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[aprssig] conveying map view

Bob Bruninga bruninga at usna.edu
Tue Sep 21 21:45:47 UTC 2004


On Tue, 21 Sep 2004, Wes Johnston wrote:

> Yes, but I don't know of a single APRS client that will allow you to
> either 1) specify by typing a view, 2)let you click on the contents of a
> message and specify a view automagically.

That is the whole idea behind the APRS concept of CENTER and RANGE.
All one needs to do is specify the center and range and then everyone
of no matter what software should see the same thing.  Problem is
many APRS clones dont have zoomable maps and fail misserably at
presenting different users with the "same view"...  Or then dont
even display "range scale" but something useless like 1X or 4X...
(One of my biggest frustrations with lack of standardization in clone
programs... as you can tell...)

> Is there one that does?  It would really be neat if we could publish map
> views (ie bookmarks) just like we do objects.  New people arriving on
> the scene of an event would have within a few minutes, a list of common
> views.... ie downtown, the county... the event... and then if someone
> said "It's in the upper right corner of your map" we'd have a fighting
> chance to see what the guy is talking about.

Yep, exactly what the Center and Range concept is supposed to solve.
My war story is from 1995 when we did our fist MarineCorps Marathon
and the entire event is within 2 miles of the pentagon.  Most users
were APRSdos users at the time and had no problem seeing the same
thing.  Just say to other users, "center on the pentagon" at the 1mi range
scale, or cener on the white house at the half mile scale... etc...

Some Windows users at the time, said they had the "Wash DC" map
"loaded" but could not even see a marathon and the 14 mobiles...
because they had no concept of range, and didnt notice that there
were 14 ICONS all underneath one, because they were on a view of the
entire area going out 150 miles in all directions.

We added more voice comms to the event just trying to resolve these
ambiguities than the air-time that APRS was supposed to *save* if
everyone was on the same "view" so to speak...

Eventually the Windows application did add a "legend" that showed at least
a length in miles on the map, but it was still far from the desired
universal concept of Center-and-Range that is so fundamental to tactical
real-time displays...(across platforms)...

And, unfortunately, we *still* dont have that simple cross-platform
consistency (of cener and range) that is so fundamental to really using
APRS in the field for something other than pretty maps...

Soap-box off...

de WB4APR, Bob

> ----- Original Message -----
> From: Jason Winningham <jdw at eng.uah.edu>
> Date: Tue, 21 Sep 2004 14:26:49 -0500
> To: Wes Johnston <wes at johnston.net>
> Subject: Re: [aprssig] conveying map view
>
> >
> > On Sep 21, 2004, at 2:15 PM, Wes Johnston wrote:
> >
> > > It sure would be nice if there were an APRS packet which would allow
> > > me to send a map view to someone else... for example, I could send my
> > > center position and the height of the map
> >
> > Isn't that what range scale is for?  Your center coordinates + range
> > scale should do it.
> >
> > -Jason
> > kg4wsv
> >
>
>
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>

de WB4APR at amsat.org, Bob

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