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A nautical mile is a unit of length used in air, marine, and space navigation, and for the definition of territorial waters. [2] [3] [4] Historically, it was defined as the meridian arc length corresponding to one minute ( 1 / 60 of a degree) of latitude at the equator, so that Earth's polar circumference is very near to 21,600 nautical miles (that is 60 minutes × 360 degrees).
The geographical mile is an international unit of length determined by 1 minute of arc ( 1 / 60 degree) along the Earth's equator. For the international ellipsoid 1924 this equalled 1855.4 metres. [1] The American Practical Navigator 2017 defines the geographical mile as 6,087.08 feet (1,855.342 m). [2]
A second of arc, arcsecond (abbreviated as arcsec), or arc second, denoted by the symbol ″, [2] is a unit of angular measurement equal to 1 / 60 of a minute of arc, 1 / 3600 of a degree, [1] 1 / 1 296 000 of a turn, and π / 648 000 (about 1 / 206 264.8 ) of a radian.
As one degree is 1 / 360 of a circle, one minute of arc is 1 / 21600 of a circle – such that the polar circumference of the Earth would be exactly 21,600 miles. Gunter used Snellius's circumference to define a nautical mile as 6,080 feet, the length of one minute of arc at 48 degrees latitude. [24]
1 meridian minute: 1,853.181: Turkish (nautical) mile: Turkey: 1933: today: 1,855.4 (for comparison) 1 equatorial minute: Though the NM was defined on the basis of the minute, it varies from the equatorial minute, because at that time people could only estimate the circumference of the equator to be 40,000 km. 1,894.35: Ottoman mile: Ottoman ...
A diagram illustrating great-circle distance (drawn in red) between two points on a sphere, P and Q. Two antipodal points, u and v are also shown. The great-circle distance, orthodromic distance, or spherical distance is the distance between two points on a sphere, measured along the great-circle arc between them. This arc is the shortest path ...
Geographical distance or geodetic distance is the distance measured along the surface of the Earth, or the shortest arch length. The formulae in this article calculate distances between points which are defined by geographical coordinates in terms of latitude and longitude. This distance is an element in solving the second (inverse) geodetic ...
where φ (°) = φ / 1° is φ expressed in degrees (and similarly for β (°)). On the ellipsoid the exact distance between parallels at φ 1 and φ 2 is m(φ 1) − m(φ 2). For WGS84 an approximate expression for the distance Δm between the two parallels at ±0.5° from the circle at latitude φ is given by