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A chip log, also called common log, [1] ship log, or just log, is a navigation tool mariners use to estimate the speed of a vessel through water. The word knot, to mean nautical mile per hour, derives from this measurement method.
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 ...
Impeller log:A variation of this approach is known as a patent log, which is towed from the stern of a ship. The patent log includes a mechanical register that counts the log's rotations as it is being towed. The patent log was invented in 1688 by the English instrument maker Humphry Cole. The patent log is also known as a screw log or taffrail ...
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 ...
The knot ( / nɒt /) is a unit of speed equal to one nautical mile per hour, exactly 1.852 km/h (approximately 1.151 mph or 0.514 m/s ). [1] [2] The ISO standard symbol for the knot is kn. [3] The same symbol is preferred by the Institute of Electrical and Electronics Engineers ( IEEE ), while kt is also common, especially in aviation, where it ...
Chip log and sand glass serve to measure the ship's speed through the water. Sounding line used to measure the depth of the water and to pick up samples from the bottom. Drift meter optically measures the effects of wind on an aircraft in flight. Position finding instruments Celestial navigation instruments
Chip-log sandglass Ship log sandglass in the left of the chip log. From the 16th century a much smaller 30-second "glass" was used along with the chip log, to measure the speed (in knots) of the vessel over the water. The procedure was as follows: A sailor ran the chip log and another sailor the sandglass. The slide of the pulled over the stern ...
Sea trial. A sea trial is the testing phase of a watercraft (including boats, ships, and submarines ). It is also referred to as a "shakedown cruise" by many naval personnel. It is usually the last phase of construction and takes place on open water, and it can last from a few hours to many days. Sea trials are conducted to measure a vessel's ...