phones dont actually need gps at all any more, but gps has nothing to do with cell towers. BUT youre more correct than you think. between signal strength triangulation and the sensors in your phone, it always knows exactly where you are, as do the people who can read the data that the phone sends out simply being connected to a cell network. the whole 'you have no gps connection, live navigation will not work' thing is kind of illusory. you can download your route so 'it still navigates while offline' and it will work out where on that map you are simply from the movements from your phone alone. im willing to bed that if you get a phone, completely remove its gps chip, and its cell antenna, and messed with google maps so maps *thinks* you have gps and cell reception, it would navigate just fine on its own no warning... cos im willing to bet thats what google sees. even when your phone is 'off' (you really think removable cell batteries are an issue? or make engineering or design difficult? or less profitable? no, it means you dont have the ability to completely remove the power source from your comms and tracking device should you so choose for whatever reason.