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androidgpslocationbearing

Calculate the opposite of the current android GPS walking direction

I'm having this small code snippet here. What I'm looking for is to get the current GPS walking direction (bearing) of the user and then get the opposite walking direction.

I seem to be missing some crucial information here since the code seems to mostly work when I walk North East and West but fails when I walk South.

Any idea how to fix my snippet?

private static Location lastValidLocation;

private float getOppositeGPSMovementDirection(Location lastLocation){

    float bearing;
    if (!lastLocation.hasBearing){
        //Use bearing of the last Location with a valid bearing.
        bearing = lastValidLocation.getBearing();
    }else{
        lastValidLocation = lastLocation;
        bearing = lastLocation.getBearing(); 
    }

    //Calculate backwards direction
    int direction = (int) (bearing - 180);
    direction = direction<0?direction*-1:direction;

    return direction;
}
Solution

  • Your math is faulty. If you're at 10 degrees, your opposite is 190. Your math would give it 170. The correct math is:

    direction = (bearing + 180) % 360;

    Basically, your assumption that you can multiple a negative angle by -1 to get the correct angle is wrong.