OpenSprinkler Forums OpenSprinkler Unified Firmware Comparision of different Weather Adjustment Methods for August 2019

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    In order to get a better understandig of the different Weather Adjustment Methods available with OpenSprinkler I have run a comparision for Ausgust 2019. Our weather in August was typical for a middle European summer. We have had temperatures close to 85 °F (30 °C) during the day, which are also sometimes gone down to 59 °F (10 °C) at the early morning. There have been also a mix of rain showers and local thunderstorms.

    The attached diagrams schow the Watering % results of the ET and Zimmerman Weather Adjustment Methods. My OpenSprinkler is programmed to water the garden at 7 am in the morning. The diagrams and the corresponding weather data are related to this 7 am sprinkler operation.

    The baseline ETo value for my specific location is retrieved as 0.113 inch/day. The baseline humidity is set to 65%. All other Weather Adjustment baseline parameters are kept to the default values.

    The different watering % results for the Zimmerman Weather Adjustment Method are caused by the discrepant precipitation values received from DarkSky. They don’t describe the actual rainfall at my home location as measured by the rain gauge installed with my local PWS.

    The ET Weather Adjustment Method results in greater changes of the watering % values. It is maybe necessary to modify the baseline ETo value to reflect the watering needs for my home location? Another good idea will be to use the local rainfall measurements as input for the ET watering % calculation? However this requires some OpenSprinkler weather service program modifications.

    I’m actually using the Zimmerman (Local PWS) Weather Adjustment Method to water my garden, as this gives the best results for me. However I’m free for any changes in the future. I hope this short analysis gives some ideas what can be achieved by using the OpenSprinkler’s Weather Adjustment Methods?




    I have the same problem with DarkSky — the precipitation amounts are wildly different than what my PWS reports (and the station apparently used by DarkSky is less than one mile away). I often see DarkSky reports of small amounts of precipitation when I know there has been absolutely none. This may be caused by morning dew accumulating on that weather station’s rain sensor. I stuck with Zimmerman and the data from my local PWS (delivered locally through a local instance of weatherserver).

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OpenSprinkler Forums OpenSprinkler Unified Firmware Comparision of different Weather Adjustment Methods for August 2019