At all? How would it drive to the mall on the other side of town without GPS?
A map, plus the assumption that it never moves without being powered on.
(I'm sure it does use GPS for navigation. But it's hypothetically possible to do without.)
Seems like it might need GPS at times, or some other means to know where it is at certain moments. Once it establishes where it is then I could see it no longer needing GPS, as it should be bright enough to keep track of location by itself using a map.
Using just dead reckoning you would pretty quickly have issues with accumulated error.