The iPad GPS seems very accurate to me. We used it with Navionics to navigate from Woy Woy through to Pittwater at night and it was spot on. I used it from Nelson to Newcastle too, and it seemed fine. Not that you can really tell out there but it seemed to always agree with our Garmin GPS. I had a Nexus 7 too, with a very basic nav app, as Navionics wasn't available for Android then. But its GPS seemed fine too. I don't remember seeing many phone towers.