Use range finder for height control instead of height aiding #18864
Conversation
Range aid was introduced to stabilize the EKF estimates during takeoff and landind of large vehicle having their barometer highly affected by ground effects. This feature has undesired effects on the reference altitude given that it produces measurements relative to a different datum (i.e.: the ground). While switching in and out of range aid, the estimator accumulates an offset that can grow over time (known as ratcheting), leading to an undesired offset of the estimated global position. After discussion, it has been agreed that the range finder should only be used as an assistance for takeoff and landing in the height controller and not as an aiding source for navigation.
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For vehicles where the Baro disturbance in ground effect is higher than the EKF's ability to compensate, removing this feature will require them to use GPS for height with a reduction in robustness to GPs glitches or IMU clipping during up and away flight. I don't know how many users would be affected in this way. Other that this I don't see any blockages to removal of this feature. If we leave it in, the documentation would need to be updated to clearly caveat the intended use. |
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Replaced by #19944 where the range finder can be used during landing to stabilize the EKF without changing the height reference |
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This pull request has been mentioned on Discussion Forum for PX4, Pixhawk, QGroundControl, MAVSDK, MAVLink. There might be relevant details there: |
PR opened for discussion.
This is another step required to enable simultaneous baro and GPS height aiding.
Describe problem solved by this pull request
Range aid was introduced to stabilize the EKF estimates during takeoff and landing of large vehicle having their barometer highly affected by ground effects.
This feature has undesired effects on the reference altitude given that it produces measurements relative to a different datum
(i.e.: the ground). While switching in and out of range aid, the estimator accumulates an offset that can grow over time (known as ratcheting), leading to an undesired offset of the estimated global position.
Describe your solution
After discussion with @priseborough , it has been agreed that the range finder should only be used as an assistance for takeoff and landing in the height controller and not as an aiding source for navigation.
TODO:
dist_bottomfor auto takeoff and landing