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Eng ID Term Definition
1501
duck blinds
Nonfloating structures used for concealing waterfowl hunters. They usually consist of a wooden framework covered with brush. They are essent... more
Nonfloating 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.
1502
duct
A LAYER in the OCEAN or ATMOSPHERE where REFRACTION and, probably, REFLECTION result in the trapping and propagation within the LAYER of SOU... more
A LAYER in the OCEAN or ATMOSPHERE where REFRACTION and, probably, REFLECTION result in the trapping and propagation within the LAYER of SOUND WAVES or ELECTROMAGNETIC WAVES.
1503
due publicity
Notification of a given action for general information through appropriate authorities within a reasonable amount of time in a suitable mann... more
Notification 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.
1504
dumb compass
See PELORUS.
1505
dumping ground
A sea area where dredged material or other potentially more harmful material e.g. explosives, chemical waste, is deliberately deposited. Se... more
A sea area where dredged material or other potentially more harmful material e.g. explosives, chemical waste, is deliberately deposited. See also SPOIL GROUND.
1506
dumpy level
See LEVELLING INSTRUMENT: DUMPY LEVEL.
1507
dune
A mound, RIDGE or HILL of drifted SAND on the sea coast or in a desert. See SAND DUNE and DOWN.
1508
duplex
A method in which TELECOMMUNICATION between two STATIONS can take place in both directions simultaneously.
1509
duplexer
A switching device used to connect a TRANSMITTER and a RECEIVER to the same ANTENNA.
1510
duration of fall
See DURATION OF RISE AND FALL.
1511
duration of flood and duration of ebb
Duration 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 ebbin... more
Duration 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.
1512
duration of rise and duration of fall
Duration 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 t... more
Duration 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.
1513
duration of tide
The time interval between LOW WATER and the following HIGH WATER or between HIGH WATER and the following LOW WATER.
1514
dust
Any substance com­minuted or pulverized, especially EARTH or other solid matter in a minute and fine state of subdivision, so that the parti... more
Any 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.
1515
duststorm
Ensemble of particles of DUST or SAND energetically lifted to great HEIGHTS by a strong and turbulent WIND. Also called sandstorm. Also writ... more
Ensemble 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.
1516
Dutchman's log
See LOG.
1517
DX90-Format
Format for supply or interchange of digital cartographic data. DX90 provides two modes: the sequential, and the chain mode.
1518
dyke
See DIKE.
1519
dynameter
An instrument for measuring the MAGNIFYING POWER of a TELESCOPE.
1520
dynamic positioning
Manoeuvring of a vessel to keep a position relative to a seabed feature; normally underwater acoustic position fixing systems are used for t... more
Manoeuvring of a vessel to keep a position relative to a seabed feature; normally underwater acoustic position fixing systems are used for this purpose.