Geographic coordinates are used on the surface of the Earth. An equivalent system called planetographic coordinates is used for other planets. Alternative titles, such as areographic coordinates on Mars, selenographic coordinates on the Moon, and heliographic coordinates on the Sun, are sometimes used to refer to the equivalent systems. The definition of planetographic coordinates requires a scheme for assigning longitude and latitude lines. For each planet, a system of longitude lines is set up by first defining a prime meridian to act as the origin of longitude. A meridian is any line that begins at one pole of the planet and ends at the other pole. The prime meridian is an arbitrarily chosen meridian, typically passing through a prominent feature of the planet, such as a crater. [ - ]

Geographic coordinates are used on the surface of the Earth. An equivalent system called... [ + ]