Are there instructions for calibrating the compass? Is it even necessary (wiki says no but is there really no other difference than “It takes a few minutes of flying to get right, so the compass is inaccurate at first launch”)? Feel free to call me stupid, but I have no idea what I’m supposed to do when I start the calibration. Not even after watching the youtube video that is linked on MP.
The wiki does not put enough emphasis on how important the compass calibration is, but it is vital for a great flying copter or plane. The process is not complicated: youtube.com/watch?v=-_mjfPlHL9o
Press the button in the Mission Planner marked live calibration and do the dance.
Hmm, I thought I did what the video says, but MP says “compass 2 more data needed”. What do the graphics mean? Sometimes it moves, sometimes it doesn’t. What does the “aim for [color]” mean? Aim how?
Some more info here: groups.google.com/forum/#!searc … OiKlvRxisJ
Thanks for the link, interesting read.
Well what do you know, compasses don’t like magnets. I removed the hatch magnets from my Bixler 2 and stuff actually started to happen - the graphics moved consistently (they were completely still half the time earlier even though I moved the plane) and I started to get way more data points. I feel dumb now, but somehow I subconsciously remembered reading that the small magnets wouldn’t be a problem. Anyway…
Attached are the results I got - I didn’t press done but MP just stopped by itself and presented these screens. How do I know if these are OK?
Have a look at “Live Calibration of offsets” on this page: copter.ardupilot.com/wiki/ac_com … padvanced/
If the offsets are under 250 then they are normally OK but the higher ones in your calibration are from the internal compass which is not really used for navigation if you are using an external compass so basically yours look pretty good.
Excellent, thank you. I have the APM facing backwards, maybe that has something to do with the internal compass values.
If you don’t mind, I’d have one last question. Does the compass calibration only need to be made once? What if I change the plane or remount the compass in a different place?
Compass calibration should be redone anytime there’s a notable change, the calibration takes not only the compass heading into account but also the influence from metals in the airframe and even magnets like those in servo’s. The APM should be facing forwards unless you’ve changed it’s orientation in the firmware but even then I would always place it facing forward as the designers intended.