I talked about this in another thread about the INS waaaaaaaaaaaaaay back. If you load a FSX FP after you are in the sim, you simply use the NAV AP function and it tracks it just like you were using a GPS. As I recall there were a few comments after that about 'why would I want to, its not realisitic".

My reply was I upgraded my avionics   ::) So yes asanal, you are correct sorta, no actual GPS but it will track a FP just fine without programing the INS.