How do GPS and cellphones interract so that you must have both in the car?

Can you have a GPS without any cellphone involvement? If so which one is best for that?|||They don't have to interact. A GPS unit is a receiver of signals. It does not need to send any. It uses maps programmed with latitude and longitude coordinates, and computes where you are going and how to get there, using the signals sent from the GPS satellites.





Now certainly cellphones can interact and in those circumstances you can have the cell phone send out the GPS data of where you are at the moment to whoever might needed it, like 9/11 or perhaps some application you have on the phone.





If you are looking for a navigation unit for giving driving directions, I have a Garmin Nuvi. It seems to do just fine. There's several model numbers in that line with various options and screen sizes.