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Compass Error - my noob calibration tips

Discussion in 'Pro/Adv Discussion' started by Mimoid, May 13, 2016.

  1. Mimoid

    Apr 18, 2016
    Likes Received:

    After having struggled for the longest time with those dreaded reoccurring red "Compass Error" messages and the Phantom autonomously deciding to venture into P-ATTI or even P-OPTO mode in flight (sometimes nearly a kilometer away, giving me brown pants time), I finally realized what I have been doing wrong.

    Maybe for all of you Drone Pilot Veterans this is a "d'uh stoopid!" moment, but for me it was a sudden realization that it was caused by me, being over-careful and recalibrating the compass before every flight, thinking that it will be the for the best.

    Make no mistake - some spots are simply killing your calibration. And it's not because you have your Humvee, a nuclear power station or a humongous metal silo nearby. It can be in a bloody field in the middle of bloody nowhere. The compass of the P3 is so sensitive, that it's enough if you have some rocks with high iron content under the soil to throw the calibration way into the twilight zone. Such an area is by geophysicists called a "GMA area" (geophysical magnetic anomaly).

    After having calibrated the compass at such an GMA area, the Phantom thinks that this is normal, and will expect the same anomaly to persist everywhere it flies. So when you take off, everything is initially fine and dandy, but as soon as you start leaving that crooked area, the Phantom goes haywire, going into Atti mode, drifting with the wind. The gimbal starts tilting like a ship at sea and you will wonder what the hell is going on. If you manage to navigate back to the home point, things are slowly going back to normal (remember, you are back in the GMA area). So you start flying off, and then everything goes wrong again.

    So how will you know when to calibrate the compass and when not to? Well, the tricky thing is, you don't. If you have a favorite takeoff spot, try the calibration there. Do the DJI dance. Do a short test flight. Fly away a few hundred meters, do some turns and twists and then fly back. If things are fine, your calibration is most likely OK. From there on, don't recalibrate!

    If you take your drone hundred kilometers or more to a different place where you will want to fly, you may need to do it anyway (as you have now moved to a different spot in the earth's magnetic field), but otherwise, just stick with your functioning calibration.

    So what happens if you want to take off from a wonky GMA area with a perfectly calibrated Phantom? The Phantom might warn you that it thinks that the magnetic field seems suspicious. It may say "Compass Error" right at start. If you would take off here, the Phantom would most likely not be able to hover in place, but would start reel and stagger like a drunkard. Land immediately, but keep your cool and refrain from recalibrating! Just move to a different takeoff point. Sometimes it is enough if you move just a few meters. Sometimes more.

    Well, that was my five minutes on the soapbox!

    #1 Mimoid, May 13, 2016
    Last edited: May 13, 2016
    vipercubic likes this.
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