[wxqc] Cumulative rainfall value in APRS

[Bill]

Interesting discussion from the other thread...
> APRS has four rain values, cumulative (limited to Peet stand-alone  
> weather stations) 1 hour, local midnight, and 24 hour.
The ideal rainfall value for use in hydrologic forecasting would be the 
cumulative value. This need only be reset once a year. The benefit being 
one can avoid the hassle of trying to determine when the particular 
reading was reset but instead let software grab the cumulative value and 
determine the desired increment and associated value from the previous 
accumulated value. This is how many of the tipping buckets installed at 
river gaging locations report. Another advantage is that missing data is 
not a major problem as long as the accumulator has continued and the 
updated value is available once the gage begins reporting.

Having all stations report a cumulative value would be a good thing but 
not sure how difficult it would be to implement(?).

Bill
CWOP KC9DNQ-3 (AR794)
http://www.gooselakeweather.com



Steve Dimse wrote:
> On Aug 19, 2007, at 8:20 PM, Armin Schwarz wrote:
>
>   
>> I noticed that the rain graph on my findu page does never display any
>> values other than zero eventhough the header line "Last report  
>> from ..."
>> does display the "Rain last 24hrs x.xx inches" as uploaded.
>>     
>
> APRS has four rain values, cumulative (limited to Peet stand-alone  
> weather stations) 1 hour, local midnight, and 24 hour. Last 24 hours  
> is not displayed graphically, as it makes a very confusing image.  
> Whether the line goes up or down at each time bin depends on two  
> values, the rain that has fallen now, and the rain which fell 24  
> hours ago.
>
> Think about a 48 hours of constant rain at .1 inch/hour. For 24 hours  
> the graph is a ramp up, then it is level for 24 hours, then it ramps  
> down for 24 hours. While ramping down there is no rain, but the graph  
> still shows a value. While the ramp is up and while it is level, it  
> is raining. Now imagine 24 hours of 0.1 inch/hr, then 24 hours of .2  
> inch per hour. Now the graph is a straight ramp for the full 48  
> hours, even though the rate changed halfway through. In other words,  
> to make sense of the 24 hour parameter, you have to look at all the  
> data over the las 24 hours to figure out the current rain. Graphs are  
> supposed to make data easier to interpret, graphing 24 hour rain  
> makes it harder. One hour is a little better because of the shorter  
> term, but it still suffers from the same problem on a local time scale.
>
> I don't know which software you are using, but you should beg the  
> program author to modify it to send the rain since local midnight  
> data as well as the 24 hour data. With rain since local midnight,  
> anytime the level goes up more rain has fallen, and the daily reset  
> is very clear.
>
> Steve K4HG
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