GPS doesn't care about population density. The signal comes from a satellite constellation in a geosynchronous orbit in space. it does require a more or less unobstructed path overhead to the sky. do not confuse this system with a cell-tower communication system which does have a dependency on population as towers are put where people are. Some phones use GPS info that has been retransmitted to the device via cell technology and gives the impression that there is such a dependency. A dedicated GPS speedometer will work fine.