[Gdal-dev] GDAL data model, caching, GDALProjDef

Ed McNierney ed at topozone.com
Sun Feb 16 14:53:32 EST 2003

Derrick -

I have some relevant experience, having collar-clipped over 60,000 USGS
quads <g>.  There are a few commercial tools out there that will do it
for you.  We used to use the GeoTransform DLL from Blue Marble
Geographics (www.bluemarblegeo.com) built into our own application, but
it appears that product is no longer available.  They do offer a
GeoTransformer application that will do the collar-clipping.  Peak
Geo-Systems offers the QuadCompanion Pro package that seems to do the
same sort of thing at the application level (www.colorview-peak.com).
Both are, I think, Windows-only apps.

Clipping the collars is trickier than it might appear.  I'm not sure
what you mean by "the problem with images that fall at the center of the
UTM zone" is, but the Blue Marble tools have a long-reported and unfixed
bug with those quads (they clip to the bounding rectangle formed by the
projected four corners of the ROI, which clips off the middle of
southern edge of the DRG).  You also need to remember that the datum of
the latitude / longitude bounding box for the DRG may NOT be the same as
the datum of the DRG itself.  The USGS, TVA, and Teale metadata that
describes the bounding box is also often quite buggy, so you need to
check your results carefully.

If you don't care about the tools, but simply want to produce some
collar-clipped USGS DRGs, I've got plenty.  Contact me off-list and I'll
see if we can help.

	- Ed

Ed McNierney
President and Chief Mapmaker
TopoZone.com / Maps a la carte, Inc.
73 Princeton Street, Suite 305
North Chelmsford, MA  01863
Phone: (978) 251-4242  Fax: (978) 251-1396
ed at topozone.com

-----Original Message-----
From: Derrick J Brashear [mailto:shadow at dementia.org] 
Sent: Sunday, February 16, 2003 2:30 PM
To: gdal-dev at remotesensing.org
Subject: RE: [Gdal-dev] GDAL data model, caching, GDALProjDef

On Sun, 16 Feb 2003, Ed McNierney wrote:

> Derrick -
> 1) No, you'll need to do that externally.  If you can give me some
> about what kind of images you're working with, I'll try to make
> suggestions.

Everything I want to decollar are USGS quads. I'm willing to forgo
decollaring the 1:250k images to avoid the problem with the images that
fall at the center of the UTM zone if I have to, and just deal with
and 1:100k images. 

> 2) I never noticed the "viewer" subdirectory before <g>.  It's there
> CVS but not in the distribution - the code looks pretty old.  There
> lots of viewers out there - what kind of data are you trying to view?

It's not that I'm trying to view data, it's that I wanted to point
who has a raster viewer now at a simple GDAL (presumably raster) viewer
illustrate that it's not a big deal to integrate GDAL support. Basically
taking a section of image through the GDAL api and blatting it to a
displayed canvas. 

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