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[aprssig] Why all the "Vicinity Stations" on APRSDOS?

Robert Bruninga bruninga at usna.edu
Wed Mar 16 21:51:15 UTC 2005


>>> kliegle at rcn.com 3/16/05 3:00:16 PM >>>
>I recently upgraded my local ...Digi to a KPC-3 w 8.2 Software,
>Now, I get several stations that appear on my map 
>as "Vacinity Stations".  Usually it's a WX station...
>35.3 miles away from me. Is the upgraded digi
>doing it or what?

This is common for WX stations using the ambiguous
positionless WX and weatherless-position formats.  If the
first packet your station receives is a WEATHER packet
with no position data, then APRSdos witout having any
previous position data will put that station on the map 
as a vicinity plot near the firts digi that that station used
until it does get a position packet.

Since these positionless WX stations only send a position
packet once an hour or so, then you will see a vicinity
plot for up to an hour or two before you get the position packet.

This is the "advantage" of vicininty plotting, beacuse even
without the posiiton data, at least APRSdos lets you know
approximatley where the WX station is.  Other software
will IGNORE the WX station until a position is finally received.
THus, you may have to wait an hour or two to even see it.

That is why I hate the "positionless Weather format" and 
weatherless position format!  It violates the fundamental 
principle of APRS that every packet of data is completely
self contained and is not dependent on aprioir data (which
may or may not arrive)...

de WB4APR, Bob






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