Why there is a terrible drift in my GPS?

Hi, All
Something really strange with my quadrotor, I need some help.
My log file shown as bellow:

crash:(arm- > test RC -> switch to AUTO.TAKEOFF -> everything is fine -> fall down -> kill)


What I did is, first arming the throttle, second waiting GPS ready for a few seconds, then I switch to TAKEOFF mode, everything is OK but suddenly my quadrotor fall down so I have to push KILL switch.

My quadrotor did not fly away, but when I check log files, the GPS status looks very strange.

Why there is a terrible drift in my GPS, and is there any wrong in my configuration?

Any advice will be appreciated, thanks…

based on the large acceleration jolt it looks like you hit the ground at 16:46, which is when the GPS drift started happening. This is common to see GPS go a bit nuts on a hard landing. Also if it landed under trees then that can also mess with the GPS.

1 Like

@clovett Thank you, I will try again later…


Some observations on your flight:

  • Altitude Estimate between 16:46:43 and 16:46:48 the GPOS.Alt snaps down after a seeming runaway
    • Q: What is the difference between GPOS.Alt and GPS.Alt?
  • Roll Angular Rate: At around that same time, the roll angle begins to oscillate. The oscillations grow, attenuate, then grow until the vehicle crashes.

I would suspect an unexpected measurement caused instability in a x-gyro bias estimate and the closed-loop control finally lead to a crash.

GPOS.Alt is the estimated altitude from the EKF
GPS.Alt is the measured altitude from the GPS sensor

Thanks @CarlOlsson. The EKF altitude snapping back is highly suspect and it seems things did not recover after that.