I regularly check my compass calibration value and have always found it between 1482 and 1500 although it jumps around constantly between those figures. Thanks to posts by many of you I realize the importance of a re-cal every location change. Also, I usually do one even if flying in the same location a week later (with no other location in between). Some might call me obsessive but "there are bold pilots and old pilots but no old bold pilots". Anyway, what I'm wondering is what precisely the 1500 value 'goal' means? 1500 what? And how was the 1500 read, is it the sum of values from cardinal points or what? A sort of gausmeter? Another thing I wonder is this. What if you did a calibration with your P3 turned 180 degrees during both the horizontal and vertical calibration circles. Would it then have its calibrations reversed and think N is S and E is W? And theoretically, would that even matter since no inputs are compass points? I know someone here knows, and then I will too.