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Eng ID Term Definition
1361
differential levelling
See LEVELLING.
1362
differential mode
A method of accurate positioning; transmissions of an electromagnetic position fixing system are received at known positions ashore and the ... more
A method of accurate positioning; transmissions of an electromagnetic position fixing system are received at known positions ashore and the offsets between absolute known positions and system positions are transmitted to the ship in the vicinity. The offsets are applied to the measurements of the ship's receiver.
1363
differential shrinkage
In mapping, the difference in unit contraction along the grain structure of the material as compared to the unit contraction across the grai... more
In mapping, the difference in unit contraction along the grain structure of the material as compared to the unit contraction across the grain structure; frequently refers to photographic film and papers and to map materials in general.
1364
diffraction
The 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 ... more
The 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 WAVE LENGTH of component WAVES, producing, for visible WAVE LENGTHS, the chromatic SPECTRUM. The bending of a WAVE as it passes an obstruction.
1365
digital
A method of representing information by combinations of discrete and discontinuous data.
1366
digital chart
See ELECTRONIC CHART.
1367
digital computer
See COMPUTER.
1368
digital imagery processing system
A system which processes images which are stored in digital form.
1369
digital terrain model (DTM)
A model representing the terrain surface by a collection of digital data, mainly coordinates in three dimensions, x, y, and z, and a digital... more
A model representing the terrain surface by a collection of digital data, mainly coordinates in three dimensions, x, y, and z, and a digitally defined method to interpolate arbitrary terrain heights in between the stored values. Not to be confused with digital cartographic model which may also contain digital data representing terrain, but in a form suitable for the drawing of a particular kind of map.
1370
digitization (or digitisation)
The process of converting analog data to digital data.
1371
digitizer
A computer aided device equipped with a digitizing table and a CURSOR for digitally capturing graphical data (pictures, charts), usually bas... more
A 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.
1372
dike (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 b... more
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.
1373
dilution of precision (DOP)
A parameter relating the precision of the position (and/or an unknown auxiliary) provided by a positioning system to that of the "observed q... more
A parameter relating the precision of the position (and/or an unknown auxiliary) provided by a positioning system to that of the "observed quantities" directly measured by the system. DOP is a measure of the influence of the geometry of loci on the precision of position fixing. DOP is frequently used with a qualifying term such as geometric (GDOP), horizontal (HDOP), vertical (VDOP) etc. to indicate that DOP is related to all or some unknown quantities.
1374
diopter
A unit of refractive power of an optical system in the SI system.
1375
dioptric light
See LIGHT.
1376
dip
The 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 h... more
The 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.
1377
dip circle
An instrument for measuring MAGNETIC DIP. It consists essentially of a DIP NEEDLE or MAGNETIC NEEDLE, suspended in such manner as to be free... more
An 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.
1378
dip correction
That CORRECTION to SEXTANT ALTITUDE due to the DIP OF THE HORIZON. Also called height of eye correction.
1379
dip (or dipping) needle
A MAGNETIC NEEDLE suspended in such a manner as to be free to rotate about a horizontal AXIS. See DIP CIRCLE.
1380
dip of a sea horizon
The vertical angle, at the eye of an observer, between the horizontal and the line of sight to the sea horizon.