Re: Ground ground station question
NAZA is a black box. We KNOW the barometer is used for real-time altitude adjustment. I think it makes sense that GPS altitude information is somehow taken into account as well, but there's not a lot of data out there either way. Between the GPS, compass, gyros/accelerometers, and barometer, there are a lot of complementary systems for determining relative and absolute position, how the NAZA mixes all that is part of the secret sauce.
In either case, altitude is entirely based off recorded reading at takeoff point. If you take off on a cliff and drop down 300ft, it will go up 360ft if told to ascend to 60ft height (as in RTH). It is entirely blind to hills, trees, buildings, altitudes it has previously traveled, etc.