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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