http://developer.android.com/guide/topics/sensors/sensors_position.html

Orientation Sensor 方向 Sensor

private SensorManager mSensorManager;
private Sensor mSensor;
…
mSensorManager = (SensorManager) getSystemService(Context.SENSOR_SERVICE);
mSensor = mSensorManager.getDefaultSensor(Sensor.TYPE_ORIENTATION);

  @Override
  public void onSensorChanged(SensorEvent event) {
    float azimuth_angle = event.values[0];
    float pitch_angle = event.values[1];
    float roll_angle = event.values[2];
    // Do something with these orientation angles.
  }

azimuth_angle
正北邊為0
往東順時鐘遞增
上限359.999….