GPS - Garmin eTrex - locks on to up to 7 satellites and I use it when hiking - works under most forest canopies as well. It has helped me navigate back to my car from some great places in it's time (all around the world)
SatNav - TomTom
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I've used TomTom, Garmin and NavMan - I'd recommend TomTom without hesitation. Difficult to pinpoint exactly what makes it better but I found it so much easier to drive to new places with the TomTom