Cumulus Support

Upgrading from v1.8.8 to v1.9.0 fixed my barometric pressure error at CWOP. I assume this is the fix referred to?

"Altimeter Pressure now same as SL pressure for non-Davis"

The results of the upgrade are plainly visiable in the quality control graphs.
http://weather.gladstonefamily.net/site/D4194

I'm surprised there was such a difference. In the old code, it took the absolute pressure and adjusted it using your configured altitude. I realised that this was pointless for non-Davis stations, so changed it to take the supplied sea-level pressure instead. Davis stations display genuine sea-level pressure as opposed to altimeter pressure as required by CWOP. With other stations, the sea-level pressure they provide is actually more like altimeter pressure, i.e. it is only adjusted for altitude, so the later code just uses that.

It should only have made a significant difference, assuming you had configured your altitude correctly, if your station's absolute pressure reading was some way off and you were having to over-compensate with your relative pressure setting, i.e. you are compensating for both altitude and an inaccurate reading.

But anyway, it's good that the change was of some benefit.

Calibrating the barometer seems to be a difficult task. The La Crosse stations do not have a direct setting for altitude - so it's a guess work thing. And since the console pressure reading and WeatherUnderground and PWS take Relative Pressure in inches while CWOP wants a different value, and in millibars too, it's even more confusing. But - the only change was at CWOP - the Cumulus screen, the WS 2317 console, WeatherUnderground and PWS did not show the sudden, instantaneous jump in pressure CWOP recorded.

I'd been researching here and on the CWOP forums for advice on this issue. It is the primary reason I upgraded to v1.9.0, not that I expected it to resolve the problem - but I knew I should be running the latest version before I brought the issuet up. So I was most pleased when the upgrade fixed things.

I don't know if this is relevant?
http://server.gladstonefamily.net/piper ... 11752.html

steve wrote:I'm surprised there was such a difference. In the old code, it took the absolute pressure and adjusted it using your configured altitude. I realised that this was pointless for non-Davis stations, so changed it to take the supplied sea-level pressure instead. Davis stations display genuine sea-level pressure as opposed to altimeter pressure as required by CWOP. With other stations, the sea-level pressure they provide is actually more like altimeter pressure, i.e. it is only adjusted for altitude, so the later code just uses that.

It should only have made a significant difference, assuming you had configured your altitude correctly, if your station's absolute pressure reading was some way off and you were having to over-compensate with your relative pressure setting, i.e. you are compensating for both altitude and an inaccurate reading.

But anyway, it's good that the change was of some benefit.