EKF2 not resetting position state when stopping GPS use and EV is already running

[artifactz]

Description
"Failsafe enabled: no local position" when EKF2 switches from GPS to external vision. You can read my diary on discuss.px4.io, which is a lot more detailed.

To Reproduce
Steps to reproduce the behavior:

1. drone with GPS and SLAM, visual odometry or similar via /mavros/vision_pose, VISION_POSITION_ESTIMATE or similar
2. EKF2_AID_MASK is GPS + EV_POS + EV_YAW
3. take off, hover/fly for at least 30 seconds (due to some internal EKF2 checks, see forum post)
4. fly into a GPS-denied area (tunnel, hall etc.)

Expected behavior
EKF2 recognizes a decrease in GPS quality and switches to EV as primary localization source.
Because GPS was bad and EV can be imperfect as well, it needs to reset its position state, to avoid failing _vel_pos_test_ratio checks.

Log File
https://logs.px4.io/plot_app?log=b7f5fb21-808a-42eb-844d-18901eb24620

Screenshot

• pos_test_ratio explodes as soon as stopping GPS use
• EKF states[7..8] (position) are only reset after dead reckoning and failsafe

Drone

• rotary wing

[julianoes]

@priseborough would be great if you could comment.

[mhkabir]

@artifactz is your vision yaw in the NED frame? Because if it's not, then your settings are inappropriate - you should be using rotate external vision instead of vision yaw in EKF2_AID_MASK.

[artifactz]

@mhkabir My vision yaw is in ENU, because I use Mavros:

ROS uses ENU frames as convention, therefore position feedback must be provided in ENU.
(https://dev.px4.io/v1.9.0/en/ros/external_position_estimation.html)

Is that incorrect?

Also, the vision orientation is initialized using the IMU orientation.
Position control without GPS using only vision works in my case.

[LorenzMeier]

@jkflying Could you please assist the review?