[aprssig] Re: TIGER maps what-s the problem?
archer at eskimo.com
Tue Jun 13 10:32:26 CDT 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!"
More information about the aprssig