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Author Topic: A question about WD rain rate calculation  (Read 157 times)

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Offline atsio

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A question about WD rain rate calculation
« on: May 13, 2018, 12:11:59 PM »
Last Thursday, we've had a storm with extremely high rain rates and flood incidents at the city of Thessaloniki, northern Greece region of Central Macedonia.

WD has reported maximum rain rate 430.3 mm/hr, but WeatherLink which i run simultaneously using VPP has reported 606.4 mm/h!!!  8O

Look at the attached screenshots. there's a big difference between the two applications!   :scratch:

Which one is correct? Both programs, read same data coming from the ISS of my Vantage Pro2 Plus wireless weather station.

Thanks,

Thanos

Offline Dale Reid

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Re: A question about WD rain rate calculation
« Reply #1 on: May 13, 2018, 04:09:53 PM »
The spreadsheet is a helpful piece of information.

I cannot claim it is the reason, but if one program took the minute to minute value due to tips, and calculated on that number per minute, you found the highest rate at the time the most rain was accumulated in that minute, according to the data in your printout.

If the other system 'averaged' it over a couple minutes, for this very reason, it would have found the same number but averaged for a longer time, which of course reduces the peaks from what the real exact moment reading would be.

Welcome to the world of digital vs. analogue.....


Offline niko

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Re: A question about WD rain rate calculation
« Reply #2 on: May 13, 2018, 04:24:55 PM »
Exactly, it's not an obvious calculation and WD and Davis use different algorithms.

If you prefer the Davis method there is an option on the Davis tab of station setup to use the VP's rain rate instead.

Offline atsio

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Re: A question about WD rain rate calculation
« Reply #3 on: May 13, 2018, 05:40:00 PM »
If you prefer the Davis method there is an option on the Davis tab of station setup to use the VP's rain rate instead.

Thanks for the answers so far!

Niko, as you can see on screenshot, the option for rain rate in Davis setup has been already enabled!  :roll:

I believe Brian will explain how rain rate calculation in WD works!

Thanos
« Last Edit: May 13, 2018, 05:41:54 PM by atsio »

Offline niko

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Re: A question about WD rain rate calculation
« Reply #4 on: May 13, 2018, 05:44:09 PM »
...and hopefully someone will explain how rain rate calculation in WL works too  :wink:

Offline Weather Display

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Re: A question about WD rain rate calculation
« Reply #5 on: May 14, 2018, 01:37:09 AM »
maybe WD missed the LOOP data packet that had the very max rain rate value  :roll:

Offline atsio

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Re: A question about WD rain rate calculation
« Reply #6 on: May 14, 2018, 05:15:17 AM »
Brian, although I don't know how WD calculates rain rate, I am not sure that it lost that data packet,
because it gets data not from ISS directly, but from a common source(database?) like VVP together with WL.

As far as I know, VVP works like a "buffer" between ISS and datalogger to give the ability to other programs to run at the same time.

Does WD use an algorithm to calculate rain rate or just show the value read from the station?

Thanos

Offline Weather Display

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Re: A question about WD rain rate calculation
« Reply #7 on: May 14, 2018, 07:16:34 PM »
it should be using the data provided in the LOOP data if you have set to use that

 

cumulus