.... so I leave it to our Avionics bod.
In one old squadron, our avionics bod held the (hand-held) landing compass for our engines running compass swings. To make life easier he used to shade off the larger errors he was measuring, to more what he thought they ought to be, before hand signalling them to us inside. Din't 'arf give rise to some interesting calculations/corrections til we cottoned on and re-educated him.
Then there was the bod who had a metal plate in his skullbone from an old prang, so when he put his head down to read the landing compass ......
LFH