[aprssig] Vicinity plotting

Steve AB3LT at RoseAndSteve.us
Tue Nov 22 16:39:23 CST 2011

I have been considering something like this for APRS messages heard
via satellite.

If one of the ISS aliases is in the path of a message, I'd need to
calculate the ISS's position and footprint at the time of the message,
and then use that as the basis for both stations locations 'vicinity
plots'.  as more messages are heard those 'vicinity plots' would
overlap some and the calculated 'vicinity plot' would reduce in size
each time, by eliminating the non-overlapping areas. eventually I'd
have a much better 'vicinity plot' for the stations heard via ISS.

Something similar could be done with terrestrial paths, by using all
the path elements as chained 'vicinity plots' and reducing by the
non-overlapping areas on subsequent packets.

This would get you a city on the first packet (somewhere between DC
and New York) and a little more specific after a couple of packets
(somewhere near a cheesesteak place in south philly).

If I remember correctly, the guidance on 'vicinity plot'-ing the
symbols on a map was to not show the symbols until the user zoomed out
high enough that the ambiguity was irrelevant (in my case looking at
Philly, New York and DC at the same time).

73, Steve AB3LT

On Tue, Nov 22, 2011 at 11:30 AM, Andrew P. <andrewemt at hotmail.com> wrote:
> Greetings, all.
> I've been trying to implement vicinity plotting of stations that don't send position reports, and I'm having a tough time of it. Many of them were originated over TCPIP, so they never had an initial digipeater to use for vicinity plotting. Others digipeated over a path without tracing, so their path only reports the WIDEn aliases. Yet others had an initial digipeater, but I never got a position report from the digi itself to use for vicinity plotting.
> So how should I handle these? Right now, they are being plotted off the coast of Africa at lat/lon 0,0. Should I be querying the invisible digis as to their position? That would at least help with some, but that would cause more spurious radio traffic.
> Thanks in advance.
> Andrew Pavlin KA2DDO
> Sent from my Verizon Wireless BlackBerry
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