CODEWITHSUNDEEP
androidandroid-sensorsgyroscope
user1819127
user1819127

Reputation: 53

Getting rotation degree from gyroscope android sensor

Ive searched the internet thin so far. I am trying to develop a problem where i need the degrees of rotation from the phones starting point. To know if the users it moving the phone up or down i am using the accelerometer, which in start was a bit unstable, but however i managed to make it stable. I now need the the degree of rotation around it self. Like the orientation sensor, which is deprecated. I then tryid using the Magnometer, but i was way to unstable. I then determed that i wanted to try using the gyroscope, when i use the sample code: 

 // This timestep's delta rotation to be multiplied by the current rotation
 // after computing it from the gyro sample data.
 if (timestamp != 0) {
     final float dT = (event.timestamp - timestamp) * NS2S;
     // Axis of the rotation sample, not normalized yet.
     float axisX = event.values[0];
     float axisY = event.values[1];
     float axisZ = event.values[2];

     // Calculate the angular speed of the sample
     float omegaMagnitude = (float) Math.sqrt(axisX*axisX + axisY*axisY + axisZ*axisZ);

     // Normalize the rotation vector if it's big enough to get the axis
     if (omegaMagnitude > EPSILON) {
         axisX /= omegaMagnitude;
         axisY /= omegaMagnitude;
         axisZ /= omegaMagnitude;
     }

     // Integrate around this axis with the angular speed by the timestep
     // in order to get a delta rotation from this sample over the timestep
     // We will convert this axis-angle representation of the delta rotation
     // into a quaternion before turning it into the rotation matrix.
     float thetaOverTwo = omegaMagnitude * dT / 2.0f;
     float sinThetaOverTwo = (float) Math.sin(thetaOverTwo);
     float cosThetaOverTwo = (float) Math.cos(thetaOverTwo);
     deltaRotationVector[0] = sinThetaOverTwo * axisX;
     deltaRotationVector[1] = sinThetaOverTwo * axisY;
     deltaRotationVector[2] = sinThetaOverTwo * axisZ;
     deltaRotationVector[3] = cosThetaOverTwo;
 }
 timestamp = event.timestamp;
 float[] deltaRotationMatrix = new float[9];
 SensorManager.getRotationMatrixFromVector(deltaRotationMatrix, deltaRotationVector);
 // User code should concatenate the delta rotation we computed with the current rotation
 // in order to get the updated rotation.
 // rotationCurrent = rotationCurrent * deltaRotationMatrix;

This code is taking from their documentation, is there anyway i could convert this to 360 degrees? or i could get values like how many degrees the phone was turned away from the starting point?

Thanks in advance.

Upvotes: 5

Views: 14038

Answers (1)

Ali
Ali

Reputation: 58501

Get the 3x3 rotation matrices, R1 and R2, with getRotationMatrix() at the two timepoints of interest. You would like to know the angle of the rotation R that brings R1 to align with R2.

First calculate R:

R = R1 * transpose(R2)

Then calculate the angle of this rotation:

angle = acos((trace(R)-1)/2)

That is all.

Upvotes: 2

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