Author Topic: Feature Request: THSW Index  (Read 19783 times)

Steve

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Re: Feature Request: THSW Index
« Reply #15 on: February 16, 2012, 02:45:40 PM »
I received a reply from my contact at Davis. The engineer she talked to said that Davis' interpretation of the THSW Index uses proprietary formula, and they are not able to share it. He did say that it requires a quite complex relational database and the calls to the database probably wouldn't be scriptable.

I'll keep looking. I did find a reference to a guy that was trying to program it for his web site, and had a 45 page set of information to convert into a database.

Steve
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elagache

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Maybe need to get data off console instead? (Re: THSW Index)
« Reply #16 on: February 16, 2012, 04:45:48 PM »
Hi Steve and WeatherCat fans,

The THSW index sounds even more miserable to compute than the Penman-Monteith model of evapotranspiration.  Still, Davis allows weather station software to get those values off of a VP-2.  Something seems out of whack here.  If this computation is as miserable is it appears, I would be surprised if other weather station software could be computing this value on their own - especially if there is no standard formula.  The THSW index can only be computed on a weather station that has a solar sensor.  So as far as I now, the only stations within reach of serious amateurs is the Davis Vantage Pro-2 line.  Tim, are you sure the VP-2 isn't able of sending this data to weather station software?  If Davis's own WeatherLink is displaying the data, wouldn't it be simpler to fetch the data from the station console than to try to replicate the very same calculations on the PC?

Thanks Steve for going to so far to get Davis's input on this.  Sorry to impose, but could you perhaps ask the Davis engineers if the THSW values can be simply downloaded from the console like the evapotranspiration values?  If it is displayed on the console, why wouldn't they make it available to software?  If there was a way to get the THSW Index off of the VP-2 console that is a much simpler job for Stu to incorporate it into WeatherCat.  Since practically speaking, the only stations that could compute THSW Index are VP-2s with a solar sensor, trying to compute the value within WeatherCat is a waste of time.

Thanks again Steve for exploring this matter.  [tup]  Certainly not as simple I would have imagined it.  Kinda sad to think companies would have proprietary formulas to compute values like this.  Oh well.

Cheers, Edouard  [cheers1]

Steve

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Re: Feature Request: THSW Index
« Reply #17 on: February 16, 2012, 05:47:13 PM »
Edouard,

The THSW Index is calculated within the console for display on its own screen but is definitely not available via the data streamed from the console. This has been examined and tested by various sites, and people have been in contact with Davis confining this elsewhere. The WeatherLink software compiles the index within its programming for display on WeatherLink's screen and web tags. WeatherData is where the 45 page database info came from, and they've compiled it into a database that Weather Display uses to calculate its iteration of the THSW Index. In comparisons, the Davis and WeatherD numbers don't always match, but they are close. No one knows how Davis calculates it, so WeatherD does its best to replicate the results.

So WeatherLink only works with Davis stains that provide temp, humidity, solar , and wind readings, and WeatherD works with any station that can provide the same, be it a Vue with a separate solar sensor, an assortment of individual sensors, or a Davis VP2 with solar. WeatherD is much more flexible as towhee it gets its information to calculate and display.

So yes, with WeatherCat's current capability, it would seem a very limited potential audience would want this feature, which would most likely put it at the bottom or not even on Stu's priority list.

Regards,
Steve
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elagache

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Bummer dude :( (Re: Feature Request: THSW Index)
« Reply #18 on: February 16, 2012, 08:09:00 PM »
Hi Steve and WeatherCat fans,

Well, you've definitely done all that you could.  Thanks for trying!  [tup]

Certainly most unfortunate that Davis has handled things in this way.  :(

Cheers, Edouard

Steve

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Re: Feature Request: THSW Index
« Reply #19 on: February 17, 2012, 01:28:29 AM »
Perseverance wins the day!

Attached is the THSW Index formula and look-up table as calculated by Davis for the VP2 Console and in WeatherLink software. This is from a previous version of the AN-28 Derived Weather Variables (also attached.) Now, what to do with it is anybody's guess, as it is way beyond my simple math skills.

If you decide to add this to some future version of WeatherCat, Stu, it would be a nice feature. If not, I completely understand and appreciate the effort involved.

Thanks,
Steve
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elagache

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Formula appears to be in a academic paper (Re: THSW Index)
« Reply #20 on: February 17, 2012, 03:16:28 AM »
Hi Steve and WeatherCat fans,

Attached is the THSW Index formula and look-up table as calculated by Davis for the VP2 Console and in WeatherLink software. This is from a previous version of the AN-28 Derived Weather Variables (also attached.) Now, what to do with it is anybody's guess, as it is way beyond my simple math skills.

Well, it may be well beyond my math skills too . . . but I'm a sucker - I'll download anything!!  :P  (Not!!  [wink])

However, making a quickly cruise though everything and finding some interesting stuff like a discussion on how Davis computes rainfall (you thought it was obvious, but there are some interesting details.)  I don't see the killer formula.  ???

Instead both documents insist you need to get your grubby paws on this paper:

Steadman, R.G., 1979: The Assessment of Sultriness, Part II: Effects of Wind, Extra Radiation and Barometric Pressure on Apparent Temperature.  Journal of Applied Meteorology, 1979

If you decide to add this to some future version of WeatherCat, Stu, it would be a nice feature. If not, I completely understand and appreciate the effort involved.

So the plot remains uncertain.  I didn't see anything that couldn't be swallowed by an AppleScript, but without the key formula . . . kinda stuck.

On the other hand this is very good news generally.  That paper has to be available at any university and clearly the THSW index does have a solid academic basis that isn't owned by anybody.  So it shouldn't be a problem to incorporate this index into WeatherCat.  Stu will have to "use his connections" go get hold of this paper, but I assume that isn't beyond someone who actually can get cats to do all the coding!!  [cat] After all managers have to earn their keep every now and then!!  8)

Cheers, Edouard  [cheers1]

Steve

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Re: Feature Request: THSW Index
« Reply #21 on: February 17, 2012, 05:14:44 AM »
THSW=Humidity + Wind quotient (from the look-up table based on temp) + Sun (which is Q1+Q2+Q3+Q4 as calculated on the third page)  Easy Peasy! :D

Both just refer to the Steadman formula as what it is based on.
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elagache

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Just in case - here are the papers (Re: THSW Index)
« Reply #22 on: February 17, 2012, 04:22:44 PM »
Howdy Steve and WeatherCat fans,

It's early in the morning here so . . . .  [coffee]

THSW=Humidity + Wind quotient (from the look-up table based on temp) + Sun (which is Q1+Q2+Q3+Q4 as calculated on the third page)  Easy Peasy! :D

Golly, I just went over the documents again and I don't see that formula jumping out at me . . . . however . . . . see above!  [coffee]

Still, I have enough brain power (if brains have anything to do with it) to type the titles of the Steadman papers into Google and . . . . let Google do the work!

I'd attach the two papers here, but they are PDF files that exceed the 1024KB size limit.  So I'll just email them to Stu.  If anybody else want to take a gander, let me know and I'll drop them in the email for ya'!

Cheers, Edouard  [cheers1]

P.S. Thanks Steve for doing all this digging around!  [tup]  I've certainly learned a lot about the THSW Index and there is an added bonus with all those interesting details on the VP-2 in the supporting document.  Great Job!!   [bounce]

P.P.S. I repeat . . . .  [coffee]
Here are (after all) the download links for your all:
Steadman, R.G., 1979: The Assessment of Sultriness, Part I
Steadman, R.G., 1979: The Assessment of Sultriness, Part II

Steve

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Re: Feature Request: THSW Index
« Reply #23 on: February 17, 2012, 04:44:56 PM »
It doesn't give the formula as I wrote it above. But in the 4th paragraph is says "The index is calculated by adding a series of successive terms. Each term represents one of the three parameters: (Humidity, Sun & Wind)." And then goes on to tell how each term is derived and/or calculated.

Steve
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WCDev

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Re: Feature Request: THSW Index
« Reply #24 on: February 17, 2012, 04:59:34 PM »
Got them, thanks folks  [tup]

Stu.

elagache

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Ya' expect me to find that before coffee!! :-) (Re: THSW Index)
« Reply #25 on: February 17, 2012, 09:33:06 PM »
Howdy Steve and MacWeather fans . . . .

It doesn't give the formula as I wrote it above. But in the 4th paragraph is says "The index is calculated by adding a series of successive terms. Each term represents one of the three parameters: (Humidity, Sun & Wind)." And then goes on to tell how each term is derived and/or calculated.

And you expected me to see that before coffee!! [coffee]

Okay, okay, I got it now!

Cheers, Edouard  [cheers1]