How does the ADSBX Radar View display obtain QNH for individual aircraft ? It displays QNH as well as 'Barometric' and 'Geometric' altitudes. If QNH is in the REST API feed, I cannot locate it. If I had QNH (in my REST API feed) I could correct the 'alt' parameter for non-standard conditions on my feeder's local display. Thanks, Joe
QNH in the aircraft details is not the local QNH but whatever the pilots set in the altimeter. So once they go above transition altitude it will just show standard. Also not all aircraft transmit it. Just check the local aircraft json ... if you use a non outdated decoder it should be in there. Really no reason to use the API if you're doing a local feeder display.
Thanks for responding but I'm using the API to fill in and extend my local monitoring coverage, especially at low altitude. Not interested in airliners or anything above the transition altitude (FL180 here) for that matter. But I would like to display proper pressure altitude when a Cessna is in the traffic pattern or lands when the altimeter setting is something other than 29.92 inHG. With a high pressure system in place, it's not unusual for 'alt' to display -400 feet at this 180' MSL airport. Totally unsatisfactory. So if I had QNH I could convert 'alt' to MSL altitude. I've captured the API info and can't identify anything that looks like QNH, either in inHG or hPa. Hence, my request.
