To use Google Navigation, you need a cell signal to get the maps, unless you precache the area you will be in while you are in a WiFi area. Or you can buy a navigation app that has its own maps stored onboard, then you can use the navigation without a data connection. I bought CoPilot Live USA just for this. The GPS will still get its signal from the satellites, and if I'm in an area with no cell coverage, I can still navigate around.