Rel Alt climbs while sitting on the ground

ArduCopter Copter 3.1
1

Running the 3.1 firmware on an Iris, when powered up the Rel. Alt climbs steadily to maybe +10-15m after about 10 minutes.

This makes it impractical to use waypoints with rel alt. Is there a reset procedure to drive this value to 0 prior to launch?

Thanks.

2

[quote=“johnsmallberries”]Running the 3.1 firmware on an Iris, when powered up the Rel. Alt climbs steadily to maybe +10-15m after about 10 minutes.

This makes it impractical to use waypoints with rel alt. Is there a reset procedure to drive this value to 0 prior to launch?

Thanks.[/quote]

Weather conditions can do that. Is CTUN.BarAlt doing the same thing?