EKF3: GSF alignment cannot occur below 5m/s

[rmackay9]

As reported in this discussion it appears that GSF alignment cannot occur unless the vehicle is traveling over 5m/s.

The issue appears to be that a new check was added in PR #23515 that the vehicle is travelling above GPS_VEL_YAW_ALIGN_MIN_SPD (5m/s).

The issue can be replicated in SITL by doing the following with Copter:

• sim_vehicle.py --map --console -L CMAC2
• param set EK3_SRC1_YAW 8 (GSF)
• reboot
• ALT_HOLD
• arm throttle
• rc 3 2000 (wait 5 sec to allow the vehicle to climb)
• rc 3 1500 (to level out)
• rc 2 1400
• rc 2 1600
• rc 2 1500

At this point a message, "EKF yaw reset to GPS" should appear but it does not. Next change GPS_VEL_YAW_ALIGN_MIN_SPD to 1.0 and repeat the above test.

[priseborough]

As suggested by @rmackay9 the way to resolve this is to use a different value of GPS_VEL_YAW_ALIGN_MIN_SPD for different vehicle types. Maybe it also needs to be smaller for copters (or a parameter) as small copters flying without a magnetometer will not want to fly at 5m/s to complete an in flight yaw alignment.

[rmackay9]

This report may also be caused by this issue https://discuss.ardupilot.org/t/copter-4-4-1-released/107005/9

[rmackay9]

This has been resolved in master now and the fix is included in Copter-4.5.2.