There are 3 primary variants of coordinate system and reference frame combinations.
| Domain | Coordinates | Reference Frame Type | Examples |
|---|---|---|---|
| Ground / Surface | Longitude & Latitude | Fixed (rotates with body) | IAU_EARTH, IAU_MOON, IAU_MARS, ITRF93, etc |
| Space | Right Ascension & Declination | Inertial (Non-rotating) | J2000, ECLIPJ2000 |
| Math | Rectangular | Intertial (Non-rotating) | J2000, ECLIPJ2000 |
For objects attached to a celestial body’s surface it is typical to reference positions in a “fixed” frame attached to the body by Longitude/Latitude/Altitude.
When discussing objects that are floating freely through space, a non-rotating Reference Frame is given, along with Right Ascension, Declination, and Range.
Almost all actual math is done in rectangular coordinate systems in non-rotating reference frames.
In the list above, Humans think most easily from top-down, while computers and mathematics think most easily from bottom-up.
These 3 variations cover the vast majority of cases.
