Indeed I am using METRIC, and interval of 300 (5 minutes). I was not aware
of that the stored unit is cm! Then I get very close to 25.8 but still not
exactly the same!
Unfortunately I have no idea how Netatmo calculates daily rainfall, it
justs reports it. Of course I could use Netamo's API to retrieve the values
from the Netatmo server (it is impossible to gain access to the local
receiver, everything has to go via the Netatmo server). However I thought
reading the weewx database was a quicker way for me than digging into
Netatmo's coding examples. Netatmo has an example, returning all modules
data from the last 30 days, and among other things I get:
27 August:
sum_rain: 25.8 mm
So, if I look at table archive_day_rain, field "sum" has a unit of cm.
What about the "unit" of date and time, are we talking UTC or local time?
If I look at the record that has the value closest to 25.8 (25.654) the
dateTime is 1535320800 which corresponds to 2018-08-27 00:00:00, so I guess
the date and time are in local values?
When it comes to "daily" rain we have another complicating factor: In
official reporting "daily" is NOT the calendar day (00-24). To be more
precise: Officially, the total amount of rain of the 27th of Aug should
actually have been measured starting 27th of Aug at 08:00, and ending on
the 28th (!) of Aug 08:00. This is for Sweden (DST, in winter it is 07:00
instead).
This led me to query "archive" with "select 10*sum(rain) as rain_mm from
archive where (dateTime >= UNIX_TIMESTAMP('2018-08-27 08:00:00')) and
(dateTime <= UNIX_TIMESTAMP('2018-08-28 08:00:00')). Result 25.86 which
indeed is closer to Netatmo's own value of 25.8!
Querying "archive" with the calendar day "select 10*sum(rain) as rain_mm
from archive where (dateTime >= UNIX_TIMESTAMP('2018-08-27 00:00:00')) and
(dateTime <= UNIX_TIMESTAMP('2018-08-27 23:59:59')) results in the same
value as archive_day_rain, namely 25,65.
This means that table "archive_day_rain" is a calendar day? For all other
parameters (pressure, wind etc) this is the same as in official reporting
but in my opinion "archive_day_rain should be calculated between DAY
06:00:00 (UTC) and DAY+1 06:00:00 (UTC).
/Valley
On Thursday, August 30, 2018 at 2:42:36 AM UTC+2, Thomas Keffer wrote:
>
> First of all, I suspect you are using a database with a unit system of
> METRIC, which measures in centimeters (not millimeters).
>
> As for the difference between 25.654 and 25.8, there can be several
> explanations. Here's one example: say you are using a 5 minute archive
> interval. For WeeWX, the first archive interval of the day is timestamped
> 0005. It measures the rain that fell between 0000 and 0005. However, many
> weather services include the measurement timestamped 0000.
>
> To get any more specific, we would need more information, such as exactly
> what unit system you are using, and how the Netatmo app is calculating
> daily rainfall.
>
> -tk
>
>
> On Wed, Aug 29, 2018 at 2:23 PM Valley <[email protected] <javascript:>>
> wrote:
>
>> I use weewx with a Netatmo rain gauge. It works well but I cannot figure
>> out how the total amount of daily rain is calculated.
>>
>> Since Python is too hard for me to learn, I use php coding to query the
>> database.
>>
>> The other day we got 25.8 mm of rain. A figure reported by my Netatmo app
>> on the iPhone and on the Netatmo web page. Also very close to what I could
>> read on an old fashioned measuring glass in the garden. So the figure 25.8
>> mm is definitely ok.
>>
>> The graph in weewx also shows 25.8 (hard to read exactly, but somewhere
>> between 25 and 26) (see image). Now: If I look at the
>> table archive_day_rain for that specific day it says sum=2.5654 (also
>> wsum=2.5654). How is 2.5654 becoming 25.8? Difference between sum and wsum?
>>
>> I also queried the archive table with sum(rain) for all records for that
>> date. As a result I got 2.5654, the same as in the sum column in table
>> archive_day_rain.
>>
>> So the question is: How is the original data from Netatmo actually
>> stored, and how is it that the graph shows me the correct amount?
>>
>> Very puzzling for me!
>>
>> /Valley
>>
>> Here is a picture of the graph
>>
>> [image: raingraph.png]
>>
>> --
>> 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] <javascript:>.
>> For more options, visit https://groups.google.com/d/optout.
>>
>
--
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].
For more options, visit https://groups.google.com/d/optout.
