OpenSprinkler and PWS

[John Park]

Hi guys,

I just bought an OSPi and absolutely love it. I also have my own PWS which is uploading data to Ecowitt and Wunderground and I have a couple of questions regarding this.

I note that in the Wunderground API key section of the help system (https://openthings.freshdesk.com/support/solutions/articles/5000017485-getting-a-weather-underground-wu-api-key) it says “you cannot choose ET as the weather adjustment method, because WU PWS data lacks ‘solar radiation’ parameter required by ET” but my PWS (https://www.wunderground.com/dashboard/pws/ISUNSH720) reports solar radiation?

I see that I can host my own weather service but it appears that all I’m doing is redirecting the same WU data stream to a local weather server, how is this different to obtaining the data directly from WU? If there’s not enough information being provided from a WU data source, can I use a more comprehensive data source such as Ecowitt?

[Ray]

1) At the time the ET algorithm was implemented, solar radiation was not a required field by WU. So while some WU stations report solar radiations, a lot didn’t. I am not sure about what’s the current situation, whether it’s required now or not, but if you are able to host your own weather service, then

2) You can modify the weather code to allow using ET with WU. In fact, users who host their own weather service primarily because they want to customize the weather code. So what you were asking regarding the ‘difference’ is mainly that you can modify the code and enable ET with WU, or you can customize it in any other way you want. I am not familiar with Ecowitt. The OpenSprinkler weather code:
https://github.com/OpenSprinkler/OpenSprinkler-Weather
supports several weather providers, it’s relatively easy to add additional providers, as long as you have their APIs.

[John Park]

Thanks for your response Ray. I’m now hosting my own weather server but waiting for the 24 hour gathering period to conclude. Will ETo work ‘out of the box’ when hosting my own weather server if my PWS reports solar radiation? Or do I need to modify code to achieve this?

[Ray]

You need to modify the code. Most noticeably, the ETo algorithm will throw an error if the weather data source is pws:
https://github.com/OpenSprinkler/OpenSprinkler-Weather/blob/master/routes/adjustmentMethods/EToAdjustmentMethod.ts#L20

[John Park]

Thanks again for your response Ray. The eto calculation seems to work using my PWS without any code modification (see screenshot attached). I can see that solar radiation, humidity etc. are being logged in the observations.json file.

Attachments:

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   Screenshot_2024-06-01-21-37-53-61_e4424258c8b8649f6e67d283a50a2cbc-scaled.jpg
   

[cameronaltman]

Hey John what model PWS are you using? I have an Ambient Weather WS-2902D that also records solar radiation data (https://www.wunderground.com/dashboard/pws/KCASANJO1826) but unfortunately I can’t get it to work with the ETo calculation. I’m not technically savvy enough to modify the weather code, so I’m trying to see if there’s anything else I may be able to do to have it work “as is.”

[John Park]

Hi, I didn’t have to modify any code to get ETo working, I just had to host my own weather server. In the end I gave up on ETo and I’m just using a basic rain delay now.

[Ray]

So I looked into this issue, and it seems that if you have 1) provided a WUnderground API key, and 2) selected a specific PWS station; 3) chosen ETo as the algorithm, then you will get a WUnderground Method Not Supported Error. But if you didn’t select a specific PWS station, instead, you just selected a GPS location, then it will fall back to WeatherKit and calculate ETo using that. This is indicated in the System Diagnostics, where it will say the weather data is powered by Apple.

We will be looking into getting ETo and PWS supported. If I remember correctly, partly the issue in the beginning was solar radiation is not guaranteed by PWS, in fact, I just did a few tests, and it’s true that some PWS stations don’t provide solar radiation data (the value is null). But I agree that for those that do provide this data, it should be possible to use ETo. We will look into this.

[cameronaltman]

Much appreciated Ray. Thank you for looking into this.

[Author]

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