> How about doing periodic GPS nav, and using inertial navigation
> in the interim.  If you can tolerate the accumlated errors between
> GPS fixes, might be a way to go.  Accelerometers are getting
> small and cheap

How large would you expect the errors to be ? He's aiming for
10 - 15m positional accuracy updated every 15 seconds

He's asked me if it's possible to use the unit's movement to
charge it. All I know is that it's being shaken (possibly worn
on a person). If that's the case, ie no large or fast movement,
then 80mAh charging seems a little hopeful. Especially if one
objective is to keep weight and size down

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