Detect device orientation detection for Unity. It works even if the device rotation is locked.

DetectDeviceOrientation.cs

public void DetectDeviceRotation(){
  Vector3 acc = Input.acceleration;

  if(Mathf.Abs(acc.x) > Mathf.Abs(acc.y)){
    if(acc.x < 0){
      Debug.Log("Landscape Left");
    }else{
      Debug.Log("Landscape Right");
    }
  }else{
    if(acc.y < 0){
      Debug.Log("Portrait");
    }else{
      Debug.Log("Upsidedown Portrait");
    }
  }
}