Dumbass. That's the problem with electonic devices, they're not infallable. Even though we had loran, GPS, chart plotter and radar my father made damn sure we could plot a course, keep a log, navigate by compass and watch and compensate for the tide for this very reason.
Even though I have a handheld GPS, I always have a trail/topo map in a pocket somewhere along with compass. Then again, I generally expect the worst case scenario and when it turns out better am pleasantly surprised.
Although I suspect "manual" navigation/hiking/exploring/etc. are becoming a lost art.