Possible causes of "Failsafe enabled: no global position" on a multirotor

Flight Testing & Log Analysis
1

Hello,

During flight testing of one of our quadrotor vehicles we are getting “Failsafe enabled: no global position”. What could be the cause of this? There are no GPS-related issues according to flight logs, so this must be something else.

Here is a flight with failsafe triggering: https://logs.px4.io/plot_app?log=e226431c-9515-456c-8d45-d2fd22d0d68b

Here’s a flight of the same airframe without it triggering (same day, same conditions): https://logs.px4.io/plot_app?log=0fcd3c8e-6ec2-4de1-bdf0-17735c1e9779

Here’s another flight with another battery configuration (failsafe not triggered): https://logs.px4.io/plot_app?log=f37989a5-3cf8-464c-ba06-200f681498cd

What is the cause of this error / behaviour? And, in general, how can I diagnose problems such as this one? To me, there is nothing in the flight log, that might suggest the cause of this error.

2

AFAIK only debugging info for EKF logs is here: http://dev.px4.io/en/tutorials/tuning_the_ecl_ekf.html#how-do-i-check-the-ekf-performance. We’ll see if we can get some eyes on those logs in the coming days.