Alllowing Lidar as primary height source while in Auto mode

It would be great if someone could take some time to allow the use of Lidar as primary height source while in Auto mode and BTW answer to some questions about Lidar exposed in the following discussion:

https://discuss.ardupilot.org/t/is-lidar-used-as-primary-height-source-only-during-landing-mode-or-also-in-auto-mode/26899/14

Thanks to all the developers that will reply to this message.

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Not sure what you mean, Lidar will be used as primary height source in auto mode as long as height is not out of range (defined with RNGFND_MAX_CM parameter).

Thanks for the reply Olivier

Well from the actual documentation it do not seems possible to use the range finder in Auto mode but only during LAND stage/Mode since value 1 of Ek2_Alt_Source “use range finder” is only available with optical flow navigation, a legacy of Arducopter code I guess.

And from the actual beta code: https://github.com/ArduPilot/ardupilot/blob/master/ArduPlane/altitude.cpp
It looks to me that Lidar is used only

flight_stage == AP_Vehicle::FixedWing::FLIGHT_LAND ||

The Test
I tested on my plane some days ago setting EK2_ALT_SOURCE to 1 “use Rangefinder” and EK2_RNG_USE_HGT (range finder switch height percentage) set to 50% so a setting where Rangefinder should be used from 0 to 20 meters of altitude .

What happened was that when switched to Auto while above 20 meters, the plane went to the sky.
Tecs seems to update ground altitude to actual Rangefinder reading…
So finally Lidar actually cannot be used as primary height source.


.

EK2_RNG_USE_SPD
There is also this other point that seems a Arducopter legacy and if active would mean no plane will ever use a Lidar since only a few planes can fly at less than 6 m/s speed.

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Olivier , I have done some other test and I confirm that Lidar is active only when in LAND mode.
In AUTO mode LIdar is not used as primary height source.

It would be great if someone of the developers can implement this feature or just answer to the my questions above.

I have the feeling that all the energy and the interest of developers today is towards Quadplanes, traditional planes are , IMHO, a bit forgotten.

You are right, it works in copter and this threw me off earlier as I didn’t realize you were flying fixed wing.

I brought it up at the dev call, the general reason it’s in plane only for landing is because typically they fly higher (and faster) and lidar has been found to not be very reliable in auto for the kinds supported, also due to existing lighting and reflections. So there hasn’t really been a good use case for lidar as primary in auto for plane. But if you have one …

Definitely not the case than trad. planes are forgotten :wink:

Was not a criticism, the new girl in town is always the prettiest :slight_smile:

Well I bought last December 3 different Lidars and I was quite surprize by their perfromance.
Even a 110$ Lidar as Leddar One has a really good performance in 30 meters range.
I have done around hundred flights simulating landing and Lidar is by far the most reliable sensor for altitude when close to the ground.
Baro has well known issues , GPS is not reliable when there are fast altitude changes.

Great , thanks !