Understanding accelerometer data

Robin Paulson robin.paulson at gmail.com
Thu Oct 29 23:16:53 CET 2009

2009/10/30 Neil Jerram <neiljerram at googlemail.com>:
> I'd expect the x and y values to be much smaller than the z values
> (compared to the ratios here) because of the z value including
> gravity.  Am I misunderstanding what the data is telling me?

yes. acceleration is change of velocity. if there is no change in
velocity, there will be no acceleration. hence, if the phone is still,
all acc values should be zero. gravity or not, there is no net acc on
the phone. i don't know the format the accelerometers output data in,
but i'd take a punt that the values shown are noise. try running one
of the acc scripts on the wiki and going for a walk/run/climbing
steps/waving it around/car ride with it, to see what sort of acc
values you can get for different activities

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