Given:
Aug 20 6:35 pm
Altitude (true) = 1865 ft
WeeWX altitude = 70 ft
WeeWX altimeter= 29.86 inHg (rounded))
WeeWX barometer = 29.85 inHg (rounded)
WeeWX pressure = 29.78 inHg (rounded)
NOTE: at altitude = 70 ft we are very close to sea level (altitude = 0). As
mentioned in my previous post, all three pressures hypothetically, should
be the same at sea level. We can see that clearly happening at the 70 ft
altitude where the readings start getting closer together.
Aug 20 18:35 (from mesowest):
KPSK elevation = 2106 ft
KPSK pressure = 27.74
KPSK altimeter = 29.95
EXAMPLE station elevation calculation:
LaCrosse true altitude = 1865 ft
KPSK altimeter= 29.95 inHg
Solving for LaCrosse "pressure" = 27.99 inHg
As reported LaCrosse "pressure" = 29.78 inHg
It looks like your current pressure of 29.78 is much too high.
In order to calculate altimeter, at a location with a 1865 ft altitude,
your relative pressure on your console should always be reading 1.96 Hg
higher than your current live absolute pressure ("pressure").
To re-calibrate your display console:
1. Calculate your station pressure (follow the example above) and then add
1.96 to this number to get your corrected relative pressure. Modify the
existing relative pressure in your display console.
2. Your pressure is wrong and you will have to fix it. I was unable to find
a way to modify your absolute pressure from your manual. You may have to
contact LaCrosse and see how this may be done.
3. Alternatively, I believe there is a way to add a pressure calibration
offset in the WeeWX config file.
4. Once you fixed your absolute pressure and relative pressure,, don'forget
to put back your correct station altitude of 1865 ft.
---
On Wednesday, August 20, 2025 at 7:11:02 PM UTC+4 kufuu wrote:
> Correction , I have weewx set at 70ft elevation to try and match another
> weather station, sorry about that.
>
>
> On Wednesday, August 20, 2025 at 6:50:00 PM UTC-4 kufuu wrote:
>
>> Im about 15 miles away
>>
>> On Wednesday, August 20, 2025 at 6:47:42 PM UTC-4 kufuu wrote:
>>
>>> My actual elevation is 1865ft , weewx is set to 0
>>>
>>> Using configuration file /etc/weewx/weewx.conf
>>> REC: 2025-08-20 18:35:00 EDT (1755729300) 'altimeter':
>>> '29.856197863702114', 'appTemp': '84.16620032955495', 'barometer':
>>> '29.850973617639387', 'cloudbase': '1750.7310847902036', 'dateTime':
>>> '1755729300', 'dewpoint': '69.42478322692313', 'ET': 'None', 'heatindex':
>>> '77.86800000000002', 'humidex': '91.66911741879971', 'inDewpoint':
>>> '56.232061622715676', 'inHumidity': '56', 'inTemp': '72.86000000000001',
>>> 'interval': '5', 'maxSolarRad': '192.36417227192797', 'outHumidity': '78',
>>> 'outTemp': '76.82000000000002', 'pressure': '29.778039395', 'rain': '0.0',
>>> 'rainRate': '0.0', 'usUnits': '1', 'windchill': '76.82000000000002',
>>> 'windDir': 'None', 'windGust': '0.0', 'windGustDir': 'None', 'windrun':
>>> '0.0', 'windSpeed': '0.0'
>>>
>>> LOOP: 2025-08-20 18:35:44 EDT (1755729344) 'altimeter':
>>> '29.856197863702114', 'appTemp': '84.16620032955495', 'barometer':
>>> '29.850973617639387', 'cloudbase': '1750.7310847902036', 'dateTime':
>>> '1755729344', 'dewpoint': '69.42478322692313', 'ET': 'None', 'heatindex':
>>> '77.86800000000002', 'humidex': '91.66911741879971', 'inDewpoint':
>>> '56.232061622715676', 'inHumidity': '56', 'inTemp': '72.86000000000001',
>>> 'inTempBatteryStatus': '0', 'maxSolarRad': '189.6877965534115',
>>> 'outHumidity': '78', 'outTemp': '76.82000000000002',
>>> 'outTempBatteryStatus': '0', 'pressure': '29.778039395', 'rain': 'None',
>>> 'rainBatteryStatus': '0', 'rainRate': '0.0', 'rxCheckPercent': '100',
>>> 'usUnits': '1', 'windBatteryStatus': '0', 'windchill': '76.82000000000002',
>>> 'windDir': 'None', 'windGust': '0.0', 'windGustDir': 'None', 'windrun':
>>> 'None', 'windSpeed': '0.0'
>>>
>>> KPSK dublin VA
>>>
>>>
>>> *Current conditions at* Dublin / New River Valley (KPSK) *Lat: *37.13°N
>>> *Lon: *80.68°W*Elev: *2106ft.
>>>
>>> Mostly Cloudy
>>>
>>> 76°F
>>>
>>> 24°C
>>>
>>> *Humidity*
>>> 76%
>>> *Wind Speed*
>>> E 7 mph
>>> *Barometer*
>>> 29.95 in
>>> *Dewpoint*
>>> 68°F (20°C)
>>> *Visibility*
>>> 10.00 mi
>>> *Heat Index*
>>> 77°F (25°C)
>>> *Last update*
>>> 20 Aug 6:35 pm EDT
>>>
>>> *More Information:*
>>>
>>> Local Forecast Office <https://www.weather.gov/rnk>More Local Wx
>>> <http://forecast.weather.gov/obslocal.php?warnzone=VAZ013&local_place=2%20Miles%20N%20Dublin%20VA&zoneid=EDT&offset=14400>3
>>>
>>> Day History <http://forecast.weather.gov/data/obhistory/KPSK.html>Hourly
>>> Weather Forecast
>>> <https://forecast.weather.gov/MapClick.php?lat=37.1333&lon=-80.6833&unit=0&lg=english&FcstType=graphical>
>>>
>>>
>>>
>>> On Wednesday, August 20, 2025 at 6:00:53 PM UTC-4 [email protected]
>>> wrote:
>>>
>>>> The three pressures on your LOOP was "altimeter", "barometer" and
>>>> "pressure".
>>>> If you set station altitude = 0 then you are telling your weather
>>>> station's barometer that it is located at sea level.
>>>> Therefore all three pressures shouldl read the same.
>>>>
>>>> "pressure" is just your local atmospheric pressure at your location's
>>>> altitude..
>>>> "altimeter" is a sea level pressure that factors in your altitude above
>>>> sea level and "corrects" your local pressure (station pressure) and
>>>> calculates an equivalent pressure at sea level.
>>>> "barometer" is also a sea level pressure except it factors in your
>>>> station pressure "(pressure" in WeeWX) , local temperature and humidity
>>>> and "corrects" it to an equivalent pressure at sea level.
>>>>
>>>> I took a quick look at your weather station's manual and it appears
>>>> that your display console reads "relative pressure" only. So in your case
>>>> if you set station altitude = 0 in WeeWX, WeeWX's SLP correction will
>>>> calculate a correction = 0. It makes sense because you told WeeWX you are
>>>> located at sea level so there is no need to correct your "pressure" to sea
>>>> level - you are already at sea level! Therefore "pressure" = "barometer"
>>>> at
>>>> sea level ( altitude = 0).
>>>>
>>>> I am not familiar with LaCrosse barometer operations- but I'll try to
>>>> help. Other LaCrosse owners can certainly jump in...
>>>>
>>>> Things to check.
>>>>
>>>> 1. What have you entered as your station altitude in WeeWX? Did you
>>>> ensure that the station altitude you entered in WeeWX is the altitude of
>>>> the barometric sensor (total height above sea level?) How did you
>>>> calculate
>>>> your station altitude?
>>>>
>>>> 2. Your weather station manual makes no mention of sea level pressure
>>>> calculations, entering an altitude or elevation in your display console.or
>>>> using an offset. The manual implies that the console only displays
>>>> relative
>>>> pressure? Can you confirm that?
>>>>
>>>> 3. How close are you to an official weather station at an airport? Can
>>>> you provide the ICAO code for it? Or the name of the airport?
>>>>
>>>> 4. Your July 31 LOOP altimeter and barometer readings appear to be
>>>> unseasonably high for typical summertime weather.
>>>>
>>>> 5. WeeWX is calculating altimeter correctly but WeeWX barometer seems
>>>> high compared to the Starpath online SLP calculator using the same input
>>>> parameters. WeeWX "barometer" should be close to be the same or less than
>>>> "altimeter" at the temperatures you reported.
>>>>
>>>> 6. Does your weather station use PC software from the manufacturer? If
>>>> so, what is it reporting currently for absolute pressure and relative
>>>> pressure? Can you adjust your absolute pressure?
>>>>
>>>> 7. Can you do another LOOP and give us the three pressures (altimeter,
>>>> barometer, and pressure)?
>>>>
>>>> At the same time you do a LOOP ,can you obtain the altimeter setting of
>>>> a close-by airport. And finally, can you obtain the elevation of that
>>>> airport.
>>>>
>>>> Summing up, we need: your station altitude, your weather station's
>>>> absolute pressure, relative pressure and the current WeeWX LOOP pressure
>>>> values (altimeter, barometer, and pressure) and the LOOP outside
>>>> temperature. In order to make some pressure comparisons and accuracy
>>>> checks. We would also need , the name(s) of any close-by airport(s) and
>>>> how
>>>> close you are to these airports. lus we need the airport altimeter setting
>>>> reading and elevation. As Tom mentioned in the wiki, you have to be
>>>> careful
>>>> about comparing your relative pressure on your display console with the
>>>> WeeWX "barometer" calculation. They could be two different things.
>>>>
>>>> Michael's advice is I think, correct. You probably need to re-calibrate
>>>> or at least verify if your station pressure/absolute value is accurate.
>>>>
>>>> On Wednesday, August 20, 2025 at 1:33:38 AM UTC+4 [email protected]
>>>> wrote:
>>>>
>>>>>
>>>>> Which obs_type "reads what is on the display", when altitude is set to
>>>>> 0? pressure, altimeter or barometer or all three? (It should be all
>>>>> three)
>>>>> When setting your altitude, pressure should always "read what is on the
>>>>> display", altimeter and barometer will change with the altitude you
>>>>> configure.
>>>>>
>>>>> You should calibrate your station to the real pressure provided by a
>>>>> reliable station near you, which is located at the same altitude. Then
>>>>> configure the altitude of the station in weewx, then choose the obs_types
>>>>> you want to have displayed in your report. Depending on what you choose,
>>>>> the may or may not "read what is on the display", which is perfectly
>>>>> fine
>>>>> for altimeter and barometer.
>>>>> kufuu schrieb am Dienstag, 19. August 2025 um 21:09:21 UTC+2:
>>>>>
>>>>>> If I put 0 altitude in weewx config then it reads what is on the
>>>>>> display, is there any way to correct or just leave it 0 ?
>>>>>>
>>>>>> On Thursday, July 31, 2025 at 9:29:40 AM UTC-4 kufuu wrote:
>>>>>>
>>>>>>> It can wait till then and good luck,
>>>>>>>
>>>>>>> On Thursday, July 31, 2025 at 9:06:30 AM UTC-4 kufuu wrote:
>>>>>>>
>>>>>>>> Let me redo this and put the dates in order,
>>>>>>>> LOOP: 2025-07-31 08:45:20 EDT (1753965920) 'altimeter':
>>>>>>>> '31.994965595814566', 'appTemp': '82.83203424777768', 'barometer':
>>>>>>>> '31.942483641883886', 'cloudbase': '2805.6732703464695', 'dateTime':
>>>>>>>> '1753965920', 'dewpoint': '70.70103761047554', 'ET': 'None',
>>>>>>>> 'heatindex':
>>>>>>>> '76.113', 'humidex': '90.81599237942409', 'inDewpoint':
>>>>>>>> '55.52280883736111', 'inHumidity': '58', 'inTemp': '71.06',
>>>>>>>> 'inTempBatteryStatus': '0', 'maxSolarRad': '357.687499228319',
>>>>>>>> 'outHumidity': '87', 'outTemp': '74.84', 'outTempBatteryStatus': '0',
>>>>>>>> 'pressure': '29.919783335', 'rain': '0.0', 'rainBatteryStatus': '0',
>>>>>>>> 'rainRate': '0.0', 'rxCheckPercent': '100', 'usUnits': '1',
>>>>>>>> 'windBatteryStatus': '0', 'windchill': '74.84', 'windDir': 'None',
>>>>>>>> 'windGust': '0.0', 'windGustDir': 'None', 'windrun': 'None',
>>>>>>>> 'windSpeed':
>>>>>>>> '0.0'
>>>>>>>> REC: 2025-07-31 08:45:00 EDT (1753965900) 'altimeter':
>>>>>>>> '31.994965595814566', 'appTemp': '82.83203424777768', 'barometer':
>>>>>>>> '31.942483641883886', 'cloudbase': '2805.6732703464695', 'dateTime':
>>>>>>>> '1753965900', 'dewpoint': '70.70103761047554', 'ET': 'None',
>>>>>>>> 'heatindex':
>>>>>>>> '76.113', 'humidex': '90.81599237942409', 'inDewpoint':
>>>>>>>> '55.52280883736111', 'inHumidity': '58.0', 'inTemp': '71.06',
>>>>>>>> 'inTempBatteryStatus': '0.0', 'interval': '5.0', 'maxSolarRad':
>>>>>>>> '351.7781598061274', 'outHumidity': '87.0', 'outTemp': '74.84',
>>>>>>>> 'outTempBatteryStatus': '0.0', 'pressure': '29.919783335', 'rain':
>>>>>>>> '0.0',
>>>>>>>> 'rainBatteryStatus': '0.0', 'rainRate': '0.0', 'rxCheckPercent':
>>>>>>>> '97.5',
>>>>>>>> 'usUnits': '1', 'windBatteryStatus': '0.0', 'windchill': '74.84',
>>>>>>>> 'windDir': 'None', 'windGust': '0.0', 'windGustDir': 'None',
>>>>>>>> 'windrun':
>>>>>>>> '0.0', 'windSpeed': '0.0'
>>>>>>>> Traceback (most recent call last):
>>>>>>>> File "/usr/share/weewx/weewx/reportengine.py", line 248, in run
>>>>>>>> obj.start()
>>>>>>>> File "/usr/share/weewx/weewx/reportengine.py", line 465, in start
>>>>>>>> self.run()
>>>>>>>> File "/usr/share/weewx/weewx/reportengine.py", line 621, in run
>>>>>>>> ncopy += weeutil.weeutil.deep_copy_path(path, html_dest_dir)
>>>>>>>> File "/usr/share/weewx/weeutil/weeutil.py", line 1811, in
>>>>>>>> deep_copy_path
>>>>>>>> shutil.copy(path, d)
>>>>>>>> File "/usr/lib/python3.9/shutil.py", line 418, in copy
>>>>>>>> copyfile(src, dst, follow_symlinks=follow_symlinks)
>>>>>>>> File "/usr/lib/python3.9/shutil.py", line 264, in copyfile
>>>>>>>> with open(src, 'rb') as fsrc, open(dst, 'wb') as fdst:
>>>>>>>> PermissionError: [Errno 13] Permission denied:
>>>>>>>> '/var/www/html/weewx/seasons.css'
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
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