I double checked and Meteohub (v4.9u) as well as Meteobridge (1.4) do now report altimeter values to CWOP according to NOAA calculation.
Nevertheless, this results in deviations compared to neighbouring stations as most of those seem to report SLP. So the ones providing true altimeter pressure are marked as false, as they are minority.
At least this is what it looks like to me. Effect is only relevant for significant altitudes...
@Old Tele Man: Looks like this is what you experienced as well.
How is altimeter pressure calculated for Meteohub and Meteobridge? The pressure reported to CWOP seems to fall in between the values given by the NOAA and Davis formulas. For example, my current raw station pressure is 968.8mb, and my elevation is 380 meters. The
NOAA altimeter formula gives me 1013.3mb and the
Davis formula gives me 1013.6mb, however MeteoBridge reports 1013.5mb to CWOP.
I'm not really worried about 0.1mb either direction, but it piques my curiosity about how MeteoBridge works. The difference is small enough to be a rounding error, but since the Davis and NOAA formulas are so close I can't tell which is being used.
If anyone is interested, I created a
Google spreadsheet to calculate NOAA and Davis altimeter pressure from raw station pressure and elevation.