Science Fair Project Encyclopedia
In some sailing ships, speed was measured by casting the log from the stern. The log was relatively immobile, and attached by line to a reel. Knots placed at a distance of 47 feet 3 inches (14.4018 m) passed through a sailor's fingers, while another used a 28 second sandglass to time the operation. The knot count would be reported and used in the sailing master's dead reckoning and navigation. This method gives a value for the knot of 20.25 in/s, or 1851.66 m/hr. The difference from the accepted value today is a bit less than 0.02%.
- KTAS is "knots true airspeed", a measure of an aircraft's true airspeed through the air
- KIAS is "knots indicated airspeed", meaning the airspeed shown on the airspeed indicator
- KCAS is "knots calibrated airspeed", or indicated airspeed corrected for position error
- KEAS is "knots equivalent airspeed", which is calibrated airspeed corrected for compressibility effects.
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