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Correct Run time for RM Mixer ET calcs



  • Official comment
    RainMachine Nicholas

    Hi Glen,


    In RainMachine, if you don't have Correction for Past/Forecast Correction enabled, the calculation done for today are based always only on the future data (from the today,  until next run date exclusive). In your examples you are looking into past instead of future.

    Also you need to take in account:

    1. Rain Sensitivity - rain amounts are reduced to this percentage 

    2. Available Water in soil - any extra water that wasn't required by plants. The needed water will be reduced by the available water amount.

    3. Crop Coefficient/Exposure Coef - the computed ET will be scaled with these coefficients ( for example day ET * 0.7 (if it's Lawn) * 0.85 (partial shade))


    This is what comes up in my mind by looking at your table for now.


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    Glenn G.


    Thanks for the info. and perspective.

    Can you point me to where the Correction for Past/Forecast Correction is enabled.  Can't seem to find a "Correction for Past" setting.

    Using Firmware Ver: 4.0.845.

    I do have "Forecast Correction" enabled in the Settings>Weather screen.


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    RainMachine Nicholas

    Yes, "Forecast Correction" is the new name for "Correction for Past". What it does it looks from last run until today and computes the difference between ET known at the time of program run (on last run) and the best ET computed from weather received that day. For example NOAA updates forecast for current day every 4 hours, at the end of the day you have the best forecast available.

    Same thing for QPF but also if you have a weather service enabled with local weather station, it will use the reported RAIN instead of program last run known QPF.

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