OK. But that would mean, that CumulusMX must store the sealevel figure (which apparently it does under the assumption that the weather station makes the correction):Big Daddy wrote: ↑Fri 01 May 2020 7:48 amMy understanding is that pressure is always meteorogically reported as the Relative (sea level) figure, this way you get a constant "global" reading. If you report Absolute (station) then it could vary greatly even within a short distance as the house on top of the hill will report a different (lower) value to the house in the valley.
Cumulus apparently stores the uncorrected pressure as measured since version 1.8.6 and not the MSLP (in sending to CWOP).All weather stations allow you to adjust the pressure for sea level. You should not make the adjustment within Cumulus.
On the other hand in the Wiki article on realtime.txt it says that webtag <#press>, field 11 gives the Sea level Pressure.
I am confused and maybe it is time @mcrossley says something about this.
This seems pretty important to me. Where and when are these corrections to MSLP made? And how do we know if and how the weather station actually makes the MSL correction before being read/stored by Cumulus?
Apparently I have to tell my Davis to correct the measurement it is taking, to Sea level. Is that correct?
And btw. no matter what, talking about sea level correction when calibration is meant, seems incorrect to me.
NOTE: my confusion comes from the fact that I live just below sealevel (-1 meter for which I use 0) so I never bothered. I should have, so now I am catching up. And it is very relevant for my pwsFWI / Fire Weather Index module.