Geodetic coordinates

By convention for the Earth, Moon and Sun, it is expressed in degrees ranging from −180° to +180°.

For other bodies a fixed surface feature is usually referenced, which for Mars is the meridian passing through the crater Airy-0.

The geodetic latitude is the angle between the equatorial plane and a line that is normal to the reference ellipsoid.

Depending on the flattening, it may be slightly different from the geocentric latitude, which is the angle between the equatorial plane and a line from the center of the ellipsoid.

Geodetic latitude is defined as the angle between the equatorial plane and the surface normal at a point on the ellipsoid, whereas geocentric latitude is defined as the angle between the equatorial plane and a radial line connecting the centre of the ellipsoid to a point on the surface (see figure).

There is no standard notation for geocentric latitude; examples include θ, ψ, φ′.