[wxqc] Rain graph not displaying value

[Steve Dimse]

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