I've entered declintion.
When I point my plane to what it thinks is west, one would think the east would be in perfectly opposite direction, no , east is almost 40degree off. Same, but smaller error in north-south direction.
Throttle have no influence on compass, and there's no power close to the magnetometer.
The magnetometer is mounted on top of APM. (as suggested by wiki.)
Replies
Sounds like the magnetometer null offsets are not calibrated. This is done automatically, but you must rotate the plane around the z axis a few times. Then hold it sideways and rotate a few more times.