[Xastir] Wind Gusts

[Gerry Creager]

I'll try to respond more, later, if needed but realize that the APRS 
Weather Spec was compiled without the interference of working 
meteorologists.

One thing I'd like to start doing is to munge the reporting into APRS 
Weather, and then to do something like a compressed feed in 
miscellaneous data... an ad hoc data feed... that provides the 
resolution NWS is looking for.

Now for the tricky part: Peet and Davis stations don't generally have 
the available precision to meet NWS spec.  I've got a dream of managing 
CWOP/APRSWx metadata to the point that it's more (emphasis on MORE) 
useful by NWS and others like me, for forecasting and verification, if 
not climo uses.

Gotta get back to my meeting...

gerry

Clay Jackson wrote:
> Heads up, I'm messing about with weather data again!
> 
> We're having an "interesting" weather here in the NW, and I noticed that 
> my station seemed to be "under-reporting" wind gusts - here's the deal:
> 
> I have a Davis WMII, feeding meteo (basically a MySQL database), which 
> is then read by db2APRS (converted to an APRS wx string) and then fed to 
> Xastir.
> 
> The Davis reports observations to meteo about once/minute - the 
> observations include wind speed and direction, which are "instantaneous" 
> and wind gust, which the Davis reports as the highest wind speed since 
> the last time the device was polled (in this case, about a minute).
> 
> db2APRS polls the database about once/minute and so was reporting the 
> same things.
> 
> When I looked at findu, it didn't appear that the gusts I was seeing in 
> the DATABASE were getting reported correctly to findu.
> 
> So, I took a look at the db2APRS code, the Xastir code, and the NWS 
> standards.
> 
> According to NWS, the definition of "gust" for reporting purposes is the 
> highest wind speed recorded within 10 minutes of the observation; and 
> wind speed and direction are to be averaged over 2 minutes.   So, I 
> modified db2APRS to do this (find the highest GUST reported by the Davis 
> in the 10 minutes prior to an observation, and average the wind speed 
> and direction over the past 2 minutes.
> 
> But, when I looked at "Own weather data" in Xastir, I was still seeing 
> really low gust figures.
> 
> So, I looked at the Xastir code - there appears to be some "averaging" 
> going on there as well (I haven't yet read it well enough to understand 
> exactly what it's doing)
> 
> Can someone shed some light on what Xastir's doing, and more 
> importantly, WHY it might be doing that?  I'll also post my analysis of 
> what it's doing....
> 
> Thanks!
> 
> Clay
> N7QNM
> 
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-- 
Gerry Creager -- gerry.creager at tamu.edu
Texas Mesonet -- AATLT, Texas A&M University	
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