Author Topic: Comparing my neighbors davis pro 2 to my pro 2.  (Read 772 times)

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Offline Ajward7976

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Comparing my neighbors davis pro 2 to my pro 2.
« on: December 09, 2018, 02:52:03 PM »
My neighbor has a 12 or so year old vantage pro 2. I just bought a new one. His is showing .3 inches and mine is showing .2inches.... of rain.
Variables to consider:
Mine is 48 feet above sealevel... his is about 8 ft
Mine is on my roof his is on a dock over water
Mine is catching between 8 and 15 mph winds more then his.
Mine is the new model with bird spikes and updated rain guage shape... his is old shape and no spikes..
We are 150 yards apart.
Rain conditions were slow steady rain ergo no storm cells to consider deviating measures with distance.

Can that little bit of wind and distance make this difference in measurements? Or is one inaccurate?
« Last Edit: December 09, 2018, 03:17:33 PM by Ajward7976 »

Offline Ajward7976

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Re: Comparing my neighbors davis pro 2 to my pro 2.
« Reply #1 on: December 09, 2018, 03:10:34 PM »
My mistake,  no this is precipitation.

Offline ocala

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Re: Comparing my neighbors davis pro 2 to my pro 2.
« Reply #2 on: December 09, 2018, 03:34:16 PM »
You wouldn't think 150 yards could make a difference but it can.
Not going to say yours is wrong or his is wrong but that is the nature of tipping gauges. They are hard to calibrate. One thing you could do is pour an exact amount of water into each gauge and compare the totals. From there you can calibrate it +/-.
Yes wind can cause a loss of measured rain but to what degree I don't know. Obviously with yours being higher it could have an effect on a windy day.
The blues had a baby and they named it Rock & Roll

Offline Ajward7976

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Re: Comparing my neighbors davis pro 2 to my pro 2.
« Reply #3 on: December 09, 2018, 03:43:14 PM »
Hmmmm....thanks.

Offline Ajward7976

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Re: Comparing my neighbors davis pro 2 to my pro 2.
« Reply #4 on: December 09, 2018, 04:01:32 PM »
Could the new design be more accurate? They changed it for a reason right? Any input?

Offline CW2274

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Re: Comparing my neighbors davis pro 2 to my pro 2.
« Reply #5 on: December 09, 2018, 04:55:02 PM »
There's a ton of reasons for the difference, some stated above. The only way you'll truly know is to get a manual gauge like a Cocorahs and put it as close to your ISS as you can and preferably the same height.

Offline ocala

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Re: Comparing my neighbors davis pro 2 to my pro 2.
« Reply #6 on: December 09, 2018, 05:02:37 PM »
There's a ton of reasons for the difference, some stated above. The only way you'll truly know is to get a manual gauge like a Cocorahs and put it as close to your ISS as you can and preferably the same height.
FWIW I use a Cocorahs gauge as my official gauge and it's what I input into my software. I use the Davis to just get an idea of what the total was. Like today. The Davis said .92, Cocorahs 1.00.
As for the new design I think t was just an external modification with the spikes. I don't think anything has changed inside. Somebody with knowledge of that could maybe chime in. 
The blues had a baby and they named it Rock & Roll

Offline vreihen

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Re: Comparing my neighbors davis pro 2 to my pro 2.
« Reply #7 on: December 09, 2018, 05:04:20 PM »
As the saying goes...the truth is out there.  :lol:  My Stratus and aerocone VP2 have agreed with each other +/- 0.01" on just about every storm.....


WU Gold Stars for everyone! :lol:

Offline CW2274

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Re: Comparing my neighbors davis pro 2 to my pro 2.
« Reply #8 on: December 09, 2018, 05:07:53 PM »
How do you catch rain sideways....

 :-P

Offline CW2274

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Re: Comparing my neighbors davis pro 2 to my pro 2.
« Reply #9 on: December 09, 2018, 05:10:21 PM »
Could the new design be more accurate? They changed it for a reason right? Any input?
The tipping mechanism is the same, the "aerocone" is suppose to help decrease the effects of the wind. Whether it does or not....

Offline Ajward7976

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Re: Comparing my neighbors davis pro 2 to my pro 2.
« Reply #10 on: December 09, 2018, 06:43:32 PM »
Thx

Offline Aardvark

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Re: Comparing my neighbors davis pro 2 to my pro 2.
« Reply #11 on: December 09, 2018, 07:24:30 PM »
is it perfectly level?   

and did you consider that your gauge is reporting correctly and your friend's off?

Offline CW2274

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Re: Comparing my neighbors davis pro 2 to my pro 2.
« Reply #12 on: December 09, 2018, 07:34:38 PM »
and did you consider that your gauge is reporting correctly and your friend's off?
He'll never factually know without a manual comparison.

Offline Ajward7976

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Re: Comparing my neighbors davis pro 2 to my pro 2.
« Reply #13 on: December 09, 2018, 08:13:13 PM »
No I wasn't assuming one or the other was the inaccurate one... but I am thinking this wind has played a big factor...... we had one previous rain and both units said .03 inches... but that is not much to go on other then the fact that with this rain.... when his said .05 mine said .02..... you all have been a big help. I think I need to observe a few more rain events to determine inaccuracy...... I used to have an acurite..... I could calibrate that... does my pro 2 have the ability to be calibrated?

Offline CW2274

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Re: Comparing my neighbors davis pro 2 to my pro 2.
« Reply #14 on: December 09, 2018, 08:15:09 PM »
does my pro 2 have the ability to be calibrated?
Of course, but to what??

Offline Ajward7976

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Re: Comparing my neighbors davis pro 2 to my pro 2.
« Reply #15 on: December 09, 2018, 08:44:24 PM »
A rain calibration.

Offline CW2274

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Offline SLOweather

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Re: Comparing my neighbors davis pro 2 to my pro 2.
« Reply #17 on: December 09, 2018, 11:59:13 PM »
I agree with Ocala. Having worked with rain gauges for years, I would not compare rainfall measure in gauges more than a few feet apart and at the same height. The conditions you describe are ripe for differences between measured rainfalls, and inconsistent differences between storms. (Meaning that you can't reliably say, for instance, that yours always reads 2/3 of his...)

Offline Mattk

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Re: Comparing my neighbors davis pro 2 to my pro 2.
« Reply #18 on: December 10, 2018, 04:28:55 AM »
.....Can that little bit of wind and distance make this difference in measurements? Or is one inaccurate?

Could definitely make such a difference, inaccuracy (as such) is really not a term that is relevant, calibration is possible plus a few other posibilities 
« Last Edit: December 10, 2018, 04:42:32 AM by Mattk »

 

anything