Plane: Disable autonomous descent when using Terrain Following

[Lazydude]

Take the following example: I'm flying in cruise mode with terrain following (TF) enabled. If I start flying along a big river channel with lots of side channels I get terrible bobbing as I go along. It would be nice to have an option with TF that it doesn't descend but only climbs if necessary to avoid obstacles. If there isn't an obstacle in my flight path don't dive down into that channel just fly across nice and level but fly over that big hill that's coming up.

I believe this could be done with only one added option - "Terrain Descend" Disable autonomous descent. Stay at current height unless climbing is necessary to avoid an obstacle.

Describe alternatives you've considered The only alternative is to disable TF altogether. I consider this a better alternative than the "Non-Auto Terrain Following" option 86 that is still being considered.

Platform [ ] All [ ] AntennaTracker [ ] Copter [ X ] Plane [ ] Rover [ ] Submarine

See picture for example of previous flight exhibiting this.

[Naterater]

While this could be added as an enhancement, I think that for many users including myself, the descending is necessary to meet regulations of altitude ceilings that reference the ground. It is also used to keep a camera at constant altitude above the ground.

[magicrub]

@Lazydude have you tried changing param TERRAIN_LOOKAHD?

[Lazydude]

I don't disagree that this is a specific use scenario and for now I've just disabled TF. The river channel is miles long so although I considered playing with the look ahead variable I decided against it.

[iNotMario]

Time for a bump - because i got a bit of a scare flying over a hilly valley. :D I second this request ... or endeavor for a better option, as the sentiment is valid.

This could be particularly useful for Failsafe RTL scenarios - where the last thing you want is for the plane to descend - worsening the comm situation.

Perhaps a TERRAIN_AVOID bitmask would be a good way to represent this - acts the same as TERRAIN_FOLLOW for the modes selected, except only climbs to maintain AGL, never descends.

I'm still looking at the code to figure this one out, but if i understand the way it works correctly, it would effectively be a hybrid of Absolute Reference and Terrain Reference: Altitude error would be computed both ways, and the minimum value returned. Still looking into how i can get it to compute both errors simultaneously, as it looks like switching the alt_frame destroys the prior amsl_cm of the prior alt_frame.