This system has its Z axis parallel to the Earth's rotation axis (positive to the North) and its X axis towards the intersection of the Equator and the Greenwich Meridian. Thus it is convenient for sp
ecifying the location of ground stations and ground-based experiments as these are fixed quantities in the GEO system.
When GEO coordinates are expressed in spherical form, the latitude component is identical what is termed geocentric latitude by astronomers and geographers. However, note that this is different to the system of geodetic latitude used in normal map-making. The geodetic latitude at any location is the angle between the equatorial plane and the local normal to the Earth's surface. In general that normal is NOT parallel to a radius vector because the shape of the Earth is an oblate spheroid and not a sphere.
Geographic - geocentric corotating - Acoordinate system where the Z axis is along Earth's spin vector, positivenorthward. X axis lies in Greenwich meridian, positive towards Greenwich.See Russell, 197
1.
The Geocentric Solar Equatorial System (GSEQ) as with the GSE system has its X-axis pointing towards the Sun from the Earth. However, instead of having its Y-axis in the ecliptic plane, the GSEQ Y-axi
s is parallel to the Sun's equatorial plane which is inclined to the ecliptic. We note that since the X-axis is in the ecliptic plane and therefore is not necessarily in the Sun's equatorial plane, the Z-axis of this system will not necessarily be parallel to the Sun's axis of rotation. However, the Sun's axis of rotation must lie in the X-Z plane. The Z-axis is chosen to be in the same sense as the ecliptic pole, i.e. northwards.