Develop Reference

How to calculate pitch and roll without magnetometer

In my app I am calculating azimuth, pitch and roll using accelerometer and magnetometer values:
float[] rotationMatrix = new float[9];
float[] inclinationMatrix = new float[9];
private float[] mMagnetometerValue = new float[3]; //event.values
private float[] mAccelerometerValue = new float[3]; //event.values
SensorManager.getRotationMatrix(rotationMatrix, inclinationMatrix, mAccelerometerValue, mMagnetometerValue);
// Orientation.
float[] orientation = new float[3];
SensorManager.getOrientation(rotationMatrix, orientation);
Now orientation array returns azimuth, pitch and roll.
As documentation says getOrientation function:
values[0]: Azimuth, angle of rotation about the -z axis
values1: Pitch, angle of rotation about the x axis
values2: Roll, angle of rotation about the y axis.
Now good.
But testing in another phone failed, because this phone has only accelerometer, not magnetometer, nor gyroscope or rotation vector sensor. After debugging I found that phone has device orientation sensor. Only doc I am found is this google gist.
Okay give a try. But this sensor returns only one float value, not float array.
So I can not pass this as parameter to SensorManager.getRotationMatrix function.
Now question:
How to retrieve pitch and roll with SensorManager.getRotationMatrix and SensorManager.getOrientation or without this functions using accelerometer and this device orientation sensor.

use of rotation vector sensor

I want to implement rotation vector sensor. I searched as much as I could about this sensor but I confused some points. I understand that I need to use quaternions other than Euler angles for my app to be more stable. I will use this sensor datas for gesture recognition. So I want to use quaternions but I don’t understand how can I convert them to quaternions after using remapCoordinateSystem method? Or am I wrong about what I want to do? Even a little bit help will be very useful for me.
#Override
public void onSensorChanged(SensorEvent event) {
float[] rotationMatrix = new float[9];
SensorManager.getRotationMatrixFromVector(rotationMatrix, event.values);
float[] adjustedRotationMatrix = new float[9];
SensorManager.remapCoordinateSystem(rotationMatrix, SensorManager.AXIS_X, SensorManager.AXIS_Z, adjustedRotationMatrix);
float[] orientation = new float[3];
SensorManager.getOrientation(adjustedRotationMatrix, orientation);
float pitch = orientation[1];
float roll = orientation[2];
float yaw = orientation[0];
yawTextView.setText(getResources().getString(
R.string.yaw_sensor,yaw));
pitchTextView.setText(getResources().getString(
R.string.pitch_sensor,pitch));
rollTextView.setText(getResources().getString(
R.string.roll_sensor,roll));
}
Thank you.

See Euler angles to quaternion conversion.
Or otherwise, if you'd like to calculate quaternion components directly from the rotation matrix, see this page.

how to detect if android device screen facing down\up\towards user using the sensors?

i need to find out the device orientation, however i must do it after data sample from the sensors is done and not waiting for an event to happen.
i saw this code:
float[] rotationMatrix = new float[9];
float[] inclinationMatrix = new float[9];
float[] accelerometer; // values from sensor
float[] magnetic; // values from sensor
SensorManager.getRotationMatrix(rotationMatrix, inclinationMatrix,
accelerometer, magnetic)
int inclination = (int)
Math.round(Math.toDegrees(Math.acos(rotationMatrix[8])));
if (inclination < 90)
{
// face up
}
if (inclination > 90)
{
// face down
}
but the accelerometer, magnetic arguments must me initlized.
please help me out

Android ROTATION_VECTOR sensor to local axis rotation

I need to extract rotation of an Android device about the device Z-axis
I am currently using the ROTATION_VECTOR sensor and the following code, where rotVec is cloned from the values member of the SensorEvent:
float[] q = new float[4];
float[] globalRot = new float[9];
float[] localRot = new float[9];
float[] euler = new float[3];
SensorManager.getQuaternionFromVector(q, rotVec);
SensorManager.getRotationMatrixFromVector(globalRot,q);
SensorManager.remapCoordinateSystem(globalRot, SensorManager.AXIS_Y, SensorManager.AXIS_Z, localRot);
SensorManager.getOrientation(localRot, euler);
float rotation = euler[1];
As the device gets closer to flat, the value reported drifts from the true value. Also, the value is inverted after +- 90 degrees (0 is defined as Y pointing straight up).
What am I doing wrong, and what calls should I be using?

Rotating around X affects Roll. How to eliminate this?

I'm using android's TYPE_ROTATION_VECTOR sensor to determine rotation around x,y and z and use these measures in my application in a certain way. But when I rotate phone around X axis, roll value (rotation around Y) also changes. And I don't want that. How can I ignore changes in roll when I rotate around X? Here is piece of my code
private final float[] mRotationMatrix = new float[16];
private float[] orientationVals = new float[3];
if (event.sensor.getType() == Sensor.TYPE_ROTATION_VECTOR) {
SensorManager.getRotationMatrixFromVector(
mRotationMatrix , event.values);
SensorManager.getOrientation(mRotationMatrix, orientationVals);
azimuthVal = (Math.round((Math.toDegrees(orientationVals[0]))*100.0)/100.0);
pitchVal= (Math.round((Math.toDegrees(orientationVals[1]))*100.0)/100.0);
rollVal = (Math.round((Math.toDegrees(orientationVals[2]))*100.0)/100.0);
}