Thanks again! On Sunday, January 10, 2021 at 6:02:00 PM UTC-8 [email protected] wrote:
> The note *Derived variables > <https://www.davisinstruments.com/product_documents/weather/app_notes/AN_28-derived-weather-variables.pdf>* > from > Davis has a pretty good discussion of this. > > On Sun, Jan 10, 2021 at 5:38 PM Brent Dowell <[email protected]> wrote: > >> Correct Altitude is entered. >> >> I'm getting an average error of 3.5 millibars. >> >> My altitude is pretty close to the local airport, and I used a fairly >> calm day to adjust my barometer to match that. Our altitude is also >> relatively close, i.e. the airport is 4403ft and I'm at 4410. Althought >> that 4410 could be off, I had used that for my altitude for years. >> >> Took another reading via gps today and have adjusted that to 4293, which >> seems like it could be a significant differences. >> >> Thanks so much for your help in getting me to understand it. I've >> managed to learn to ignore the wind errors, as I live on a hillside and >> don't see anyway my wind data will ever match. if I need to do that for >> barometer, I'll work on it. lol. >> >> Would just like to figure out what I'm doing wrong. >> >> >> >> >> 1. That you have a Vantage console; >> Vantage Vue Console >> 2. That you are using regular LOOP packets, not the newer LOOP2 packets; >> loop_request = 1 >> 3. That you are using hardware record generation. >> prefer_hardware >> >> From the wee_device command. >> >> BAROMETER CALIBRATION DATA: >> Current barometer reading: 30.222 inHg >> Altitude: 4293 feet >> Dew point: 24 F >> Virtual temperature: 32 F >> Humidity correction factor: 1.1 >> Correction ratio: 1.175 >> Correction constant: +0.000 inHg >> Gain: 0.000 >> Offset: -16.000 >> >> >> On Sunday, January 10, 2021 at 5:01:53 PM UTC-8 [email protected] wrote: >> >>> I'm assuming: >>> >>> 1. That you have a Vantage console; >>> 2. That you are using regular LOOP packets, not the newer LOOP2 packets; >>> 3. That you are using hardware record generation. >>> >>> If all this is true, then what's happening is that WeeWX is downloading >>> altitude and temperature corrected barometric data (what pilots call QFF) >>> from the console. However, CWOP wants pressure corrected only for altitude >>> (not temperature; pilots call this QNH). So, WeeWX uses an algorithm to >>> calculate that. This is then what is uploaded. >>> >>> First thing is to make sure you have the correct altitude entered in >>> your console. You will also want to know whether the console is applying >>> any barometric corrections. Both can be checked using the utility >>> wee_device, >>> with the --info <http://www.weewx.com/docs/hardware.htm#vantage_info> >>> command. >>> >>> *wee_device --info* >>> >>> This will tell you what altitude your console thinks it's at, as well as >>> any barometric calibration data. >>> >>> -tk >>> >>> >>> >>> On Sun, Jan 10, 2021 at 4:24 PM Brent Dowell <[email protected]> wrote: >>> >>>> I've been chasing my tail a bit trying to get my data that I upload to >>>> CWOP to pass the madis checks, which, from what I've read is a bit >>>> problematic. >>>> >>>> My question though is what should I have my console set as far as >>>> altitude and barometer reduction. Right now I have it set for my correct >>>> altitude and am using the altimeter setting. My readings are consistently >>>> 'low' compared to the madis QC Check. >>>> >>>> It looks like to me that the values being uploaded are in fact low >>>> (raw aprs data) and do not match whats on my console. So it appears that >>>> weewx must be doing some altimeter calculation on my data and is sending >>>> that on to cwop? I'm wondering if I'm missing a setting somewhere in my >>>> weewx config to accout for that? >>>> >>>> Some of the research I've done on the issue talks about davis being a >>>> bit of a pain because they out put the altimeter corrected data already >>>> and >>>> that setting altitude to 0 and using the altimeter reduction fixes it? >>>> >>>> Sorry about dredging up an old issue, but I couldn't find much recent >>>> information on this. >>>> >>>> Thanks in advance for any help. >>>> >>>> -- >>>> You received this message because you are subscribed to the Google >>>> Groups "weewx-user" group. >>>> To unsubscribe from this group and stop receiving emails from it, send >>>> an email to [email protected]. >>>> To view this discussion on the web visit >>>> https://groups.google.com/d/msgid/weewx-user/d425ef32-4da0-49e1-b2d4-fd21dffdfbaen%40googlegroups.com >>>> >>>> <https://groups.google.com/d/msgid/weewx-user/d425ef32-4da0-49e1-b2d4-fd21dffdfbaen%40googlegroups.com?utm_medium=email&utm_source=footer> >>>> . >>>> >>> -- >> You received this message because you are subscribed to the Google Groups >> "weewx-user" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to [email protected]. >> > To view this discussion on the web visit >> https://groups.google.com/d/msgid/weewx-user/49100cc7-7e2f-478f-9065-f0f42a92db3bn%40googlegroups.com >> >> <https://groups.google.com/d/msgid/weewx-user/49100cc7-7e2f-478f-9065-f0f42a92db3bn%40googlegroups.com?utm_medium=email&utm_source=footer> >> . >> > -- You received this message because you are subscribed to the Google Groups "weewx-user" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/weewx-user/9c6cfc66-af04-4813-83cc-8fc021e39074n%40googlegroups.com.
