Question

i am creating an augmented reality app that simply visualices a textview when the phone is facing a Point of Interest (wich gps position is stored on the phone). The textview is painted on the point of interest location in the screen.

It works ok, the problem is that compass and accelerometer are very “variant”, and the textview is constantly moving up and down left and right because the innacuracy of the sensors.

there is a way to solve it?

Answer 1

Our problem is same. I also had same problem when I create simple augmented reality project. The solution is to use exponential smoothing or moving average function. I recommend exponential smoothing because it only need to store one previous values. Sample implementation is available below :

private float[] exponentialSmoothing( float[] input, float[] output, float alpha ) {
        if ( output == null ) 
            return input;
        for ( int i=0; i<input.length; i++ ) {
             output[i] = output[i] + alpha * (input[i] - output[i]);
        }
        return output;
}

Alpha is smoothing factor (0<= alpha <=1). If you set alpha = 1, the output will be same as the input (no smoothing at all). If you set alpha = 0, the output will never change. To remove noise, you can simply smoothening accelerometer and magnetometer values.

In my case, I use accelerometer alpha value = 0.2 and magnetometer alpha value = 0.5. The object will be more stable and the movement is quite nice.