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[aprssig] RE: Position Ambituity in APRS!

Alex Carver kf4lvz at yahoo.com
Thu Jan 10 18:26:52 UTC 2008


> Message: 3
> Date: Wed, 9 Jan 2008 11:23:56 -0800
> From: "Keith VE7GDH" <ve7gdh at rac.ca>
> Subject: Re: [aprssig] RE: Position Ambituity in
> APRS!

> 
> Richard N1JDU wrote...
> 
> > This message not read because the poster
> apparently quoted an *entire* 
> > digest before leaving his comments at the bottom.


Yes yes my apologies.  I scrolled down to figure out
where the message was in the digest and forgot to
scroll back up to delete above what I was quoting.  If
you'll notice, I did in fact remove everything below
where I was typing so I didn't quote the entire digest
as you say.  However, you didn't have to waste time
quoting my entire message either just to take a jab at
me.  I've posted many times, this was one of the rare
accidental messages where I forgot to erase text. 
I'll continue reading your messages even if you never
read one of mine again.

Then Keith VE7GDH wrote...

> 
> Yeah, it's too bad his message (and yours) wasn't
> truncated!
> On the bright side, he didn't top post - hi!

I hate top posting.  Closest I'll get is interleaved
posting.

 
> I just had a D700 user enable ambiguity to see how
> it displays in 
> UI-View. As expected (from earlier comments about
> APRS clones) it 
> displayed the symbol that the user specified and
> with the position shown 
> as if zeros were transmitted instead of spaces. It
> may not show 
> ambiguity at a glance like apparently APRSDOS, but
> if I'm at all 
> interested in a particular station, it would stand
> out like a sore thumb 
> that there were missing digits and what was going
> on. Of course, the 
> user could change the callsign to AMBIG or something
> like that and enter 
> their callsign in the status text... or perhaps use
> e.g. WBRAPR-A with 
> the A standing for ambiguity.




What I don't understand is Bob's fascination with a
circle over a box.  If I were lost in the woods and I
knew I was somewhere between 35 and 36 degrees north
and 85 and 86 west, I'll transmit 35 N 85 N and hope
that the SAR people will search a box.  Why?  I might
be lost in the corner of that box and no one will look
for me if they hunt around in a circle but they will
know that if I truncated my position, I'm in a box
somewhere where the coordinates when truncated match
what I sent.

Plus, where exactly do you center the circle?  On 35 N
85 W?  In the middle at 35.5 N 85.5 W?  I could be
lost near 35.9 N 85.9 W and a circle centered on 35 N
85 W probably won't reach me.  So I end up dying in
the wilderness and coming back to haunt everyone.

Every other coordinate system on this planet uses
grids for uncertainty.  The grid square system (it's
right there in the name, square), UTM, Maidenhead, all
of those are some kind of polygon not circles.


Bob, I know we're picking on you rather harshly but
this is really frustrating because what you say and
what is in your head is not what is on paper in an
understandable way.  I would suggest as you modify the
specifications, have a few people look over your
shoulder and discuss it.  The hard part about writing
documentation about a subject you know well is that
you can quite easily gloss over much needed
information because it's already in your head and
never makes it to the paper.  Having a dozen eyes
looking at the same document as it's generated and
then talking about it would prevent these issues
because the clarifications (and maybe some very useful
examples) could be included.

As for position ambiguity, I think you may have lost
that war due to documentation ambiguity (pun
moderately intended).  It should be obvious from the
multitude of interpretations that the documentation
was not clear about circles, squares, triangles,
starfish, horseshoes, or four leaf clovers.


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