[basementcat]

Earth orbiting GNSS provides excellent position information near the surface of the Earth but poorer position information near the surface of the Moon. That said, the Falcon 9 is equipped with a decent inertial navigation system.

[m4rtink]

Yep, not sure about the high altitude flight, but terminal guidance is certainly not GPS based. I think it's mostly radar & they even painted their landing zone with some special paint a while ago to get better radar returns.