The latitude of a point on a Sphere is the elevation of the point from the Plane of the equator. The latitude is related to the Colatitude (the polar angle in Spherical Coordinates) by . More generally, the latitude of a point on an Ellipsoid is the Angle between a Line Perpendicular to the surface of the Ellipsoid at the given point and the Plane of the equator (Snyder 1987).
The equator therefore has latitude 0°, and the north and south poles have latitude , respectively. Latitude is also called Geographic Latitude or Geodetic Latitude in order to distinguish it from several subtly different varieties of Auxiliary Latitudes.
The shortest distance between any two points on a Sphere is the so-called Great Circle distance, which can be directly computed from the latitudes and Longitudes of the two points.
See also Auxiliary Latitude, Colatitude, Conformal Latitude, Great Circle, Isometric Latitude, Latitude, Longitude, Spherical Coordinates
Snyder, J. P. Map Projections--A Working Manual. U. S. Geological Survey Professional Paper 1395. Washington,
DC: U. S. Government Printing Office, p. 13, 1987.