High Quality Content by WIKIPEDIA articles! Geocentric coordinates are an Earth-centered system of locating objects in the solar system in three-dimensions along the Cartesian X, Y and Z axes. They are differentiated from topocentric coordinates which use the observer`s location as the reference point for bearings in altitude and azimuth. Both systems, however, share a common difficulty in that the Earth is constantly moving, which requires the addition of a time component to fix objects.