coordinate system

A means of specifying the position of a point or object, either in space or on a surface, in terms of its linear or angular distance from some specified plane, line or point. Latitude and longitude, for example, are the coordinates commonly used to specify the location of a place on the surface of the Earth. In astronomy, several different systems of celestial coordinates are used to define positions on the celestial sphere, each of which is designed for a particular application. Other coordinates are also used, such as the X, Y, Z three-dimensional spatial coordinates of the planets for defining their positions relative to the Sun and Earth.