How to remove Gravity factor from Accelerometer readings in Android 3-axis accelerometer

user_315619 0
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Can anyone help on removing the g factor from accelerometer readings?

I am using SensorEventListener with onSensorChanged() method for getting Sensor.TYPE_ACCELEROMETER data. I need only pure acceleration values in all directions. So at any state if the device is stable (or in constant speed), it should give (0.0,0.0,0.0) roughly.

Currently, depending on its pitch and roll, it gives me variable output depending on the g forces acting on each axis.

I hope there is some formula to remove this, as I also get orientation values (pitch and roll) from Sensor.TYPE_ORIENTATION listener. I have used some but it didn't work.

accelerometer android
7 Answers

One way (for devices only with accelerometer) is to remove gravity vector from accelerometer data by subtracting the values that would come in static case for same orientation. But as orientation is again calculated by taking acceleration readings and not independently, its not very accurate.

Gyroscope may help in this case. But few androids still have a true gyroscope. And using its raw readings is not so simple.

user_3156190

you need to assume two coordinate systems: 1- fixed global system. 2- moving coordinate system in which the origin moves & rotates as sensor does. in global system, g is always parallel to z axis but in moving system it is not. so all you have to do is to compute 3*3 rotation matrix from orientation angles or yaw, pitch & roll. (you can find formulas everywhere). then multiply this rotation matrix by 3*1 acceleration vector measured by sensor. this will transform coordinates and declare the values in fixed global system. the only thing afterward is to simply subtract g from z value.

user_98024050
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