Hi, I'm working on location sensing by using 1 accelerometer and
magnetometer only (so called "dead reckoning") but now I realize that whe
I move my device, it is always possible to tilt the device a little bit
such that the gravity is decomposed onto 3 axes, which causes that the rea
motion acceleration and the gravity cannot be told apart. Thus, if
perform integration(dead reckoning) on the acceleration directly given b
the accelerometer, the result is largely inaccurate.

So I have to offset G first to get the real motion acceleration. Is thi
possible to be done by only using the accelerometer and one mor
magnetometer (since my device has it built in too)?

I read an old thread on this web
http://www.dsprelated.com/showmessage/39145/1.php

It talks about using Kalman filter to filter out G and sort o
things...but I couldn't really see any straight answers related to my cas
here.
So do Kalman filter help? Thank you very much!

PS. just for your info. Initially I wanted to figure out the orientatio
(yaw, pitch and roll) first , so that based on the 3 angles I coul
decompose G, and therefore offset G on each of the 3 axes. And th
orientation can actually be calculated by rotation matrix on acceleratio
and magnetic field. But the orientation obtained in this way cannot b
really used for decomposing G during the acceleration motion, because th
orientation is calculated from the acceleration and thus affected by th
acceleration change, meaning during the acceleration motion the orientatio
calculated is not the real orientation of the device.