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POfinding orientation using getRotationMatrix() and getOrientation()
 

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  1. POfinding orientation using getRotationMatrix() and getOrientation()
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    <p>Im trying to get the direction of the vector pointing out of the camera, with respect to magnetic north. I'm under the impression that I need to use the values returned from getOrientation(), but I'm not sure what they represent. The values I get from getOrientation() don't change predictably when I change the orientation of the phone (rotating 90 degrees does not change values by 90 degrees). I need to know what the values returned by getOrientation() mean. What I have so far is written below:</p> <pre><code>package com.example.orientation; import android.app.Activity; import android.content.Context; import android.hardware.Sensor; import android.hardware.SensorEvent; import android.hardware.SensorEventListener; import android.hardware.SensorManager; import android.os.Bundle; import android.widget.Toast; public class Orientation extends Activity{ private SensorManager mSM; private mSensorEventListener mSEL; float[] inR = new float[16]; float[] outR= new float[16]; float[] I = new float[16]; float[] gravity = new float[3]; float[] geomag = new float[3]; float[] orientVals = new float[3]; final float pi = (float) Math.PI; final float rad2deg = 180/pi; /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); mSM = (SensorManager) getSystemService(Context.SENSOR_SERVICE); mSEL = new mSensorEventListener(); mSM.registerListener(mSEL, mSM.getDefaultSensor(Sensor.TYPE_ACCELEROMETER), SensorManager.SENSOR_DELAY_NORMAL); mSM.registerListener(mSEL, mSM.getDefaultSensor(Sensor.TYPE_MAGNETIC_FIELD), SensorManager.SENSOR_DELAY_NORMAL); } private class mSensorEventListener implements SensorEventListener{ @Override public void onAccuracyChanged(Sensor arg0, int arg1) {} @Override public void onSensorChanged(SensorEvent event) { // If the sensor data is unreliable return if (event.accuracy == SensorManager.SENSOR_STATUS_UNRELIABLE) return; // Gets the value of the sensor that has been changed switch (event.sensor.getType()){ case Sensor.TYPE_ACCELEROMETER: gravity = event.values.clone(); break; case Sensor.TYPE_MAGNETIC_FIELD: geomag = event.values.clone(); break; } // If gravity and geomag have values then find rotation matrix if (gravity != null &amp;&amp; geomag != null){ // checks that the rotation matrix is found boolean success = SensorManager.getRotationMatrix(inR, I, gravity, geomag); if (success){ // Re-map coordinates so y-axis comes out of camera SensorManager.remapCoordinateSystem(inR, SensorManager.AXIS_X, SensorManager.AXIS_Z, outR); // Finds the Azimuth and Pitch angles of the y-axis with // magnetic north and the horizon respectively SensorManager.getOrientation(outR, orientVals); float azimuth = orientVals[0]*rad2deg; float pitch = orientVals[1]*rad2deg; float roll = orientVals[2]*rad2deg; // Displays a pop up message with the azimuth and inclination angles String endl = System.getProperty("line.separator"); Toast.makeText(getBaseContext(), "Rotation:" + outR[0] + " " + outR[1] + " " + outR[2] + endl + outR[4] + " " + outR[5] + " " + outR[6] + endl + outR[8] + " " + outR[9] + " " + outR[10] + endl +endl + "Azimuth: " + azimuth + " degrees" + endl + "Pitch: " + pitch + " degrees" + endl + "Roll: " + roll + " degrees", Toast.LENGTH_LONG).show(); } /*else Toast.makeText(getBaseContext(), "Get Rotation Matrix Failed", Toast.LENGTH_LONG).show();*/ } } } } </code></pre> <p>I've looked at the documentation on the sensorManager class, but it hasn't helped solve this. If anyone could help me get meaning out of the this I would really appreciate it. I'm testing on a Nexus One running Android 2.1</p>
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