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[aprssig] Vicinity Plotting in the original APRS

Randy Allen ka0azs at earthlink.net
Fri Jun 16 22:56:07 UTC 2006


I did a sort of vicinity tracking through Find-U several years ago.  My 
wife (licensed ham) and my daughter drove to Florida one summer, and had 
my first attempt at a dumb tracker (Tiny-Trak, 2mHT, GPS-II+ and a 7ah 
gel cell in a MTM dry box).  On the way down, the gps cable came 
disconnected.

The Tiny-Trak started reporting her position as being at 0.00 0.00 off 
th West coast of Africa (where there is usually a convention of new APRS 
users ;-) ).

However, by looking at the raw packet data on Find-U and noting the Digi 
and I-Gate info, I was able to track their progress to within a few 
miles over the course of the trip by looking up the location of the Digi 
on Find-U.  While not as precise as the GPS coordinates, it was good 
enough for my purposes at the time (Tracker has since been refined and 
the XYL has a D700 in her car).

I've also used the Vicinity feature in DOS APRS to help new stations 
diagnose problems they may be having, at least confirming that they are 
putting out packets on RF.  It's been handy a couple of times at public 
service events as well when a tracker loses GPS signal.

Often, SOME information, no matter how imprecise, is better than NO 
information, so as long as you can quantify the precision (or lack 
thereof) of the data

73









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