I wonder if somebody could explain why we have a separate compass and why we have to calibrate it? I have a satnav in my car, and it always knows which way I'm going and pointing. I also have a Garmin and it also seems to know where I am and where I'm going. So why does the Phantom need a separate compass, which carries the overhead of needing to be calibrated, when it has what amounts to a satnav? (Mind you, this morning, at least a mile away from my previous location, I had the all-clear for takeoff LED indications before calibration. 9 satellites.) Thanks.