroid: ProlateAn ellipsoid of revolution, the major axis of which is the axis of revolution. [14]
2837Spirit Level AxisSee axis of spirit level. [14]
2838Spring High WaterSee mean high water springs. [14]
2839Tidal Constituentalso known as a Constituent Tide; One of the harmonic elements in a mathematical expression for the tide-producing force and in corresponding formulas for the tide or tidal current. Each constituent represents a periodic change or variation in the relative positions of the Earth, Moon and Sun. [21]
2840Tidal ConstituentSee harmonic constituent. [14]
2841Velocity Of SoundSee sound velocity. [14]
2842Angle Of ElevationThe angle in the vertical plane between the horizontal and the line to an object above the horizon. Also called positive altitude. [14]
2843Apparent ShorelineThe seaward limit of marine vegetation, such as mangrove, marsh grass, or trees in water that would reasonably appear to the mariner from a distance to be the fast shoreline. The seaward limit of kelp, low grass in water, and other low ‘lying vegetation normally does not constitute an apparent shoreline. A line drawn on the chart in lieu of the mean high-water line or the mean water level line in areas where either may be obscured by marsh, mangrove, cypress, or other type of marine vegetation. This line represents the intersection of the appropriate datum with the outer limits of vegetation and appears to the navigator as shoreline. [14]
2844Archipelagic StateA state constituted wholly by one or more archipelagos, eventually including other islands. [14]
2845Artificial HorizonSee horizon. [14]
2846Celestial LatitudeSee latitude. [14]
2847Centre Of BuoyancySee buoyancy. [14]
2848Compass AdjustmentSee compensation of magnetic compass. [14]
2849Compressional WaveSee wave. [14]
2850Cooling Degree-DayA form of degree-day used in estimating the amount of energy necessary to reduce the effective temperature of warm air. A cooling degree-day is a day on which the average temperature is one degree above a desired base temperature. [1]
2851Coordinates: FalseGrid coordinates obtained by adding fixed numerical quantities to all grid values. These quantities are so large that none of the resultant false coordinates are negative. Such a procedure introduces a false origin to the south and west of the true origin. See coordinates: origin of. [14]
2852Coordinates: PlaneSee coordinates: plane rectangular. [14]
2853Diurnal AberrationSee aberration of light. [14]
2854Eyepiece: ErectingAn eyepiece containing an auxiliary re-imagining system of one or two lenses which inverts the primary image before it reaches the eyepiece proper. The device is now obsolescent, the inversion being performed by prism systems. Also called inverting eyepiece. [14]
2855Fundamental CircleSee primary great circle. [14]
2856Geometric LatitudeSee latitude: parametric. [14]
2857Great Circle TrackSee track. [14]
2858Gyroscopic CompassSee compass. [14]
2859Gyroscopic InertiaThe property of a gyroscope of resisting any force which tends to change its axis of rotation. A gyroscope tends to maintain the direction of its axis of rotation in space. [14]
2860Hand Lead SoundingSee sounding. [14]
2861Harmonic ConstantsThe amplitude and epochs of the harmonic constituent of the tide, or tidal current at any place. [14]
2862Horizontal ControlSee control. [14]
2863Illuminated ReliefThe representation of relief with the appearance of lighting from one or more directions, giving a three-dimensional impression. Also called shaded relief. [14]
2864Isometric ParallelSee parallel. [14]
2865Large Scale SurveySee survey. [14]
2866Latitude: GeodeticThe angle which the normal at a point on the spheroid makes with the plane of the geodetic equator. [14]
2867Lithographic ImageAn ink-receptive image on the lithographic press plate, either photographic or direct hand or transfer image. The design or drawing on stone or metal plate. [14]
2868Magnetic DeviationSee deviation. [14]
2869Magnetic IntensitySee magnetic field intensity. [14]
2870Micrometer: OcularA filar micrometer so placed that its wire moves in the principal focal plane of a telescope. Also called an eyepiece micrometer. [14]
2871Nautical AstronomySee astronomy. [14]
2872Orientation: BasalIn photogrammetry, the establishment of the position of both ends of an air base with respect to a ground system of coordinates. In all, six elements are required. These are essentially the three-dimensional coordinates of each end of the base. [14]
2873Position: DetachedIn hydrographic survey, an expression indicating a position taken, to locate rocks, floating aids to navigation, least depths on shoals or other dangers or features of importance. [14]
2874Preliminary SurveySee survey: reconnaissance. [14]
2875Principal ParallelSee parallel: photograph. [14]
2876Reciprocal BearingSee bearing. [14]
2877Resonant FrequencySee frequency. [14]
2878Shallow Water WaveSee wave: transitional water. [14]
2879Sonic Depth FinderSee echo sounder. [14]
2880Static InstabilitySee instability. [14]
2881Stereoscopic ImageThe mental impression of a three-dimensional model which results from viewing two overlapping perspective views. Also called stereoscopic model or stereo model. [14]
2882Tape Correction(S)Corrections applied to a distance measured with a tape to eliminate errors caused by the physical condition of the tape, and to the manner in which it is used. [14]
2883Tidal ObservationsSee observation. [14]
2884Topographic SignalSee signal. [14]
2885Track: RecommendedA track, shown on a chart by either a dashed or a continuous line, recommended to all or only certain vessels. [14]
2886Transit InstrumentSee transit. [14]
2887Transit MicrometerSee micrometer. [14]
2888Transponder BeaconA beacon having a transponder. Also called responder beacon. [14]
2889Unit Magnetic PoleIn magnetic theory, a fictitious entity analogous to a unit electric charge in electrostatic theory. [14]
2890Aeronautical BeaconSee beacon. [14]
2891Angle Of DepressionThe angle in the vertical plane between the horizontal and the line to an object below the horizon. Also called negative altitude. [14]
2892Angle Of ReflectionThe angle between the line of motion of a reflected ray and the perpendicular to a surface at the point of reflection. [14]
2893Apparent Solar TimeSee time. [14]
2894Broadcast EphemerisEphemeris transmitted by a satellite which describes its position and orbital parameters. [14]
2895Celestial LongitudeSee longitude. [14]
2896Condensation NucleiAlso called cloud condensation nuclei. Tiny particles upon whose surfaces condensation of water vapor begins in the atmosphere. [1]
2897Depth Anomaly GraphA graph constructed to determine the difference between the computed or thermometric depth and the ideal or assumed depth of reversal of thermometers attached to a nansen bottle. [14]
2898Ekman Current MeterA widely used instrument for measuring the speed and direction of the current at any depth. It is designed for use from a ship or boat at anchor when the stream does not attain a rate of more than 3 to 3 1/2 knots. [14]
2899Error: PolarizationError in a radio bearing or the course indicated by a radio beacon, due to horizontally-polarized components of the electric field under certain transmission conditions. The terms night error or night effect have become obsolete. [14]
2900Great Circle CourseSee course. [14]
2901High Water IntervalSee lunitidal interval. [14]
2902Hydrographic SignalSee signal. [14]
2903Instability: StaticState of hydrostatic equilibrium of the atmosphere in which a particle of air moved from its initial level undergoes a hydrostatic force which tends to remove it further from this level. Also called hydrostatic instability. [14]
2904Local Apparent TimeSee time. [14]
2905Longitude: GeodeticThe angle between the plane of the geodetic meridian and the plane of an initial meridian, arbitrarily chosen. [14]
2906North Magnetic PoleSee magnetic pole. [14]
2907Offshore NavigationSee navigation. [14]
2908Parametric LatitudeSee latitude. [14]
2909Permanent MagnetismSee magnetism. [14]
2910Photograph MeridianSee meridian. [14]
2911Photograph ParallelSee parallel. [14]
2912Radio Range StationA radio navigation land station in the aeronautical radio navigation service providing radio equisignal zones. In certain instances a radio range station may be placed aboard a ship. [14]
2913Range Of VisibilityThe extreme distance at which an object or light can be seen. See range: geographical, and range: luminous. [14]
2914Reference EllipsoidSee reference spheroid. [14]
2915Repeatable AccuracyIn a navigation system, the measure of the accuracy with which the system permits the user to return to a position as defined only in terms of the coordinates peculiar to that system. For example, the distance specified for the repeatable accuracy of the system such as loran’s is the distance bet-ween two loran’s positions established using the same stations and time difference readings at different times. The correlation between the geographical coordinates and the system coordinates may or may not be known. [14]
2916Self-Aligning LevelSee levelling instrument: self-aligning level. [14]
2917Sidereal Hour AngleSee hour angle. [14]
2918Stereoscopic FusionThe mental process which combines the two perspective views to give an impression of a three-dimensional model. [14]
2919Supercell TornadoesTornadoes that occur within supercell thunderstorms that contain well-developed, mid-level mesocyclones. [1]
2920Surface TemperatureTemperature of the water of the surface layer of the sea (or lake, river, etc.). [14]
2921Transient MagnetismSee magnetism: temporary. [14]
2922Triangulation PointSee station: triangulation. [14]
2923Tropical RainforestA type of forest consisting mainly of lofty trees and a dense undergrowth near the ground. [1]
2924Universal Time (Ut)Time as defined by the rotational motion of the earth and determined from the apparent diurnal motions which reflect this rotation. Because of variations in the rate of rotation, universal time is not rigorously uniform. Also called Greenwich mean time. [14]
2925Vertical CollimatorSee collimator. [14]
2926Amplitude ModulationSee modulation. [14]
2927Azimuthal ProjectionSee projection. [14]
2928Compass CompensationSee compensation of magnetic compass. [14]
2929Conformal ProjectionSee projection. [14]
2930Dangerous SemicircleRegion of a tropical cyclone, situated to the right of its path in the northern hemisphere and to the left of its path in the southern hemisphere, in which the seas are higher and the winds more violent and tend also to carry shipping forward on to the cyclone's path. The other half of the cyclone is termed the navigable semicircle. [14]
2931Dead Reckoning TrackSee track. [14]
2932Direction Of CurrentThe direction toward which a current is flowing, called the set of the current. Also called current direction. [14]
2933Direction Of GravitySee gravity. [14]
2934Geometric ProjectionSee projection: perspective. [14]
2935Great Circle BearingSee bearing. [14]
2936Great Circle SailingSee sailing. [14]
2937Illuminated ContoursAn application of illuminated relief in which contours appear lighter on illuminated slopes and darker on the shadow slopes. [14]
2938Inferior ConjunctionSee conjunction. [14]
2939International VoyageA voyage from a country to which the 1974 solas convention applies to a port outside that country or conversely (solas chapter 1, regulation 2d). [14]
2940Interocular DistanceSee interpupillary distance. [14]
2941Intersection StationSee station. [14]
2942Latitude: GeocentricThe angle at the center of the earth between the plane of the equator and a line to a point on the surface of the earth. [14]
2943Lead Line CorrectionA correction to be applied to the depths taken with a rope lead line to take into account the shrinking and stretching. This difficulty has been overcome by inserting a wire heart in the rope. [14]
2944Magnetic ObservatoryA place where buildings are equipped for observing temporal changes in the earth's magnetic field. [14]
2945Magnetic RetentivityThe ability to retain magnetism after removal of the magnetizing force. Also called remanence. [14]
2946Magnetism: TemporaryMagnetism of craft which changes in amount with every change of heading. Also called transient magnetism. [14]
2947Nonsupercell TornadoA tornado that occurs with a cloud that is often in its growing stage, and one that does not contain a midlevel mesocyclone, or wall cloud. Landspouts and gustnadoes are examples of nonsupercell tornadoes. [1]
2948Operating ConditionsMost severe combination of environmental conditions under which a given operation will be permitted to proceed. NOTE Operating conditions are determined for operations that exert a significant action on the structure. Operating conditions are usually a compromise: they are sufficiently severe that the operation can generally be performed without excessive downtime, but they are not so severe that they have an undue impact on design. [15]
2949Parallel Of LatitudeSee parallel. [14]
2950Plane Table TraverseSee traverse. [14]
2951Quadrantal DeviationSee deviation. [14]
2952Repeating InstrumentSee theodolite: repeating. [14]
2953Saint Hilaire MethodSee marcq st. Hilaire method. [14]
2954Satellite NavigationA positioning method using satellites. [14]
2955Terrestrial MeridianSee meridian: astronomical. [14]
2956Three-Arm ProtractorSee protractor: three-arm. [14]
2957Tropical Wet ClimateA tropical climate with sufficient rainfall to produce a dense tropical rainforest. [1]
2958Altitude: Ex-MeridianAn altitude of a celestial body near the celestial meridian of the observer, to which a correction is to be applied to determine the meridian altitude. Also called circummeridian altitude. [14]
2959Face(S) Of TheodoliteEither of the two positions, 'face left' (f.l.) And 'face right' (f.r.) Of the theodolite, when observations are made with the vertical circle on the left or on the right of the telescope respectively. [14]
2960Hyperbolic NavigationSee navigation. [14]
2961Leeward Tidal CurrentSee tide: leeward. [14]
2962Light CharacteristicsSee characteristics of light. [14]
2963List Of Radio SignalsA publication tabulating and combining particulars of: coast radio stations, port radio stations, radio direction finding stations, radio beacons, etc., as well as other information on radio services useful to a navigator. [14]
2964Long Range NavigationSee navigation. [14]
2965Magnetic CompensationSee compensation of magnetic compass. [14]
2966Magnetic PermeabilityThe property of a magnetizable substance that determines the degree in which it modifies the magnetic flux in the region occupied by it. [14]
2967Most Probable MaximumValue of the maximum of a variable with the highest probability of occurring. NOTE The most probable maximum is the value for which the probability density function of the maxima of the variable has its peak. It is also called the mode or modus of the statistical distribution. [15]
2968Navigational TriangleSee astronomical triangle. [14]
2969Ocean Weather StationStation aboard a suitably equipped and staffed ship which tries to maintain a fixed maritime location and which observes and reports for international exchange the observations of specified elements. [14]
2970Orientation: InteriorIn photogrammetry, the determining (analytically or in a photogrammetric instrument) of the interior perspective of the photograph as it was at the instant of exposure. Elements of interior orientation are the calibrated focal length, location of the calibrated principal point, and the calibrated lens distortion. Also called inner orientation. [14]
2971Quadrantal CorrectorsMasses of soft iron placed near a magnetic compass to correct for quadrantal deviation. Spherical quadrantal correctors are called quadrantal spheres. [14]
2972Spherical CoordinatesSee coordinates. [14]
2973Theodolite: RepeatingA theodolite so designed that successive measures of an angle may be accumulated on the graduated circle, and a final reading of the circle made which represents the sum of the repetitions. The observed value of the angle is obtained by dividing the total arc passed through in making the series of observations by the number of times the angle has been observed. Also called repeating instrument. See repetition method of observation. [14]
2974Tide-Generating ForceSee tide-producing force. [14]
2975Triangulation: Arc OfA system of triangulation of limited width designed to progress in a single general direction. Also called chain of triangulation. [14]
2976Trigonometric StationSee station: triangulation. [14]
2977Wave: ElectromagneticWave(s) of associated electric and magnetic fields characterized by variations of the fields. The electric and magnetic fields are at right angles to each other and to the direction of propagation. An electromagnetic wave is coherent if the phase-time relationship is constant throughout the propagation path. [14]
2978Automatic Gain ControlA circuit which automatically maintains a constant output volume regardless of input signal strength. Also called automatic volume control. [14]
2979Design Crest ElevationExtreme crest elevation measured relative to still water. [14]
2980Eccentricity Of CircleThe distance between the center of figure of a graduated circle of an instrument and its center of rotation. [14]
2981Flux-Gate MagnetometerSee magnetometer. [14]
2982Long-term DistributionProbability distribution of a variable over a long time scale. NOTE The time scale exceeds the duration of a sea state, in which the statistics are assumed constant (see shortterm distribution in Short-term Distribution). The time scale is hence comparable to a season or to the design service life of a structure. NOTE The time scale exceeds the duration of a sea state, in which the statistics are assumed constant (see shortterm distribution in Short-term Distribution). The time scale is hence comparable to a season or to the design service life of a structure. [15]
2983Meteorological ElementAtmospheric variable or phenomenon which characterize the state of the weather at a specific place at a given time: air temperature, atmospheric pressure, wind, humidity, thunderstorm, fog, precipi-tation, etc. [14]
2984Perspective ProjectionSee projection. [14]
2985Projection: Equal AreaA projection having a constant area scale. Such a projection is not conformal and is not used for navigation. Also called equivalent projection. [14]
2986Sonic Line Of PositionA line of position determined by means of sound waves. Also called acoustic line of position. [14]
2987Station: TriangulationA recoverable point on the earth, whose geographic position has been determined by angular methods with geodetic instruments. A triangulation station is a selected point, which has been marked with a station mark, or it is a conspicuous natural or artificial object. Also called trigonometric station or triangulation point. [14]
2988Terrestrial PhotographSee photograph. [14]
2989Tide(S): Shallow WaterA distortional effect upon astronomically generated tide caused by shallow waters. See also tide(s): quarter-diurnal. [14]
2990Track Line Of SoundingA continuous record of soundings obtained by a ship on an extended voyage en route between its home port and the working ground. Also called cruise line of sounding. [14]
2991Vertical Control DatumSee datum. [14]
2992Artificial Intelligence1. The capability of a device to perform functions that are normally associated with human intelligence, such as reasoning, learning, and self ‘improvement. 2. Research and study in methods for the development of a machine that can improve its own operations. The development or capability of a machine that can proceed or perform functions that are normally associated with human intelligence, as learning, adapting, reasoning, self ‘correction, automatic improvement. 3. The study of computer and related techniques to supplement the intellectual capabilities of man. As man has invented and used tools to increase his physical powers, he now is beginning to use artificial intelligence to increase his mental powers. In a more restricted sense, the study of techniques for more effective use of digital computers by improved programming techniques. [14]
2993Difference Of LongitudeThe angle at the pole or intercepted arc of equator between the meridians of two places. [14]
2994Eccentricity Of AlidadeThe distance between the center of figure of the index points of an alidade and the center of figure of the graduated circle. [14]
2995Electrical ThermometersThermometers that use elements that convert energy from one form to another (transducers). Common electrical thermometers include the electrical resistance thermometer, thermocouple, and thermistor. [1]
2996Equivalent Focal LengthSee focal length. [14]
2997Exclusive Economic ZoneThe exclusive economic zone is an area, not exceeding 200 nautical miles from the baselines from which the breadth of the territorial sea is measured, subject to a specific legal regime established in the united nations convention on the law of the sea under which the coastal state has certain rights and jurisdiction. [14]
2998Geostationary SatelliteA satellite that orbits the earth at the same rate that the earth rotates and thus remains over a fixed place above the equator. [1]
2999Geostationary SatelliteAn earth satellite moving eastward in an equatorial, circular orbit at an altitude (approximately 35,900 kilometers) such that its period of revolution is exactly equal to (synchronous with) the rotational period of the earth. Such a satellite will remain fixed over a point on the earth's equator. Although geostationary satellites are frequently called geosynchronous or synchronous satellites, the orbit of an eastward moving synchronous satellite must be equatorial if the satellite is to remain fixed over a point on the equator. Otherwise, the satellite moves daily in a figure-eight pattern relative to the earth. Also called fixed satellite. [14]
3000Significant Wave HeightThe average height of the one-third highest waves of a given wave group or sample. [9]
3001Significant Wave PeriodTs ; The significant period is apt to be the average period of all waves whose troughs are below and whose crests are above the mean water level (zero up-crossing method). The significant wave period usually obtained by visual observations of waves is likely to be the average period of 10 to 15 successive prominent waves. [26]
3002Submarine Sound ChannelA water layer with minimum sound velocity and high concentration of sound energy in which sound waves are propagated without reflection from sea surface or bottom. [14]
3003Tape: Length CorrectionThe difference between the nominal length of a tape and its effective length under conditions of standardization. [14]
3004Kelvin Temperature ScaleThermodynamic scale of temperature (t°k) defined by assigning to the triple point of pure water, considered as a fundamental fixed point, the temperature of 273.16°k. Also called absolute temperature scale. [14]
3005Swath(E) Sounding SystemA multi-beam system which is capable of obtaining a lane of soundings from a single ship's track. [14]
3006Celsius Temperature ScaleA thermodynamic scale of temperature (t°c) defined as a function of the kelvin temperature scale (t°k) by the relationship t°c = t°k 273.15. Name for anders celsius (1701-44), swedish astronomer who first described, in 1742, the centigrade temperature scale. Note. According to a resolution of the ninth international conference on weights and measures (1948), temperature should be designated 'degrees Celsius' and the designation 'degrees centigrade' should be discontinued. [14]
3007Deviation Of The VerticalSee deflection of the vertical. [14]
3008Harmonic Analysis Of TideThe mathematical process by which the observed tide at a place is analyzed by breaking it down into a number of constituent tides of simple periodic forces, each having a fixed period. In this process the sun and moon are replaced by a number of hypothetical tide-producing bodies which move in circular orbits around the earth in the plane of the equator. See harmonic constants, harmonic constituent. [14]
3009Hydrographic Survey SheetAn inclusive term used to designate both boat sheets and smooth sheets. Also called survey sheet. [14]
3010International Atomic TimeSee atomic time: international. [14]
3011Meteorological VisibilitySee visibility. [14]
3012Rotating Loop RadiobeaconSee rotating radio beacon station. [14]
3013Shallow Water ConstituentA short-period harmonic term introduced into the formula of astronomical tide constituents to take account of the change in the form of a tide wave resulting from shallow water conditions. Shallow water constituents include over tides and compound tides. See harmonic constituent. [14]
3014Traffic Separation SchemeA routing measure aimed at the separation of opposing streams of traffic by appropriate means and by the establishment of traffic lanes. [14]
3015Deflection Of The VerticalThe angle at a point on the earth (geoid) between the vertical (direction of the plumb line) and the direction of the normal to the spheroid of reference through the point. Also called deflection of the plumb line, deviation of the vertical, or station error. [14]
3016Eccentricity Of InstrumentThe combination of eccentricity of circle and eccentricity of alidade. The effect of eccentricity of instruments on an observed direction is eliminated by having the verniers or micrometer microscopes, with which the circle is read, spaced at equal distances around the circle. [14]
3017Underwater Position FixingA method of position fixing for surface vessels, submersibles or towed devices in relation to a network of underwater acoustic beacons on the seabed with known relative positions. [14]
3018Hunter Short Base ApparatusA base apparatus designed for measuring short bases by the subtended method. It consists of a jointed steel tape made up of four sections suspended in catenary between regularly spaced supports. The hunter short base apparatus may be used over rough ground which is unsuitable for ground taping. [14]
3019Initial Great Circle CourseSee course: great circle. [14]
3020Error Of Closure Of TriangleThe amount by which the sum of the three observed angles of a triangle fails to equal exactly 180° plus the spherical excess of the triangle. Also referred to as closure of triangle. [14]
3021Continental (Or Island) ShelfA zone adjacent to a continent (or around an island), extending from the low water line to the depth at which there is usually a marked increase of slope to greater depth. See shelf.- 2- in UNCLOS article 76:- the continental shelf of a coastal state comprises the sea bed and subsoil of the submarine areas that extend beyond its territorial sea throughout the natural prolongation of its land territory to the outer edge of the continental margin, or to a distance of 200 nautical miles from the baselines from which the breadth of the territorial sea is measured where the outer edge of the continental margin does not extend out to that distance. [14]
3022Protected Reversing Thermometersee thermometer. [14]
3023Equinoctial System Of CoordinatesSee celestial equator system of coordinates. [14]
3024Distance Measuring Equipment (Dme)See electronic distance measuring equipment. [14]
3025Duration Of Flood And Duration Of EbbDuration of flood is the interval of time in which a tidal current is flooding, and the duration of ebb is the interval in which it is ebbing; these intervals being reckoned from the middle of the intervening slack waters or minimum currents. Together they cover, on an average, a period of 12.42 hours for a semidiurnal tidal current or a period of 24.84 hours for a diurnal current. In a normal semidiurnal tidal current, the duration of flood and duration of ebb will each be approximately equal to 6.21 hours, but the times may be modified greatly by the presence of a non-tidal flow. In a river the duration of ebb is usually longer than the duration of flood because of the fresh water discharge, especially during the spring months when snow and ice melt are the predominant influences. [14]
3026Duration Of Rise And Duration Of FallDuration of rise is the interval from low water to high water, and duration of fall is the interval from high water to low water. Together they cover, on an average, a period of 12.42 hours for a semidiurnal tide or a period of 24.84 hours for a diurnal tide. In a normal semidiurnal tide, the duration of rise and duration of fall will each be approximately equal to 6.21 hours, but in shallow waters and in rivers there is a tendency for a decrease in the duration of rise and a corresponding increase in the duration of fall. [14]
3027Witness MarkA mark placed at a known distance and direction from a property corner, base terminal, or survey station, to aid in its recovery and identification. [14]
3028Absolute ZeroA temperature reading of 2273°c, 2460°f, or 0k. Theoretically, there is no molecular motion at this temperature. [1]
3029Abyssal HillsA tract of small elevations on the deep-sea floor. [14]
3030Active SystemAny electromagnetic or sonic position fixing system operating with an interrogation-response procedure. See also passive system. [14]
3031Advection FogOccurs when warm, moist air moves over a cold surface and the air cools to below its dew point. [1]
3032Ambient NoiseThe erratic electromagnetic or sonic background noise emitted by natural or artificial sources contaminating the proper signal. [14]
3033Angle: DangerSee danger angle. [14]
3034Angular SpeedSee speed. [14]
3035Arctic CircleThe geographical parallel having a north latitude equal to the complement of the declination of the summer solstice (latitude = 66 deg 33' n approximately). [14]
3036Astro CompassSee under compass. [14]
3037Axis: OpticalSee axis of lens. [14]
3038Azimuth: TrueAzimuth relative to true north. [14]
3039Basal CoplaneSee coplane: basal. [14]
3040Basic ControlSee control. [14]
3041Beacon: RadioSee radio beacon. [14]
3042Bearing PlateSee pelorus. [14]
3043Bearing: GridBearing relative to grid north. See also azimuth: grid. [14]
3044Bearing: TrueSee bearing. [14]
3045Bowditch RuleA method of adjustment of traverses. [14]
3046Bridge: SwingA movable bridge which rotates in a horizontal plane about a vertical pivot to allow the passage of vessels. [14]
3047Buoy: FairwayA buoy intended to be the first to be seen during an approach from the open sea to a fairway. [14]
3048Buoy: LateralA buoy used to indicate a lateral limit of navigable water. [14]
3049Buoy: MooringA buoy secured to the bottom by permanent moorings with means for mooring a vessel by use of its anchor chain or mooring lines. [14]
3050Buoy: SpecialA buoy primarily used to indicate an area or feature referred to in nautical documents rather than to assist navigation. [14]
3051Cable: LeaderCable lying on the bottom and carrying an electric current by which ships equipped with appropriate instruments, can be guided. [14]
3052Calendar LineSee date line. [14]
3053Cardinal BuoySee cardinal mark [14]
3054Cardinal MarkIn the iala maritime buoyage system a navigation mark used in conjunction with the compass to indicate where the mariner may find the best navigable water. It is placed in one of the four quadrants (north, east, south and west) bounded by inter-cardinal bearings from the point marked. [14]
3055Cellular WaveSee wave. [14]
3056Celsius ScaleA temperature scale where zero is assigned to the temperature where water freezes and 100 to the temperature where water boils (at sea level). [1]
3057Chart ReadingInterpretation of the symbols, lines, abbreviations, and terms appearing on charts. May be called map reading when applied to maps generally. [14]
3058Chart: MarineSee chart: nautical. [14]
3059Charted DepthSee depth. [14]
3060Circle: GreatThe intersection of a sphere and a plane through its center. See also orthodrome. [14]
3061Circle: SmallThe intersection of a sphere and a plane which does not pass through its center. [14]
3062Cleared DepthThe effective depth over a feature, obtained by a wire drag survey. [14]
3063Clearing LineA straight line, on a chart, that marks the boundary between a safe and a dangerous area; or that passes clear of a navigational danger. Sectors of lighthouse lights are usually bounded by them. [14]
3064Clock: AtomicA precision clock that depends for its operation on an electrical oscillator regulated by the natural vibrational frequency of an atomic system (such as a beam). The combination of two (or more) radionuclides whose activities can be utilized to ascertain time intervals. [14]
3065Clock: CesiumAn atomic clock using the properties of cesium. [14]
3066Clock: QuartzSee clock: crystal. [14]
3067Cloud SeedingThe introduction of artificial substances (usually silver iodide or dry ice) into a cloud for the purpose of either modifying its development or increasing its precipitation. [1]
3068Coastal ChartSee chart: coast. [14]
3069Coaxial CableSee cable. [14]
3070Compass NorthSee north: compass. [14]
3071Compass: BoatA small portable compass mounted in a box for convenient use in small water craft. [14]
3072Compass: DumbSee pelorus. [14]
3073ConstellationFormerly a number of fixed stars grouped within an imaginary outline. Now, a region of the celestial sphere marked by arbitrary boundary lines. [14]
3074Co-Range LineA line through points of equal tide range. [14]
3075Corer: PistonA corer equipped with a piston inside the core tube that is connected to the lowering cable. When the corer penetrates the ocean bottom the stopped cable and piston, in effect, provides a suction which overcomes the frictional forces acting between the sediment and the interior wall of the coring tube. [14]
3076Cotidal ChartSee chart. [14]
3077Crystal ClockSee clock. [14]
3078Cumulus StageThe initial stage in the development of an ordinary cell thunderstorm in which rising, warm, humid air develops into a cumulus cloud. [1]
3079Current ChartSee chart. [14]
3080Cut: Angle OfSee angle: crossing. [14]
3081Day: SiderealThe duration of one rotation of the earth on its axis, with respect to the vernal equinox over the upper branch of a meridian. Because of the precession of the equinoxes, the sidereal day thus defined is slightly less than the period of rotation with respect to the stars, but the difference is less than 0.01 second. The length of the sidereal day is 24 hours of sidereal time or 23h56m04.091s of mean solar time. [14]
3082Deep Sea LeadSee lead. [14]
3083Density LayerA layer of water in which density increases with depth enough to increase the buoyancy of a submarine. [14]
3084Digital ChartSee electronic chart. [14]
3085DiscriminatorA radar circuit that produces a response which depends upon the frequency of the input signal. A transponder beacon circuit which accepts pulses of proper duration and rejects others. That part of a frequency modulation receiver which converts the modulated signals directly into audio frequency signals. [14]
3086Dock: GravingSee dock: dry. [14]
3087Dredging BuoyA buoy marking the limit of an area where dredging is being performed. [14]
3088Drift StationA scientific station established on the ice of the arctic ocean. A term sometimes used in shoran operations to designate the ground station about which the aircraft flies. The second station is then referred to as rate station. [14]
3089Dry LightningLightning that occurs with thunderstorms that produce little, if any, appreciable precipitation that reaches the surface. [1]
3090Due PublicityNotification of a given action for general information through appropriate authorities within a reasonable amount of time in a suitable manner. Used in the context of the united nations' law of the sea convention. [14]
3091ElectrometeorVisible or audible manifestation of atmospheric electricity, either corresponding to discontinuous electrical discharges (lightning, thunder) or occurring as more or less continuous phenomena (saint elmo's fire, polar aurora). [14]
3092Envelope EdgeThe fore part of an envelope. [14]
3093Eotvos EffectThe east-west component of the movement of a ship, including the effect of marine currents, modifies the centrifugal force of the earth's rotation. It is a vertical force experienced by a body moving in an east-west direction on the rotating earth. [14]
3094Equator: HeatSee equator: thermal. [14]
3095Error: RandomSee error: accidental. [14]
3096Expert SystemA knowledge-based computer system which utilizes artificial intelligence to do some of the inferential computation/decision making. [14]
3097Exposure TimeThe time during which a light-sensitive material is subjected to the action of light. [14]
3098ExtrapolationThe process of estimating the value of a quantity beyond the limits of known values by assuming that the rate or system of change between the last few known values continues. [14]
3099Extreme ValueDesign value of a parameter used in ultimate limit state checks, in which a structure's global behavior is intended to stay in the elastic range. NOTE Extreme events have probabilities of the order of 10^-2 per annum. [15]
3100False HorizonSee horizon. [14]
3101Fix: CircularA useless fix resulting from the observations of two angles establishing as loci three coinciding circles of position. Also called revolver, or swinger. [14]
3102Floating DockSee dock. [14]
3103Flux: RadiantPower emitted, transferred or received in the form of radiation. [14]
3104Following SeaA sea in which the waves move in the general direction of the heading. [14]
3105Fracture ZoneAn extensive linear zone of irregular topography, mountainous or faulted, characterized by steep-sided or asymmetrical ridges, clefts, troughs, or escarpments. [14]
3106Fringing ReefA reef closely attached to a shore, as contrasted with a barrier reef which is separated from the shore by a lagoon. [14]
3107Gaussin ErrorSee error. [14]
3108General ChartSee chart. [14]
3109Geodetic DataInformation concerning points established by a geodetic survey, such as descriptions for recovery, coordinate values, height above sea level, and orientation. [14]
3110GeomorphologyA branch of both geography and geology that deals with the form of the earth, the general configuration of its surface, and the changes that take place in the evolution of land forms. [14]
3111Grab SamplingA random mode of collecting samples. [14]
3112Gradient WindA theoretical wind that blows parallel to curved isobars or contours. [1]
3113Graphic ScaleSee scale: bar. [14]
3114Gravity MeterSee gravimeter. [14]
3115Harbour ChartSee chart. [14]
3116Harbour ReachThe reach of a winding river or estuary which leads directly to the harbor. [14]
3117Hazard BeaconSee beacon. [14]
3118Height FinderA stereoscopic range finder so constructed as to indicate vertical heights rather than slant range. [14]
3119Horizon ShadeOne of the pivoted coloured glasses which can be swung before the horizon glass of a sextant to regulate the intensity of light. [14]
3120Horizon: TrueIn photogrammetry, a horizontal plane passing through a point of vision or perspective center. The apparent horizon approximates the true horizon only when the point of vision is very close to sea level. [14]
3121Icelandic LowThe subpolar low-pressure area that is centered near iceland on charts that show mean sea-level pressure. [1]
3122Indian SummerAn unseasonably warm spell with clear skies near the middle of autumn. Usually follows a substantial period of cool weather. [1]
3123Indirect WaveSee wave. [14]
3124Insular ShelfA zone around an island that extends from the low water line to a depth at which there is usually a marked increase of slope towards oceanic depths. [14]
3125Isoporic LineA line connecting points of equal annual rate of change of a magnetic element. Also called isopor. [14]
3126Kalman FilterIn electronics, a mathematical-statistical method for predicting a time-variable signal in the presence of disturbances. The method exploits the fact that certain characteristic parameters of the process vary slowly with time, so that a best estimate of the signal can be obtained as a function of time. [14]
3127Landfall BuoySee farewell buoy. [14]
3128Layer TintingSee layering. [14]
3129Light: LinearA luminous signal having perceptible length, as contrasted with a point light. [14]
3130Light: MarineA light intended primarily for marine navigation. [14]
3131Line Of ForceA line indicating the direction in which a force acts, as in a magnetic field. See magnetic lines of force. [14]
3132Line Of NodesThe straight line connecting the two points of intersection of the orbit of a planet, planetoid, or comet and the ecliptic, or the line of intersection of the planes of the orbits of a satellite and its primary. See node. [14]
3133LithificationThe process of induration, cementation, petrification, consolidation, and crystallization which convert magma and newly deposited sediments into rock. [14]
3134Local HorizonSee horizon: apparent. [14]
3135Local TransitSee transit. [14]
3136Log: ElectricA graphic recording of the various electrical properties of a sediment or rock through which a hole has been drilled. [14]
3137Log: TaffrailA log consisting essentially of a rotator towed through the water by a braided log line attached to a distance registering device usually secured at the taffrail, the railing at the stern. Also called patent log. [14]
3138Lunar RainbowSee moonbow. [14]
3139Make The LandTo sight and approach or reach land from seaward. [14]
3140Map: ThematicA map designed to demonstrate particular features or concepts. In conventional use, this term excludes topographic maps. [14]
3141Marine GrowthLiving organisms attached to an offshore structure. [15]
3142Marsden ChartA system introduced by marsden early in the nineteenth century for showing the distribution of meteorological data on a chart especially over the oceans. A Mercator map projection is used; the world between 90°n and 80°s being divided into marsden 'squares' each of 10 degrees latitude by 10 degrees longitude. These squares are systematically numbered to indicate position. Each square may be divided into quarter squares, or into 100 one-degree subsquares numbered from 00 to 99 to give the position to the nearest degree. [14]
3143Measured MileA measured distance of one nautical mile. [14]
3144MedimarimeterAn apparatus for recording the mean sea level. [14]
3145Melting PointTemperature of change from the solid to the liquid phase of a substance. It is a function of pressure. [14]
3146Meteoric DustAtmospheric dust originating from meteors. [14]
3147Middle GroundA shallow area in otherwise deeper water with channels on both sides of it. [14]
3148Mixed CurrentSee current. [14]
3149Moirã© EffectThe effect created by transmitting light through two separate, overlapping families of parallel lines. See also inogen light. [14]
3150Monochromatic(Adj.). Of, or having one colour. Of, or producing light of one wavelength. [14]
3151Nadir: GroundThe point on the ground vertically beneath the perspective center of the camera lens. [14]
3152Natural ScaleSee scale. [14]
3153Nautical PlanA large scale nautical chart or a large scale inset of a nautical chart. [14]
3154Nitrogen (N2)A colorless and odorless gas that occupies about 78 percent of dry air in the lower atmosphere. [1]
3155Nominal RangeSee range. [14]
3156Oceanic RidgeA long elevation of the ocean floor with either irregular or smooth topography and steep sides, often separating ocean basins. [14]
3157Off SoundingsSaid of a vessel navigating beyond the 100-fathom line. In earlier times, said of a vessel in water deeper than could be sounded with the hand lead. [14]
3158Open Pack IceFloes seldom in contact with many leads and pools. Ice concentration 4/10th to 9/10th. [14]
3159Open TraverseSee traverse. [14]
3160Origin: FalseSee coordinates: false. [14]
3161Oropesa SweepTowed wire used for sweeping sea bottom when surveying shoals or wrecks. It consists of a wire running from the stern of the vessel and held out on the water by an otter which also pulls down against a towed float. The amount of wire between float and otter determines the depth of the outer end of the sweep. The inner end of the sweep is held to the required depth and in line with the stern of the vessel by a kite. [14]
3162OrthophotomapA photomap made from an assembly of orthophotographs. It may incorporate special cartographic treatment, photographic edge enhancement, colour separation, or a combination of these. [14]
3163ParantiselenaPhotometeor of the halo family, analogous to the paranthelion, the luminary being the moon. [14]
3164Pilot StationThe office or headquarters of pilots; the place where the services of a pilot may be obtained. [14]
3165Polar BearingSee bearing. [14]
3166Port HandbookA handbook for a specific port. [14]
3167Primary RadarSee radar. [14]
3168Print: OzalidA photographic contact print developed by a dry diazo process. The process produces a positive from a positive image or a negative from a negative image. [14]
3169Quarter PointThe fourth of the distance from one point of the compass to another, equivalent to about two degrees and forty-nine minutes. [14]
3170Radar BearingSee bearing. [14]
3171Radial: NadirA radial from the nadir point. See nadir: photograph. [14]
3172Radiation FogA major type of fog, produced over a land area when radiational cooling reduces the air temperature to or below its dew point. [14]
3173Radio HorizonThe line at which direct rays from a transmitting antenna become tangent to the earth's surface. Its distance from the transmitting antenna is greater than that of the visible horizon, and increases with decreasing frequency. [14]
3174Radio Wave(S)See wave. [14]
3175Ratio Of RiseThe ratio of the height of tide at two places. [14]
3176Relative WindFor a moving object, wind vector relative to this object. Also called apparent wind. See true wind. [14]
3177RepeatabilitySee repeatable accuracy. [14]
3178Return StrokeThe luminous lightning stroke that propagates upward from the earth to the base of a cloud. [1]
3179River HarbourA harbor which lies on the banks of a river. [14]
3180Rod: SoundingSee sounding pole. [14]
3181Rodded PointsPoints where the rod was actually held, as opposed to points sketched in between. [14]
3182Roentgen RaysSee x-rays. [14]
3183Sailing ChartSee under chart. [14]
3184Sallying ShipProducing rolling motion of a vessel by the running in unison of a group from side to side. This is usually done to help float a vessel which is aground or to assist it to make headway when it is beset by ice. [14]
3185Scale: BorderA scale drawn along the border of chart. [14]
3186Scale: LinearSee scale: bar. [14]
3187ScintillationRapid variations, often in the form of pulsations, of the brightness of the stars or terrestrial light sources. [14]
3188Sediment CoreSee core. [14]
3189Sediment TrapA device used to measure the rate and amount of sedimentation in a location. [14]
3190SedimentationThe process of breakup and separation of particles from the parent rock, their transportation, deposition, and consolidation into another rock. [14]
3191SedimentologyThe science concerned with the description, classification, origin, and interpretation of sediments and sedimentary rock. [14]
3192Sensible HeatThe heat we can feel and measure with a thermometer. [1]
3193Sextant ChartSee circle sheet. [14]
3194Sextant ErrorSee error. [14]
3195Sextant: GyroA sextant provided with a gyroscope to indicate the horizontal. [14]
3196Siberian HighA strong, shallow area of high pressure that forms over siberia in winter. [1]
3197Signal: SoundSee sound signal. [14]
3198Signal: WaterA hydrographic signal erected in shallow water. [14]
3199Sketch SurveySee survey. [14]
3200Solitary WaveSee wave. [14]
3201Sonic BearingSee bearing. [14]
3202Sounder: EchoSee echo sounder. [14]
3203Sounding PoleA graduated pole or rod used for sounding in shallow water. Also called sounding rod. [14]
3204Sounding TubeA glass tube of small diameter, used with certain types of sounding machines in determining depth. [14]
3205Speed: GroundSee ground speed. [14]
3206Speed: LinearRate of motion in a straight line. [14]
3207Spirit BubbleSee level: spirit. [14]
3208Storm WarningSee warning. [14]
3209Straight-EdgeA bar of wood, metal, etc. With one edge accurately straight for drawing straight lines in cartographic applications. [14]
3210StratocumulusA low cloud, predominantly stratiform, with low, lumpy, rounded masses, often with blue sky between them. [1]
3211Stream: FloodSee flood stream. [14]
3212Stream: TidalSee current: tidal. [14]
3213Sumner MethodThe establishing of a line of position from the observation of the altitude of a celestial body by assuming two latitudes (or longitudes) and calculating the longitudes (or latitudes) through which the line of position passes. [14]
3214Sun: ApparentThe actual sun as it appears in the sky. Also called true sun. [14]
3215Sunspot CycleThe time interval (11.2 years) during which the number of sunspots progresses from a minimum to a maximum and decreases again to a minimum. [14]
3216Super TyphoonA tropical cyclone (typhoon) in the western pacific that has sustained winds of 130 knots or greater. [1]
3217Survey: SonarHydrographic survey using a sonar. [14]
3218Swallow FloatA tubular buoy, usually made of aluminium, that can be adjusted to remain at a selected density level to drift with the motion of that water mass. The float is tracked by shipboard listening devices and current velocities can be determined. [14]
3219Swash ChannelA channel across a bank, or among shoals. [14]
3220Tangent ScrewA slow motion screw of a surveying instrument or sextant. [14]
3221Target: FalseSee echo: false. [14]
3222Thermal BeltsHorizontal zones of vegetation found along hillsides that are primarily the result of vertical temperature variations. [1]
3223Thermal LayerSee thermocline. [14]
3224Tidal HarbourSee harbor. [14]
3225Tide RegisterSee gauge: tide. [14]
3226Tide(S): NeapThe tides of decreased range occurring near the times of first and last quarter. [14]
3227Tide: FallingThe portion of the tide cycle between high water and the following low water. Also called ebb tide. The opposite is rising tide. [14]
3228Tide: OceanicThe periodic rise and fall of the earth's oceans resulting from gravitational interactions between the sun, moon, and earth. [14]
3229Tide: PartialOne of the harmonic components comprising the tide at any point. The periods of the partial tides are derived from various combinations of the angular velocities of earth, sun, moon, and stars relative to each other. See harmonic constituent. [14]
3230Tide: PrimaryThat part of a tidal undulation that is the direct response to a tide-producing force. [14]
3231Tide: WeatherSee tide: windward. [14]
3232TopoangulatorAn instrument used to measure vertical angles in the principal plane of an oblique photograph. [14]
3233Tornado AlleyA region in the great plains of the united states extending from texas and oklahoma northward into kansas and nebraska where tornadoes are most frequent. [1]
3234Tornado WatchA forecast issued to alert the public that tornadoes may develop within a specified area. [1]
3235Total EclipseSee eclipse. [14]
3236Tracing PaperA thin tough semitransparent paper suitable for making tracings of drawings, or for miscellaneous use in hydrographic work, where permanence is not important or when pencil work is sufficient. [14]
3237Track PlotterA plotter used to plot the track or course of a craft. [14]
3238Training WallA wall, bank, or jetty, often submerged, built to direct or confine the flow of a river or tidal current. [14]
3239TranslocationA method to improve the accuracy of satellite positioning by simultaneously using several receivers. One receiver is deployed on a known position to obtain corrections required to match the known position and that derived from satellite signals. These corrections are then transmitted to the other receivers. [14]
3240TrilaterationA method of surveying wherein the lengths of the triangle sides are measured, usually by electronic methods, and the angles are computed from the measured lengths. Compare with triangulation. [14]
3241Tripod SignalSee signal. [14]
3242True MeridianSee meridian. [14]
3243Turning BasinAn enlargement of a channel for turning vessels. Also called manoeuvering basin. [14]
3244Uplifted ReefA coral reef exposed above water level. [14]
3245Violent StormWind with a speed between 56 and 63 knots (beaufort scale wind force 11). [14]
3246Warning: GaleMeteorological message intended to warn those concerned of the occurrence or expected occurrence of a wind of beaufort force 8 or 9 over a specified area. [14]
3247Water ContentA ratio; 100 multiplied by the weight of water in a bottom sediment sample divided by the weight of the dried sample, expressed as a percentage. [14]
3248Water SamplerAny device for obtaining a water sample. Also called water sampling device. See water bottle. [14]
3249Water-PartingA summit or boundary line separating the drainage districts of two streams or coasts; a divide or watershed. [14]
3250Wave VelocityThe speed at which the individual wave form advances. A vector quantity that specifies the speed and direction with which a sound wave travels through a medium. [14]
3251Wave: CarrierA radio wave used as a vehicle for conveying intelligence, generally by modulation. Also called carrier. [14]
3252Wave: GravityA wave whose velocity of propagation is controlled primarily by gravity. Water waves of length greater than 2 inches are considered gravity waves. [14]
3253Wave: SurfaceA progressive gravity wave in which the disturbance (that is, the particle movement in the fluid mass as well as the surface movement) is confined to the upper limits of a body of water. Strictly speaking this term applies to those progressive gravity waves whose celerity depends only upon the wavelength. [14]
3254Weather ShoreShore that is to windward of a vessel. See lee shore. [14]
3255Weather TypesCertain weather patterns categorized into similar groups. Used as an aid in weather prediction. [1]
3256Weather WatchA forecast indicating that atmospheric conditions are favorable for hazardous weather to occur over a particular region during a specified time period. [1]
3257Weathered IceHummocked polar ice subjected to weathering which has given the hummocks and pressure ridges a rounded form. If the weathering continues, the surface may become more and more even. [14]
3258Weighted MeanA value obtained by multiplying each of a series of values by its assigned weight and dividing the sum of those products by the sum of the weights. [14]
3259Well: PluggedA borehole which has been sealed with a plug and permanently abandoned. [14]
3260Wind MachinesFans placed in orchards for the purpose of mixing cold surface air with warmer air above. [1]
3261Wind ProfilerA doppler radar capable of measuring the turbulent eddies that move with the wind. Because of this, it is able to provide a vertical picture of wind speed and wind direction. [1]
3262Windward TideSee tide. [14]
3263Working ChartSee chart. [14]
3264X-CoordinatesSee coordinates: plane rectangular. [14]
3265Y-CoordinatesSee coordinates: plane rectangular. [14]
3266Zenith CameraA special camera so designed that its optical axis may be pointed accurately toward the zenith. It is used for the determination of astronomical positions by photographing the position of the stars. [14]
3267Zone MeridianThe central meridian of each zone of a grid system. [14]
3268Abnormal ValueDesign value of a parameter of abnormal severity used in accidental limit state checks in which a structure is intended not to suffer complete loss of integrity [15]
3269Absolute ErrorSee error. [14]
3270Altitude: TrueThe apparent altitude of a celestial body after all corrections have been applied. In American terminology usually referred to as observed altitude. [14]
3271Anaglyphic MapSee under map. [14]
3272Anallatic LensA convergent lens fitted between the objective lens and the diaphragm of telescopes of instruments for direct measurements of distances between the optical center of the instrument and a graduated staff called stadia. [14]
3273Area ClearanceThe effective depth, within specified limits, obtained by a wire drag survey. [14]
3274Ascending NodeSee node. [14]
3275AutocollimatorSee collimator. [14]
3276Axis Of CameraA line perpendicular to the focal plane of the camera and passing through the emergent nodal point of the lens system. Also called camera axis. See nodal point. [14]
3277Axis: TrunnionSee axis: horizontal. [14]
3278Axis: VerticalIn a theodolite or transit, the line through the center of the instrument about which the alidade rotates. [14]
3279Band Of ColourSee stripes (of colour) [14]
3280Base DirectionSee direction. [14]
3281Base TerminalsThe two extremes of a base line. Usually marked on a monument or metal stake buried beneath a visible surface mark. See also reference mark. [14]
3282Beacon: HazardA beacon marking an obstruction or hazard. [14]
3283Bearing CircleA ring designed to fit snugly over a compass or compass repeater, and provided with vanes for observing bearings. A similar ring provided with means for observing azimuth of the sun is called an azimuth circle. [14]
3284Bearing: PolarIn a system of polar or spherical coordinates, the angle formed by the intersection of the reference meridional plane and the meridional plane containing the point. [14]
3285Bearing: RadarA bearing obtained by radar. [14]
3286Bearing: RadioThe angle between the apparent direction of a definite source of emission of electro-magnetic waves and a reference direction, as determined at a radio direction-finding station. [14]
3287Bottom CurrentThe movement of water along the bottom of reservoirs or rivers. [2]
3288Bottom SamplerAny device for obtaining a bottom sample. See also corer, dredge, driver rod, grab and snapper. [14]
3289Boundary LayerThe layer of fluid in the immediate vicinity of a bounding surface. It is the layer in which frictional forces are not negligible. [14]
3290Bubble SextantSee sextant. [14]
3291Buoy: CardinalA buoy used to indicate that the best navigable water is to be found in one particular of the quadrants that are bounded by the four bearings nw, ne, se and sw taken from the position of the mark. [14]
3292Buoyant BeaconSee articulated light. [14]
3293Cable: CoaxialA transmission cable consisting of two concentric conductors insulated from each other. [14]
3294Camera: AerialA camera specially designed for use in aircraft. [14]
3295Capillary WaveSee wave. [14]
3296Careening GridA structure in the intertidal zone serving as a support for vessels at low stages of the tide to permit work on the exposed portion of the vessel's hull. Also called gridiron. [14]
3297Chart: CotidalA chart showing cotidal lines. [14]
3298Chart: CurrentA chart on which current data are graphically depicted. [14]
3299Chart: FisheryA chart with additional details required for the exploitation of marine natural resources. [14]
3300Chart: GeneralA nautical chart intended for offshore coastwise navigation. [14]
3301Chart: HarbourA nautical chart intended for navigation and anchorage in harbors and small waterways. [14]
3302Chart: SailingA small scale nautical chart for offshore navigation. [14]
3303Chart: WorkingIn hydrographic survey, a working document (chart or projection) by means of which a survey programme can be broadly planned. [14]
3304Circular LevelSee level: spirit. [14]
3305Civil TwilightSee twilight. [14]
3306Clamping ErrorSee error. [14]
3307Clear SweepingA form of bar sweeping. A sweep, set at a predetermined depth, and passed over an area to ensure that no obstructions have been missed. [14]
3308Clearing MarksSelected marks, natural or otherwise, used to help vessels keep clear of dangers. [14]
3309Clock: CrystalA precision clock essentially consisting of a generator of constant frequency controlled by a resonator made of quartz crystal with suitable methods for producing continuous rotation to operate time-indicating and related mechanisms. Also called quartz clock. [14]
3310Close Pack IcePack ice composed of floes mostly in contact, such that navigation becomes difficult even for specially constructed vessels. Ice concentration 7/10th to 9/10th. [14]
3311Coastal SurveySee survey. [14]
3312Cocurrent LineA line through places having the same tidal current hour. [14]
3313Compass CourseSee course. [14]
3314Compass PointsThe 32 divisions of a compass, at intervals of 11°1/4. [14]
3315Compass: AstroAn instrument which, when oriented to the horizontal and to the celestial sphere, indicates a horizontal reference direction relative to the earth. This compass is designed primarily for the observation of celestial bodies to determine the orientation of an aircraft relative to the azimuth of a celestial body. [14]
3316Composite PathA wave track which lies partly over land and partly over water. [14]
3317Constant ErrorSee error. [14]
3318Contour: DepthSee depth curve. [14]
3319Control: BasicSee control. [14]
3320Control: MinorSee control: photogrammetric. [14]
3321CorrespondenceIn stereoscopy, the condition that exists when corresponding images on a pair of photographs lie in the same epipolar plane; the absence of y-parallax. [14]
3322Co-Tidal ChartA chart of a major harmonic constituent (or of a semi-diurnal tide) constructed to illustrate the propagation patterns and to assist in the interpolation of tidal conditions and datum assessment at locations where no observations exist (especially offshore). Now frequently replaced by numerical modelling. [16]
3323Country BreezeA light breeze that blows into a city from the surrounding countryside. It is best observed on clear nights when the urban heat island is most pronounced. [1]
3324Cross BearingsTwo or more bearings used as intersecting lines of position for fixing the position of a craft. [14]
3325Crossing AngleSee angle. [14]
3326Current: DriftA wide, slow-moving ocean current principally caused by winds. [14]
3327Current: EarthSee current(s): telluric. [14]
3328Current: FloodSee flood stream. [14]
3329Current: MixedThe type of tidal current characterized by a conspicuous difference in speed and duration between the two flood currents or two ebb currents occurring each tidal day. [14]
3330Current: SurgeThe coastal current influenced by remote waves. [14]
3331Current: TidalThe alternating horizontal movement of water associated with the rise and fall of the tide caused by tide-producing forces. Also called tidal stream. [14]
3332Cycloidal WaveSee wave. [14]
3333Damped Wave(S)See wave. [14]
3334Danger BearingSee bearing. [14]
3335Dangerous RockA sunken rock of a small area (pinnacle), at such a depth as to be considered dangerous to surface navigation. [14]
3336Data RetrievalThe extraction of data which meet certain criteria from a file or data bank. [14]
3337Data TelemetryMeasuring a quantity, and transmitting the measured value to a distant station where further processing takes place. [14]
3338Depressed PoleSee pole. [14]
3339Depth: ChartedThe vertical distance from the chart datum to the bottom. [14]
3340Dike (Or Dyke)An artificial ditch to hold, or control the flow of water. An artificial embankment to contain or hold back water. In geology, a tabular body of igneous rock molded from molten rock within a fissure. [14]
3341Dioptric LightSee light. [14]
3342Dock: FloatingA form of dry dock consisting of a floating structure of one or more sections which can be partly submerged by controlled flooding to receive a vessel, then raised by pumping out the water so that the vessel's bottom can be exposed. [14]
3343Dolphin BeaconA minor light structure consisting of a number of piles driven into the bottom in a geometric or random pattern and drawn together, with a light mounted at the top. [14]
3344Doppler EffectThe apparent change in wavelength, and therefore in frequency of radiant energy, when the distance between the source and the observer or receiver is changing. This effect is exploited in underwater acoustics and satellite positioning. [14]
3345Drift Ice FootSee ramp. [14]
3346Drift SoundingSee sounding. [14]
3347Dumping GroundA sea area where dredged material or other potentially more harmful material e.g. Explosives, chemical waste, is deliberately deposited. See also spoil ground. [14]
3348Dutchman'S LogSee log. [14]
3349Earth InductorAn electric instrument used to measure the inclination of the earth's magnetic field. [14]
3350Earth'S MantleThe relatively plastic region between the crust and core of the earth. Also called asthenosphere. [14]
3351Echo(Es): SideSee echo(es): false. [14]
3352Eclipse: LunarAn eclipse of the moon. When the moon enters the shadow of the earth, it appears eclipsed to an observer on the earth. [14]
3353Eclipse: SolarAn eclipse of the sun. When the moon passes between the sun and the earth, the sun appears eclipsed to an observer in the moon's shadow. [14]
3354Eclipse: TotalAn eclipse in which the entire source of light is obscured. [14]
3355Eotvos BalanceSee torsion balance. [14]
3356Epipolar PlaneAny plane which contains the epipoles; therefore any plane containing the air base. Also called basal plane. [14]
3357Equiphase ZoneSee zone. [14]
3358Error: ClosingSee error of closure. [14]
3359Error: GaussinDeviation of a magnetic compass due to transient magnetism which remains in a vessel's structure for short periods after the inducing force has been removed. This error usually appears after a vessel has been on the same heading for a considerable time. [14]
3360Error: HeelingThe change in the deviation of a magnetic compass when a craft heels, due to the change in the position of the magnetic influences of the craft relative to the earth's magnetic field and to the compass. [14]
3361Error: RegularSee error: systematic. [14]
3362Error: SextantThe error in the reading of a sextant, due either to lack of proper adjustment or to imperfection of manufacture. [14]
3363Error: StationSee deflection of the vertical. [14]
3364European DatumConstituted by the international spheroid located at the potsdam origin. [14]
3365Field PositionSee position. [14]
3366Fish Trap BuoyA buoy marking the limits of a fish trap area. [14]
3367Flux: LuminousQuantity, characteristic of radiant flux which expresses its capacity to produce a luminous sensation. [14]
3368Focal DistanceSee focal length. [14]
3369Fog: AdvectionFog which forms in the lower part of a moist air mass which moves over a colder surface. [14]
3370Following WindWind blowing in the general direction of a vessel's course. [14]
3371Free GyroscopeSee gyro: free. [14]
3372GeneralisationThe omission of less important detail when compiling a chart. Its purpose is to avoid overloading charts where space is limited. [14]
3373GeoengineeringThe use of global scale technology fixes to mitigate climate changes. [1]
3374Glacier TongueProjecting seaward extension of glacier, usually afloat. [14]
3375Global ClimateClimate of the entire globe. [1]
3376Gnomonic ChartSee chart. [14]
3377Gravity CoringA method to obtain cores by bottom penetration solely as a result of gravity. [14]
3378Grid DirectionSee direction. [14]
3379Grid VariationSee variation. [14]
3380Ground EffectsInfluence exerted by the ground on the propagation of electromagnetic waves. [14]
3381Group VelocityThe velocity of a wave disturbance as a whole, i.e., of an entire group of component simple harmonic waves. [14]
3382Harbour MasterA local official who has charge of mooring and berthing of vessels, collecting harbor fees, etc. [14]
3383Harbour: InnerThe part of a harbor more remote from the sea, as contrasted with the outer harbor. These expressions are usually used only in a harbor that is clearly divided into two parts, as by a narrow passageway or man-made structures. The inner harbor generally has additional protection and is often the principal berthing area. [14]
3384Harbour: OuterThe part of a harbor towards the sea, through which a vessel enters the inner harbor. [14]
3385Harbour: TidalA harbor affected by the tides, in distinction from a harbor in which the water level is maintained by caissons or gates. [14]
3386Heat LightningDistant lightning that illuminates the sky but is too far away for its thunder to be heard. [1]
3387Heat LightningLightning flash at a distance which may be observed as a short illumination of the sky or of a cloud, close to the horizon. [14]
3388Horizon MirrorThe mirror part of the horizon glass. The expression is sometimes used somewhat loosely to refer to the horizon glass. [14]
3389Horizon: FalseA line resembling the apparent horizon but above or below it. [14]
3390Horizon: RadioSee radio. [14]
3391Image: VirtualAn image that cannot be shown on a surface but is visible, as in a mirror. [14]
3392Ingoing StreamSee flood stream. [14]
3393Intended TrackSee track. [14]
3394IntervalometerA timing device for automatically operating the shutter of a camera at selected intervals. [14]
3395Inverted ImageSee image. [14]
3396Island HarbourSee under harbor. [14]
3397Isopycnic LineA line connecting points of equal density. Also called isopycnic. [14]
3398Katabatic WindAn offshore wind produced by cold air draining from high ground by convection. The cold air replaces the lighter warm air which is rising over the sea. [14]
3399Kinetic EnergyThe energy within a body that is a result of its motion. [1]
3400Lateral SystemA buoyage system generally used for well defined channels; buoyage marks indicate the position of dangers in relation to the route to be followed by mariners in their vicinity. [14]
3401Latitude ScaleSee scale. [14]
3402Lead: Deep SeaA heavy sounding lead the weight of which may be varied from about 15 to over 50 kilos depending on the depths to be sounded. Also called dipsey lead. [14]
3403Lead: SoundingA lead attached to a line used for measuring the depth of water. Also called plummet. [14]
3404Level: TiltingSee levelling instrument: tilting level. [14]
3405Line Of LevelsA continuous series of measured differences of elevation. [14]
3406Liquid CompassSee compass. [14]
3407Little Ice AgeThe period from about 1550 to 1850 when average temperatures over Europe were lower, and alpine glaciers increased in size and advanced down mountain canyons. [1]
3408Louver ShutterSee shutter. [14]
3409Low Water MarkThe intersection of the plane of low water with the shore. The line along a coast, or beach, to which the sea recedes at low water. Also called low water line. [14]
3410Lunar DistanceThe angle, at an observer on the earth, between the moon and another celestial body. This was the basis of a method formerly used to determine longitude at sea. [14]
3411Magnetic ChartSee chart. [14]
3412Magnetic RangeSee range. [14]
3413Magnetic StormA disturbance in the earth's magnetic field, associated with abnormal solar activity, and capable of seriously affecting both radio and wire transmission. [14]
3414Manuscript MapSee map. [14]
3415Map: CadastralA map showing the boundaries of subdivision of land, usually with the bearings and lengths thereof and the area of individual tracts, for purposes of describing and recording ownership. A cadastral map may also show culture, drainage, and other features relating to the value and use of land. See also plat. [14]
3416Marine BiologySee biology. [14]
3417Marine ClimateA climate controlled largely by the ocean. The ocean's influence keeps winters relatively mild and summers cool. [1]
3418Marine RailwayA track, cradle, and winding mechanism for hauling vessels out of the water so that the hull can be exposed as in a dry dock. This is also called a patent slip in British terminology. [14]
3419Mark: GeodeticSee mark. [14]
3420Master StationThe governing station of two or more synchronized transmitting stations. Often shortened to master. See slave station. [14]
3421Matthews TableAn echo sounding correction table. [14]
3422Mean Neap RiseThe height of mean high waters neaps above the chart datum. Also called neap rise. [14]
3423Meridian AngleAngular distance east or west of the local celestial meridian; the arc of the celestial equator, or the angle at the celestial pole, between the upper branch of the local celestial meridian and the hour circle of a celestial body, measured eastward or westward from the local celestial meridian through 180°, and labelled e or w to indicate the direction of measurement. See hour angle. [14]
3424Meridian: GridOne of the grid lines extending in a grid north-south direction. [14]
3425Meridian: TrueA meridian. The expression is used to distinguish the great circle through the geographical poles from magnetic meridian, compass meridian, or grid meridian. [14]
3426Meridian: ZoneThe meridian used for reckoning zone time. [14]
3427MicroprocessorComponent of a data processing device made up of microcircuits integrated on a single chip. [14]
3428Mobile StationA radiolocation station intended to be used at unspecified points. As opposed to fixed station. [14]
3429Mountain ChainA complexity of several mountain ranges. [14]
3430Noon: ApparentTwelve o'clock apparent time. [14]
3431North: CompassThe direction north as indicated by a magnetic compass. [14]
3432Notch (Or Gap)A narrow passage between two elevations, as mountains; a deep close pass; a defile. [14]
3433Open RoadsteadA roadstead with relatively little protection from the sea. [14]
3434Optical SquareA small hand instrument used to set off a right angle. [14]
3435Original ChartSee chart. [14]
3436Orthochromatic(Adj.). Said of photographic surfaces sensitive to ultra-violet, blue, yellow, green and orange rays. Insensitive to red rays. [14]
3437PaleomagnetismRemanent magnetism produced by the earth's field when a material was initially formed. [14]
3438Parallel PlateAn optical disk with optically flat, parallel surfaces; used especially in optical micrometers. [14]
3439Passive SystemA system which records energy emitted or reflected but does not produce or transmit energy of its own. [14]
3440Perigean TidesSee tide. [14]
3441Periodic ErrorSee error. [14]
3442Phase VelocityVelocity, measured over a short time period, at which a particular wave crest is propagated a medium. [14]
3443PhotoengravingA process by which photographs are reproduced on printing plates especially one in which the reproduction is in relief: opposed to photogravure. A plate so made. A print from such a plate. [14]
3444Planning ChartA chart designed for use in planning voyages or flight operations or investigating areas of marine or aviation activities. [14]
3445Plotting BoardA stiff transparent polar coordinate plotting sheet for tracking other vessels and aircraft and solving problems involving relative movement. [14]
3446Pocket CompassSee compass. [14]
3447Poincarã© WaveA long period gravity wave. The superposition of incident and reflected plane waves (Sverdrup waves) such that the composite wave fronts are perpendicular to the coast with a set of nodal lines normal to the wave fronts. The term is used in tidal analysis to study ocean tides and tides in open seas and gulfs. [14]
3448Point Of AriesSee equinox. [14]
3449Pole: ElevatedThe celestial pole above the horizon, agreeing in name with the latitude. [14]
3450Pole: MagneticSee magnetic pole. [14]
3451Port AuthorityThe entity responsible for administration and maintenance of harbor facilities. [14]
3452Pressure GaugeSee gauge. [14]
3453Pressure PlateIn photography, a flat plate (usually of metal but frequently of glass or other substance) which, by means of mechanical force, presses film into contact with the focal-plane plate of a camera. [14]
3454Pressure RidgeA ridge or wall of hummocked ice where one floe has been pressed against another. [14]
3455Primary CircleSee primary great circle. [14]
3456Principal AxisSee axis of lens. [14]
3457Print: ContactA photographic print made from either a negative or a positive in contact with a sensitized material. [14]
3458Proof PlottingAn advanced copy of a map or chart produced by a plotter to check the design and registration, and to detect and correct errors before final printing. [14]
3459Quartering SeaWaves moving in a direction approximately 45° from a vessel's heading, striking the vessel on the quarter. [14]
3460RadargrammetryThe process of obtaining reliable measurements in bi- and three-dimensional image processing by means of radar. [14]
3461Radio ReceiverEquipment for receiving radio signals and converting them into usable form. [14]
3462Radio SonobuoySee sonobuoy. [14]
3463Radio SpectrumThe range of electromagnetic radiations useful for communication by radio (approximately 10 kilohertz to 300,000 megahertz). [14]
3464Raise The Land(v.t.). To sight land by approaching to the point where it appears above the horizon. [14]
3465Range Light(S)See light. [14]
3466Range: NominalThe luminous range of a light in a homogenous atmosphere in which the meteorological visibility is 10 sea miles. [14]
3467Reflected WaveSee wave. [14]
3468Refracted WaveSee wave. [14]
3469Rocket StationA life saving station equipped with line-carrying rocket apparatus. [14]
3470Rod: LevellingSee levelling rod. [14]
3471Rollers: BlindSee blind rollers. [14]
3472Rossby Wave(S)Ignoring friction or depth changes; if a parcel of water with no initial relative vorticity (i.e. No rotation) is moved northward, as f (the Coriolis parameter) increases the parcel will gain negative relative vorticity and will circulate clockwise. The Coriolis force will be greater on the poleward side of the parcel than on the equatorward side and hence the parcel will be subjected to a net south-ward restoring force. This force will push the parcel south of the latitude of zero relative vorticity overshoots and the circulation becomes counterclockwise. Due to the Coriolis variation the parcel will now experience a northward restoring force. Thus the variation of f provides a restoring force (in the horizontal plane) allowing oscillation to occur just as the effect of gravity does (vertically) for surface or internal waves. In reality rossby waves are complicated by depth variations and frictional effects. [14]
3473Rotary CurrentSee current. [14]
3474Rotating LightSee light. [14]
3475Rotating PrismSee dove prism. [14]
3476Routeing GuideA document designed to be used in conjunction with nautical charts and other nautical publications in areas where complex routing systems have been established by the IMO. [14]
3477Running SurveySee survey. [14]
3478Sailing: PlaneA sailing in which the earth or a small part of it is considered a plane. [14]
3479Santa Ana WindA warm, dry wind that blows into southern california from the east off the elevated desert plateau. Its warmth is derived from compressional heating. [1]
3480Scale: GraphicSee scale: bar. [14]
3481Seabed SamplerA device used to obtain samples of the sea floor. [14]
3482Seamount ChainSeveral seamounts in a line with bases separated by a relatively flat sea floor. [14]
3483Seamount GroupSeveral closely spaced seamounts not in a line. [14]
3484Seamount RangeSeveral seamounts having connected bases and aligned along a ridge or rise. [14]
3485Shear StrengthThe internal resistance of a body to shear stress. [14]
3486Signal StationA place on shore from which signals are made to ships at sea. [14]
3487Signal: SurveyA natural or artificial object or structure whose horizontal and sometimes vertical position is obtained by surveying methods. Survey signals are given special designation according to the kind of survey in which they are determined, or which they may later serve. [14]
3488Signal: TripodA three-legged triangulation signal. It is usually constructed in such a manner that an observer can set up his theodolite and make observations without moving any of the structure. [14]
3489Solar ParallaxSee parallax. [14]
3490Sounding: EchoSee echo sounding. [14]
3491Sounding: WireSounding with a sounding machine. To obtain a vertical wire sounding the ship or boat must be stopped while the wire is running out. [14]
3492Speed Of SoundThe speed of propagation of sound waves. [14]
3493Spherical BuoySee buoy. [14]
3494Spherical WaveSee wave. [14]
3495Spring Tide(S)See tide. [14]
3496Stepped LeaderAn initial discharge of electrons that proceeds intermittently toward the ground in a series of steps in a cloud- to-ground lightning stroke. [1]
3497StratificationThe state of a fluid that consists of two or more horizontal layers arranged according to their density. [14]
3498Stream CurrentSee current. [14]
3499Stream: RotarySee current: rotary. [14]
3500Striding LevelSee level. [14]
3501Sublunar PointThe geographical position of the moon. That point on the surface of the earth at which the moon is in the zenith at a specified time. See sub-point. [14]
3502Submarine BellA bell whose signal is transmitted through water. [14]
3503Submerged RockA rock covered at the chart sounding datum and considered to be potentially dangerous to navigation. [14]
3504Subsolar PointThe geographical position of the sun; that point on the earth at which the sun is in the zenith at a specified time. [14]
3505Substitute MapSee map. [14]
3506Sugar Loaf SeaWaves that rise into sugar loaf shapes, with little wind, possibly resulting from intersecting waves. [14]
3507Survey StationSee station. [14]
3508Survey: AerialA survey using aerial photographs as part of the surveying operation; also the taking of aerial photographs for surveying purposes. [14]
3509Survey: GroundA survey made by ground methods, as distinguished from an aerial survey. A ground survey may or may not include the use of photographs. [14]
3510Survey: SketchA hydrographic survey made (due to lack of time or facilities) to a lower degree of accuracy and detail than the chosen scale would normally indicate. [14]
3511Tagline SurveySee survey. [14]
3512Tandem ControlIn hydrographic survey, a system of obtaining two or more adjacent sounding lines run simultaneously and controlled by one ship, the other ships, or launches being merely referenced to it. [14]
3513Tape StretcherA mechanical device which facilitates holding a tape at a prescribed tension and in a prescribed position. [14]
3514Tape: StandardSee reference tape. [14]
3515Telegraph BuoyA buoy used to mark the position of a submarine telegraph cable. [14]
3516Tidal Light(S)See light. [14]
3517Tidal MovementThe movement which includes both the vertical rise and fall of the tide, and the horizontal flow of the tidal currents. This movement is associated with the astronomical tide-producing fores of the moon and sun acting upon the rotating earth. [14]
3518Tidal TheoriesThe different theories trying to describe the tidal phenomena. [14]
3519Tide: AnalysisThe mathematical processes by which the observed tide or tidal current are analyzed to obtain constituents and statistics. [14]
3520Tide: CompoundA tide constituent with a speed equal to the sum or difference of the speeds of two or more basic constituents. Compound tides usually occur in shallow water regions. See shallow water constituent. [14]
3521Tide: WindwardA tidal current setting to windward. Also called weather tide. [14]
3522Tilt: RelativeThe angular relationship between two overlapping vertical photographs with no reference to an established datum. [14]
3523Time: SiderealTime measured by the apparent diurnal rotation of the (true) vernal equinox. It is counted from 0 hour, when the vernal equinox is on the meridian, through 24 hours. Naming the meridian of reference is essential to its complete identification. [14]
3524Time: StandardA variation of zone time adapted for use on or near land, with irregular but well-defined zone limits. [14]
3525TornadogenesisThe process by which a tornado forms. [1]
3526Transit: LocalThe apparent passage of a celestial body across the meridian of the observer. See also meridian transit. [14]
3527Traverse PointSee turning point. [14]
3528Traverse TableA table giving relative values of various parts of plane right triangles, for use in solving such triangles, particularly in connection with various sailings. [14]
3529Tribrach PlateA demountable, three-armed plate which is attached to an instrument stand or survey tower and on which the bottoms of the footscrews of the instrument rest in milled grooves. [14]
3530Trough CompassSee declinatoire. [14]
3531Turbulent FlowA flow characterized by turbulence. [14]
3532Twilight StarsStars suitably placed for astronomical observation during morning or evening twilight. [14]
3533Underwater IceSee anchor ice. [14]
3534Valley: MedianSee median valley. [14]
3535Vanishing LineIn photogrammetry, the straight line on a photograph upon which lie all the vanishing points of all systems of parallel lines parallel to one plane. [14]
3536Visible RegionRadiation with a wavelength between 0.4 and 0.7 mm. See visible radiation. [1]
3537Warning: StormMeteorological message intended to warn those concerned of the occurrence or expected occurrence of a wind of beaufort force 10 or 11 over a specified area. More generally, forecast of severe weather conditions. [14]
3538Wave DirectionThe direction from which waves are moving. [14]
3539Wave SteepnessCharacteristic of individual waves defined as wave height divided by wavelength [14]
3540Wave(S): RadioElectromagnetic waves of frequencies generally higher than those of audible sound waves but lower than those of heat and light waves. Also called hertzian waves. [14]
3541Wave: CellularSystem of surface waves in which the oscillation of water is limited as by solid boundaries. The period is the same in adjacent cells. [14]
3542Wave: IndirectAny wave which arrives by an indirect path having undergone an abrupt change of direction by refraction or reflection. See wave: sky. [14]
3543Wave: InternalA wave that occurs within a fluid whose density changes with depth, either abruptly at a sharp surface of discontinuity (an interface) or gradually. Also called boundary wave. [14]
3544Wave: PressureSee pressure wave. [14]
3545Wave: SolitaryA wave of translation consisting of a single crest rising above the undisturbed liquid level, without any accompanying trough, in contrast with a wave train. [14]
3546Weather SignalSee signal. [14]
3547Well: DeviatedA borehole drilled at an oblique angle to evaluate or remove oil or natural gas reserves not directly below the drilling structure. [14]
3548Wire: SoundingSee sounding. [14]
3549Year: SiderealThe period of one apparent revolution of the earth around the sun, with respect to a fixed point, or a distant star devoid of proper motion, being 365 days, 6 hours, 9 minutes, and 9.5 seconds in 1900 and increasing at the rate of 0.0001 second annually. [14]
3550Zodiacal LightWhite or yellowish light which spreads out, in the night sky, more or less along the zodiac from the horizon on the side on which the sun is hidden. It is observed when the sky is sufficiently dark and the atmosphere sufficiently clear. [14]
3551Achromatic LensA compound lens that has been partly corrected for chromatic aberration. Such a lens is customarily made to bring green and red-light rays to approximately the same point focus. Also called achromat. See aberration of light. [14]
3552Adjacent CoastsThe coasts lying either side of the land boundary between two adjoining states. [14]
3553Air PhotographySee photography: aerial. [14]
3554Aluminium SheetAn aluminium-mounted paper sheet occasionally used for boat-sheets, smooth sheets, or plane table boards. [14]
3555Angle: CrossingThe angle at which two lines of position intersect. Also called angle of cut. [14]
3556Angle: MastheadSee masthead angle. [14]
3557Annual ParallaxSee parallax. [14]
3558Annular EclipseSee eclipse. [14]
3559Apogean Tide(S)See under tide. [14]
3560Aurora BorealisAurora of the northern hemisphere. [14]
3561Axis Of ChannelThe center line of a channel. See also talweg. [14]
3562Axis: PrincipalSee axis of lens. [14]
3563Azimuth DiagramA diagram for obtaining graphically rather than by computation the azimuths of observed celestial bodies. [14]
3564BathythermogramThe record of temperature versus depth made by a bathythermograph. Rarely used. [14]
3565Bearing: DangerThe maximum or minimum bearing of a point for safe passage of an offlying danger. [14]
3566Biology: MarineThe study of the life, history and ecology of marine and brackish water plants and animals. [14]
3567BioluminescenceThe emission of light by living organisms. See also noctiluca. [14]
3568Bissextile YearSee year: civil. [14]
3569Border Of ChartThe neatline defining the limits of the area charted. [14]
3570Bottom FrictionThe force resulting from the interaction between the ocean bottom and water particle motion over it. [14]
3571Bottom FrictionThe friction generated by the bathymetry. [19]
3572Bottom ProfilerAn echo sounder for precision surveys of the sea bottom surface. [14]
3573Bottom SamplingThe process of collecting bottom samples. [14]
3574Bridge: BasculeA counterpoise bridge rotated in a vertical plane about an axis at one or both ends. Also called balance bridge. [14]
3575Buoy: AutomaticSee automatic floating station. [14]
3576Cardinal SystemA buoyage system generally used to indicate dangers where the coast is flanked by numerous islands, rocks and shoals as well as to indicate dangers in the open sea. In this system the bearing (true) of the mark from the danger is indicated to the nearest cardinal point. A system of buoyage in which the aids are assigned shape, colour, and number distinction in accordance with location relative to the nearest obstruction. The cardinal points delineate the sectors for buoy location. [14]
3577Catoptric LightSee light. [14]
3578Celestial GlobeSee star globe. [14]
3579Chart PortfolioA systematic grouping of nautical charts covering a specific geographical area. [14]
3580Chart: MagneticA chart showing for an established epoch the values of such magnetic elements as variation, dip, horizontal and vertical intensity of the earth's magnetic field, and total magnetic intensity. [14]
3581Chart: MercatorA chart on the Mercator projection. This is the chart commonly used for marine navigation. On a Mercator chart, a rhumb line is a straight line. [14]
3582Chart: OriginalA chart which has been drawn up as a result of direct survey. [14]
3583Closed TraverseSee traverse. [14]
3584Coastal CurrentSee current. [14]
3585Comparing WatchSee watch. [14]
3586Compass: MasterA compass controlling one or several repeaters. [14]
3587Compass: PocketA portable compass (employed in coastlining or reconnaissance survey). [14]
3588Compass: SpiritSee compass: liquid. [14]
3589Compass: TroughSee declinatoire. [14]
3590Concluded AngleSee angle. [14]
3591Constituent DaySee day. [14]
3592Continuous WaveSee wave. [14]
3593Control: GroundControl established by ground surveys, as distinguished from control established by photogrammetric methods. [14]
3594CoordinatographAn instrument used to plot in terms of plane rectangular coordinates. It may be an integral part of a stereoscopic plotting instrument whereby the planimetric motions (x and y) of the floating mark are plotted directly. [14]
3595Counter CurrentA secondary current setting in a direction opposite to that of a main current. [14]
3596Course: CompassSee course. [14]
3597Current: RotaryA tidal current that flows continually, with the direction of flow changing through 360° during a tidal cycle. Called rotary stream in British terminology. [14]
3598Current: StreamA narrow, deep, and fast-moving current as opposed to a relatively wide and weak drift current. [14]
3599Danger SoundingSee sounding. [14]
3600Dangerous WreckA wreck submerged at such a depth as to be considered dangerous to surface navigation. [14]
3601Day: Mean SolarSee day: solar. [14]
3602Deep-Sea CameraSee camera. [14]
3603Depth: StandardA depth below the sea surface at which water properties should be measured and reported, according to the proposal by the international association of physical oceanography in 1936. [14]
3604Descending NodeSee node. [14]
3605DesertificationA general increase in the desert conditions of a region. [1]
3606Deviation TableA table of the deviation of a magnetic compass on various headings, magnetic or compass. [14]
3607Dipping CompassSee dip circle. [14]
3608Direction: BaseIn photogrammetry, the direction of the vertical plane containing the air base which might be expressed as a bearing or an azimuth. [14]
3609Direction: GridHorizontal direction expressed as angular distance from grid north. [14]
3610Dracontic MonthSee month: nodical. [14]
3611Echo(Es): FalseIn echo sounding, echoes caused by a foreign matter such as kelp or fish, or by layers of water differentiated by sudden changes of temperature or salinity (or both). False echoes are occasionally recorded by echo sounders, and might be interpreted erroneously as the correct depth. Also called side echo(es) or false target. See phantom bottom. [14]
3612Ekman TransportNet surface water transport due to the ekman spiral. In the northern hemisphere the transport is 90° to the right of the surface wind direction. [1]
3613Enamelled PlateIn cartography, enamelled working surface (normally white), on aluminium, zinc or other dimensionally stable medium. Used to prepare colour separation originals. [14]
3614Energy: RadiantEnergy transmitted by radiation. [14]
3615Entrance WindowThe image of the field stop formed by all the lens elements on the object side of the field stop. [14]
3616Equation MethodIn tidal terminology, an elaborate non-harmonic method for the prediction of tides. [14]
3617Equation: ErrorThe probability equation which expresses the laws of the occurrence of accidental errors. The error equation is the basis of the method of least squares, used in the adjustment of observations for determining the most probable value of a result from those observations. [14]
3618Error: AbsoluteAbsolute deviation (the value taken without regard to sign) from the corresponding true value. [14]
3619Error: ClampingA systematic error in observations made with a repeating theodolite caused by strains set up by the clamping devices of the instrument. [14]
3620Error: ConstantA systematic error which is the same in both magnitude and sign through a given series of observations. [14]
3621Error: ExternalSee error: theoretical. [14]
3622Error: PeriodicAn error whose amplitude and direction vary systematically with time. [14]
3623Error: PersonalThe result of the inability of an observer to perceive dimensional values exactly. Personal errors may be either random or systematic in behavior. See also personal equation. [14]
3624Error: ProbableAn error (or deviation from the mean) of such magnitude that the likelihood of its being exceeded in a set of observations is equal to the likelihood of its not being exceeded; its value is that of the standard error multiplied by 0.6745. The use of standard error is sometimes preferred in statistical studies. [14]
3625Error: ResidualThe difference between any value of a quantity in a series of observations, corrected for known systematic errors, and the value of the quantity obtained from the adjustment of that series. Sometimes termed as residual. [14]
3626Facility (Port)See harbor works. [14]
3627Fixing IntervalThe time or distance elapsed between two subsequent fixes. [14]
3628Foot (Pl. Feet)A unit of length equal to 12 inches, 1/6 of a fathom, or 30.480 centimeters. [14]
3629Free AtmosphereSee atmosphere. [14]
3630Free ConvectionSee convection. [14]
3631Frontal SurfaceSee front. [14]
3632Gate: HydraulicA form of valve used to regulate the flow of a liquid in a pipeline, river or dam. [14]
3633Gauge: PressureAn instrument for measuring pressure. A tide gauge operated by the change in pressure at the bottom of a body of water, due to the rise and fall of the tide. [14]
3634General NoticesAll information and instructions that hydrographic offices may wish to bring to the attention of mariners but the nature of which is such that they may not properly refer to any specific nautical document. [14]
3635Grad (Or Grade)A unit of angle measurement, equal to the angle at the center of a circle, subtended by one four-hundredth part of its circumference. [14]
3636Grid NavigationSee navigation. [14]
3637Ground DistanceThe great-circle distance between two ground positions, as contrasted with slant distance. Also called ground range. [14]
3638Ground ParallelSee parallel. [14]
3639Gyroscope: FreeSee gyro: free. [14]
3640Hanging CompassSee compass. [14]
3641Harbour: IslandA harbor formed, or mainly protected, by islands. [14]
3642Heat Index (Hi)An index that combines air temperature and relative humidity to determine an apparent temperature how hot it actually feels. [1]
3643High Water MarkThe mark left by the tide at high water. The line or level reached, especially the highest line ever reached. Also called high water line. A permanent mark which indicates the maximum observed stage of tide. [14]
3644HydrophotometerAn instrument used to measure the extinction coefficient of transmission of light in water. It consists of a constant light source placed at a specific distance from a photocell. When placed in water, the electrical output of the photocell is proportional to the amount of light striking the cell which, in turn, depends upon the transparency of the water. The instrument is calibrated to read 100 percent light transmission in air. [14]
3645Image: InvertedAn image that appears upside down in relation to the object. [14]
3646Inner Neat LineSee neat line. [14]
3647Input ImpedanceThe complex opposition to alternating current between the input terminals of any device. [14]
3648Intertidal ZoneThe zone generally considered to be between mean high water and mean low water levels. [14]
3649Isodynamic LineA line connecting points of equal magnetic intensity, either the total or any component. [14]
3650Land NavigationSee navigation. [14]
3651Latitude FactorThe change in latitude along a celestial line of position per 1' change in longitude. [14]
3652Level: CircularSee level: spirit. [14]
3653Level: StridingA spirit level so mounted that it can be placed above and parallel with the horizontal axis of a surveying or astronomical instrument, and so supported that it can be used to measure the inclination of the horizontal axis to the plane of the horizon. Generally, its mounting has supports in the form of inverted eyes which rest directly upon the pivots on which the telescope of the instrument rotates. [14]
3654Levelling PlateA plate designed to support the levelling rod as an aid to accuracy in levelling. [14]
3655Levelling ScrewOne of the three screws of surveying and astronomic instruments used for levelling same. Also called footscrew. [14]
3656Levelling StaffSee levelling rod. [14]
3657Light(S): RangeTwo or more lights in the same horizontal direction, particularly those lights so placed as navigational aids to mark any line of importance to vessels, as a channel. The one nearest the observer is the front light and the one farthest from the observer is the rear light. See light(s): leading. [14]
3658Light(S): TidalLights shown at the entrance of a harbor to indicate tide and tidal current conditions within the harbor. [14]
3659Light: DioptricA light concentrated into a parallel beam by means of refracting lenses and prisms (as opposed to catoptric). [14]
3660Light: FlashingA rhythmic light in which the total duration of light in a period is clearly shorter than the total duration of darkness and all the appearances of light are of equal duration. [14]
3661Light: IsophaseSee light: equal-interval. [14]
3662Line Of ApsidesThe line connecting the two orbital points (called apsides) that are nearest and farthest from the center of attraction, as the perigee and the apogee in the case of an orbit about the earth, and the perihelion and the aphelion in the case of an orbit about the sun. [14]
3663Log: Dutchman'SA buoyant object thrown overboard to determine the speed of a vessel by timing its passage between two marks, of known distance apart, on the vessel. [14]
3664Lookout StationA distinctive structure or place on shore from which personnel keep watch upon events at sea or along the coast. [14]
3665Low Water StandSee stand of tide. [14]
3666Magnetic CourseSee course. [14]
3667Magnetic MomentThe quantity obtained by multiplying the distance between two magnetic poles by the average strength of the poles. [14]
3668Magnetic SurveySee survey. [14]
3669Mammatus CloudsClouds that look like pouches hanging from the underside of a cloud. [1]
3670Map: AnaglyphicA map specially printed in two complementary colors in such a way that, when viewed through a twin eyepiece of the same colors, a three-dimensional impression of relief is seen. [14]
3671Map: ManuscriptThe original drawing of a map as compiled or constructed from various data, such as ground surveys, photographs, etc. [14]
3672Map: SubstituteA hasty reproduction of wide-coverage aerial photographs, photomaps, or mosaics, or of provisional maps, or any document used in place of a map, when the precise requirements of a map cannot be met. [14]
3673Marks And DeepsThe divisions used in marking a hand lead line. [14]
3674Maunder MinimumA period from about 1645 to 1715 when few, if any, sunspots were observed. [1]
3675Mean Neap RangeSee neap range. [14]
3676Mean Tide LevelSee half tide level. [14]
3677Meridian: LocalThe meridian through any particular place or observer, serving as the reference for local time, in contrast with Greenwich meridian. [14]
3678Meridian: PrimeThe meridian of longitude 0°, used as the origin for measurement of longitude. The meridian of Greenwich, England, is almost universally used for this purpose. [14]
3679Meridional FlowA type of atmospheric circulation pattern in which the north-south component of the wind is pronounced. [1]
3680Micrometer DrumA graduated drum by which the motion of a traveling wire in a microscope can be measured. [14]
3681Minimum SquaresSee least squares. [14]
3682Month: SiderealThe interval of time between two successive passages of the moon past as fixed star. The length of the sidereal month averages 27.321661 mean solar days. [14]
3683Month: TropicalThe average period of revolution of the moon about the earth with respect to the vernal equinox. The length of the tropical month averages 27.321582 mean solar days. [14]
3684Nacreous CloudsClouds of unknown composition that have a soft, pearly luster and that form at altitudes about 25 to 30 km above the earth's surface. They are also called mother-of-pearl clouds. [1]
3685North: MagneticThe direction indicated by the north seeking pole of a freely suspended magnetic needle influenced only by the earth's magnetic field. [14]
3686Oceanic PlateauA comparatively flat topped elevation of the sea-bed which rises steeply from the ocean floor on all sides, and is of considerable extent across the summit. [14]
3687Operative SheetSee field board. [14]
3688Opposite CoastsThe geographical relationship of the coasts of two states facing each other. [14]
3689Orchard HeatersOil heaters placed in orchards that generate heat and promote convective circulations to protect fruit trees from damaging low temperatures. Also called smudge pots. [1]
3690OrthophotoscopeA photomechanical device, used in conjunction with a double-projection anaglyphic instrument, for producing orthophotographs. [14]
3691Outgoing StreamSee ebb stream. [14]
3692Overlay TracingA plotting on tracing cloth at the scale of the smooth sheet used in conjunction with the smooth sheet. See fair chart. [14]
3693Parallax: SolarThe equatorial horizontal parallax of the sun. [14]
3694Partial EclipseSee eclipse. [14]
3695PhosphorescenceThe production of light without sensible heat. Emission of electromagnetic radiation by a substance as a result of previous absorption of radiation of shorter wavelength. In contrast to fluorescence, the emission may continue for a considerable time after cessation of the existing irradiation. [14]
3696PhotogoniometerAn instrument for measuring angles from the true perspective center to points on a photograph. [14]
3697Photograph AxesSee fiducial axes. [14]
3698PhotolithographA lithograph produced by photolithography. See lithography. [14]
3699PhototopographyThe science of surveying in which the detail is plotted entirely from photographs taken at suitable ground stations. [14]
3700Pilotage WatersSee pilot waters. [14]
3701Plane: VerticalAny plane passing through a point on the earth and containing the zenith and nadir of that point. In surveying, a plane at right angles to a horizontal plane and within which angles and distances are observed. [14]
3702Planimetric MapSee map. [14]
3703Platform JacketThe section of a platform from base to deck level, on which deck modules are fitted. [14]
3704Platform: PiledA platform with a steel jacket fixed by piles to the seabed. [14]
3705Pole: DepressedThe celestial pole below the horizon, of opposite name to the latitude. [14]
3706Position AnglesThe two sextant angles observed on a survey ship for determining its position. [14]
3707Position: FieldA position computed while field work is in progress to determine the acceptability of the observa-tions or to provide a preliminary position for other purposes. [14]
3708Preferred DatumA geodetic datum selected as a base for consolidation of local independent datums within a geographical area. Also called major datum. [14]
3709Pressure: SoundThe instantaneous pressure at a point in a medium in the presence of a sound wave, minus the static pressure at that point. [14]
3710Prevailing WindThe wind direction most frequently observed during a given period. [1]
3711Principal ScaleSee scale. [14]
3712Printing PlatesAny one-piece printing surface of any size, strength, or surface preparation, bearing an image made manually, mechanically or photographically, specifically for the purpose of printing such an image onto some other material. [14]
3713Prohibited AreaAn area shown on charts within which navigation and/or anchoring is prohibited. In aviation terminology, a specified area within the land areas of a state or territorial waters adjacent thereto over which the flight of aircraft is prohibited. [14]
3714Quality ControlAll procedures which ensure that the product meets certain standards and specifications. [14]
3715Quarantine BuoyA buoy marking the location of a quarantine anchorage. [14]
3716Radar ReflectorA device capable of or intended for reflecting radar signals. [14]
3717Radar-ResponderSee radar beacon. [14]
3718Radio FrequencySee frequency. [14]
3719RadiotheodoliteElectronic theodolite designed to give the direction in space of a radio transmitter carried by a free balloon. [14]
3720Range: Cruisingsee cruising radius. [14]
3721Range: MagneticA range oriented in a given magnetic direction and used to assist in determination of the deviation of a magnetic compass. See deviation: magnetic. [14]
3722Ratio Of RangesThe ratio of the height of tide at the subordinate station to the height of tide at the reference station. [14]
3723Resolving PowerA mathematical expression of definition in a radar or optical system, usually stated as the maximum number of lines per millimeter that can be seen as separate lines in the image. [14]
3724Reverse AzimuthSee azimuth: back. [14]
3725Revolving LightSee light: rotating. [14]
3726Rho-Teta SystemPositioning system measuring the distance (rho) and direction (teta) from an existing control station to a mobile or another point. [14]
3727River DischargeThe rate of flow of water past a point in a stream, expressed as volume per unit time (usually cubic feet per second). [14]
3728River RoadsteadA roadstead which lies in a river. [14]
3729Roaring FortiesAn expression often used to denote that belt in the oceans, between 40° and 50° south latitude, where strong westerly winds prevail. [14]
3730Rocket SoundingDetermination of one or more upper-air meteorological elements by means of rocket-borne instruments. [14]
3731Runway Light(S)See light. [14]
3732Safe Water Markin the IALA maritime buoyage system a navigation mark used to indicate that there is navigable water around its position with no known hazards nearby. [14]
3733Scale: LatitudeThe subdivided east and west borders of a Mercator chart into degrees and minutes. A variant of the bar scale, since a minute of latitude is very nearly equal to a nautical mile. [14]
3734Secondary RadarSee radar: primary. [14]
3735Sediment SurveyA survey to determine the nature and distribution of types of sea bottom sediments. [14]
3736Separation LineSee separation zone. [14]
3737Sextant: BubbleA sextant with a bubble or spirit level to indicate the horizontal. [14]
3738Sextant: MarineA sextant designed primarily for marine navigation. [14]
3739Shoaling EffectThe alteration of a wave proceeding from deep water to shallow water. [14]
3740Shutter: LouverA shutter consisting of a number of thin metal strips or louvers which operate like a venetian blind to make the exposure; usually located just in front of or just behind the lens. [14]
3741Signal: WeatherA visual signal displayed to indicate a weather forecast. [14]
3742Single Day TideSee tide: diurnal. [14]
3743Solar RadiationRadiation emitted by the sun. [14]
3744Sonic FrequencySee audio frequency. [14]
3745Sono-Radio BuoySee sonobuoy. [14]
3746Sound IntensitySee intensity. [14]
3747Sounding BottleA strong metal container fitted with non-return valves for taking water samples at great depths. See also water bottle. [14]
3748Sounding RecordBound record book in which all of the data taken on a hydrographic survey are entered, and become part of the permanent records of the survey. Also called sounding book. [14]
3749Sounding: DriftA method of finding the least depth in a shoal area by letting the boat drift along a series of closely spaced, previously run parallel sounding lines, while the leadsman sounds or 'feels' along the bottom. The operation is repeated until the shoal is found or the area is covered. [14]
3750Speed Made GoodThe actual velocity of the ship along a course measured in relation to the ocean bottom or to fixed objects ashore. [14]
3751Speed: RelativeSee relative motion. [14]
3752St. Elmo'S FireA bright electric discharge that is projected from objects (usually pointed) when they are in a strong electric field, such as during a thunderstorm. [1]
3753Stadia ConstantThe constant which is multiplied by the stadia interval to obtain the length of a sight in meters. [14]
3754Stadia IntervalThe length of rod subtended between the top and the bottom cross wires in the levelling instrument as seen projected against the face of the levelling rod. [14]
3755StandardizationThe comparison of an instrument or device with a standard to determine the value of the instrument or device in terms of an adopted unit. See calibration. [14]
3756Star IdentifierSee star finder. [14]
3757Station: 'Lost'See station: unrecoverable. [14]
3758Station: SurveySee station. [14]
3759Stationary WaveSee wave: standing. [14]
3760Stream: IngoingSee flood stream. [14]
3761Streamline FlowSee laminar flow. [14]
3762Submarine CableAn assembly of wires or fibres, or a wire rope or chain, which has been laid underwater or buried beneath the sea floor. [14]
3763Submarine RidgeAn elongated elevation of the sea floor, with either irregular or relatively smooth topography and steep sides which constitutes a natural prolongation of land territory. [14]
3764Subtense MethodA procedure by which distance measurements are obtained by use of a subtense bar. [14]
3765Summer SolsticeApproximately June 21 in the northern hemisphere when the sun is highest in the sky and directly overhead at latitude 231d2°n, the tropic of cancer. [1]
3766Summer SolsticeSee solstice. [14]
3767SupersaturationA condition whereby the atmosphere contains more water vapor than is needed to produce saturation with respect to a flat surface of pure water or ice, and the relative humidity is greater than 100 percent. [1]
3768Surface CurrentSee current. [14]
3769Surface CurrentThe current at the sea surface, which is partly due to the effects of wind and waves. Empirically, it is found that the drift current at the surface is 2.5%–3.0% of the wind speed, and it decreases rapidly in the uppermost meter. [5]
3770Surge: NegativeAn occasion when the level of the sea is lower than the predicted level. It is caused by meteorological conditions. [14]
3771Surge: PositiveAn occasion when the level of the sea is higher than the predicted level. It is caused by meteorological conditions. [14]
3772Surging BreakerSee breaker. [14]
3773Survey TraverseSee traverse. [14]
3774Survey: CoastalHydrographic survey of coastal area including coast lining. [14]
3775Survey: HarbourHydrographic survey of a harbor area. [14]
3776Survey: RunningA hydrographic survey in which the greater part of the work is done from the ship steaming along the coast. A line of sounding is run on the course made good and any additional information of a hydrographic nature which can be obtained whilst under way, is collected. [14]
3777Survey: TaglineA large scale survey made by employing a tagline. An accurate method sometimes adopted in river and harbor work. [14]
3778Swath(E) SystemAny of a number of systems which are capable of obtaining a strip or lane of elevations or soundings from a single survey platforms ™s track. In hydrography, systems that fall into this category are multi beam echo sounders (mbes), interferometric echo sounders and lidar. [14]
3779Tape: ReferenceSee reference tape. [14]
3780TeleconnectionsA linkage between weather changes occurring in widely separated regions of the world. [1]
3781Theodolite AxesSee axis: horizontal and axis: vertical. [14]
3782Theodolite DragSee drag (of theodolite). [14]
3783Thermal EquatorSee equator. [14]
3784Threshold SpeedThe minimum speed of current at which a particular current meter will measure at its rated reliabi-lity. [14]
3785Tidal AmplitudeThe average difference between water levels at high and low tide ; One-half of the difference in height between consecutive high water and low water; hence, half of the tidal range. [6][8]
3786Tide(S): SpringThe tides of increased range occurring near the times of full moon and new moon. [14]
3787Tide: VanishingThe phenomenon occurring when a high and low water 'melt' together into a period of several hours with a nearly constant water level. The tide is in the diurnal category but is known as a 'vanishing tide'. [14]
3788Time: UniversalSee universal time (ut). [14]
3789Tornado WarningA warning issued when a tornado has actually been observed either visually or on a radar screen. It is also issued when the formation of tornadoes is imminent. [1]
3790Torsion BalanceA device for measuring very small forces of attraction resulting from gravitation, magnetism, etc., and consisting of a bar suspended horizontally by an elastic filament, one end of the bar being subjected to the influence of the attracting force to a greater degree than the other end. The attracting force is balanced and its comparative strength measured by the torsional reaction of the filament. [14]
3791Track: IntendedThe anticipated path of a vessel relative to the earth. [14]
3792Transit BearingSee bearing. [14]
3793Tripping DeviceA device to pull equipment out of or to lower it into water. [14]
3794Tubular CompassSee compass. [14]
3795Ultrashort WaveSee wave. [14]
3796Universal LevelSee level: spirit. [14]
3797Unsurveyed AreaAn area where hydrographic survey data is non-existent. [14]
3798Vanishing PointIn photogrammetry, the image in the plane of a photograph, of the point toward which a system of parallel lines in the object space converges. [14]
3799Visible HorizonSee horizon: apparent. [14]
3800Water LevellingSee levelling. [14]
3801Wave GenerationThe creation of waves by natural or mechanical means. In wave forecasting the growth of waves caused by a wind blowing over a water surface for a certain period of time. The area involved is called the generating area or fetch. [14]
3802Wave(S): DampedWave(s) the amplitude of which becomes progressively smaller. [14]
3803Wave: CapillaryA wave whose velocity of propagation is controlled primarily by the surface tension of the liquid in which the wave is travelling. Water waves of length less than one inch are considered to be capillary waves. [14]
3804Wave: CycloidalA very steep, symmetrical wave whose crest forms an angle of 120 degrees. The wave form is that of a cycloid. A trochoidal wave of maximum steepness. [14]
3805Wave: ReflectedA wave that has had its direction of motion changed by reflection. [14]
3806Wave: RefractedA wave that has had its direction of motion changed by refraction. [14]
3807Wave: SphericalA wave whose wave front surfaces are concentric spheres. Such waves propagate from a point source. [14]
3808Weather WarningA forecast indicating that hazardous weather is either imminent or actually occurring within the specified forecast area. [1]
3809Well: AppraisalA borehole drilled to evaluate an oil field or gas field. [14]
3810Well: SuspendedA borehole that has been temporarily abandoned pending future development. An obstruction up to 5 meters high may remain on the sea-floor. [14]
3811Yaw (Or Yawing)The ship's oscillation about a vertical axis approximately through the center of gravity of the vessel. [14]
3812Zonal Wind FlowA wind that has a predominate west-to-east component. [1]
3813Zone Of SilenceSee blind zone. [14]
3814Zone: EquiphaseThat region in space within which the difference in phase of two radio signals is indistinguishable. [14]
3815Accidental ErrorSee error. [14]
3816Acoustic BearingSee bearing: sonic. [14]
3817Active SatelliteAn artificial satellite which transmits an electromagnetic signal. A satellite with the capability to transmit, repeat, or retransmit electromagnetic information as contrasted with passive satellite. 2. As defined by the international telecommunication union (itu), an earth satellite carrying a station intended to transmit or retransmit radiocommunication signals. [14]
3818Aeromarine LightSee light. [14]
3819Altimeter: RadarSee altimeter: radio. [14]
3820Altitude: FlightThe vertical distance above a given datum, usually mean sea level, or an aircraft in flight. [14]
3821Angle: ConcludedIn a triangulation, the third angle of a triangle, not measured, but computed from the other two angles. [14]
3822Angle: VectorialSee coordinates: plane polar and coordinates: polar. [14]
3823Anomalistic YearSee year. [14]
3824Anomaly: GravitySee gravity anomaly, bouguer anomaly, free air anomaly, isostatic anomaly. [14]
3825Antarctic CircleThe geographic parallel having a south latitude equal to the complement of the declination of the winter solstice (latitude = 66 deg 33' s approximately). [14]
3826Atmosphere: FreeThat part of the atmosphere above the friction layer, in which the air motion is affected to a negligible degree by surface friction. [14]
3827Atmosphere: IcaoStandard atmosphere adopted by the international civil aviation organization (ICAO). Its main features are mean sea-level pressure of 1013.25 mb, and a temperature lapse rate of 6.5° c/km from surface to the tropopause situated at 11 km. [14]
3828Atmospheric DragA major perturbation of close artificial satellite orbits by the resistance of the atmosphere. [14]
3829Aurora AustralisAurora of the southern hemisphere. [14]
3830Autumnal EquinoxThe equinox at which the sun approaches the southern hemisphere and passes directly over the equator. Occurs around September 23. [1]
3831Axis: HorizontalIn a theodolite or transit, the axis about which the telescope of the instrument rotates when moved vertically. Also called trunnion axis, or transit axis. [14]
3832Azimuth: ForwardSee azimuth: geodetic. [14]
3833Azimuth: LaplaceA geodetic azimuth derived from an astronomic azimuth by means of the Laplace equation. [14]
3834Azimuth: ReverseSee azimuth: back. [14]
3835Backrush CurrentSee current: backrush. [14]
3836Ballistic CameraSee camera. [14]
3837Baseline: NormalThe low-water line along the coast as marked on large-scale charts officially recognized by the coastal state. [14]
3838BathythermographA device for obtaining a record of temperature against depth in the ocean, from a ship underway. [14]
3839Bay Closing LineA line dividing the internal waters and territorial seas in a bay. [14]
3840Bearing: CompassSee bearing. [14]
3841Bearing: TransitA bearing taken of two objects when in line. [14]
3842Bifurcation BuoySee buoy: bifurcation. [14]
3843Block CorrectionSee chartlet. [14]
3844Bottom SedimentsSee sediments: bottom. [14]
3845Bridge ClearanceSee clearance. [14]
3846Broad On The BowBearing 045° relative (broad on the starboard bow) or 315° relative (broad on the port bow). If the bearings are approximate, the expression on the bow should be used. See also on the bow. [14]
3847Bull'S Eye LevelSee level: spirit. [14]
3848Cable: SubmarineAn insulated, waterproof wire or bundle of wires for carrying an electric current under water. [14]
3849Cadastral SurveySee survey. [14]
3850Calling-In Pointa designated position at which vessels are required to report to a traffic control center. Also called reporting point or radio reporting point. [14]
3851Camera: Deep SeaA camera system specially designed for obtaining photographs of the ocean bottom. [14]
3852Camera: TrackingSee camera: ballistic. [14]
3853Cathode-Ray TubeA vacuum tube in which electrons emitted by a hot cathode are formed into a narrow beam, accelerated at high velocity and directed towards a specially prepared screen which fluoresces at the point where the electrons strike. [14]
3854Chain AdjustmentA mathematical adjustment of a whole series of figures, for example, a chain of triangulation. [14]
3855Chart ProductionAll processes in the design, compilation, draughting and reproduction of a chart. [14]
3856Chart ProjectionSee projection. [14]
3857Chronometer RateThe amount gained or lost by a chronometer in a unit of time. It is usually expressed in seconds per 24 hours, and is sometimes called daily rate. [14]
3858Circle: VerticalA great circle on the celestial sphere passing through the zenith and nadir. Vertical circles are perpendicular to the horizon. In a surveying instrument, the graduated circle used for measuring vertical angles. [14]
3859Collimator: AutoA collimator provided with a means of illuminating its cross hairs so that, when a reflecting plane is placed normal to the emergent light beam, the reflected image of the cross hairs appears to be coincident with the cross hairs themselves. This device is used in calibrating optical and mechanical instruments. [14]
3860Comb: MicrometerSee micrometer. [14]
3861Compact Pack IcePack ice in which the concentration is 10/10 (8/8) and no water is visible. [14]
3862Compass: DippingSee dip circle. [14]
3863Compass: TubularA compass supplied for attachment to certain types of levels and theodolites. [14]
3864Contour IntervalThe difference in elevation between adjacent contours. [14]
3865Contour SweepingA form of bar sweeping. A sweep, set at a predetermined depth, and passed over the bottom at right angles to the depth contours. When contact is made the position is recorded. [14]
3866Convection: FreeIn the atmosphere, convection caused by density differences within the air. [14]
3867Convergence ZoneIn oceanography, region of convergence. The region in the deep ocean where sound rays, refracted from the depths, arrive at the surface in successive intervals of 30 to 35 nautical miles. [14]
3868Corer: PolyvinylSee corer: hydroplastic. [14]
3869Cosmic RadiationRadiation, of very high energy and great penetrative power, which emanates from cosmic regions. [14]
3870Course: MagneticSee course. [14]
3871Crepuscular RaysAlternating light and dark bands of light that appear to fan out from the sun's position, usually at twilight. [1]
3872Current: CoastalA relatively uniform drift usually flowing parallel to the shore in the deeper water adjacent to the surf zone. [14]
3873Current: DensityA gradient current caused by the horizontal gradient of water density. [14]
3874Current: DiurnalThe type of tidal current having only one flood and one ebb period in a tidal day. [14]
3875Current: SurfaceA current that does not extend more than a few (2-3) meters below the surface. [14]
3876Cycle Per SecondA unit of frequency more and more superseded by the hertz. [14]
3877Cylindrical BuoySee can buoy. [14]
3878Datum: LevellingSee datum: vertical control. [14]
3879Day: ConstituentThe duration of one rotation of the earth on its axis, with respect to a fictitious star representing one of the periodic elements in the tidal forces. It approximates the length of a lunar or solar day. The expression is not applicable to a long-period constituent. [14]
3880Deadbeat CompassSee compass. [14]
3881Deep Water RouteA route in a designated area within defined limits which has been accurately surveyed for clearance of sea bottom and submerged obstacles to a minimum indicated depth of water. [14]
3882Degaussing CableSee cable. [14]
3883DendrochronologyThe analysis of the annual growth rings of trees as a means of interpreting past climatic conditions. [1]
3884Direct LevellingSee levelling. [14]
3885Distortion: LensSee distortion. [14]
3886Double Low WaterSee low water. [14]
3887Drafted OriginalA scribed or drafted chart or portion of a chart on stable base material, which may be processed for final reproduction. [14]
3888Drifting LogshipA logship employed for the measurement of tidal streams and currents. It is allowed to drift freely while its positions are fixed, during the period of observation, by an accompanying boat, or from stations ashore. [14]
3889Duration Of TideThe time interval between low water and the following high water or between high water and the following low water. [14]
3890Eagre (Or Eager)See bore. [14]
3891Eclipse: AnnularAn eclipse in which a thin ring of the source of light appears around the obscuring body. Annular solar eclipses occur, but never annular lunar eclipses. [14]
3892Eclipse: PartialAn eclipse in which only part of the source of light is obscured. [14]
3893ElectrostrictionTerm applied to the creation of elastic tension and changes of shape and volume of an uncharged isolator by an electrical field. [14]
3894Equation Of TimeThe correction to be applied to 12 hours plus universal time to obtain the Greenwich hour angle of the sun, or more generally the correction to be applied to 12 hours plus local mean time to obtain the local hour angle of the sun. [14]
3895Equation: NormalOne of a set of simultaneous equations derived from observation, condition or correlate equations. In a least-squares adjustment, values obtained from the solution of normal equations (either directly or through the correlate equations) are applied to the observation or condition equations to obtain the desired corrections. [14]
3896Equator: ThermalLine which circumscribes the earth and connects all points of highest mean annual temperature on each meridian. Also called heat equator. [14]
3897Equatorial CalmsZone of calm or light variable winds encountered, in certain regions, between the trade winds of the two hemispheres. [14]
3898Equinoctial YearSee year: tropical. [14]
3899Equivalent ScaleSee scale. [14]
3900Error: IrregularSee error: accidental. [14]
3901Everest SpheroidSee reference spheroid. [14]
3902Expansion FactorIn radiolocation, factor representing the degree to which the hyperbolae belonging to a given group of hyperbolic lines of position move apart as the distance from the base line increases. [14]
3903Eye Of The StormSee tropical cyclone. [14]
3904Fahrenheit ScaleA temperature scale where 32 is assigned to the temperature where water freezes and 212 to the temperature at which water boils (at sea level). [1]
3905Field InspectionIn photogrammetry, the process of comparing aerial photographs with conditions as they exist on the ground, and of obtaining information to supplement or clarify that not readily discernible on the photographs themselves. [14]
3906Fiord (Or Fjord)A long narrow arm of the sea, running up between high banks or cliffs, as on the coast of norway. Often has a relatively shallow sill across its entrance. [14]
3907Fix: Three-PointA fix obtained by simultaneously observing, with sextants, the two adjacent angles between three suitably disposed objects whose positions are known, and plotting the position by a station pointer. See also resection and three-point problem. [14]
3908Flat-Bed PlotterA plotter which uses a flat surface to mount the drawing base. [14]
3909Fractional ScaleSee scale: natural. [14]
3910Free-Air AnomalyThe difference between observed gravity and theoretical gravity which has been computed for latitude and corrected for elevation of the station above or below the geoid, by application of the normal rate of change of gravity for change of elevation, as in free air. Also called faye anomaly. [14]
3911Geostrophic WindThat horizontal wind velocity for which the coriolis force exactly balances the horizontal pressure force. [14]
3912Grid DeclinationThe angular difference in direction between grid north and true north. It is measured east or west from true north. [14]
3913Hanging TraverseSee traverse: open. [14]
3914Helmert SpheroidSee reference spheroid. [14]
3915High Water (H.W)The highest level reached at a place by the water surface in one oscillation. Also called high tide. [14]
3916High Water StandSee stand of tide. [14]
3917Highland ClimateThe climate of high elevations. Also called mountain climate. There is no single climatic type but a variety of different climate zones often characterized by a rapid change in temperature and precipitation as one ascends or descends in elevation. [1]
3918Hydrologic CycleA model that illustrates the movement and exchange of water among the earth, atmosphere, and oceans. [1]
3919Hydrologic FrontA relatively narrow transition zone separating two water masses in the ocean. [14]
3920Index CorrectionThat correction due to index error. [14]
3921Innocent PassageNavigation through certain sea areas of a coastal state without being prejudicial to the peace, good order or security of that state. See also transit passage. [14]
3922Intensity: SoundAt a point, the average rate of sound energy transmitted in a specified direction through a unit area normal to this direction at the point considered. The square of the sound pressure. [14]
3923Inverted CompassSee compass: hanging. [14]
3924Ionospheric WaveSee wave: sky. [14]
3925Isomagnetic LineA line connecting points of equality in some magnetic element. [14]
3926Laplace EquationSee equation. [14]
3927Large Correction(British terminology). A new printing of a chart corrected from important information which is too comprehensive to promulgate by admiralty notices to mariners or to insert conveniently by hand on existing copies of the chart. When large corrections are made, the chart is not revised throughout but all copies in circulation are cancelled. [14]
3928Leading Light(S)See light. [14]
3929Lenticular CloudA cloud in the shape of a lens. [1]
3930Level: UniversalSee level: spirit. [14]
3931Levelling: WaterA method of obtaining relative elevations by observing heights with respect to the surface of a body of still water, such as a lake. The relative elevations of objects along its shores are obtained by taking the differences of their heights with respect to the surface of the water. [14]
3932Light(S): RunwayLights marking a runway. [14]
3933Light: CatoptricA light concentrated into a narrow beam by means of one or more reflectors (as opposed to dioptric). [14]
3934Light: OccultingA rhythmic light in which the total duration of light in a period is clearly longer than the total duration of darkness and all the eclipses are of equal duration. [14]
3935Light: RevolvingSee light: rotating. [14]
3936Light: UnwatchedA navigational light, usually automatic in operation, without any permanently stationed personnel to superintend it. [14]
3937Litre (Or Liter)The basic unit of capacity in the metric system. It is equal to one cubic decimetre. [14]
3938Local Hour AngleSee hour angle. [14]
3939Log Factor ScaleSee scale. [14]
3940Longitude FactorThe change in longitude along a celestial line of position per 1' change in latitude. [14]
3941Longitude SignalSee signal. [14]
3942Low Water (L.W.)The lowest level reached at a place by the water surface in one oscillation. Also called low tide. [14]
3943Lowest Low WaterAn arbitrary level conforming to the lowest tide observed at a place, or somewhat lower. [14]
3944Loxodromic CurveA loxodrome. A rhumb line. [14]
3945Lunar InequalityVariation in the moon's motion in its orbit, due to attraction by other bodies of the solar system. See evection, perturbation. A minute fluctuation of a magnetic needle from its mean position, caused by the moon. [14]
3946Magnetic AzimuthSee azimuth. [14]
3947Magnetic EquatorSee equator. [14]
3948Magnetic StationSee station. [14]
3949Magnifying GlassA lens or combination of lenses that increases the apparent size of an object seen through it. [14]
3950Magnifying PowerThe ratio of the apparent length of a linear dimension as seen through an optical instrument to that seen by the unaided eye. Sometimes shortened to power. [14]
3951Maintained DepthThe depth at which a channel is kept by human influence, usually by dredging. [14]
3952Map: PlanimetricA map which presents only the horizontal positions for the features represented; distinguished from a topographic map by the omission of relief in measurable form. [14]
3953Map: TopographicA map which represents the horizontal and vertical positions of the features represented; distinguished from a planimetric map by the addition of relief in measurable form. A topographic map uses contours or comparable symbols to show mountains, valleys and plains. [14]
3954Marine BarometerSee barometer. [14]
3955Mean Spring RiseThe height of mean high water springs above the chart datum. Also called spring rise. [14]
3956Mercator SailingSee sailing. [14]
3957Meridian SailingSee sailing. [14]
3958Meridional PlaneAny plane containing the polar axis of the earth. [14]
3959Metre (Or Meter)The basic unit of length in the si system. [14]
3960Mid-Channel BuoyA buoy for marking the middle of a channel. [14]
3961Middle LatitudesThe region of the world typically described as being between 30° and 50° latitude. [1]
3962Mid-Extreme TideSee tide. [14]
3963Mirage: InferiorParticular case of mirage, occurring over stretches of water, land, shores, roads, etc. Strongly heated by insolation, and in which the virtual image is found below the actual object. The case in which objects situated on or slightly above the normal horizon become invisible is popularly termed sinking. [14]
3964Mirage: SuperiorSpecial case of mirage, observable over snow-fields, cold seas, etc., in which the virtual image is above the actual object. The case in which objects below and beyond the normal horizon become visible is popularly termed looming. [14]
3965Month: DraconticSee month: nodical. [14]
3966Month: SynodicalThe interval of time between two successive conjunctions or oppositions of the moon. The length of the synodical month is 29.5305888 mean solar days. Also called lunation or lunar month. [14]
3967Morse Code LightSee light. [14]
3968Navigable WatersWaters usable, with or without improvements, as routes for commerce in the customary means of travel on water. [14]
3969Navigation: GridNavigation by the use of grid directions. [14]
3970Nontidal CurrentSee current. [14]
3971Obstruction BuoyA buoy marking an obstruction. [14]
3972Occasional LightSee light. [14]
3973Operating SystemSystem which controls and monitors the execution of programs in the computer. [14]
3974OrthophotomosaicAn assembly of orthophotographs forming a uniform-scale mosaic. [14]
3975Outfall DiffuserA structure on an outfall through which liquids are discharged. The structure will usually project above the level of the outfall and can be an obstruction to navigation. [14]
3976Outflow BoundaryA surface boundary separating cooler more-dense air from warmer less-dense air. Outflow boundaries formed by the horizontal spreading of cool air that originated inside a thunderstorm. [1]
3977Overlapping PairIn photogrammetry, two photographs taken at different exposure stations in such a manner that a portion of one photograph shows the same terrain as shown on a portion of the other photograph. This term covers the general case and does not imply that the photographs were taken for stereoscopic examination. See also stereoscopic pair. [14]
3978Overshooting TopA situation in a mature thunderstorm where rising air, associated with strong convection, penetrates into a stable layer (usually the stratosphere), forcing the upper part of the cloud to rise above its relatively flat anvil top. [1]
3979Parachute DrogueSee drogue. [14]
3980Parallactic GridSee grid. [14]
3981Parallax: LinearSee parallax: absolute stereoscopic. [14]
3982Parallel SailingSee sailing. [14]
3983Parallel: GroundIn photogrammetry, the intersection of the plane of the photograph with the plane of reference of the ground. See also axis of homology. [14]
3984Particular ScaleSee scale. [14]
3985Peak Wave PeriodTp ; The wave period with the highest energy. ; Determined by the inverse of the frequency at which a wave energy spectrum reaches its maximum. ; Reciprocal of the frequency corresponding to the largest value (peak) of the frequency wave spectrum. The frequency wave spectrum is obtained by integrating the two-dimensional wave spectrum over all directions. [9][10][11]
3986Pelagic DivisionIn the classification of the marine environment and its inhabitants, a primary division of the sea which includes the whole mass of water. The division is made up of the neritic province which includes that water shallower than 200 meters, and the oceanic province which includes that water deeper than 200 meters. The other primary division of the sea is the benthic division. [14]
3987Pendulum SextantSee sextant. [14]
3988Periodic CurrentSee current. [14]
3989Periodic Wave(S)See wave. [14]
3990Perspective GridSee grid. [14]
3991Phase InequalityVariations in the tides or tidal currents associated with changes in the phase of the moon. [14]
3992Phase ModulationSee modulation. [14]
3993PhotodelineationThe delineation of features on a photograph. See also compilation. [14]
3994PhotolithographyThat branch of lithographic printing in which photography is employed for production of the image on the final printing surface. The original printing surface, lithographic stone, has been almost completely displaced by thin and flexible sheets of metal (zinc, aluminium, stainless steel, bimetallic plates, polymetallic plates). [14]
3995PhotozincographyThe use of a zinc plate in photoengraving. [14]
3996PiezoelectricityThe property exhibited by some asymmetrical crystalline materials which when subjected to strain in suitable directions develop electric polarization proportional to the strain. Inverse piezoelectricity is the effect in which mechanical strain is produced in certain asymmetrical crystalline materials when subjected to an external electric field; the strain is proportional to the electric field. [14]
3997Planet(S): MajorThe four largest planets (jupiter, saturn, uranus and neptune). [14]
3998Planet(S): MinorSee asteroid. [14]
3999Plunging BreakerSee breaker. [14]
4000Point Of ArrivalSee arrival: point of. [14]
4001Polar EasterliesA shallow body of easterly winds located at high latitudes poleward of the subpolar low. [1]
4002Progressive WaveSee wave. [14]
4003Prolate SpheroidSee spheroid. [14]
4004Prominent ObjectObjects which are easily identifiable, but do not justify being classed as conspicuous. [14]
4005Propagated ErrorAn error which occurs in one operation and contaminates subsequent operations. [14]
4006Protractor: CustSquare or rectangular sheet of transparent xylonite engraved with a circle graduated in degrees and half degrees. Observed angles are drawn, in general, on the under side. See protractor: three arm. [14]
4007Pulse ModulationSee modulation. [14]
4008Radar: SecondarySee radar: primary. [14]
4009Radio Fog SignalSee fog signal. [14]
4010Radiobeacon BuoySee buoy. [14]
4011Radius: CruisingSee cruising radius. [14]
4012Reduced LatitudeSee latitude: parametric. [14]
4013Reference ObjectA well-defined object selected as a starting point in the direction method of observation. [14]
4014Relative BearingSee bearing. [14]
4015Scale: NumericalSee scale: natural. [14]
4016Scale: PrincipalThe scale of a reduced or generating globe representing the sphere or spheroid defined by the fractional relation of their respective radii. [14]
4017Scales Of MotionThe hierarchy of atmospheric circulations from tiny gusts to giant storms. [1]
4018Seasonal CurrentSee current. [14]
4019Seismic Sea WaveSee tsunami. [14]
4020Sensible HorizonSee horizon. [14]
4021Sensitive BubbleSee level: spirit. [14]
4022Sequence Of TideThe order in which the tides of a day occur, with special reference to whether the higher high water immediately precedes or follows the lower low water. [14]
4023Signal: LuminousIn surveying, a signal consisting of heliotrope or heliostat by day, and selenotrope or signal lamp by night. [14]
4024Skew ConvergenceThe angle, on a skewed projection, between true north and skew north. [14]
4025Solsticial PointSee solstice. [14]
4026Sonic NavigationSee navigation. [14]
4027Sounding MachineAn instrument for measuring depth of water, consisting essentially of a reel of wire to one end of which is attached a weight which carries a device for recording the depth. A crank or motor is provided for reeling in the wire. [14]
4028Sounding: DangerA minimum sounding chosen for a vessel of specific draft in a given area to indicate the limit of safe navigation. [14]
4029Space ModulationSee modulation. [14]
4030Specific Gravity