Sure Kevin, :)

The thing i meant is the sensor warming up problem.

It is related to a design flow of the hardware. (It should measure external temp, not "internal")

Like the barometric sensor is located on the main board, it heats up wit APM a bit.

But as it has temperature compensation it makes APM think that the air around is warmer, so the hight measurement is wrong.

So your home alt can be a few meters wrong.

Also it can be a problem for other sensors we use.

I overcome this by powering up my APM than wait, than reboot, so my HA on zero alt will be accurate.

It would be a very useful feature to be able to do this without reconnecting the battery. (full reboot) 

In MP, i have just noticed this function. it is on actions tab called PREFLIGHT_CALIBRATION.

(It also has PREFLIGHT_REBOOT)

If you could add this, i would be pleased. (Even more! ;) )

Thank you for your attention,

Gábor