GPS sats aren't geosynchronous. That would be an orbital period of one (sidereal) day which matches the Earth's rotation. GPS has an orbital period which is half that. So after 11 hours and 58 minutes, you'll have the same satellites over you in the same positions, but they will have gone around the planet twice in the meantime. Cool animation here: http://en.wikipedia.org/wiki/Global_Positioning_System#Space...