I’ve noticed that the altitude shown in the Taranis transmitter differs from the one shown in Mission Planner after being flying for several minutes. I’ve seen a difference of almost 2 meters.
I guess that the interface that you have created for the Taranis transmitter does nothing else but showing the information provided by pixhawk through the telemetry port. How is it possible that there is such a difference in the value of the altitud?.
A review of the ArduPilot source code shows it corresponds to the difference between altitude above home and altitude above EKF origin. The EKF origin is set when the Pixhawk is initialized, and altitude above home when the motors are armed. The difference between the two, however, shouldn’t be varying in flight. Most parts of the code use EKF origin, others (such as RTL) use the home altitude, so it is more of a matter of preference as to which one the user would prefer to be displayed…
I’ll check what values in the “status” tab in Mission Planner match both altitude above home and ekf origin and I will perfom some tests to check which value seems to be more accurate and when and why they differ so much.