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Doppler Velocity Log (DVL): Some ships are equipped with sonar instruments that can measure the Doppler shift in a sound pulse generated by the ship's motion as it reflects off the ocean bottom or off particles in the water. The speed measurements from a Doppler instrument can therefore be relative to the ground, or to the water.
Electromagnetic log. An Electromagnetic Log, sometimes called an "EM log", is an electronic sensor which measures the speed of a vessel through sea water. Like many other technologies, its name derives from the traditional chip log. It makes use of Faraday's law of induction by measuring the EMF induced in water moving through a magnetic field ...
A chip log consists of a wooden board attached to a line (the log-line). The log-line has a number of knots at uniform intervals. The log-line is wound on a reel so the user can easily pay it out. Over time, log construction standardized. The shape is a quarter circle, or quadrant with a radius of 5 inches (130 mm) or 6 inches (150 mm), [1] and ...
The automatic identification system (AIS) is an automatic tracking system that uses transceivers on ships and is used by vessel traffic services (VTS). When satellites are used to receive AIS signatures, the term Satellite-AIS (S-AIS) is used. AIS information supplements marine radar, which continues to be the primary method of collision ...
The Decca Navigator System was a hyperbolic radio navigation system that allowed ships and aircraft to determine their position by using radio signals from a dedicated system of static radio transmitters. The system used phase comparison of two low frequency signals between 70 and 129 kHz, as opposed to pulse timing systems like Gee and LORAN.
A logbook (a ship's logs or simply log) is a record of important events in the management, operation, and navigation of a ship. It is essential to traditional navigation, and must be filled in at least daily. The term originally referred to a book for recording readings from the chip log that was used to estimate a ship's speed through the ...
Radar is a system that uses radio waves to determine the distance (ranging), direction (azimuth and elevation angles), and radial velocity of objects relative to the site. It is a radiodetermination method [1] used to detect and track aircraft, ships, spacecraft, guided missiles, motor vehicles, map weather formations, and terrain.
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