Author Topic: Barometric pressure settings  (Read 3978 times)

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Offline Trafcon

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Barometric pressure settings
« on: April 09, 2021, 08:23:14 AM »
Probably somewhere else on another thread, if so redirect me please.  I wanted to know what I set my WS-5000 barometric pressure to.  I live at about 450 foot altitude.  I can get a barometric reading from the local airport 10 miles away and it it at 100-150 foot elevation.  Example, right now the airport is reading 30.90.  What would I set my station to and should I use Relative or Absolute ??  Thanks for assisting a newbie.   [tup]
« Last Edit: April 09, 2021, 09:39:12 AM by Trafcon »

Offline gszlag

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Re: Barometric pressure settings
« Reply #1 on: April 12, 2021, 07:38:17 AM »
Probably somewhere else on another thread, if so redirect me please.  I wanted to know what I set my WS-5000 barometric pressure to.  I live at about 450 foot altitude.  I can get a barometric reading from the local airport 10 miles away and it it at 100-150 foot elevation.  Example, right now the airport is reading 30.90.  What would I set my station to and should I use Relative or Absolute ??  Thanks for assisting a newbie.   [tup]

Just need a bit more info..
Which airport are you comparing to?
Are you comparing to SLP (sea level pressure) or to Altimeter?

According to the WS-5000 manual:

" The display tablet displays   two   different   pressures:   absolute   (measured)   and   relative (corrected to sea-level).To compare pressure conditions from one location to another, meteorologists correct pressure to sea-level conditions. "

Ambient's "short-cut method" in the manual advises you to set the Relative Pressure on your console to match your local airport's sea level pressure (SLP). There is actually a bit more to it than that but it is a start.

Your Station Pressure is the atmospheric pressure reading on your indoor WH32 device and is pre-populated as Absolute Pressure(ABS) in your display console.

Sea level pressure(SLP) from your airport would be entered in your console as Relative Pressure (REL). Your airport's elevation is irrelevant as its station pressure has been converted down to sea level elevation. That's the SLP reading you might see in your airport's METAR report.

There are different ways to calibrate your barometer and there are many posts on this subject. Try searching the forum posts for the term "barometric pressure" for more background.

In the meantime, you can set your REL (Relative Pressure) in your console to the airport's  SLP. reading. As you are close to the airport we'll make the assumption for now that your weather station and the airport's weather station is in the same pressure zone.

Here is a link https://www.digitaldutch.com/atmoscalc/table.htm that you might find useful. Just enter in your Altitude/elevation. You can uncheck the Density, Speed of sound and Dynamic viscosity parameters . We just want to generate a table showing the relationship between Altitude/Elevation, temperature and atmosheric pressure. For the row levels start at zero altitude (sea level). Put in your 450 as "max" and use perhaps 50 ft as the increment.

The difference in pressure between 450 feet and zero (sea level) is sometimes referred to as the correction for elevation. Essentially what it means is that anyone in the world that is also at an elevation of 450 feet above sea level would have to add the same fixed elevation correction to their station pressure in order to obtain SLP.

Take note of the temperatures in the table. Not only does the atmospheric pressure drop with altitude so does temperature. It is also interesting to note that the formula assumes that the temperature at your weather station is at a constant 57.3952 degrees.

Over a period of time - several days, check to see how closely your weather station's Relative Pressure is tracking the airport's SLP reading. Report back to us.

BTW. Your post I think, should have gone into the Ambient/Fine Offset forum. Perhaps a moderator can move it. It should get more eyeballs over there.
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Offline Great.Gonzos

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Re: Barometric pressure settings
« Reply #2 on: April 12, 2021, 11:45:22 AM »
I realize I am not an expert by any means, but isn't setting your relative pressure to an absolute pressure wrong? If the pressure reported by the airport is SLP (which would be the absolute pressure adjusted to what it would be a sea level), then that is adjusted to sea level. They do this to make the pressure standardized for any location. The absolute pressure is the exact pressure at your location, regardless of elevation. That is, say your absolute pressure is 29.05. your relative pressure may be 29.92 (the standard average for relative pressure).  For somebody else at their elevation, their absolute may be 29.45, with a relative pressure of 29.85, meaning they are in a low pressure. When you are asked your pressure, giving them your relative pressure then gives them a standardized pressure they can compare to as they would then compare THEIR relative pressure to yours, eliminating the calculations for elevation. That is, my understanding, the whole intent of the relative pressure value.

So setting your absolute pressure to a local relative pressure/SLP it would seem cause their station to be off, more so the higher in elevation they may happen to be. For example, let's take it to a bit more of an extreme. When I was in Nepal, at 15,000 feet, the absolute pressure was down to about 19.00 in/hg or 650 mbar, yet the relative pressure (SLP) would still have been 29.92in hg/1013mbar. If it were going to snow, it would drop further, say 625mbar (18.45 in hg) or a relative pressure of 29.85/1010, again indicating I was in a low pressure situation. In this case, setting your absolute pressure to the local relative pressure, would then give you a relative pressure something in the range of 49.5 or more. That is ridiculously WAAAAY off.

So if you want to use the local relative pressure to set your station, but want to set it using absolute pressure, THEN you need to the the conversion based on your elevation. But to set your stations absolute pressure to the local relative pressure is, well, just plain wrong.

Please correct me if I'm mistaken.
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Offline Gyvate

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Re: Barometric pressure settings
« Reply #3 on: April 12, 2021, 02:55:52 PM »
There are many posts in this forum where the proper calculation and calibration of air pressure is described.
e.g. https://www.wxforum.net/index.php?topic=40750.msg418125#msg418125

But @Great.Gonzos, you are right (and maybe @gszlag phrased his post in a way that can be misunderstood): the equation: abs Pressure = rel Pressure is only true at sea level.
Otherwise, the higher you go, the smaller the absolute pressure (=local pressure) gets. That's natural law - the higher you go, the smaller the weight of the air on one square meter (pressure = force/area)
- same thing the other way around under water (water pressure).

There are formulas (and calculators) which calculate what would be the corresponding pressure of the local pressure at sea level - that's the relative pressure.
The difference between these two values (local pressure/abs pressure and relative pressure)) you enter as calibration in the rel Pressure entry in the  HP2551/WS-5000 console.
This difference will be a positive value unless you are located under sea level.

So
Find your elevation: e.g. https://www.freemaptools.com/elevation-finder.htm
calculate the relative air pressure: e.g. https://keisan.casio.com/exec/system/1224579725
find the offset (= rel pressure - abs pressure) and enter it into the rel pressure calibration field.
[abs pressure will be the pressure reading on your WH32B, the indoor temp/hum/pressure sensor]

Once you have done this, you can go into fine tuning and start comparing around: nearby airports, other PWS etc. - and if you feel there's some adjustment needed,
you can enter now this adjustment into the abs Pressure field in the calibration.

A good way to check is e.g. using the AWEKAS service (https://www.awekas.at/wp/?lang=en) where you can add your station and become a member - it's free.
It provides a service where you can compare the main measurements (temperature, humidity, rel Pressure, wind, precipitation) with other AWEKAS stations in a radius of 10, 20, 50, 100 km. ( 1 mile = 1.6 km).
That gives you a good idea if you are too much "off" or in a reasonable corridor. Don't forget that there is always a micro climate - so wanting to be exact on one or even two place(s) after the decimal point with hectopascals (hPa) is probably not a very useful thing to do.
« Last Edit: April 12, 2021, 03:21:09 PM by Gyvate »
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Offline galfert

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Re: Barometric pressure settings
« Reply #4 on: April 12, 2021, 03:34:27 PM »
I live at about 450 foot altitude.
Then you can expect the difference between your Relative and Absolute pressure to be 0.48 inHg difference (the offset between the two). Better to calibrate with the station set to hPa though and set the offset difference to 16.3 hPa, and then when you are done, then you can switch back the units to inHg. But if you just want to be close enough then just use 0.48 inHg.

How did I find that out? Using the Keisan Casio calculator:
https://keisan.casio.com/exec/system/1224579725

When using that calculator do not change the default 1013.25 sea-level pressure, and do not change the standard pressure of 15°C. It doesn't matter what pressure nor what temperature it is now. You are looking for a standard offset that would be most correct for year-round calibration offset. The only number you enter is the one that corresponds to your elevation....which needs to be entered in meters. The resulting Atmospheric pressure is what you then subtract from 1013.25 to find out by how much your Relative and Absolute should differ from each other.

Quote
...the local airport 10 miles away and it it at 100-150 foot elevation.
The elevation of the airport is irrelevant. You are getting a barometric pressure from the airport that has been corrected to sea level.

Quote
What would I set my station to and should I use Relative or Absolute ??
Your Relative is what should match the airport's sea level pressure.  And your Absolute will be about 0.48 inHg lower (16.3 hPa lower) if you are in fact at 450 feet of elevation. But you shouldn't guess your elevation. You should try and be more precise and use the free map tool link the Gyvate linked to find out your elevation.
https://www.freemaptools.com/elevation-finder.htm

One last tip....Your elevation is ground elevation plus the added height above the ground for your indoor temp/hum/pressure sensor. Which means that if that sensor is on a second floor or first floor, then that makes a difference.
« Last Edit: April 13, 2021, 10:31:04 AM by galfert »
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Offline galfert

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Re: Barometric pressure settings
« Reply #5 on: April 12, 2021, 03:41:34 PM »
Still confused? Want more help? Then post your Latitude and Longitude and I can do the math for you.
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Offline tricky

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Re: Barometric pressure settings
« Reply #6 on: April 13, 2021, 03:23:39 PM »
Apologies for jumping on the back of this thread but I am really confused!! (Doesn't take much)

I am running a Ecowitt GW1000 (showing 1030.9mbar ABS and 1003.3mbar REL) although whilst checking in WS View its just dropped to 1003 on both.  I also have a Ventus W830 which is showing 1005.5 (ABS) 1011.5 (REL) and a EcoWitt WH32 which is showing 1001.6 (All devices sat next to each other).

I am at ~232m / 761ft Elevation according to https://www.freemaptools.com/elevation-finder.htm

Whilst I am not expecting 100% accuracy it'd be nice to try understand and get it somewhere near if you can help me!!!  I've not touched any of my devices in terms of trying to amend the calibration.




Nearest reading I would trust is Leeds Bradford Airport https://www.weatherhq.co.uk/weather-station/leeds-and-bradford is presently showing 1028 SL Pressure (hPa)?

I noticed that WeeWx is showing the 1031.1mbar from the data feed --> 2021-04-13 20:06:55 BST (1618340815): UV: 0, dateTime: 1618340815, dayRain: 0.0, daymaxwind: 5.6, extraHumid1: 34, extraHumid2: 35, extraHumid3: 36, extraHumid4: 40, extraHumid5: 41, extraHumid6: 44, extraHumid7: 38, extraHumid8: 62, extraTemp1: 23.2, extraTemp2: 23.2, extraTemp3: 22.4, extraTemp4: 21.4, extraTemp5: 20.8, extraTemp6: 20.7, extraTemp7: 22.7, extraTemp8: 10.3, inHumidity: 37, inTemp: 22.1, luminosity: 0.0, monthRain: 3.5, outHumidity: 62, outTemp: 7.8, pressure: 1003.6, rain: None, rainRate: 0.0, relbarometer: 1003.6, stormRain: 0.0, usUnits: 17, uvradiation: 0.4, weekRain: 1.2, wh31_ch1_batt: 0, wh31_ch1_sig: 4, wh31_ch2_batt: 0, wh31_ch2_sig: 4, wh31_ch3_batt: 0, wh31_ch3_sig: 4, wh31_ch4_batt: 0, wh31_ch4_sig: 4, wh31_ch5_batt: 0, wh31_ch5_sig: 4, wh31_ch6_batt: 0, wh31_ch6_sig: 4, wh31_ch7_batt: 0, wh31_ch7_sig: 4, wh31_ch8_batt: 0, wh31_ch8_sig: 4, wh65_batt: 0, wh65_sig: 4, windDir: 319, windGust: 0.5, windSpeed: 0.1, yearRain: 14.9
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Offline galfert

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Re: Barometric pressure settings
« Reply #7 on: April 13, 2021, 03:51:26 PM »
I'm confused by your mention of the WH32. I don't not know for sure if you are referring to the indoor WH32B or to the outdoor WH32. The indoor WH32B has barometric pressure but neither the GW1000 nor the Ventus W830 can make use of it as they have their own indoor sensor with their own internal barometric sensor. Therefore if what you have is an outdoor WH32 then that has no barometer. If you do have a separate WH32B with barometer indicator in the LCD then that can not be adjusted on that device itself but the data that it does send can be calibrated by the receiving console. The compatible console for that would be the HP2551 or equivalent....or a WH2650.

If you are at 232 meters, then the difference between your Relative an Absolute pressure should be a 27.4 hPa offset. That would apply to all your consoles. That would be step 1. Then step 2 is to calibrate with your local airport. All your barometers should be fairly close and track relatively in unison. But if the 232 meters that you gave me is ground level then you need to add the elevation of the barometric sensor....and then recalculate the proper offset.

With the numbers you gave me you currently have the following situation.
Your GW1000 currently is set for 229 meters.
Your Ventus W830 is set for 50 meters.

The issues with WeeWX should only be something we address after you have completed the necessary calibrations on the GW1000. It would be relevant to know if you are using WeeWX with the Interceptor driver or with the GW1000 API driver.

« Last Edit: April 13, 2021, 04:00:51 PM by galfert »
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Offline tricky

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Re: Barometric pressure settings
« Reply #8 on: April 13, 2021, 04:41:10 PM »
I'm confused by your mention of the WH32. I don't not know for sure if you are referring to the indoor WH32B or to the outdoor WH32. The indoor WH32B has barometric pressure but neither the GW1000 nor the Ventus W830 can make use of it as they have their own indoor sensor with their own internal barometric sensor. Therefore if what you have is an outdoor WH32 then that has no barometer. If you do have a separate WH32B with barometer indicator in the LCD then that can not be adjusted on that device itself but the data that it does send can be calibrated by the receiving console. The compatible console for that would be the HP2551 or equivalent....or a WH2650.

If you are at 232 meters, then the difference between your Relative an Absolute pressure should be a 27.4 hPa offset. That would apply to all your consoles. That would be step 1. Then step 2 is to calibrate with your local airport. All your barometers should be fairly close and track relatively in unison. But if the 232 meters that you gave me is ground level then you need to add the elevation of the barometric sensor....and then recalculate the proper offset.

With the numbers you gave me you currently have the following situation.
Your GW1000 currently is set for 229 meters.
Your Ventus W830 is set for 50 meters.

The issues with WeeWX should only be something we address after you have completed the necessary calibrations on the GW1000. It would be relevant to know if you are using WeeWX with the Interceptor driver or with the GW1000 API driver.

Sorry yes I have a HP2551 as well which the INDOOR WH32B reports too - the Ventus W830 is from an old weather station that died but is on the same frequency so I use as a 2nd console.

WeeWx is using the https://github.com/gjr80/weewx-gw1000 driver

So if I follow your suggestion on the GW1000 (in WS View) I'd change one or both of ABS/REL offset to be 27.4hPa from 0 which they are both set at ... I'd also do this on the consoles (W830 and HP2551).  Sorry which would I add onto if not both?

The consoles/sensors would be ~3meters higher than the ground based on the point and click on the map!



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Offline Gyvate

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Re: Barometric pressure settings
« Reply #9 on: April 13, 2021, 05:03:02 PM »
I'm confused by your mention of the WH32. I don't not know for sure if you are referring to the indoor WH32B or to the outdoor WH32. The indoor WH32B has barometric pressure but neither the GW1000 nor the Ventus W830 can make use of it as they have their own indoor sensor with their own internal barometric sensor. Therefore if what you have is an outdoor WH32 then that has no barometer. If you do have a separate WH32B with barometer indicator in the LCD then that can not be adjusted on that device itself but the data that it does send can be calibrated by the receiving console. The compatible console for that would be the HP2551 or equivalent....or a WH2650.

If you are at 232 meters, then the difference between your Relative an Absolute pressure should be a 27.4 hPa offset. That would apply to all your consoles. That would be step 1. Then step 2 is to calibrate with your local airport. All your barometers should be fairly close and track relatively in unison. But if the 232 meters that you gave me is ground level then you need to add the elevation of the barometric sensor....and then recalculate the proper offset.

With the numbers you gave me you currently have the following situation.
Your GW1000 currently is set for 229 meters.
Your Ventus W830 is set for 50 meters.

The issues with WeeWX should only be something we address after you have completed the necessary calibrations on the GW1000. It would be relevant to know if you are using WeeWX with the Interceptor driver or with the GW1000 API driver.

Sorry yes I have a HP2551 as well which the INDOOR WH32B reports too - the Ventus W830 is from an old weather station that died but is on the same frequency so I use as a 2nd console.

WeeWx is using the https://github.com/gjr80/weewx-gw1000 driver

So if I follow your suggestion on the GW1000 (in WS View) I'd change one or both of ABS/REL offset to be 27.4hPa from 0 which they are both set at ... I'd also do this on the consoles (W830 and HP2551).  Sorry which would I add onto if not both?

The consoles/sensors would be ~3meters higher than the ground based on the point and click on the map!
Please change only the rel pressure offset in the first step.
Changing the abs pressure offset is a second step if you find that the result of the rel pressure calibration for your location still differs from another value of your trust, e.g. airport value.
And you have to do the calibration on/with each of your consoles (GW1000, HP2551, ...)
« Last Edit: April 13, 2021, 05:05:53 PM by Gyvate »
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Offline galfert

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Re: Barometric pressure settings
« Reply #10 on: April 13, 2021, 05:11:06 PM »
Your total elevation is 235 meters after adding the 3 meters from the ground elevation. This means that your Relative offset should be 27.8 hPa.

 [ You are not allowed to view attachments ]

1013.25 - 985.48 = 27.77 which rounds to 27.8.

This means that a Relative offset of 27.8 hPa corresponds to an elevation of 235 meters of total elevation.

The method of adjusting the Relative and Absolute pressures on all of the consoles that you have will require a slightly different method. But the end result should be that the indicated Relative pressure should be 27.8 hPa greater than the shown Absolute pressure. On the GW1000 you don't adjust both offsets with this number. Rather you only adjust the Relative pressure with this offset. The Absolute offset on the GW1000 is what you then adjust to impart a final calibration by comparing to your local METAR. On the HP2551 what you have to do is first adjust the Relative to be 27.8 hPa greater than whatever is showing for Absolute. Then back out to the main display to confirm (this step is important not just to confirm but to finalize the setting). Then you adjust the Absolute by however much is required to cause the Relative pressure to end up matching the METAR. On the Ventus W830 the process requires knowing how to adjust both the Relative and the Absolute...so be sure to read the manual to learn how to adjust both. In the case of both the HP2551 and the W830 you are not directly entering in the offset ...but rather you are manually adjusting the displayed pressure so that the end result is that the Relative is 27.8 hPa greater than the Absolute.

« Last Edit: April 14, 2021, 02:28:02 PM by galfert »
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Offline tricky

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Re: Barometric pressure settings
« Reply #11 on: April 14, 2021, 06:30:17 AM »
Thanks for the excellent feedback ...

So looking at the ABS:
I take mine elevation 235m gives an REL offset of 27.77 (1013.25 - 985.48) which I can set across my different devices
I take Leeds Bradford elevation 208m gives a REL offset of 24.63 (1013.25 - 988.62)

Is my ABS offset therefore the difference between 27.77 and 24.63 = 3.14?
My 3 devices report different values for ABS at present (GW1000=1005.7, Wh32B-Indoor=1003.9, Ventus W830=1007.8)

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Offline broadstairs

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Re: Barometric pressure settings
« Reply #12 on: April 14, 2021, 06:40:44 AM »
Your REL offset is 27.77 hpa at your elevation of 235m. You dont need an ABS offset because the ABS reading is you actual pressure at you location, the REL offset give a Sea Level Pressure based on your ABS pressure.

Stuart
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Offline tricky

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Re: Barometric pressure settings
« Reply #13 on: April 14, 2021, 06:59:21 AM »
Your REL offset is 27.77 hpa at your elevation of 235m. You dont need an ABS offset because the ABS reading is you actual pressure at you location, the REL offset give a Sea Level Pressure based on your ABS pressure.

Stuart

ABS is different on 3 devices though which are all sat next to each other in a row:
(GW1000=1005.7, Wh32B-Indoor=1003.9, Ventus W830=1007.8 )

I was therefore assuming that I need to get these to match in some way? or am I just amending the REL +/- to ensure that REL is correct and matching across all 3?
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Offline broadstairs

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Re: Barometric pressure settings
« Reply #14 on: April 14, 2021, 07:17:56 AM »
Which one of those is closest to a reliable local source bearing in mind that METARs report Sea Level Pressure and then use that one as your standard, then use ABS offset to bring the others in line (assuming you can do that). That's what I'd do. I have the advantage of a UKMO buoy reporting close enough to me to gauge actual SLP and then set the REL offset to match.

Stuart
Ecowitt GW1003 with ultrasonic wind gauge, lightning sensor and PM2.5 sensor with Personal Weather Tablet as a console.

Offline tricky

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Re: Barometric pressure settings
« Reply #15 on: April 14, 2021, 07:27:36 AM »
Which one of those is closest to a reliable local source bearing in mind that METARs report Sea Level Pressure and then use that one as your standard, then use ABS offset to bring the others in line (assuming you can do that). That's what I'd do. I have the advantage of a UKMO buoy reporting close enough to me to gauge actual SLP and then set the REL offset to match.

Stuart

So this site https://www.weatheronline.co.uk/weather/maps/current?LANG=en&SI=mph&CEL=C&WMO=u3003&TIME=std&CONT=ukuk&R=310&LEVEL=140&REGION=0003&LAND=__&ART=luftdruck&NOREGION=0&PLZ=&PLZN=&SORT=__&TEMP=___&WETTER=__&&TYP=__&SEITE=0 shows Sea Level Pressure hPa at 1034 presently
Likewise this site https://metar-taf.com/EGNM

So if METAR for LBA is EGNM 141020Z 04005KT 360V080 CAVOK 08/M00 Q1034  --> the Q1034

So does this mean that all 3 of my devices are way off for ABS? I thought that the METAR data was showing the REL value?

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Offline gszlag

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Re: Barometric pressure settings
« Reply #16 on: April 14, 2021, 07:35:32 AM »
Thanks for the excellent feedback ...

So looking at the ABS:
I take mine elevation 235m gives an REL offset of 27.77 (1013.25 - 985.48) which I can set across my different devices
I take Leeds Bradford elevation 208m gives a REL offset of 24.63 (1013.25 - 988.62)

Is my ABS offset therefore the difference between 27.77 and 24.63 = 3.14?
My 3 devices report different values for ABS at present (GW1000=1005.7, Wh32B-Indoor=1003.9, Ventus W830=1007.8)
You've got the same issue I had, My GW1000 and WH32B readings are 2.55 hPA apart. Which one is out - one or both?

galfert has calculated your elevation offset for your specific elevation. Just take the current value of Leeds Bradford airport and subtract the offset. This will give the ABS that you can set/adjust in your display consoles and WSview app.

There is a slight complication. Leeds Bradford reports QNH (Altimeter) which uses a different formula. However it should be close enough.

Right now Leeds Bradford is showing SLP (elevation corrected) of 1034. Subtract your calculated elevation correction of 27.8. Your ABS on all devices should be set to that amount which is 1006.2

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Offline tricky

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Re: Barometric pressure settings
« Reply #17 on: April 14, 2021, 09:21:47 AM »
OK I've got all 3 of my devices reporting the same ABS/REL now - Thanks all ...

So I arrived at my calculations through (your help!):
Nearest Metar site is 208m the elevation calculation gives them an offset of 988.62 but running at 1034hpa therefore trusted read

My elevation of 235m gave me a offset of 985.48
Taking my reading (985.48) away from Sea Level at 1013.25 gave me a REL change of 27.77hpa
I then took the REL change of 27.77 away from 1034 (current trusted read) which gave me 1006.23

On the WH32 (via the HP2551 Console) I amended the calibration of ABS to be 1006.2 and REL to be 1034.1 - Nice and easy
On the GW1000 (via the WS View App) I added 0.9 hPa to ABS and 27.8 to REL (From the readings it had)
On the W830 (via the console) Calibrate Mode to set the ABS and SET mode to do the REL - Not as easy!!

All 3 devices now working on the same readings...
Thanks again

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Ecowitt WH65B
Ecowitt HP2551-C
Ecowitt WH32B
Ecowitt WH31 x8
Ecowitt GW1000
Ecowitt BP1000 Battery Extension

Ventus W830 from a Dead weather sensor

2x Raspberry Pi's with WeeWX (RTL-SDR and GW1000 feeds), Synology Docker with CumulusMX

Offline galfert

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Re: Barometric pressure settings
« Reply #18 on: April 14, 2021, 12:20:10 PM »
Nearest Metar site is 208m the elevation calculation gives them an offset of 988.62 but running at 1034hpa therefore trusted read
Performing this exercise of figuring out the METAR absolute pressure would not lead to any conclusion regarding the trustworthiness of the METAR data.

The elevation of the METAR location is irrelevant. Figuring out what the METAR absolute pressure would be based on their elevation is of no use for your station's calibration.

Glad to hear that you got all of your barometers sorted.
« Last Edit: April 14, 2021, 12:34:25 PM by galfert »
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