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Pressure difference on WU

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Bablefish
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Pressure difference on WU

Postby Bablefish » Sat Sep 30, 2017 6:05 pm

I seem to be having an issue with the pressure that is being shown on Cumulus and the pressure that is being sent to Weather Underground.

www,larbertweather.co.uk

https://www.wunderground.com/weathersta ... =IBONNYBR3

The pressure in WU is nearly 8Hpa higher than what is on the WMR88 screen and on Cumulus.

I do have a altitude correction in the WMR88 of 80m but no correction in Cumulus. ( the pressure in the WMR is correct as per my nearest airport)

Is their any way to correct the info on WU?

I

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steve
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Re: Pressure difference on WU

Postby steve » Sat Sep 30, 2017 6:34 pm

Turn off rapid fire and restart Cumulus, see if that makes a difference. Assuming that it doesn't, you can then turn on debug logging, and the debug log will show the values being sent to WU (pressure is sent in inHg).
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steve
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Re: Pressure difference on WU

Postby steve » Sat Sep 30, 2017 6:45 pm

I had your WU page open just now, and the pressure briefly changed to the correct value. So I think that perhaps this is either a WU problem, or you have two things updating WU at the same time - the other may be a second instance of Cumulus that you didn't realise was running.
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Mapantz
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Re: Pressure difference on WU

Postby Mapantz » Sat Sep 30, 2017 10:54 pm

I think I've read elsewhere that somebody else had this issue, but they were using WD. It turned out to be WU automatically adjusting their pressure because they thought it was wrong, or didn't match up to nearby stations.
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Bablefish
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Weather Station: WMR88
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Re: Pressure difference on WU

Postby Bablefish » Sun Oct 01, 2017 4:26 pm

I think it may well be WU "correcting" the reading.

But i cant understand why as my station is reporting the same pressure as Edinburgh airport, about 25 miles away and similar to surrounding WU stations.

Is there some way of stopping WU "correcting"

Bablefish
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Joined: Sat Sep 30, 2017 5:57 pm
Weather Station: WMR88
Operating System: windows 7

Re: Pressure difference on WU

Postby Bablefish » Sun Oct 01, 2017 5:41 pm

just looked in the log file and found out that I am sending WU the correct pressure, but it is being sent in In+HG

when I do the conversion the Hpa is correct.

So WU must be "correcting it for some reason"

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steve
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Re: Pressure difference on WU

Postby steve » Sun Oct 01, 2017 6:27 pm

The stations near you have the correct pressure on WU. Your data is updating every few seconds, but to view the data in the debug log in Cumulus, you must have turned off rapid fire - or have you turned it back on again?
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Bablefish
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Re: Pressure difference on WU

Postby Bablefish » Mon Oct 02, 2017 6:47 pm

here is a copy of the upload that is going to WU

http://weatherstation.wunderground.com/ ... =updateraw

this was at 19:30 tonight

The pressure setting being sent to WU is baromin=29.681 I work this out to be 1005.11402 hPa

Cumulus is also reporting 1005 hPa

WU is reporting 1012.75 hPa

Like someone else noticed, when you first log into WU, it displays the correct pressure setting then immediately changes to the higher setting.

I have also started sending APRS and this is reporting a lower pressure

FW1630
--- Report received 4 minutes 52 seconds ago
Wind from 244 degrees @ 6.0 MPH Gusts to 11.0 MPH
Temp 51F Humidity 88% Dewpoint 47F Rain last 24 hours 0.21 inches Pressure 999.7 mb



So that is 3 pressures all coming from the one station


Robert

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steve
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Re: Pressure difference on WU

Postby steve » Mon Oct 02, 2017 7:27 pm

APRS actually requires a different pressure to WU. APRS requires Altimeter Pressure rather than MSLP. Cumulus calculates Altimeter Pressure from the raw station (local) pressure supplied by your station using the altitude you have configured in Cumulus. If this is coming out too low (the difference should be small at low altitudes) and your altitude in Cumulus is configured correctly, then your station's barometer is reading too low.

Regarding the WU pressure display, Cumulus is clearly sending the correct data, so I think you will have to take this up with WU.
Steve
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Bablefish
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Joined: Sat Sep 30, 2017 5:57 pm
Weather Station: WMR88
Operating System: windows 7

Re: Pressure difference on WU

Postby Bablefish » Tue Oct 03, 2017 6:33 pm

Thanks Steve,

I've Emailed WU to ask them why its "correcting" the pressure.


Thanks For the advice

Bablefish
Posts: 8
Joined: Sat Sep 30, 2017 5:57 pm
Weather Station: WMR88
Operating System: windows 7

Re: Pressure difference on WU

Postby Bablefish » Wed Oct 04, 2017 7:06 pm

well at 3.21am this morning the pressure setting on WU dropped by 7hPa looks like WU have sorted the problem

Bablefish
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Joined: Sat Sep 30, 2017 5:57 pm
Weather Station: WMR88
Operating System: windows 7

Re: Pressure difference on WU

Postby Bablefish » Sun Oct 08, 2017 9:04 am

Now that the pressure setting seems to have settled down, it seems to have caused another issue.

My WMR 88 seems to be only reporting pressure in 1hPa steps.

Looking at the graphs in Cumulus, its very blocky and not smooth curves.

The same thing has happened to the internal temperature, its not a smooth curve.

www.larbertweather.co.uk

Does anyone know what I have done to cause this?

As far as I am aware, the only setting I change was the altitude to 80m.

I've also reset the WMR88 by pushing the reset button, but it has made no difference.

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steve
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Re: Pressure difference on WU

Postby steve » Sun Oct 08, 2017 10:16 am

All looks fine to me. The WMR88 has a resolution of 1 hPa. Your temp graph looks like that because it’s only covering a small range. Cumulus doesn’t do any smoothing, it accurately plots the data.
Steve
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Please read the posts in the Announcements section about the current status of Cumulus development now that I have retired

Bablefish
Posts: 8
Joined: Sat Sep 30, 2017 5:57 pm
Weather Station: WMR88
Operating System: windows 7

Re: Pressure difference on WU

Postby Bablefish » Sun Oct 08, 2017 10:23 am

Thanks Steve

I appreciate your help :-)


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