Barometric Pressure way off (corrected once CL system is deployed)

Moved a few posts over to this one though it isn’t always easy where to cut … hope it is still cleanr

the discussions started in this topic and drifted to barometric values
Hope everyone can still follow …

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I understand what you are saying now, and it seems to me that you might have a dodgy Air module. Out of interest though, how does the station pressure measured by the Air compare to the station pressure measured by your Davis unit before you apply your manual adjustment to make the Davis unit match your trusted source?

I ask because I don’t see the same issue as you. Once I have entered the correct elevation for my Air, it reads the same SLP (within 1 mb) as a professional grade station about 10 km away.

(@moeythomas I moved this down to try and keep the thread flowing after the merge!)

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If I put in my elevation of 33ft asl, then the sea level pressure is 3mb too high. Station pressure remains the same regardless of putting in a positive or negative number.

edit:

Bournemouth airport: 1014.4 hPa
My Davis stations: 1014.4 hPa
WF slp with correct elevation: 1017.2 hPa
WF slp with -40 feet: 1014.4 hPa

That’s the problem right there… you shouldn’t need to adjust the elevation until it matches a sea level pressure. Firstly, that’s the incorrect way to do it. Secondly, I have to put in a minus figure to get it to match anyway.

I’m wondering if anybody here is using a Davis or Oregon station? I have both a VUE console and a VP2 console, as the manual states, you put in your elevation, and then adjust the console/station pressure. It’s the same on an Oregon WMR200. If you search any weather forums eg Cumulus, Netweather, Weather-Watch, WX forum, people with Davis hardware will say that it is the station pressure that get’s adjusted. Once your elevation settings have been correctly put in, the sea level pressure will be calculated.

I assume the 1014.4 hPa is SLP from your Davis station. What is station pressure for your Davis station, before you have made any adjustments? How does it compare to the 1015.7 mb currently being reported as station pressure from your Air?

What a time to run out of popcorn.

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Hi @moeythomas . We agree that having to fudge your elevation to calibrate your sea level pressure is NOT THE RIGHT APPROACH…and to be clear, this is not the approach that WF is taking.

Here is how it actually works: AIR will sense the pressure at it’s location (station pressure). To normalize and compare against other stations in the area, total elevation needs to be taken into consideration…which is then used to calculate sea-level pressure…so that everyone is comparing apples to apples. For your WF system, total elevation = [elevation at your location automatically determined when you set your geo-location] + [height above ground at which the AIR is mounted].

In-situ sensor calibration is typically done by comparing known good data sources and applying a calibration. Unlike Davis et. al. we don’t think this should be something that the average home user (or anyone for that matter) should need to do. INSTEAD, the WF auto-calibration / continuous learning (CL) system will automatically identify and monitor a variety of known good data sources for your immediate area and automatically compare them to your AIR data on an ongoing basis and apply any required calibration.

As mentioned previously, the WF CL system has not yet been fully deployed. As of today 19 Sept, only RH is run through the daily CL calibration system. Other parameters including Pressure is in final testing and will be rolled out soon.

So there you have it…we agree! Have faith, we’re not idiots. :wink: Will announce when the CL system is deployed for Pressure.

And PS - we suspect that a batch of AIRs did not receive a proper pressure sensor calibration at the factory which might explain the 2-3mb deltas being reported.

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In other words… WeatherFlow IS doing it correctly.

WeatherFlow is an expert company staffed by experts in weather.

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No. 1014.4 hPa is my station pressure - relative pressure. I set my elevation to (10m on Davis stations) and then set the station pressure by looking at amateur stations around me, and two official Met Office stations that I live between. This was done years ago, during a time when pressure was stable.

If you lower the elevation, down to zero for example. Station pressure drops to 1012 hPa.

OK, and do you remember the size of the correction you needed to make? I’m trying to get an idea of the raw, uncalibrated difference in station pressure between your Air module and your Davis station.

Then why does adjusting the elevation change the sea level pressure on the dashboard? It shouldn’t according to what you’ve just said - which is what I have been saying all along. Sea level pressure should be calculated from your station pressure and elevation - you should never need to adjust the sea level pressure.

Guys - threads are impossible to navigate long after the fact.

Can you start to save this kind of ‘great’ stuff someplace so all the info coming out recently telling us how stuff ‘really’ works rather than us speculating is captured someplace.

Maybe create a wiki if you want the community to lend a hand ?

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Because surely as, by definition, SLP depends on elevation, changing elevation changes the SLP? The point of course is that you shouldn’t have to fudge the elevation to get the correct SLP, which @WFstaff discussed above.

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Stop and look at what you just said… SLA IS Calculated from station data, adjusted by height. The absolute is STATION data, and yours is wrong. When WF roll out the CL for pressure, yours will be corrected and all would be good.

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Point I raised some weeks back, even for me as moderator, I remember I saw a reply but hell where was it …

I have started a local litlle database with things as the forum isn’t handy for wiki style info. I hope WF will do this once they have some more time spare …

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dare I suggest one of the field testers set up an unauthorized (so to speak) wiki for the interim ?

setting one up and populating it takes time. If it is as a temp solution … maybe a pity except if the WF staff decides to use the same script, hence database move … but again, better know before and not too late

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Here is the formula used for calculating Sea Level Pressure: https://weatherflow.github.io/SmartWeather/api/derived-metric-formulas.html#sea-level-pressure

Relax and smile everyone.

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I feel as though i’m not getting my point across. I have tried my very best, but it seems not to be working.

I just want to add, i’m not the only one who thinks this is wrong. On another weather forum, users with other weather stations agree with me.

Here’s some other points I want to raise.

I keep reading about how the weather data is supposed to be ‘user friendly’ and kept ‘simple’ for those that might not be savvy when it comes to this sort of thing. But, in all honesty (owning stations for over ten years) some of the options and output on the dashboard are the most complicated I have ever seen in a weather station.

If there’s going to be a problem with the barometric side of things, then you should include an option to show either station pressure, or SLP, on the main dashboard page. If my station get’s calibrated correctly, by that I mean; I can put in my correct elevation and get the right station pressure, then I have no choice in having sea level pressure showing on my dashboard page which will look wrong when comparing it to my Davis and surrounding stations.

I’ll support WF all the way, as I really do like this station. But, as I touched upon above, I find some things completely and utterly baffling about it - some of it is straight forward, but the pressure side of things is completely bonkers. What you may think of as intuitive is actually over-complicated.

One thing I have learned in the tech business over the years is to give people options. on/off - stop/go etc. It makes life far easier.

I’m going to stop posting for a while. So, best regards and enjoy mother nature!

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Maybe, just maybe…

The reason that the reading is wrong is because …

wait for it…

The Air is defective.

I said Maybe.

Don’t fret @moeythomas . Seems to be simply a matter communication. It also seems that WE ACTUALLY AGREE on everything you note here. For example:

We agree, and this is how the system works.

This is a good idea. We’ll certainly consider it !

We love your feedback and your passion and we’re listening. All good.

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