[aprssig] Snow and Visibility on APRS

[Robert Bruninga]

The original APRS defines SNOW Sxxx and LUMINOSITY Lxxx fields
for the weather format, and I thought it included visibility
Vxxx, though I cannot find it right now.  Does anyone recall if
anyone uses these.  If not, I propose a Vxxx field if someone
can recommend the right units.

Lets look at this original APRSdos file:

www.aprs.org/APRS-docs/WX.TXT  see extract below

And it appears to cover Snow, but not Visibility.  Though I was
sure I had proposed Visibility at some time or other....  SO
check the original spec, or the addendum
www.aprs.org/aprs11.html and there find this link:
http://www.aprs.org/aprs11/spec-wx.txt

> FORMATS:  APRS re-formats data from attached WX units 
> and transmits the data as shown below.  For remote 
> Ultimeters, where there is no PC, the TNC just transmits 
> the raw data, but APRSdos converts them to these formats
> for display on the P-LIST.

_DIR/SPDgXXXtXXXrXXXpXXXdU-II              Original U-II auto
_DIR/SPDgXXXtXXX#XXXdU2r                   Original U-II remote
_DIR/SPDgXXXtXXXrXXXpXXXbXXXXhXXdDvs       Davis WX station
_DIR/SPDgXXXtXXXrXXXpXXXbXXXXhXXdU2k       U-500/2000 with APRS
_DIR/SPDgXXXtXXXPXXXbXXXXhXXdU2kr          Remote
UltimeterLogger
_DIR/SPDgXXXtXXX#XXXbXXXXhXXdUpkm          Remote Ultimeter
PktMode
_DIR/SPDgXXXtXXXrXXXpXXXPXXXhXXbXXXXX%type NEW FORMAT June 97
                                              

Where:

CSE/SPD is wind direction and sustained 1 minute speed
txxx   is in degrees F
Rxxx   is Rain per last 60 minutes
pxxx   is precipitation per last 24 hours (sliding 24 hour
window)
Pxxx   is precip per last 24 hours since midnight
sxx    is snow in inches
bxxxxx is Baro in tenths of a mb
hxx    is humidity in percent.  00=100
gxxx   is Gust (peak winds in last 5 minutes)
#xxx   is raw rain counts for remote stations. See notes on
remotes
%xxx.. 1st letter shows software d=Dos, m=Mac, w=Win, U=Uiview,
etc
       and remainder shows type of WX instrument

Note, in the complete WX format, the _DIR/SPDgxxxtxxx fields
must exist.  All the others are optional.  Though there is no
confidence that all clients implemented it that way...

Bob, WB4APR