[startrek66]

The value indicated by the altimeter which sensor comes?

[f5soh]

Altitude is a mlx between GPS altitude and baro.
Without GPS, only baro.

Altitude is relative to Home altitude defined (if GPS is used)

[startrek66]

Thanks

[startrek66]

I noticed that the value displayed on the pfd is not real but is in excess.
In fact, the altitude by GPS is 177 m, while on the altimeter pfd is 46 m. How can I reset the altimeter of the pfd at the time of takeoff?

[f5soh]

Your known altitude is not the one used for HomeLocation.
https://librepilot.atlassian.net/wiki/display/LPDOC/Setting+Home+location
See about WGS84 altitude.

Reset the Home and wait the board setting the HomeLocation automatically.
or take look at "Automatically set Home Location"

[startrek66]

Thank you for your advice and the next flying session I'll gain the altitude above sea level directly from the airfield.