Can anyone explain to me, how “baro temperature calibration learning” does work ???
Somehow a “TCAL_BARO_EXP” should be learned, but this value is zero all the time :hushed:


I’m afraid even I don’t know how it works but I’ve added it to our list of docs to update for 3.6.

Setting TCAL_ENABLED=2 will enable learning of barometer error due to temperature rise. It is only useful in systems which suffer from rapid temperature changes (10s of degrees C during startup) which affects the barometer. Very few vehicles need this.

I’ve created a wiki page for this feature here.

Is it possible to completely set the altitude to “0” on the flight data screen of the mission planner?
The numbers are always moving

Is this parameter only for copters not planes?


Yes, somewhat surprisingly the parameter is only available in Copter it seems.

How do I request this parameter for planes?
Whose door I should knock, Michael?


The plane maintainer is Andrew Tridgell but I’d start with adding a request on the issues list and if possible state why you’d like it added.

Thanks @rmackay9.
I am working with Civil Aviation, and one of their requirement for Altimeter is “Programmable based on altimeter setting (in-Hg)”.

I have noticed a big deviation in altitude when flying a plane. Not accurate at all, sometimes off by 200ft.
Since Civil Aviation must work with manned aircraft, they want all UAS to report the correct altitude. I am guessing +/-50 feet deviation is ok.

Thanks for adding this request to the next build.


This is a plane issue so the discussion really should be in the plane forums but it would be good to know if the temperature calibration is really the problem.

If the plane is traveling a very long distance then the issue could just be that the pressure has changed a lot in which case it might be better to switch over to using the GPS as the altitude source.

Plane 4.1 also supports better accuracy at very high altitudes and if there have been very large temperature changes. This is not related to the temperature calibration feature though, it is just some improved calcs in the baro driver.

@rmackay9, should I create a new discussion in the plane forum or there is an existing topic related to this issue?
Not sure where is the parameter request for 4.1 release.
Apricate if you can send me a link.


It would probably be best to create a new topic in the plane forum and also include a log of a flight where the estimated altitude (based on the baro) is far off from reality.