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copied!<p>Finnaly i found the answer:</p> <p>The errors in the numbers are relative to float vars multiplication that is not the same as a double multyplication. <a href="https://stackoverflow.com/questions/8035566/android-big-fail-on-float-values-product/8039857#8039857">Here there is the solution.</a> This sums to the fact that <strong>rotation matrix isn't costant if the phone, even if with the same orientation, is accelerating</strong>. So is impossible translate acceleration vector to absolute coordinates during motion... It's hard but it's the reality.</p> <p>FYI the orientation vector is made from magnetomer data AND gravity vector. This cause a ciclic problem: convert relative acc needs oirentation needs magnetic field AND gravity, but we know gravity only if the phone is stop by relative acc..so we are return to begin.</p> <p>This is confirmed in <a href="http://developer.android.com/reference/android/hardware/SensorManager.html#getRotationMatrix%28float%5B%5D,%20float%5B%5D,%20float%5B%5D,%20float%5B%5D%29" rel="nofollow noreferrer">Android Developers where is explained</a> that rotation matrix give true result only when the phone isn't accelerate (e.g. they talk of free fall, infact there shouldn't be gravity mesaurement) or when it isn't in a non regulare magnetic field.</p> <blockquote> <p>The matrices returned by this function are meaningful only when the device is not free-falling and it is not close to the magnetic north. <strong>If the device is accelerating, or placed into a strong magnetic field, the returned matrices may be inaccurate.</strong></p> </blockquote> <p>In others world, fully un-useful... You can trust this thing doing simple experiment on the table with Android Senor or something like this..</p>

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