I think I need to find a sat nav system more suited to wandering than the Magellan RoadMate I am borrowing from bedfull_o_books. I got good and lost in the wilds of Eastern Pennsylvania while wandering around late at night, which I wouldn't have done if I had brought my paper maps. But paper maps are bulky and I thought I would try the sat nav only method. That didn't work very well.
It's also possible the better answer is to get a smart phone.