Yesterday I made IMU calibration on very level table indoors and compass calibration on field. At first flight DJI Go 4 gave twice "IMU heading error" (it was long message, but is shortened as this) and switched to ATTI. This occurred after fast speed flight and stick centered braking.

Firmware is latest and temperature was -3°C. Aircraft was about +15°C when I took it out of the car in the field and performed Compass calibration.

I'm just wondering if compass is used somehow on IMU calibration and if big 110/400kV power lines nearby (50m) could affect IMU calibration? Table I used for calibration has also metal frame and wooden surface. This environment is used countless of times for IMU calibration over years without troubles.

Next step is to perform IMU and Compass calibration again somewhere else.

The high voltage power lines would most probally be affecting the compas.  And since the compus feeds the IMU its informatoin this could have been was was causing your problem.

MadFrenchie Posted at 2017-4-6 03:41
The high voltage power lines would most probally be affecting the compas.  And since the compus feeds the IMU its informatoin this could have been was was causing your problem.

That's what I assume too. I tried IMU calibration again a little further from powerlines and on full wooden table. I have a feeling calibration went through faster but this is just a feeling. This morning on test flight flield right after startup Inspire 2 gave IMU error and asked to do calibration. Yesterday on table after calibration reboot all was fine.  Today I ignored that request and just rebooted. Then all was good and bird flew well.

I guess buzzing X4S gimbal doesn't help to initialize IMU. It makes vibration for sure. Buzzing ends like DJI representative instructed by pushing gimbal slightly. It works but needs to be done before IMU calibration I guess.