Knot (speed)

[Anzac]

1 international knot = 1 nautical mile per hour = 1.852 kilometres per hour exactly. This is based on the internationally agreed length of the nautical mile, as adopted by the US in 1954 (which previously used the US nautical mile of 1852.249 m), the UK in 1970 (which previously used the UK or Admiralty nautical mile of 1853.184 m) and other countries. This is the definition used in most, if not all, modern circumstances. Knot is sometimes mistakenly used to refer to the nautical mile itself, but this is incorrect.

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http://en.wikipedia.org/wiki/Knot_(speed)