Issue with pressure reporting **solved**

[viennaxmas]

I am using Meteobridge, latest firmware (Meteobridge 3.1 (Dec 22 2016, build 10776), FW 1.4). I am reporting to CWOP and Weather Underground.

For whatever reason, the pressure values do not line up between what I see in the bridge and what is reported.

What I should be seeing: 1012 hPa [comparison by various other stations and the closest official station].

Meteobridge shows 1028.4hPa (1016.3hPa). [ Given that the sealevel adjusted value is pretty close to what I would expect]

CWOP shows 1027.8hPa - so the non-adjusted value

Weather Underground only shows 981.6 hPa.

My elevation is correct in all services.

I have tried adjustments but I can never get WU and CWOP to match, they are usually around 40 hPa apart.

What causes this? Is there some kind of "double adjustment" for the elevation?

Could it be that meteobridge sends WU the sealevel adjusted pressure and WU adjusts it again?

Is there any way to fine tune what does get sent to which of the services?

[viennaxmas]

I did a bit more testing and it seems to me that:
1. CWOP is expecting the "Indoor pressure" level
2. Wunderground is expecting the "Indoor seapressure" level.

This way, it seems I get close to the expected values.

[admin]

Some more pieces of information around this...
1) Indoor pressure = outdoor pressure.
2) Most stations have the pressure sensor indoor (mostly in console) to keep it away from nasty outdoor conditions.
3) CWOP expects "altimeter pressure", which Meteobridge computes and delivers to CWOP.
4) All other networks (including WU) expect "sealevel pressure".
5) Live data shows station pressure as it comes from the sensor and sealevel pressure.

[viennaxmas]

Thanks - that is what I expected.

Which would mean, that the values should be correct. Unfortunately they are not. they seem to be reversed.

Is there a way to log the raw data being sent to the services for me to compare?

Thanks!

[viennaxmas]

So, I have just looked at the different systems and the reported pressures

1. Closest Airport (about 15 km away): 1028 hpa
2. My station on Wunderground: 999.21 hpa
3. neighbor stations on Wunderground: 1027 hpa (average)
4. Data reported to CWOP: 1045 hpa.
5. Meteobridge pressure: 1032 hpa
6. Meteobridge seapressure: 1046.2 hpa


So - the values are all over the place. My station is 4 off which is easy to adjust. However - how do I fix the values sent to Wunderground and CQOP?

You are stating that WU is expecting sealevel pressure. However my Wunderground values are way too low.

[admin]

I don't buy your WU pressure, that does not look ok. Please recheck, WU is sometimes a bit slow in updating so you might have seen data from the past. To get you some obviously needed help, we need a bit more information:
1) which station are you using?
2) which altitude setting did you specify on Meteobridge "station" tab?

Calibration you can do is applied to the station pressure and then effects sealevel and altimeter accordingly. It is not intended to adapt each of those separately.

[viennaxmas]

Sorry for not following up earlier.

Today I did discover that WU and CWOP all the sudden showed the same pressure values. Not sure what has changed but after adjusting the offset a little bit, I am finally reporting accurate values to both services.

Just to answer the question: I am using a accurite internet bridge with a 5 in one sensor. Pressure is coming from the bridge.

Altitude is set to 360 ft which matches my GPS position (6 satellites reporting), so that was not the problem.

Anyway, now it seems everything is good.

Thanks for your help.

[Mattk]

.... Altitude is set to 360 ft which matches my GPS position (6 satellites reporting), so that was not the problem.

Just out of curiosity is that altitude of 360 feet derived by GPS means? And if so is it a GPS height (as such) relative to Ellipsoid or height relative to sea level? (Sea level height = Ellipsoid height +/- geoid separation)