[aprssig] Vicinity plotting of stealth digipeaters

Thu Dec 11 16:16:05 EST 2014

Ok, so 1 mile ambiguity around average of all station pos reports first-repeated by that digi. I'm assuming I shouldn't count the same originating station twice because I have a history of multiple pos reports from that station unless the station is significantly moving (ie., use multiple digipeats from different positions to improve point sampling). Also, should I weight the averaging by the inverse of each pos report's ambiguity? I'm assuming that the first time I hear about a stealth digi, I can only do standard vicinity plotting because I only have one reference position. Updates won't change the vicinity plot or the algorithm until I get a different reference position to combine with the first one.

Of course, the answer would be seriously skewed if the stealth digi had a directional antenna, which would offset its coverage area. How many digis out there have other than an omnidirectional antenna?

Hmmm... this could also be useful forwards to improve vicinity plotting and locate stations with bogus position data (like the station with a U.S. callsign I saw displayed in Afghanistan, presumably with an incorrect sign in its longitude). Of course, such analysis could only occur on an RF listening station because of the duplicate stripping of the APRS-IS backbone.

Andrew, KA2DDO

-------- Original message --------
From: Robert Bruninga <bruninga at usna.edu>
Date:12/11/2014  11:49  (GMT-05:00)
To: TAPR APRS Mailing List <aprssig at tapr.org>
Subject: Re: [aprssig] Vicinity plotting of stealth digipeaters

Good idea.  But if you are going to average the positions to try to figure
out the position of a BLIND digi, then better not to plot it with 10 mile
ambiguity, but more like 1 mile so that you actually get to see the
solution of the average.  Plotting it with 10m ambiguity would place the
actual symbol somewere randomly within a 400 square mile box.

But again, that is only plotting the “solution”.  In that case, it should
be a definite different symbol and name from the actual digi and name which
might be misleading.

If one is going to plot the actual digi and name, then 10 mile ambiguity
might be OK.

Kinda depends on how it will be used.

P.S.  PSAT nearing launch will be reporting its position in 60 mile
ambiguity (1 degree) so I hope most softare is OK with that.

Bob

*From:* aprssig-bounces at tapr.org [mailto:aprssig-bounces at tapr.org] *On
Behalf Of *Randy Love
*Sent:* Thursday, December 11, 2014 11:09 AM
*To:* TAPR APRS Mailing List
*Subject:* Re: [aprssig] Vicinity plotting of stealth digipeaters

In a feeble, off the cuff, maybe-it-would-work first suggestion, how about
averaging the lat and lon of the stations digipeated by the stealth digi,
and have position ambiguity of 10 miles?

Theoretically, the digi would be somewhat central to those stations that
were digipeated by it, thus averaging the lat and long would place the digi
somewhere in the area outlined by the locations of the stations digi'd by
it.

There are exceptions to this thought, of course, but better than nothing at
all!

Randy

WF5X

On Thu, Dec 11, 2014 at 10:05 AM, Andrew P. <andrewemt at hotmail.com> wrote:

Does anyone have any advice or opinion on vicinity plotting of stealth
digipeaters? Or have I stepped into a brave new world here?

Andrew, KA2DDO

-------- Original message --------
From: "Andrew P." <andrewemt at hotmail.com>
Date:12/05/2014 13:20 (GMT-05:00)
To: TAPR APRS Mailing List <aprssig at tapr.org>
Subject: [aprssig] Vicinity plotting of stealth digipeaters

Greetings, all.

I've got a question about vicinity plotting (i.e., guessing where a station
is based on its first digipeater's position when the station hasn't
reported its position yet).

Is it reasonable to do this in reverse, i.e., guessing where a first
digipeater is, based on the position report of the digipeated station?
Because stealth (non-beaconing) digipeaters are common in my area, I have
implemented a first draft of this in my YAAC program.

I assume this needs to be improved, perhaps using direction-finding tricks
such as guessing the digipeater has to be within the PHG range circles of
all stations it has first-digipeated.

But should I be doing this kind of approximation at all?

Just curious.

Andrew, KA2DDO

(putting my asbestos shorts on now :-)

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