The ecliptic coordinate system is a spherical coordinate system used for directions in the celestial sphere, fixed to the path of the Sun in the sky as seen from Earth, i.e., the ecliptic. The name, and the ecliptic are also used with rectangular coordinates. Spherical elements:
In the most usual rectangular system, the X-Y plane is the ecliptic and the X axis is the vernal equinox. Coordinates are three dimensional (X,Y,Z), and effectively specify a radius, i.e., distance to the object. A radius of 1 can be used if distance to the object is not intended to be specified.