> > How large would you expect the errors to be ? He's aiming for
> > 10 - 15m positional accuracy updated every 15 seconds
>
>     The GPS errors alone are bigger than that ! In my tests my
> apartment windows moves more than 30 meters !

Time for a word with the builder !

> The cumulative errors from the acelerometer can get pretty big
> but if the movement is reasonably constant it might work. The error
> tends to be quite random if you make frequent readings and
> integrate them well, so part of it will cancel out

Unfortunately there's nothing constant. The unit is going to
be subject to random movement in orientation, speed and
direction. IOW, at any given time it could be anywhere in any
position. The biggest problem is still power. Even with the
best I can find that's readily available, it requires a really
hefty battery to run at 80mAh continuously for 20 days.

I estimated 130-150 x 1200mAh NiCd AA, which is "slightly"
larger than the cellphone size he wanted

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