Minimum altitude parameter

Does PX4 support a “minimum altitude” parameter where it will not allow the aircraft to fly below a certain altitude (e.g. don’t go below 40 meters to stay above trees and things)? Is MIS_LTRMIN_ALT the proper parameter to use for this?

Is it a correct assumption that MIS_LTRMIN_ALT ignored in Manual mode and in Land mode? What other modes is it used or not-used?

How does Qgroundcontrol/PX4 interact with MIS_LTRMIN_ALT? Does is not let you upload waypoints lower than this; if so what is the behavior?

Loiter min altitude is used throughout navigator when a loiter is created. Eg switching to hold mode creates a loiter at the current position with altitude max(current_altitude, loiter_min).

Are you looking for more of a minimum altitude warning/failsafe? Both in flight and as a mission feasibility check?

Thanks for your reply. It sounds like you are saying MIS_LTRMIN_ALT only applies when in Loiter mode (aka HOLD).

Mostly I am wondering if there is an existing way to have a global minimum altitude that would be used in flight in all modes except takeoff, land, manual, and stabilized.

If this capability doesn’t exist yet then I guess I’ll offer my opinion that it would be a useful feature if someone wanted to add it in the future. It would be nice if it at the same time it was used by the mission feasibility checker with an appropriate message returned if the mission is rejected.

I guess a related but separate question is how to handle Max altitude: if I want to set a MAX altitude during flight is the geofence ability the only or best way to do that? i.e. GF_MAX_VER_DIST?

edit: some wording

There are a few other cases when loiters are created and respect MIS_LTRMIN_ALT.

So it sounds like what we need is a new param for mission minimum altitude. MIS_MIN_ALT
Mission feasibility could check it. Would anything happen if you fall below that altitude in mission mode? Just a warning or failsafe trigger?

GF_MAX_VER_DIST is effectively a mission max altitude.

Hmmm. My 2 cents: Assuming a new parameter MIS_MIN_ALT was created I think the behavior should be to prevent commanded altitude lower than this with the exception of Manual, Stabilized, takeoff and Land modes. If this altitude was breached due to some flight issue or when in one of those modes then a warning should sound.