[Gdal-dev] GeoQuadTree - an open format for storinggeoreferencedimages

Ed McNierney ed at topozone.com
Tue Nov 14 15:35:35 EST 2006

Jordi -
You said you wanted to "avoid the use of tile indexes or catalogues of
images", but isn't that exactly what your XML catalogue/index does?  It
seems that the GeoQuadTree format is a different form of that same sort
of structure.  There are several different ways of doing this now,
including the TILEINDEX mechanism, tiled TIFF files, etc.  I'm sure
there are limitations to each, but I'm not sure that yet another tiling
scheme will help.
In particular, PNG is not the best format for all images, and it's
important to support other encoding mechanisms, especially JPEG.
Photographic images are huge when stored in PNG format, and JPEG is
usually a much better choice.  Conversely, scanned line art and
synthetic images generally compress and store better as PNG images.
    - Ed
Ed McNierney
President and Chief Mapmaker
TopoZone.com / Maps a la carte, Inc.
73 Princeton Street, Suite 305
North Chelmsford, MA  01863
ed at topozone.com
(978) 251-4242 


From: gdal-dev-bounces at lists.maptools.org
[mailto:gdal-dev-bounces at lists.maptools.org] On Behalf Of Brent Fraser
Sent: Tuesday, November 14, 2006 3:05 PM
To: Jordi Gilabert Vall; gdal-dev at lists.maptools.org
Subject: Re: [Gdal-dev] GeoQuadTree - an open format for

For those interested tiling,
  There is similar tiling related discussion/work going on at:
<http://lists.eogeo.org/mailman/listinfo/tiling>  (do they have a web
            http://www.stereofx.org/terrain.html, implemented in
http://vterrain.org/, particularly VTBuilder
Brent Fraser

	----- Original Message ----- 
	From: Jordi Gilabert Vall <mailto:jordi at geoquadtree.org>  
	To: gdal-dev at lists.maptools.org 
	Sent: Tuesday, November 14, 2006 3:25 AM
	Subject: [Gdal-dev] GeoQuadTree - an open format for storing

	Some time ago I needed the retrieval from very large
georeferenced raster images in a OGC WMS server, and I wanted to avoid
the use of tile indexes or catalogues of images, neither a database. I
started thinking of an open format for storing arbitrarily large
georeferenced images. I named this format "GeoQuadTree", as it would be
based on a quadtree of rectangular tiles, each in PNG format on the
filesystem, in a simple hierarchical structure of folders. I wrote a
command line utility for creating it, importing from PNG/JPEG/TIFF and
exporting to PNG/JPEG/TIFF/GDAL. I also wrote a GDAL driver for this
format. I tested successfully with my own WMS server software, and on
MapServer compiled with GDAL support. It worked very well on Blue Marble
Next Generation at a resolution of 15 arc-seconds, i.e. 86400x43200

	You can find more information on the project web site:


	I'm testing the release 1.0.0, you can test it on the subversion
repository if you want (I haven't packaged it yet).

	I think it's a useful format, open, very easy to use, and very
efficient (in terms of response time).

	Do you think it could be useful for you ? Would you like to
include it on GDAL's next release ?

	jordi at geoquadtree org



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