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[aprssig] Re: TIGER maps what-s the problem?

Curt, WE7U archer at eskimo.com
Tue Jun 13 15:32:26 UTC 2006


On Tue, 13 Jun 2006, Tom Russo wrote:

> And for regular uncompressed posits, there's something like a 60 foot
> resolution just because of the limits of the transmitted data.  If zoomed in
> to the point that the icon/symbol/pinprick is substantially smaller than 60
> feet on the map, it would be reasonable to display a 60 foot circle or
> rectangle instead, even for a posit with no deliberate ambiguity.  A similar
> argument can be made for compressed posits with their extra digit or so of
> precision, and !DAO! posits. (FWIW, Xastir is as guilty as the next program
> on this bit, but it wouldn't take much to fix just by having an extra piece of
> data stored with the station record ("how many digits of precision did we
> decode from the packet's position fields?") and drawing a circle around the
> station marker if that circle would be big enough to be visible)  This, again,
> is all that Bob said.


> All of this is completely independent of the precision of the underlying
> map data (which Bob never mentioned), and dependent only on the number of
> digits of position that come in and how zoomed in the map is, which the
> programmer of the APRS application certainly *DOES* have access to.

Correct (Like I ever stand a chance of correcting Tom?).

I got an evil glint in my eye while reading the above...  I think we
_should_ capture that data in Xastir and use it to "obscure" the
plotted position as one zooms in.  It would make the advantages of
Base-91 and OpenTrac positions that much more evident!

All those running Mic-E protocol or standard APRS-format packets
would only be able to see their position down to roughly 60 feet.

Base-91 positions would capable of showing down to 2 or 3 feet
(OpenTrac much better yet), capable of displaying the accuracy of
non-SA/WAAS/DGPS-corrected GPS positions.  ;-)

--
Curt, WE7U.   APRS Client Comparisons: http://www.eskimo.com/~archer
"Lotto:    A tax on people who are bad at math." -- unknown
"Windows:  Microsoft's tax on computer illiterates." -- WE7U
"The world DOES revolve around me:  I picked the coordinate system!"




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