> paul x wrote:
> > acceleration, a is too small comaparing with gravity g. So, little
> > tilte will
> > become huge output of a. How can I canceal g from a, becomes critical!
>
> Gravity IS accelleration from the device's point of view.  You can not
> separate the two without some additional knowledge.

        Actually, to nitpick a little, gravity CAN be distinguished from
acceleration. The reason is gravity changes with altitude, the farther you
are from Earth's surface the less it's effects. Therefore, on a rocket
traveling away from the earth the force of gravity at the tip will be
slightly less then at the tail. Acceleration OTOH is consistent along the
whole rocket. So it is theoretically possible to distinguish the two (using
two sensors you can find the difference in the force on the rocket, using
the rockets length and altitude you can figure out the force of gravity on
it, and using that you could theoretically null the effects of gravity on
your number).

        Now, for reality, this effect is so small it takes VERY sensitive and VERY
large instruments to detect. So it's pointless in the sort of app we'd all
consider, nevertheless the difference IS there. I'm just in a nitpicking
mood at the moment, forgive me! :) TTYL

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