[aprssig] Vicinity Plots on APRS

Bob Bruninga bruninga at usna.edu
Wed Jun 1 10:32:10 EDT 2011

Thanks for giving me the opportunity to comment.  First, APRS is a network
of packet stations contributing information and capturing info for the best
knowledge of what is going on. It is not a POSITION reporting system per se.
> So, if a station only transmits status and/or telemetry 
> or some other non-posit packet, what symbol do you expect 
> the program to use? And where should the station be 
> displayed?

This was WELL defined by APRSdos, but other authors who thought of APRS as
only a vehicle tracking system refused to allow my placing in the spec HOW a
non-position reporting station should be handled.  Though to me it was
FUNDAMENTAL to the network.

1) Without a position packet, a new station should be added to the station
list in any case
2) The symbol should be the VICINITY symbol (a big question mark)
3) The LAT/LON of that station should be RANDOMLY placed within about 1 mile
of the FIRST digi that heard the packet
4) The ambiguity for that symbol is set to 1 mile.
5) The callsign should not be displayed on the map unless the zoom is below
say the 8 mile range

The above puts the station in the network where heard, using a completely
well defined VICINITY symbol, suppresses the callsign (on the map) unless
asked, and in the worldwide APRS system gives about 100% of what one needs
to know about the station for the purposes of the network and communication.
See: http://aprs.org/symbols/APRSvicinity2.GIF

> Or should it simply stay hidden until a posit is received?

That is sort of what the suppressed callsign does.  Yet the cluster of
QUESTION mark VICINITY symbols around a digi, lets one see where these
stations are coming in.  Zoom in to see who they are, or ask where station
XXXXXX is, and he will be revealed as one of the Question marks...  Of
course, when an actual position report does come in, these VICINITY plots
disappear.  Its cute watching APRSdos first come up with a blank map.  You
will see these ? marks appear around some of the digis, but within a few
minutes they disappear as the actual position reports come in for proper
placement.  But at least from the first second, you could know where someone
was for the purpose of communications.

> Just imagine if you lived in West Africa and ran this programe 
> how annoying it would be having all these stations just off the 
> coast at 0 Lat 0 Long coming and going . 

Yes, that was never intended to happen...

> Why display a station anywhere on a map when it's a guess.

Because the global APRS system is a big place.  But knowing someone
originated a packet via a given digi, nails down the stations position in
the network (for communications purposes) 99.99999% from about 6 million to

> Most if not all APRS networks are designed 
> with a network cycle time of 30 mins....

For regional information, yes.  But the cycle time is 10 minutes for local
data (1 hop or less)

> As far as using [the SSID] option and taking the Source 
> Callsign SSID as the symbol goes then thats fine too.

This ONLY applies when a RAW NMEA string is received.  Not in any other

>> APRSISCE/32 also stores the status until a posit 
>> arrives with a symbol. I just chose to display 
>> the station while waiting.

Yes! Great.  That was the original intent.  Just use the VICINITY symbol as
noted above within 1 mile of the digi that heard it.  Now that most of APRS
paths should be 100% traceable, then that is the thing to do.  If the packet
was heard DIRECT or cannot otherwise, then that is within 1 mile ambiguity
of OWN station.

I can't remember if this fundamental VICINITY concept is in the spec.  At
some point I threw up my hands in frustration at the "committee effort"  and
just let the spec go.  But in any case, VICINITY plotting should be in
APRS11 or APRS12.  ARGH... I can't find it, but I did find it here:
http://aprs.org/symbols.html.  There is also a file out there called
VICINITY.TXT.  Google it.

Ill try to add it to APRS12 so it is easier to find.

Bob, Wb4APR

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