It took me awhile but I finally located the FAQ entry that explained that Cumulus records the relative air pressure rather than the absolute.
That is fine but then I discovered that the Met Office WOW site seems to be receiving this relative pressure and then correcting it again. So I seem to be getting a double correction.Cumulus displays pressure corrected to sea level, which the console calls ‘relative pressure’.
We are only 2 miles from a Met Office observation station and at similar altitude so I would expect my pressures to be close to that site.
So I read further in the FAQ but I'm now confused...
So, if I edit this setting is this something that will change frequently or can I assume it will be constant?If your relative pressure still disagrees with the Cumulus display, it may be due to the following: The Fine Offset stations only supply absolute/station pressure to Cumulus, so it has to adjust to sea level. When Cumulus starts, it reads the pressure ‘offset’ (the difference between absolute/station and relative/sea level pressure) from the station so it can use it subsequently to calculate the sea level pressure. Sometimes the offset that is read is clearly garbage, so Cumulus uses zero as a best effort.
To circumvent this, you can edit cumulus.ini, and in the [Station] section add an entry:
EWpressureoffset=x.y
where x.y is your pressure offset. Cumulus will then use this instead of reading it from the station.
BUT this doesn't seem to help with the upload to WOW which is apparently receiving my relative readings but treating them as absolute.
Any help gratefully accepted.
Andrew
