Pro2/Envoy: Strange value for Evapotranspiration

[YJB]

Well, I agree it would be nice to have the hourly difference, but keep in mind that the Vantage only reports the total value for the day. So, it would imply that MH is going to do some calculations on the data. Which will introduce other issues, like: what if we miss an hour etc.

It might be better to have a seqhour1_sol0_evotranspiration_mm variable that reports the values as they are received -1hr, -2 hr ... -25 hrs ago. The user can decide what to do with these values.

Just my EUR 0.02

Ysbrand

[Hathor27]

It might be better to have a seqhour1_sol0_evotranspiration_mm variable that reports the values as they are received -1hr, -2 hr ... -25 hrs ago. The user can decide what to do with these values.

makes sense to me, too.

Btw: My today's values
- on MH: 15.2mm
- on Vantage: 1.8mm (could also be almost 1.9mm)
=> Factor: 8.444 (with 1.9mm it would be factor 8.00)

Where the hell on earth comes a factor 8 from? An inch is 25.4mm...

And look at this (comes with http://mymeteohub/meteograph.cgi?text=all two hours after sunset)

Code: Select all

day1_sol1_et_mm 4.8
day1_sol1_et_in 0.2
hour1_sol1_et_mm 11.4
hour1_sol1_et_in 0.4
last15m_sol1_et_mm 13.7
last15m_sol1_et_in 0.5
last24h_sol1_et_mm 4.9
last24h_sol1_et_in 0.2
last60m_sol1_et_mm 7.2
last60m_sol1_et_in 0.3

absolutely rubbish, because it's treated as an aggregate-able-value and not as a total-value

A seqhour/seqday/seqmonth-value would definitely make sense, and a et_total_mm-value, too

[wfpost]

looking at meteohubs raw data, it would be interesting to know what unit the ET values stand for.

20110905105959 sol0 218 16
20110905110051 sol0 223 22

Code: Select all

20110905065045 sol0 39 0
20110905065125 sol0 35 0
20110905065217 sol0 32 0
20110905065307 sol0 28 0
20110905065359 sol0 23 0
20110905065451 sol0 19 0
20110905065541 sol0 16 0
20110905065633 sol0 21 0
20110905065723 sol0 28 0
20110905065815 sol0 39 0
20110905065907 sol0 49 0
20110905065957 sol0 56 0
20110905070049 sol0 65 2
20110905070141 sol0 70 2
20110905070231 sol0 76 2
20110905070323 sol0 79 2
20110905070413 sol0 83 2
20110905070505 sol0 84 2
20110905070619 sol0 84 2
20110905070647 sol0 88 2
20110905070739 sol0 90 2
20110905070831 sol0 91 2
20110905070933 sol0 91 2
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20110905073145 sol0 118 2
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20110905074931 sol0 114 2
20110905075021 sol0 109 2
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20110905075202 sol0 114 2
20110905075255 sol0 113 2
20110905075347 sol0 109 2
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20110905075529 sol0 97 2
20110905075621 sol0 91 2
20110905075711 sol0 93 2
20110905075802 sol0 97 2
20110905075858 sol0 98 2
20110905075959 sol0 98 2
20110905080037 sol0 100 6
20110905080129 sol0 105 6
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20110905080401 sol0 105 6
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20110905080728 sol0 114 6
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20110905081001 sol0 116 6
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20110905081559 sol0 105 6
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20110905081945 sol0 102 6
20110905082015 sol0 104 6
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20110905082157 sol0 98 6
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20110905082523 sol0 98 6
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20110905083811 sol0 123 6
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20110905083953 sol0 142 6
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20110905084147 sol0 148 6
20110905084227 sol0 156 6
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20110905084427 sol0 158 6
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20110905085151 sol0 139 6
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20110905085425 sol0 156 6
20110905085517 sol0 163 6
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20110905090023 sol0 162 12
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20110905090349 sol0 149 12
20110905090441 sol0 156 12
20110905090543 sol0 156 12
20110905090623 sol0 158 12
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20110905090805 sol0 156 12
20110905090857 sol0 148 12
20110905090947 sol0 139 12
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20110905091131 sol0 69 12
20110905091221 sol0 33 12
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20110905091415 sol0 30 12
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20110905091547 sol0 33 12
20110905091637 sol0 37 12
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20110905091911 sol0 47 12
20110905092003 sol0 51 12
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20110905093343 sol0 76 12
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20110905093941 sol0 105 12
20110905094043 sol0 105 12
20110905094145 sol0 105 12
20110905094247 sol0 105 12
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20110905094541 sol0 102 12
20110905094631 sol0 100 12
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20110905095555 sol0 118 12
20110905095647 sol0 123 12
20110905095737 sol0 125 12
20110905095829 sol0 127 12
20110905095941 sol0 128 12
20110905100011 sol0 132 16
20110905100103 sol0 137 16
20110905100153 sol0 142 16
20110905100245 sol0 148 16
20110905100337 sol0 151 16
20110905100427 sol0 149 16
20110905100519 sol0 148 16
20110905100611 sol0 146 16
20110905100701 sol0 142 16
20110905100753 sol0 139 16
20110905100854 sol0 139 16
20110905100955 sol0 139 16
20110905101057 sol0 139 16
20110905101117 sol0 141 16
20110905101209 sol0 144 16
20110905101301 sol0 146 16
20110905101351 sol0 149 16
20110905101453 sol0 149 16
20110905101533 sol0 151 16
20110905101625 sol0 153 16
20110905101717 sol0 155 16
20110905101807 sol0 158 16
20110905101859 sol0 163 16
20110905101951 sol0 167 16
20110905102041 sol0 169 16
20110905102143 sol0 169 16
20110905102223 sol0 171 16
20110905102315 sol0 169 16
20110905102407 sol0 172 16
20110905102509 sol0 172 16
20110905102549 sol0 174 16
20110905102651 sol0 174 16
20110905102753 sol0 174 16
20110905102823 sol0 172 16
20110905102913 sol0 171 16
20110905103005 sol0 169 16
20110905103057 sol0 165 16
20110905103159 sol0 165 16
20110905103239 sol0 167 16
20110905103331 sol0 171 16
20110905103421 sol0 174 16
20110905103513 sol0 179 16
20110905103603 sol0 186 16
20110905103655 sol0 193 16
20110905103747 sol0 200 16
20110905103837 sol0 204 16
20110905103929 sol0 206 16
20110905104031 sol0 206 16
20110905104111 sol0 202 16
20110905104203 sol0 197 16
20110905104253 sol0 190 16
20110905104345 sol0 186 16
20110905104437 sol0 183 16
20110905104527 sol0 179 16
20110905104629 sol0 179 16
20110905104711 sol0 178 16
20110905104801 sol0 176 16
20110905104903 sol0 176 16
20110905104943 sol0 174 16
20110905105035 sol0 172 16
20110905105137 sol0 172 16
20110905105217 sol0 174 16
20110905105309 sol0 176 16
20110905105402 sol0 179 16
20110905105451 sol0 185 16
20110905105543 sol0 192 16
20110905105633 sol0 197 16
20110905105725 sol0 202 16
20110905105817 sol0 207 16
20110905105907 sol0 213 16
20110905105959 sol0 218 16
20110905110051 sol0 223 22
20110905110141 sol0 227 22
20110905110233 sol0 232 22
20110905110323 sol0 234 22
20110905110425 sol0 234 22
20110905110507 sol0 232 22

[Hathor27]

today's values:
- on MH: 25.6mm
- on Vantage: 3.0mm
=> Factor: 8.533

[YJB]

looking at meteohubs raw data, it would be interesting to know what unit the ET values stand for.

20110905105959 sol0 218 16
20110905110051 sol0 223 22

Code: Select all

20110905065045 sol0 39 0
20110905065125 sol0 35 0

The last value on the line is the ET value (marked Bold)

[YJB]

I've tried to sum up what I see on my unit:

(Excuse the graph sizes)

The daily report over the last 7 full days using MH graphs (Interval 1 day)

MH_ET.jpg (137.99 KiB) Viewed 11539 times

The hourly report over the last 7 full days using MH graphs (Interval 1 hour)

MH_ET_1.jpg (139.64 KiB) Viewed 11539 times

The daily report over the last 7 full days using Vantage weatherlink graphs (Interval 1 day):

Vantage_ET.jpg (77.38 KiB) Viewed 11539 times

And last but not least the raw values from Meteohub:
(keep in mind that you take the time difference with GMT in consideration when looking at raw values
20110831215930 sol4 0 126
20110901215942 sol4 0 96
20110902215944 sol4 0 208
20110903215918 sol4 0 226
20110904215922 sol4 0 100
20110905215954 sol4 0 194
20110906215900 sol4 0 92

[YJB]

I've put the whole thing in an xls for comparison purposes:

compare.jpg (33.84 KiB) Viewed 11538 times

Keep in mind that I've tried to read the graphs and translate them into numbers, so might be slightly off.

So it seems that we have 2 issues:

1) The MH Daily interval is broken those numbers are not getting close to the raw values
2) The Meteohub raw numbers are in sync with the hourly reports, but about a factor 8 too high. This was reported by others as well.

Ysbrand

[Hathor27]

...is anything going on with this topic?
What can we do to slightly force solving this problem?...

[YJB]

Hi,

Boris is aware of the problem, but he will need to allocate time for this. Since it has to fit in between his real work, it might take some time before he can look into this.

Ysbrand

[Hathor27]

Hi,

Boris is aware of the problem, but he will need to allocate time for this. Since it has to fit in between his real work, it might take some time before he can look into this.

Ysbrand

Thank you for the information, Ysbrand - we'll wait patiently...

[Hathor27]

patiently asking... are there any news?

[Hathor27]

any news on Evapotranspiration?...

...please, Boris

[hberg]

Good to find the thread ...

Few days ago, after I got the SLC memory, I switched from Weather Display to Meteohub and I also have the strange ET reading (Weather Display Live via Meteohub 35mm vs. 4.3mm on the VP2 console). http://deltavolt.pe/estacion-meteorologica

Would be nice to find a solution ...

I also have another problem: the wet bulb indicator shoots high up above the instrument's limit with useless values. But this is for another thread and could easily be my newbee problem.

Best regards from sunny, summer Peru

Heinrich

[Hathor27]

it's starting dry season...
...are there any news on correct Evapotranspiration?

[admin]

I am just stepping back into that... Vantage reports in its regular LOOP protocol just ET for day, month, year.
The ET Meteohub reports is the daily one. So the graphs displayed by some users in this thread for EP
look fine in their shape. Starting as zero in midnight rising corresponding to how intense temp and solar
radiation is and coming to a hold in the night again. To get the EP of a day, when using the time resolution
"day1", you should grap the MAX value, not the average.

What is wrong is the scaling of the data. I did find a bug there and next update will hopefully heal that (even
for data you have recorded so far). It will also present the max EP values in sequence strings as
"seqday1_sol0_etmax_mm" etc.

If someone with a sloar sensor equipped vantage would like to help me test the code,
please drop a note to "info(at)meteohub.de". This will help to avoid incremental fixes, as I don't
have suitable equipped vantage right at hand to test with.

Just another thought... Vantage does not really measure EP, I think it computes that from temp, hum, baro
and solar radiation. Does someone have a formular to compute EP from that? This would make this data avail
even in a broader context. I did some google, but didn't find a ready to go formular.