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 -- [EMAIL PROTECTED]
Texas Mesonet -- AATLT, Texas A&M University
Cell: 979.229.5301 Office: 979.458.4020 FAX 979.862.3983
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