[Xastir] Map rendering anomaly?

[Tom Russo]

On Sat, Jul 21, 2007 at 11:43:42AM -0400, we recorded a bogon-computron collision of the <rtg at aapsc.com> flavor, containing:
>  This morning, I found myself zooming out so I could identify a point on the 
>  other side of the world.  (xastir is so much more convenient than my old 
>  world atlas!)
>    When I zoomed out, however, I found that the tigermap.geo data was quite 
>  distorted when overlayed with the flat mercator projection of worldhi.map

Yes.  This is well known, and is a result of the sinusoidal projection used by
the tigermap server.  What's actually happening is that the image is in 
a different coordinate system than the one that Xastir uses, but Xastir
plunks it down on the screen as if registering the corner points is 
sufficient.  It isn't.

There is nothing to be done about it, shy of not using tigermap.geo to view
large areas.  The TIGER/Line shapefiles are not subject to this problem.

I have no idea why the folks who wrote the tigermap server chose to use
the sinusoidal projection, but without significant recoding effort in xastir
(to reproject the images) there's no way to get them to work at high zoom 
levels.

Note that the distortion you see is actually always present, but not 
as noticable at the close zoom levels.

-- 
Tom Russo    KM5VY   SAR502   DM64ux          http://www.swcp.com/~russo/
Tijeras, NM  QRPL#1592 K2#398  SOC#236 AHTB#1 http://kevan.org/brain.cgi?DDTNM
"And, isn't sanity really just a one-trick pony anyway? I mean all you get is
 one trick, rational thinking, but when you're good and crazy, oooh, oooh,
 oooh, the sky is the limit!"  --- The Tick