Nautical Mile

A unit of distance defined as exactly 1,852 metres.

The international nautical mile is approximately 1.1508 statute miles and underlies the knot, which is one nautical mile per hour. Its length was chosen to approximate one minute of arc along a great circle of the Earth.

One minute of latitude is close to a nautical mile but is not the modern unit’s definition and varies slightly with latitude on the reference ellipsoid. Chart scale and projection must still be considered when transferring or measuring distance.