Originally Posted by ghettocruiser
As I understand it the bike-specific GPS units also have a magnet on your wheel and (optionally) an internal compass. When the signal from the satellites is lost it uses the wheel magnet for speed and a guestimate of your position, a technology borrowed from high-end automotive GPS systems.
Interesting. Car GPS have the same sort of vector based / dead reckoning mapping for when you go under a tunnel or lose signal.
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