Nautical mile favour of the international nautical mile in 1954. The Imperial nautical mile, often called an Admiralty mile, or more correctly, an Admiralty measured mile, was defined by its relation to the Admiralty knot, 6,080 imperial feet per hour, so 1 imperial nautical mile is about 1,853.181 metres. It was abandoned in 1970 and, legally, references to the obsolete unit are now converted to 1,853 metres. Despite the existence of precise modern definitions, in the early 21st century the old definitions are still in use. The Royal Yachting Association says in its manual for day skippers: "1 (minute) of Latitude =
Cylindrical equal-area projection many named specializations such as Gall–Peters or Gall orthographic, Behrmann, and Lambert cylindrical equal-area). This divides north-south distances by a factor equal to the secant of the latitude, preserving area but heavily distorting shapes. Any particular cylindrical equal-area map has a pair of identical latitudes of opposite sign (or else the equator) at which the east–west scale matches the north–south scale. All cylindrical equal-area projections use the formula: where "λ" is the longitude, "λ" is the central meridian, "φ" is the latitude, and "φ" is the standard latitude, all expressed in radians. Some cartographers prefer to work in degrees, rather