Just a thought I had... Given there is no stable magnetic field on Mars, our old-fashioned compasses would do no good there. Also, given there is no GPS (or MPS) network there, it isn't an option. So, what kind of technology stuff like rovers can use to keep track of what is North, East, etc... Do they rely on the Sun and other stars, relying on ephemerides and other astronomical data ? Or do rover operators navigate on sight, like knowing what those hills in the distance are, and instructing the rover to go straight on them, or leave them at a given angle on one side ? Just curious.