Acceleration from device's coordinate system into absolute coordinate system

https://stackoverflow.com/questions/11578636/acceleration-from-devices-coordinate-system-into-absolute-coordinate-system/11614404#11614404

to get acceleration vector in Earth's coordinate system you need to:

  1. get rotation matrix (float[16] so it could be used later by android.opengl.Matrix class) from SensorManager.getRotationMatrix() (using SENSOR.TYPE_GRAVITY and SENSOR.TYPE_MAGNETIC_FIELD sensors values as parameters),
  2. use android.opengl.Matrix.invertM() on the rotation matrix to invert it (not transpose!),
  3. use Sensor.TYPE_LINEAR_ACCELERATION sensor to get linear acceleration vector (in device's coord. sys.),
  4. use android.opengl.Matrix.multiplyMV() to multiply the rotation matrix by linear acceleration vector
 1 public void onSensorChanged(SensorEvent event) {
 2     if ((gravityValues != null) && (magneticValues != null) 
 3         && (event.sensor.getType() == Sensor.TYPE_ACCELEROMETER)) {
 4 
 5         float[] deviceRelativeAcceleration = new float[4];
 6         deviceRelativeAcceleration[0] = event.values[0];
 7         deviceRelativeAcceleration[1] = event.values[1];
 8         deviceRelativeAcceleration[2] = event.values[2];
 9         deviceRelativeAcceleration[3] = 0;
10 
11         // Change the device relative acceleration values to earth relative values
12         // X axis -> East
13         // Y axis -> North Pole
14         // Z axis -> Sky
15 
16         float[] R = new float[16], I = new float[16], earthAcc = new float[16];
17         SensorManager.getRotationMatrix(R, I, gravityValues, magneticValues);
18         float[] inv = new float[16];
19 
20         android.opengl.Matrix.invertM(inv, 0, R, 0);
21 　　　　android.opengl.Matrix.multiplyMV(earthAcc, 0, inv, 0, deviceRelativeAcceleration, 0); 
22         Log.d("Acceleration", "Values: (" + earthAcc[0] + ", " + earthAcc[1] + ", " + earthAcc[2] + ")");         
23     } else if (event.sensor.getType() == Sensor.TYPE_GRAVITY) {
24         gravityValues = event.values;
25     } else if (event.sensor.getType() == Sensor.TYPE_MAGNETIC_FIELD) {
26         magneticValues = event.values;
27     } 
28 }

 

posted @ 2021-08-18 22:25  耕读编码  阅读(38)  评论(0)  编辑  收藏  举报