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Position Ambiguity [was] Re: [aprssig] findu.com....

KC2MMI (Jared) kc2mmi at verizon.net
Tue Jun 13 15:11:54 UTC 2006

" I meant:  Why talk only about
APRSWorld when several other apps use the same data."

There's no reason to single out APRSWorld, I certainly did not. James complained
to a general comment I made regarding *all* such products, and when I responded
to his comment, a few list members somehow construed that as a crusade against
him in particular. If anyone still has that misapprehension, it is WRONG. Plain
and simple. I did not and do not single him out. And, I'd be more than happy to
credit him with being the first author to address this issue!

"FWIW:  I agree.  You bring up valid issues with respect to the
map limitations."

Thank you. That's my only intent, to ask how we can better address limitations
and improve the system. As I've said often before, I'm well aware that many
people have contributed generously of their time and skills and I give them due
credit for that. I don't see that that should stop us from asking "can we do
still better?" and "advancing an art", as the amateur radio service is chartered
to do.

"...otherwise the user may
be unaware of the map limitations.  The important thing here is not
limiting liability for the developers ...but whether the software + maps could
get used in some manner that causes loss of life or property."

  Fully agreed! In this day and age liability is always an issue, but it is not
the issue here. A user has to pull teeth to find the source documents for the
TIGER maps and then wade through many pages to get any hint as to their limits
versus GPS positions. Odds are, they'll never know, but we do. So, how hard is
it to say "Oh, by the way...there's quicksand on that path, use the other one."

<<Rather than continue this debate, lets all focus on one thing
that is simple to accomplish and see if authors will step up
and consider implementing it.>>

<<1) As maps zoom, below the point where the ICON is smaller
than the ambiguity, please let the ICON begin to expand
at the same rate as the zoom.  THis is so that the viewer
is never misslead to an accuracy better than is available.
2) Provide on the map display, a range scale or some other
legend that gives the user a clue as to the scale ...>>

There's probably even a way to combine the icon size and the scale indication,
or link them, so that the icon itself serves as a scale indicator on the map.
Maybe to have a scale comment that is linked to the icon data, so it says
something like:

"Icon size represents position uncertainty of XX meters"

If there are a limited number of range scales, the programming for this probably
could be a simple look-up table that supplies the scale comment, and the icon,
as a matched set when each range was selected. (That's may not be elegant but it
should be simple to do.)

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