I have noticed this since i started with my APM2,5 board but focused on other stuff until now.
I have my declination values correct (2,155041) and my satcount is 9.
Also my quadcopter icon in MP is a + Quad and not a x Quad as i have defined.
I enclosed a screenshot from MP.
The direction of my header is like the black line, not the red line.
Replies
Icon being a PLUS is correct, even if you defined X
In Mission Planner;
Configuration Hardware Options Compass perform [Live Calibration]
Configuration ArduCopter Level make sure X is selected and perform [Calibrate Now]
Have you tried the 'live calibration' using Mission Planner? You may have to do it more than once, though, some times the calibration is worse. It must have something to do with the way I moved it around or ???
APM is supposed to 'tune' the calibration during flight, I think.
Some time ago I had noticed a similar problem with my APM 1 (2560) & 'H' version IMU. [about +130 degrees out of wack!] .. My plane suddenly wanted to fall out of the sky after reach half way through a mission. I gave it every chance to recover on it's own but once it got below 25 meters I had to go manual.
A review of the logs showed the compass pointing backwards, the GPS, my gopro & two eye witnesses say otherwise.
[now to be fair, that particular IMU had been submerged in two fresh water lakes and after careful drying & cleaning it work without any trouble for several months.]...but I digress...
I put the IMU aside & assembled a spare fresh IMU board.
on the bench, with a fresh IMU I compared it with my APM 1 (1280) & the IMU from my Quad , The (1280) was closer [+15 degrees] but not quite on the mark.
I swapped IMU boards [ both H versions] & the APM (1280) was quite close without even calibration.
So then I continued to attempted the live calibration routine, again, with both boards. I did this many many times and it got pretty close..but it was still off by about +5 to +10 degrees.
Still not satisfied with the results, [ I mean this is a compass, like WTF.. even my inexpensive boy-scout type compass was exactly correct & so was my 3-year old cell phone which uses a magnetometer too]
I tried different firmware versions too.
Eventually I left them both running for six or more hours, resetting them once or twice at arbitrary times.
They now read within a degree of each other and they both show north when the board points north.
Hope this helps.
I have the same problem as you have.. I have no idea what's wrong with this??
if it takes auto-flight.. where it flies??