Rain total being rounded to tenth of an inch

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  • Problem
  • Updated 2 weeks ago
For the past several days, precipitation totals are being rounded to the nearest tenth of an inch on the website and API. This used to be 100th of an inch, as reported by stations.
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Matt Brady

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Posted 1 month ago

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Victoria Gardner, Official Rep

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I have not seen this, Matt.  Can you give me an example?

--Victoria
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Emery Wooten

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Victoria by now you have seen it.  Can you give us an update on when this will be fixed and once again show precipTotalrainfall to two decimal places?
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Matt Brady

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It's on the web dashboard for every station currently reporting rain the current day. The "Precip Accum" value in the "Current Conditions" box at the top is rounded to the nearest tenth of an inch. Now scroll down to the "Summary" section and check the "Precipitation" value. That one is not rounded and correctly shows the hundredth of an inch value. The API does the same thing (presumably the website uses the same API).I recently heard back from API support and they said the fix should be pushed out next week so thankfully it looks like this will be back to normal soon. Now if we could just get the decimal place back for temperature values...
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Paul Grace

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Mine says:

PRECIP ACCUM
0.00in

(which is correct)

Below that:
PRECIPITATION

PRECIP TOTAL
0.00in

(which is correct)

In the History summary:

                     HIGH
Precipitation 0.00in

(which is correct)

The graph is also correct (but it does not print a value)
(Edited)
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Matt Brady

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You would only see the problem if if there was any rain that day. The value is still displayed on the web page with two decimal places, but the second decimal is always 0 for the Precip Accum value.

Here are a couple examples from midday Friday (obviously these rain values will change over time so they may not be good examples after today).
https://www.wunderground.com/dashboard/pws/KMNWOODS2
Precip Accum: 0.10
Precipitation: 0.08

https://www.wunderground.com/dashboard/pws/KMNHENNI3
Precip AccumL 0.00
PrecipitationL 0.04
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Emery Wooten

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I came here to post the same thing and am glad to see it already here.   Why has the precipTotal in the API been rounded to the nearest tenth of an inch?  Victoria please look into this issue for us.  Today I have received 0.23 inches of rain but the API is returning 0.2.  At least it appears the WU website is reporting to the hundreth of an inch again but the API is still rounding.
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Matt Brady

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It still looks broken on the website too. It's been a month since I was told the fix would go live the following week...
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William J Schmidt

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You really think you can measure rain fall to 0.01 inches?
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Emery Wooten

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That is the resolution of my weather station as each tip of the rain toggle adds 0.01 inches.  I also think that rounding errors of up to 0.05 inches can produce significant inaccuracy in long term totals.
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Matt Brady

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If my station sends 0.23 and I ask the API what my station says and WU says 0.2 then that’s wrong. I want back the data I sent.
Worst of all is that anything under 0.05 is being rounded down to 0.
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Paul

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Pay no attention to the fanatics like Willian, he and ather think that everyone should be happy with temperatures that only report in two degree increments because everyone's equipment was not made by either him or NASA. Now he's doing the same with rain. So just ignore him and you will much better off.
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Mike Bloodworth

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The Davis VantagePro+ for Metric in Australia measures 0.2mm (0.0079") bucket tips accurately, I have actually checked it on the bench. 
For some reason WU convert this metric value to imperial of only 2 decimal places then converts it back to Metric to display on the PWS page (When metric set) causing an accumulative error.
So lets say we have 0.2 mm, this converts to 0.0079" and becomes 0.01" in WU software and when Metric selected on PWS page 0.01" becomes 0.25mm.  So you can see it makes a big difference to international Metric countries. The Bureau of Meteorology in Australia also have 0.2mm accuracy with a bucket tip system and wide rain fall capture area.