The following comes from the manual, all four motors have strong permanent magnets, does that mean the motors have to be removed and taken away while calibrating the compass? Also, doesn't that effect the accuracy of the compass while in flight? It will not fly without the permanent magnet motors attached? Reading the manual sure leaves a lot of unanswered questions. Mickey The following is below here. (1) DO NOT calibrate your compass where there is a chance of strong magnetic interference, such as magnetite, parking structures, and steel reinforcements underground. (2) DO NOT carry ferromagnetic materials with you during calibration such as keys or cellular phones. (3) DO NOT calibrate beside massive metal objects.