CODEWITHSUNDEEP
androidgeometryandroid-sensors
erik
erik

Reputation: 4958

how do I convert Sensor data to degrees

I am getting various sensor readings from my device (programing for android) and i am looking to get the roll (which seems to be a number 1-100) converted into an angle in degrees and also convert the magnetometer heading into degrees..

any simple equations would be appreciated.. my geometry is a fleeting memory..

public void onSensorChanged(SensorEvent evt) {
            int type=evt.sensor.getType();
            if(type == Sensor.TYPE_ORIENTATION){
                azimuth = evt.values[0]; // azimuth rotation around the z-axis
                pitch = evt.values[1];   // pitch rotation around the x-axis
                roll = evt.values[2];    // roll rotation around the y-axis
            }

            //Smoothing the sensor data a bit seems like a good idea.
            if (type == Sensor.TYPE_MAGNETIC_FIELD) {
                orientation[0]=(orientation[0]*1+evt.values[0])*0.5f;
                orientation[1]=(orientation[1]*1+evt.values[1])*0.5f;
                orientation[2]=(orientation[2]*1+evt.values[2])*0.5f;
            } else if (type == Sensor.TYPE_ACCELEROMETER) {
                acceleration[0]=(acceleration[0]*2+evt.values[0])*0.33334f;
                acceleration[1]=(acceleration[1]*2+evt.values[1])*0.33334f;
                acceleration[2]=(acceleration[2]*2+evt.values[2])*0.33334f;
            }
            if ((type==Sensor.TYPE_MAGNETIC_FIELD) || (type==Sensor.TYPE_ACCELEROMETER)) {
                float newMat[]=new float[16];
                //Toast toast = Toast.makeText(ctx.getApplicationContext(), "accel", Toast.LENGTH_SHORT);
                //toast.show();
                SensorManager.getRotationMatrix(newMat, null, acceleration, orientation);
                if(displayOri==0||displayOri==2){
                    SensorManager.remapCoordinateSystem(newMat,SensorManager.AXIS_X*-1, SensorManager.AXIS_MINUS_Y*-1,newMat);
                }else{
                    SensorManager.remapCoordinateSystem(newMat,SensorManager.AXIS_Y, SensorManager.AXIS_MINUS_X,newMat);
                }
                matrix=newMat;
            }
        }

I should add that i am not sure i just want roll.. my app locks in landscape mode but obviously the user can turn their phone to any angle on any access.. so i probably need all three of the above to get the angle im looking for.

the angle in question is as if the user is looking through their phone, no matter how they are holding it, at the real world and i want the angle they are looking off the horizon..

for instance if they are looking at the horizon i want 90degrees returned, if they are looking straight up in the sky i should get 180, straight down -180.. then i will also want the degrees from magnetic north that they are looking.. using the magnetometer

Upvotes: 1

Views: 4076

Answers (1)

Dmytro Titov
Dmytro Titov

Reputation: 3201

values[2] should allready contain degree-value, that's mentioned in a reference:

values[2]: Roll, rotation around Y axis (-90<=roll<=90), with positive values when the z-axis moves toward the x-axis.

Update

Take a look at this picture: http://developer.android.com/images/axis_device.png

Here you see blue axis - Y axis. When your phone turns around it, it's called "rolling". The angle of the rotation will be contained in values[2].

Upvotes: 1

Related Questions