Unexplained loiter drift V3.1.2


I 've got an issue on an octo build  : an explained drift  in loiter mode (seems to the right each time but could have been the Wind at that moment). Stabilize is fine.

I've looked in the log and I see a discrepancy between X, Y velocities and Desired corresponding velocities, which is indeed a sign of a bad loiter. But Why ? Accelerations are perfectly fine (AccZ) is contained to +/- 0,1g, compass calibration has been redone and is fine, using an external 3DR GPS+MAG. The frame looks fine too (nothing twisted, everything solid).

What could be the cause ? I need help of an expert on this. Log (and Tlog for vibes) attached.



Please note that the firmware is still an old one : V3.1.2 (NOT to confuse with the most recent one V3.2.1)

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  • 3701966806?profile=original...or dig deeper ;)

    • MR60

      OK lol.  I hope this is only a GPS issue. In any case I am going to upgrade this craft to the last firmware and will test again. 

  • MR60

    3701966481?profile=originalI found this in my log, velocities and desired velocities are not at all following each other. What's the cause of that ?


      The tree flights with bad GPS?, velocity is calculated with gps so I suppose that if GPS is not working well, It couldn't calculates well the velocity, If I don't have 9-10 sats and HDOP under 2 (1.5-1.7) my copter drift, but it's strange your up and down gps signal, it's look as an interference perhaps?

  • your HDOP looks worse, where is your GPS? any camera or FPV near?


    • MR60

      I checked compass and recalibrated it too. If the cause is poor GPS reception,  then I still do not understand why on three separate flights in the same afternoon it drifts exactly in the same direction ?

      PS: there is no alien base underground:)

    • Did you check your compass? but for me is GPS problem ;) , try again with 10 sats and HDOP under 2 ;)

  • Hugues, your GPS looks horrible


    • MR60

      Hi Cala, HDOP was about 2-2.1 which is at the limit for good loiter. The graph shows between 7 and 8 sats.

      This however does not explain the loiter drift where the craft rolls to the right in a straight line (keeping altitude) as if it wanted to reach a waypoint far away in a straight line to the right...

    • here, with 7 sats I can't fly in loiter....

      ...or perhaps the allien moves to there LOL

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