What is the origin of knots as a nautical speed and measurement?

Answer 1

With modern technology, speed on the water can be measured and reported in any units imaginable. Knots are the standard unit of measure for historical purposes, because sailors counted knots on a rope as the ship advanced to estimate speed on the water.

Answer 2

What knots were was a crude speed measurement developed hundreds of years ago. You would literally tie evenly spaced knots into a rope, then put a board with a hole just a little too small for the knots to fit through on the rope and drag it in the water. After one hour you would pull the rope out, and however many knots the board had slid down was your speed, for example 5 knots would mean the board slid down 5 rope knots in one hour.

Answer 3

One knot is one nautical mile per hour, a length calculated from sea-level circumference hence linked directly to angles of latitude and longitude. There have been various ways to measure it.

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The oldest method used "logs" - small pieces of wood were dropped overboard from the bow of a ship, and the latter's speed then calculated from the time taken for the stern to pass the log. Later developments in navigation meant a mean speed could be derived from position and time measurements.

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More recently, various types of knot-meter were introduced based on a small propeller-like rotor turned by the water passing over its blades as the unit holding it was towed by the vessel. In theory one could use propeller speed (rpm) and pitch to derive speed through the water, but this is inherently inaccurate due to potentially somewhat unquantifiable propeller-slip. Nowadays it is normally calculated by GPS.

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The knot is also used in aviation, and on fast aeroplanes at least, the speed is measured from the effect of the slipstream past a "Pitot Tube": the air flow induces in a small metal tube a partial vacuum proportional to the speed. Like the logs and rotary speed-indicators on ships, this only gives speed through the medium. Speed "over ground" has to be calculated by allowing for tidal currents or wind velocities. Again, now, GPS systems give direct over-ground velocities (a 'velocity' is speed and direction).

Answer 4

The unit 'knots' originated at sea when ancient sailors used a chip board to measure the speed of their vessel. Knots means nautical miles per hour.

Answer 5

Nautical