Author Topic: Davis VP2 Cwop and all of the headaches  (Read 847 times)

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Offline jpk1018

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Davis VP2 Cwop and all of the headaches
« on: April 13, 2018, 10:49:40 AM »
Trying to get a decent average accuracy with cwop and my Dvp2. My reading have been all over the place since and looking for some help with it. I have two metar stations by me and both report nearly identical pressure readings. Now if I drop my altitude to 0 in my VP2 counsel and match the readings from the metar stations my pressure reading stay pretty much the same as the metar stations. Cwop then says my pressure is garbage. So should I try to make cwop happy or report what I would think is a fairly accurate pressure reading. Iv'e tried the correct altitude in the Vp2 counsel but it's usually not even close to what the metar stations report. Using weather display to send data to cwop.
 
« Last Edit: April 13, 2018, 11:11:52 AM by jpk1018 »

Offline CW2274

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Re: Davis VP2 Cwop and all of the headaches
« Reply #1 on: April 13, 2018, 04:18:37 PM »
Now if I drop my altitude to 0 in my VP2 counsel and match the readings from the metar stations my pressure reading stay pretty much the same as the metar stations. Cwop then says my pressure is garbage. So should I try to make cwop happy or report what I would think is a fairly accurate pressure reading. Iv'e tried the correct altitude in the Vp2 counsel but it's usually not even close to what the metar stations report.
Unless you're willing to get a Vue console that reports the altimeter setting, setting the VP2 console to zero altitude and then using ASOS altimeter setting into the console will be as close as you'll get. It's fairly accurate until you get into very high or low pressure, then the error becomes greater. As far as CWOP QC, forget it, use what you know is right.

Offline Old Tele man

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Re: Davis VP2 Cwop and all of the headaches
« Reply #2 on: April 13, 2018, 04:32:16 PM »
Trying to get a decent average accuracy with cwop and my Dvp2. My reading have been all over the place since and looking for some help with it. I have two metar stations by me and both report nearly identical pressure readings. Now if I drop my altitude to 0 in my VP2 counsel and match the readings from the metar stations my pressure reading stay pretty much the same as the metar stations. Cwop then says my pressure is garbage. So should I try to make cwop happy or report what I would think is a fairly accurate pressure reading. Iv'e tried the correct altitude in the Vp2 counsel but it's usually not even close to what the metar stations report. Using weather display to send data to cwop.
 
Are you trying to use the CWOP (Gladstone) QC numbers and graphs as benchmarks for making 'adjustments' to your station?
• SYS: Davis VP2 Vue/WL-IP & Envoy8X/WL-USB;
• DBX2 & DBX1 Precision Digital Barographs
• CWOP: DW6988 - 2 miles NNE of Cortaro, AZ
• WU - KAZTUCSO202, Countryside

Offline jpk1018

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Re: Davis VP2 Cwop and all of the headaches
« Reply #3 on: April 13, 2018, 04:44:40 PM »
Trying to get a decent average accuracy with cwop and my Dvp2. My reading have been all over the place since and looking for some help with it. I have two metar stations by me and both report nearly identical pressure readings. Now if I drop my altitude to 0 in my VP2 counsel and match the readings from the metar stations my pressure reading stay pretty much the same as the metar stations. Cwop then says my pressure is garbage. So should I try to make cwop happy or report what I would think is a fairly accurate pressure reading. Iv'e tried the correct altitude in the Vp2 counsel but it's usually not even close to what the metar stations report. Using weather display to send data to cwop.
 
Are you trying to use the CWOP (Gladstone) QC numbers and graphs as benchmarks for making 'adjustments' to your station?

I was trying to use Gladstone but have pretty much given up on it. I'm just going to broadcast data that I think is correct. I.e closely matches the two metar stations near me.

Offline CW2274

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Re: Davis VP2 Cwop and all of the headaches
« Reply #4 on: April 13, 2018, 05:04:44 PM »
Trying to get a decent average accuracy with cwop and my Dvp2. My reading have been all over the place since and looking for some help with it. I have two metar stations by me and both report nearly identical pressure readings. Now if I drop my altitude to 0 in my VP2 counsel and match the readings from the metar stations my pressure reading stay pretty much the same as the metar stations. Cwop then says my pressure is garbage. So should I try to make cwop happy or report what I would think is a fairly accurate pressure reading. Iv'e tried the correct altitude in the Vp2 counsel but it's usually not even close to what the metar stations report. Using weather display to send data to cwop.
 
Are you trying to use the CWOP (Gladstone) QC numbers and graphs as benchmarks for making 'adjustments' to your station?

I was trying to use Gladstone but have pretty much given up on it. I'm just going to broadcast data that I think is correct. I.e closely matches the two metar stations near me.
As I check out your particulars, I see you're rather high in elevation, and from what I understand, that'll make the VP2 even more erroneous. Also the weather you're currently experiencing is no time to set the pressure. Shoot for benign weather (calmish wind, no storms) and when the pressure is around 29.92".

Offline jpk1018

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Re: Davis VP2 Cwop and all of the headaches
« Reply #5 on: April 13, 2018, 05:10:57 PM »
Thanks I am going to wait until things are calmer. I don't know why I get so wrapped up in this, at times I am surrounded by erroneous pressure readings and that is what I am being averaged against with cwop. Just going to send what I think is the most accurate and if cwop doesn't agree oh well.

Offline Old Tele man

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Re: Davis VP2 Cwop and all of the headaches
« Reply #6 on: April 13, 2018, 05:15:06 PM »
Thanks I am going to wait until things are calmer. I don't know why I get so wrapped up in this, at times I am surrounded by erroneous pressure readings and that is what I am being averaged against with cwop. Just going to send what I think is the most accurate and if cwop doesn't agree oh well.
Have you tried numerically determining what ratio of station-pressure (STA) to altimeter (ALT) your height/altitude above sea-level would "nominally" be?

If you're interested, take a look at this earlier posting: http://www.wxforum.net/index.php?topic=30691.0
« Last Edit: April 13, 2018, 05:18:06 PM by Old Tele man »
• SYS: Davis VP2 Vue/WL-IP & Envoy8X/WL-USB;
• DBX2 & DBX1 Precision Digital Barographs
• CWOP: DW6988 - 2 miles NNE of Cortaro, AZ
• WU - KAZTUCSO202, Countryside

Offline chief-david

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Re: Davis VP2 Cwop and all of the headaches
« Reply #7 on: April 13, 2018, 05:25:18 PM »
set it where it was .  Leave it. forget CWOP other than to upload.



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Offline jpk1018

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Re: Davis VP2 Cwop and all of the headaches
« Reply #8 on: April 13, 2018, 05:36:58 PM »
Thanks I am going to wait until things are calmer. I don't know why I get so wrapped up in this, at times I am surrounded by erroneous pressure readings and that is what I am being averaged against with cwop. Just going to send what I think is the most accurate and if cwop doesn't agree oh well.
Have you tried numerically determining what ratio of station-pressure (STA) to altimeter (ALT) your height/altitude above sea-level would "nominally" be?

If you're interested, take a look at this earlier posting: http://www.wxforum.net/index.php?topic=30691.0

I looked at the previous post, will the vantage vue console communicate with the VP2 sensor suite.

Offline CW2274

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Re: Davis VP2 Cwop and all of the headaches
« Reply #9 on: April 13, 2018, 05:42:13 PM »
Thanks I am going to wait until things are calmer. I don't know why I get so wrapped up in this, at times I am surrounded by erroneous pressure readings and that is what I am being averaged against with cwop. Just going to send what I think is the most accurate and if cwop doesn't agree oh well.
Have you tried numerically determining what ratio of station-pressure (STA) to altimeter (ALT) your height/altitude above sea-level would "nominally" be?

If you're interested, take a look at this earlier posting: http://www.wxforum.net/index.php?topic=30691.0

I looked at the previous post, will the vantage vue console communicate with the VP2 sensor suite.
Just like peas in a pod. I bought my Vue console solely because it does supply the altimeter.

Offline jpk1018

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Re: Davis VP2 Cwop and all of the headaches
« Reply #10 on: April 13, 2018, 05:46:13 PM »
So all I need to do is get the Vue console, and will the VP2 data logger fit? If it does and the pressure headaches go away it's a done deal.

Offline CW2274

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Re: Davis VP2 Cwop and all of the headaches
« Reply #11 on: April 13, 2018, 06:00:36 PM »
So all I need to do is get the Vue console, and will the VP2 data logger fit? If it does and the pressure headaches go away it's a done deal.
The logger will work exactly the same. As far as your "pressure headache" going away, I can only assume it will, don't see why it wouldn't.

Offline jpk1018

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Re: Davis VP2 Cwop and all of the headaches
« Reply #12 on: April 13, 2018, 06:08:22 PM »
Thanks for the help, it just might be a cwop headache or maybe why should I worry about this.

Offline CW2274

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Re: Davis VP2 Cwop and all of the headaches
« Reply #13 on: April 13, 2018, 06:13:07 PM »
Thanks for the help, it just might be a cwop headache or maybe why should I worry about this.
Like I and others have said, forget the CWOP stuff. I learned long ago to quit chasing that QC dragon.

Offline W3DRM

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Re: Davis VP2 Cwop and all of the headaches
« Reply #14 on: April 13, 2018, 06:37:04 PM »
This is a subject that has been around for a very long time. As has been posted in this thread, it is a complete waste of one's time and energy to attempt to rationalize the reason for the CWOP barometer readings to be so spikey and simply inaccurate. I have spent countless hours myself trying to set my VP2 barometer to a value that would fall within the CWOP Analysis ranges. It became an impossible task. I've found that when I set it close to a nearby airport setting and compare those two on a regular basis that my VP2 stays in sync with it but the CWOP Analysis readings are all over the place.

Some years back, the source of the "secret" analysis readings were changed to include many data sources that to me appear to be very unstable and of poor quality. Complaints to CWOP folks always comes back with an answer that says they have no control over those sources. Just looking at the analysis graphs clearly shows that spikey nature of the data. Normal barometer readings do not and cannot change with such rapidity except during major storms. So, find a nearby airport or source of quality barometer readings and calibrate your local barometer to be close to those and you should be fine. I do a check every week or so to make sure I'm not drifting. Occasionally, I get a surprise and see my CWOP quality has a green check-mark but not very often.
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Offline dtidmore

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Re: Davis VP2 Cwop and all of the headaches
« Reply #15 on: April 14, 2018, 08:40:14 AM »
MADIS, part of NOAA, is the culprit responsible for the QC data that Phillip Gladstone posts on his CWOP site.  As he has indicated he has NO control or even any insight in the "sausage making" at MADIS.  Here is a link to the MADIS site.https://madis.ncep.noaa.gov

I realized that lots of stations have issues tracking MADIS QC while maintaining a grip on the reality of their local weather situation.  However, I have NOT had any issues and in fact I quite successfully use MADIS QC graphs (always look at the long haul, never just a single point) to tweak my station into dead on accuracy.  My nearest ASOS station is about 10 miles to the south and it is about 200 ft lower than my station.  I have a fair number of PWS in my area and a massive amount closer into the DFW area, but I never use those for anything other than casual comparisons although I suspect that some of them do feed into the MADIS QC sausage.  Using the MADIS graphs to tweak my calibration I find that I am virtually in complete agreement with the ASOS station as long as weather conditions across the area are fairly stable. 

FYI, I am currently running Davis VP2 Plus hardware but previously I ran Ambient Weather WS series stuff.

 

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