No, you can describe any point in the universe using GPS coordinates. You just lose some resolution the further away from earth you are because it's basically spherical coordinates (like polar coordinates but for 3D). And the system isn't inertial but earth-fixed, of course, so you would have to give the coordinates together with a time.
And if you're describing the location of the moon and the sun, you would probably pick their center of gravity.
- Earth isn’t a universal reference
- GPS uses WGS84
- GPS is bound to the Earth’s surface and center
- It’s Geodetic
- There's no universal “equator” or “prime meridian” beyond Earth
- Space uses inertial frames or celestial coordinate systems (right ascension and declination, or galactic coordinates)
They are meaningless for things not near Earth because they’re tied to Earth's shape, rotation, and gravity field
And yes, you can transform between GPS coordinates and GCRS (or ECI/ECEF), depending on what you’re trying to do. The key distinction I’m making is about contextual meaning and application. GPS (WGS-84) coordinates are geodetic.
Once you're transforming positions millions of kilometers away (eg. L2, the Moon, or Mars) into lat/lon/alt, you're applying a system optimized for geodesy to a domain where the altitude is arbitrary, and "longitude" rotates with Earth.
If you’re saying it physically isn’t possible, then you’re basically saying the universe has some topological structure that cannot be projected onto the surface of a sphere. Which now that I’m thinking about it, is probably the case because of black holes? Lol maybe if the object is “in” a black hole then the coordinate actually is completely meaningless, but any other object would have some amount, even if low, of “meaning”
GPS coordinates are geodetic, tied to the WGS-84 ellipsoid and Earth’s rotating reference frame. They were designed for terrestrial navigation and near-Earth orbit, not for interplanetary space. Once you're dealing with the Moon, the Sun, or Lagrange points, you're so far outside the system's intended domain that projecting lat/lon/alt onto those locations introduces more confusion than clarity.
You're also right to point out that it's not physically impossible to describe a faraway object in that coordinate system.
There is just no practicable utility.
NASA and others use inertial frames, barycentric coordinates, and RA/Dec for a reason.
Also, love the black hole tangent - that’s where coordinate systems get seriously weird :-)