Pricise altitude using baro

doctorluhang · August 30, 2016, 6:43am

Dear all,
I want to use baro to obtain a precise altitude, and I use position_estimate_inav. I find that the altitude drifts severly during flight, even if I hold it still (never move) and watch the local_position_ned.z in QGC, it could drift -2 meters after a couple of minutes, and continue drifting to even -5 meters. I think this value must be precise if I want to get the absolute altitude during flight. Is there any way to make local_position_ned.z stable?
Thanks in advance.

LorenzMeier · August 30, 2016, 8:03am

We have switched the default to LPE. INAV is limited in precision.

doctorluhang · August 30, 2016, 8:50am

Thanks for the reply. I tried LPE, but in QGC, I see no param representing the absolute altitude.

Mark_Whitehorn · August 30, 2016, 5:35pm

Was your QNH changing during your observation interval?

doctorluhang · August 31, 2016, 2:04am

Sorry for my unfamiliarity. What is QNH? Where can I see it?

Mark_Whitehorn · September 1, 2016, 12:14am

doctorluhang · September 2, 2016, 7:39am

Thanks for the reply.
Then, how can I see the QNH? Is it observable on QGC?

Mark_Whitehorn · September 2, 2016, 3:07pm

I use this service to get the barometric pressure at a particular location: http://www.aviationweather.gov/metar. QGC doesn’t currently do it for you, though it would be a very useful capability.