I've been trying to get accurate altitude readings from my ardupilot mega using the pressure sensor. Since there doesn't seem to be any way to input the current qnh into the APM to get an accurate reading, I decided to dive into the code to see whats really going on.
It seems as though 29.271267 inches Hg is hard coded into the software, making the pressure altitude constant near ISA. It does however look like the altitude reading is being adjusted for temperature, giving us an accurate density altitude based our near ISA pressure altitude. I guess my question is, are there plans on making a QNH (sorry we used qnh in nz, I believe other countries use other figures) value configurable from something like the wireless com port? and if not, if I were to modify the code to add this feature, would you be interested in adding it to the code base?
If I've misinterpreted the code please let me know.
Any thoughts are appreciated, Cheers.