[fdo-internals] Raster Catalogs (aka Tileindexes)
traian.stanev at autodesk.com
Wed Jan 24 22:28:22 EST 2007
Here my thoughts on this. A raster catalog does not need to be exposed at the API level. For example, one way to do this would be to "connect" the raster provider to a directory containing a large number of rasters. Internally, the provider could index these in whatever way it wants.
I would personally use an SDF file for the spatial index -- like you say, insert a polygon corresponding to the bounds of the raster and use the raster name (or index) as ID property. An SHP file will probably work fine too, I've seen lots of raster catalogs stored in shp files before.
One thing I always wondered is whether it's worth it to persist the index into a file or is it easier to initialize it the first time an FDO connection is opened and then keep it in memory until the connection is closed. Given that FDO connections remain open for a while, it seems like keeping it in memory is not such a bad idea, and avoids the trouble of dealing with an index file.
From: fdo-internals-bounces at lists.osgeo.org on behalf of Frank Warmerdam (External)
Sent: Wed 1/24/2007 10:42 PM
To: FDO Internals Mail List
Cc: Jason Birch
Subject: [fdo-internals] Raster Catalogs (aka Tileindexes)
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
- 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.
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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