[Xastir] vertical lines in hi-res geotiff orthophotography

[Tom Russo]

On Tue, Jan 18, 2011 at 01:20:01PM -0500, we recorded a bogon-computron collision of the <kevin at kevinratcliff.com> flavor, containing:
> On Tue, Jan 18, 2011 at 12:17 PM, Tom Russo <russo at bogodyn.org> wrote:
> > I would expect that this is a bug in the rendering method in Xastir, not
> > a system-dependent thing (so I doubt your fresh Fedora experiment will show
> > any improvement).
> 
> I did not get to my Fedora experiment yet. I did however realize that
> I made a mistake in my posting: it works fine (no vertical lines) on
> my Ubuntu 10.10 box. I thought I had tested it there, but apparently
> not, because it works now.

Gah.  Well, that's a hole in *that* theory (maybe not a fatal one).

> > Xastir draws rectangles for each pixel using XFillRectangle, and my guess is
> > that the place where it calculates the size of the rectangles is getting the
> > calculation just a tiny bit off. ?This is just a hunch, but most of the imagery
> > that has been used in Xastir so far is far lower resolution than these, and
> > it's entirely possible there's a numerical issue in the computation. ?At least,
> > that's what this sort of thing smells like to me just from your description.
> 
> I wonder if perhaps the screen size and resolution can contribute to
> this? The (working) Ubuntu 10.10 box has a 15" monitor running
> 1024x768. I will attach a widescreen monitor and see if anything
> changes.

May very well be what's going on, as the current viewport *is* part of the
computation.

Rather than moving monitors around, why not try running Xastir on one machine,
but have it display on the other.

  largemonitormachine> ssh -Y ubuntu1010machine
    ubuntu1010machine> xastir

where "largemonitormachine>" means run in a terminal on the machine with the
large monitor, and "ubuntu1010machine" is whatever machine you've got that
has the Xastir with no display issues.  By doing this, the version running on 
the Ubuntu 10.10 will pop its window up onto the machine with the big monitor.
If it's a screen resolution or window size thing, you should be able to explore
without having to move hardware around.

Or you could just move hardware around.

> > I'd like to look into it, but it would help tremendously if you would tell me
> > exactly which imagery file you're looking at, say the one with the
> > SAR Training Center in it. ?Looks like the web site you provided has lots of
> > imagery files, and I'd rather download precisely the one that you're looking at.
> 
> I think this is a direct link to the file:
> http://spatialdata.iu.edu/DOQQS/local/atterbury/2010/tif/G8.zip
> 
> After downloading and unzipping, I ran rgb2pct.py with only the input
> and output filenames as parameters:

Thanks, I can do the rgb2pct thing myself, so no need to upload the file
elsewhere.

I won't have time to look at it until tonight, if then.  I've got a variety
of machines with different displays to test it on, so we'll see how it goes.

-- 
Tom Russo    KM5VY   SAR502   DM64ux          http://www.swcp.com/~russo/
Tijeras, NM  QRPL#1592 K2#398  SOC#236        http://kevan.org/brain.cgi?DDTNM
 "The truth will set you free, but first it will piss you off."