Latitude ( or ). It is measured in degrees, minutes and seconds or decimal degrees, north or south of the equator. The precise measurement of latitude requires an understanding of the gravitational field of the Earth, either to set up theodolites or to determine GPS satellite orbits. The study of the figure of the Earth together with its gravitational field is the science of geodesy. This article relates to coordinate systems for the Earth: it may be extended to cover the Moon, planets and other celestial objects by a simple change of nomenclature. The graticule is formed by the lines of
Latitude to radians, the arc distance is about The distance in metres (correct to 0.01 metre) between latitudes formula_7 − 0.5 degrees and formula_7 + 0.5 degrees on the WGS84 spheroid is The variation of this distance with latitude (on WGS84) is shown in the table along with the length of a degree of longitude (east-west distance): A calculator for any latitude is provided by the U.S. Government's National Geospatial-Intelligence Agency (NGA). The following graph illustrates the variation of both a degree of latitude and a degree of longitude with latitude. Historically a nautical mile was defined as the length of