The ‘standard’ nautical mile is taken as 6080 feet (1.151 statute miles or 1853 metres) and is the unit of length used in sea and air navigation.

A mile on land is equal to 5280 feet (1609.3 metres), while a sea or nautical mile is one-sixtieth of a degree of latitude, and varies from 6046 feet on the Equator, to 6092 feet at a latitude of 60°. This difference is due to the Earth not being a perfect sphere, but slightly flattened at the poles – an oblate spheroid. To avoid confusion, the standard nautical mile is accepted as 6080 feet.

Speed at sea is measured in knots, a knot being one nautical mile per hour.