[aprssig] Vicinity plotting

Andrew P. andrewemt at hotmail.com
Tue Nov 22 13:05:19 CST 2011

Hmmm..... So, does APRS-IS/CE not do vicinity plotting at all, or only do it when there is a clearly located first digi? I'm currently implementing the second choice, and trying to decide what to do about the spurious error messages from the non-located digis. I do suspect part of my problem is the APRS-IS feed is bringing me relayed stations where the digis don't have WIDEn aliases in their position beacons, but the stations they relay do use WIDEn aliases. I don't have this issue nearly as much with an RF-only feed from a TNC and radio.

Good thing there isn't a land mass at (0,0); they'd be swamped with traffic. ;-)

Andrew Pavlin KA2DDO
------Original Message------
From: Lynn W. Deffenbaugh (Mr)
To: aprssig at tapr.org
Sent: Nov 22, 2011 12:15 PM
Subject: Re: [aprssig] Vicinity plotting

Having struggled with the same thing myself, I finally decided that any 
station from which I have not received a position report will be located 
at 0,0 until I get a position report.  I examined many many paths before 
coming to the conclusion that there is NO good solution that will 
RELIABLY tell you where you should RANDOMLY position said station.  And 
cluttering the map with ambiguity circles or any other indication that 
the station really is NOT where you're drawing it was worse than just 
keeping the station off the map until a position was received.

I would also recommend against any sort of automatic query of a station 
from which you think you need additional information.  Think of the 
traffic that would be generated when you successfully replace UI-View 
and 10,000 instances of your client (yes, it works via APRS-IS too, I 
assume) "decide" they need to know exactly where that event tracker 
actually IS and fire out the requests.  Not a pretty picture in my 
mind's eye.

If you haven't heard where a station is, then my opinion is that the 
station might as well be invisible, but at least I draw them at 0,0 off 
the coast of Africa.

Lynn (D) - KJ4ERJ - Author of APRSISCE for Windows Mobile and Win32

PS.  All that said, I am considering some better approaches having 
watched the real-time plots of packet paths in APRSISCE/32.  I may (or 
may not) implement some sort of user-option for "guessing" a position 
for a non-beaconing station...

On 11/22/2011 11:30 AM, Andrew P. 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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