[fdo-internals] Raster Catalogs (aka Tileindexes)

[Greg Boone]

Hi All,

The FDO team faces a similar issue with the ATIL based raster provider
found in the MapGuide Enterprise release. At this time we are planning
to fix this issue for the next release of MapGuide Enterprise. I would
hope that we could find a solution that is common to both the ATIL based
and GDAL based providers.

The current proposal advocates that the ATIL Raster provider's XML
configuration document be updated to include the bounds of the
referenced raster images. Along with this change would come an
associated change to the API that controls the creation and access of
the XML configuration document. These additional 'bounds' definitions
would be used by the provider to filter the list of initial raster
images based on a spatial filter supplied by the user in an FDO select
command. Once the selection set of raster images has been determined,
the raster provider will directly access the images and extract the
geo-reference information to determine which images to return to the
client application.

Since the ATIL and GDAL overrides API and configuration documents are
virtually identical, a common approach could be agreed on for both
providers.

Please find the proposal attached. Comments and feedback are welcome.

Greg

-----Original Message-----
From: fdo-internals-bounces at lists.osgeo.org
[mailto:fdo-internals-bounces at lists.osgeo.org] On Behalf Of Frank
Warmerdam (External)
Sent: Wednesday, January 24, 2007 10:43 PM
To: FDO Internals Mail List
Cc: Jason Birch
Subject: [fdo-internals] Raster Catalogs (aka Tileindexes)

Folks,

Jason Birch and I are interested in some mechanism to support raster
catalogs (or tileindexes in mapserver-speak) for the GDAL raster
provider.
That is a way of listing a whole bunch of files, along with their
spatial
footprint in a single catalog so that the raster provider only has to
actually
open the files of interest for the current request.

Does such a thing exist for the other (ATIL based) raster provider?

Is there a standard scheme suggested for implementing such a thing?

My thinking was that it should be possible to use any FDO feature source
as the catalog and that the catalog would primarily devolve down to two
things.

   - A column with the filename for the raster (possibly a relative
path)
   - A polygon geometry with is the footprint of the raster.

The already existing "gdaltindex" utility can create shapefiles in this
form for a set of rasters.  I'd suggest just hardcoding things to use
shapefiles, but I suspect some people will want to use more
sophisticated
raster catalogs in an RDBMS and it just doesn't seem like the right
FDO way of doing things.

As long as we come up with a scheme that isn't too complicated, I'm
happy
to implement it for the GDAL based raster provider.

Best regards,
-- 
---------------------------------------+--------------------------------
------
I set the clouds in motion - turn up   | Frank Warmerdam,
warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | President OSGeo,
http://osgeo.org

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