When I flew from Australia to Lebanon. The Southern Hemisphere to the Northern Hemisphere. I took a compass on board to see if it matches up with the on board GPS system on the aeroplane. These are my findings.
The compass was set up so that north was facing the front of the plane.
Flight itinerary and compasses.
Passed the security.
On board Gyroscope.
Some early notes.
Check out this GPS reading
Compared to the compass reading
And some videos which prove entirely that the compass and GPS are two different readings.
A very detailed video 13 hrs into the flight, compass stayed this way for the whole way from Sydney to Lebanon.