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[aprssig] Vicinity plotting

Bob Bruninga bruninga at usna.edu
Tue Nov 22 21:53:54 UTC 2011


Throwing the baby out with the bathwater...  I don't understand your
conclusion at all.

> APRSISCE/32 doesn't do vicinity plotting at all currently.  
> There is never, IMHO, a clearly located first digi. 

I diaagree completely.  I'd say there is USUALLY a clearly located first
digi and you should use it.

> I don't care if you see a packet that says " DIGI1,WIDE1*" 
> that doesn't mean that DIGI1 was the first to see the packet.

In APRS it does 99% of the time.

> There are devices out there (albeit few) that are beaconing 
> a WIDE1-2 for their first path component..

So, it arrives as DIGI1,WIDE2-1*  Again DIGI1 is the first digi...

> and digipeaters that do callsign substitution instead of insertion. 

If you see DIGI1,ANYTHING then still DIGI1 is the first digi...

> ...you still have no idea where the station is nor what it
> might be close to.

I fail to see this conclusion at all.

> And how do you handle a packet that you see that simply says
> "WIDE1*"?  It was obviously (possibly) digipeated by something,
> but what and where?

There is an extremely rare packet.  In that case, do not plot it.

> And then you have the packet "DIGI1,WIDE2*" which may 
> or may not have been heard first by DIGI1..

No, but DIGI1 is your best guess.  And this is "vicinity plotting after all.
You are simply doing your best effort.  No monre.

> Nope, after looking at how many chances there were to get 
> it wrong, I decided to simply not place stations by inference.

I see only one out of thousands that cannot be inferred quite accurately.
Why ignore the 99.9% because you might need to not p lot the 0.1%?

> Just wait until you get someone insisting that your 
> new-kid-on-the-block APRS client "isn't showing my 
> station in the right place" when in fact, they mean 
> that his station appears in a different place on your client
> than on aprs.fi or jfindu.com or OpenAPRS and when you 
> dig even deeper you find out that they've configured their 
> Kenwood radio to beacon with 10nm (yes, 10 MILE) ambiguity.  

Then that is exactly when you should be showing ambiguity and vicinity.
Unless we show them when they are using *wrong* paths or wrongly using
Ambiguity, then your system is losing integrity because it is *not* showing
what their packet *is indicating*.

I think it is important to display exactly what their packet is INFERRING.
IF they are broken, or their loca digi is broken, then that is the only way
they learn to get it fixed.

Bob, Wb4APR





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