The knot (kn ) is a speed measurement in the maritime and aviation and meteorology, which is based on the unit of length nautical mile ( nm or NM, nmi, n.mi. nautical miles ):
- Definition: 1 knot = 1 nautical mile / hour = 1.852 km / h ≈ 0.514444 m / s
- Unit symbol: kn (English formerly kt)
The name derives from the nodes that are made in the line of Logscheits to highlight certain intervals (ideally a fraction of a mile ). The number of nodes that are covered in a given ( by the Logglas, a special hourglass specified ) time, results in the so-called speed through the water ( FoW ).
This FoW is nowadays much more accurately by other Logs ( hydrodynamic, electric, etc.). However, is important for the navigation speed over ground that is either with other navigation aids (GPS / GLONASS, terrestrial radio navigation ) or with knowledge of the ocean currents determined.
Since the nautical mile corresponds to a difference of latitude of a minute (1 '), for example, means a ship speed of 30 knots that will come to North or South course in one hour, half a degree of latitude.