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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.
This unit uses a mercury-based manometer to measure the difference in static and dynamic water pressure. Pitometer logs (also known as pit logs) are devices used to measure a ship's speed relative to the water. They are used on both surface ships and submarines. Data from the pitometer log is usually fed directly into the ship's navigation system.
Appearance. 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 generated ...
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 ...
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: [2] [3] A sailor ran the chip log and another sailor the sandglass. The slide of the pulled over the stern and let ...
A taffrail log is a mechanical speed logging device, used like a car odometer. The taffrail log was towed from the stern or taffrail of the ship by a long line. Taffrail logs were developed in the eighteenth century and became a practical device in the nineteenth century. [7]
Engine order telegraph. An engine order telegraph or E.O.T., also referred to as a Chadburn, [1] is a communications device used on a ship (or submarine) for the pilot on the bridge to order engineers in the engine room to power the vessel at a certain desired speed.
Thomas Walker & Son were inventors and makers of nautical instruments in the 19th and 20th centuries. The firm made one of the most commonly used navigation instruments, the 'log' which allowed sailors to measure distance at sea, [1][2] one of the main measurements used in nautical navigation. The firm was founded by Thomas Walker in Birmingham ...