Hi Guys, I agree that you need to know how your GPS works, but you should also need to know the basic dead-reckoning and waypoint navigation techniques, as well as radio nav aids.
A group of us were doing our cross country training at the same time, on the same routes. One chap followed the wrong railway line out of Crewe, and was told via ATC that he had entered Manchester airspace, he was still lost even after being given vectors to the river Mersey, which he mistook for the river Dee !!... Quite a good training exercise I think !
Pete