Nautical mile

Sea mile - a unit of distance used in shipping and aviation ^[1] .

Initially, a nautical mile was defined as the length of an arc of a large circle on the surface of the globe the size of one angular minute . Thus, moving one nautical mile along the meridian approximately corresponds to a change in geographical coordinates by one minute of latitude .

Since the Earth actually does not have the shape of a ball , but a geoid (flattened from the poles), one minute of the meridian corresponds to about 1862 m at the pole and 1843 m at the equator (on average about 1852 m). According to the modern definition adopted at the International Hydrographic Conference in Monaco in 1929, the International Nautical Mile is exactly 1852 meters .

The nautical mile is not a SI unit, however, by decision of the General Conference on Weights and Measures , its use is allowed, although not recommended. A generally accepted designation does not exist; sometimes the abbreviations "NM", "nm" or "nmi" are used (from the English nautical mile ). It should be noted that the abbreviation "nm" coincides with the officially accepted designation of the nanometer .

International nautical mile = 10 cable = 1/3 nautical league

The nautical mile of Great Britain before the transition to the international system (until 1970) was 6080 feet (1853.18 meters ) ^[2] . This is due to the fact that they wanted to simplify the conversion from English miles to nautical. 800 feet were added to one British land mile (5280 feet ), and the length of the nautical mile (Admiralty Mile) was 6080 feet ^[3] .

The US nautical mile before the transition to the international system (until 1954) was 6080.20 feet (1853 meters) ^[2] .