[Xastir] SHOW OF HANDS REQUESTED: Davis Weather Station users

[Tom Russo]

On Sat, Jul 21, 2012 at 09:24:50AM -0700, we recorded a bogon-computron collision of the <warpedspeed1 at yahoo.com> flavor, containing:
> Got a Davis Vantage Pro, running Meteo, db2APRS, and Xastir.? 

Nice.  Just what I need to see.

> Got a fair amount of rain this time of the year... And lightning, although I try not to collect any of that!? 

:)

> 
> The thing that I am lacking is Play Time, or even time to read E-mails, as evidenced by just now seeing these message two days later.? I will do what I can to help, when I can.??

The issue we're working through is that it seems that for the Davis APRS 
DataLogger, total rain, rain-last-24-hours, rain-since-midnight, and 
rain-last-hour are not consistent because the code does the wrong thing
with the data out of the device (it does not save the data for the shorter
periods, instead recomputing them itself, and getting it wrong).  I believe
the Davis Meteo code has the same problem.

So what you'll need to do is watch the rain data in View->Own Weather Data
and make sure that Total Rain and the others seem to be right over time.  

I've asked Mike to post a detailed description of the symptoms he saw that 
led him to report a problem.

Unfortunately, I don't see a good, quick fix to this.  

The quickest fix that lets Xastir code be minimally impacted will involve
changing the Davis Meteo interface program (db2APRS) and its cousin the
LaCrosse version so that they spit out "total rain" instead of 24-hour rain,
and have Xastir then use that data the way all the other weather stations use 
it.  This will require that everyone running meteo rebuild and restart 
db2APRS in addition to rebuilding and restarting Xastir.  It will also make 
the "APRS" weather string that those programs emit not spec-compliant APRS 
weather strings.  But it would make Xastir get rain data right --- since 
Xastir constructs its own weather report from the weather data it gets,
the non-compliance of the db2APRS output is irrelevant anyway.

The better fix is to rewrite all of Xastir's weather code to be less convoluted
and cleaner, and to use useful data emitted by weather stations rather than
recompute them.  The reason Xastir recomputes them is that some weather stations
don't emit all the data needed, so it works to the lowest common denominator
and computes derived quantities.  But because it's so convoluted, and because
the lowest common denominator it assumes isn't actually common, it's very
difficult to work on.

Ultimately, the Davis and LaCrosse codes should not be attempting to spit out
an APRS-ready data string that Xastir then has to parse and reconstruct, but 
rather report all the weather data the station can provide, and Xastir should 
use it.  But that's a lot more work.

-- 
Tom Russo    KM5VY   SAR502   DM64ux          http://www.swcp.com/~russo/
Tijeras, NM  QRPL#1592 K2#398  SOC#236        http://kevan.org/brain.cgi?DDTNM
"And, isn't sanity really just a one-trick pony anyway? I mean all you get is
 one trick, rational thinking, but when you're good and crazy, oooh, oooh,
 oooh, the sky is the limit!"  --- The Tick