[mapguide-users] GDAL Provider and Image Catalogs?

[Andy Morsell]

Hi,
This is mostly directed at Frank and other FDO folks.  I am needing to
implement MGOS for a client using some publicly available aerial photos
which we plan to expose via base layers and then pre-render via a tile
rendering script.  In this case, there are approximately 1300 MrSID images
that make up a County worth of data.  The maximum image size is 3 MB.  When
defining a data connection using the GDAL FDO provider that points to this
folder, I do not have favorable results.  I can repeatedly get MapGuide
Server to crash while this layer is rendered and the crashes occur during
the GDAL reads of the images, but never while reading the same image and
never with very meaningful debug information.  This is using MGOS 1.1.0 and
FDO 3.1 since 1.2.0 beta 1 currently does not work with the single threaded
GDAL provider.  Along those lines, it's a shame to see a quad processor
server utilizing only 25% of its potential horsepower because of single
threading..

While watching what is happening while running MapGuide Server in
interactive and debug mode, it is apparent that the GDAL provider tries to
open every image in the data connection folder for each map render.  This
happens even if the current view is zoomed to a level where only 4 images
need to be opened.  This is obviously very inefficient and probably part of
the crashing problem.  A solution to this would be to use an image tile
catalog index so that only the images needed for the view are accessed.

I see that there was some talk on this subject, mostly in the FDO mailing
list, back in January.  But, has this moved forward at all and can we expect
to see image catalogs supported by they GDAL provider in the near future?
If so, when?

By the way, I started using FWTools to attempt to mosaic these images, but
quickly discovered that a resultant Erdas image would have been in the 200
GB range.

Thanks for any insight into these matters.

Andy Morsell, P.E.
Spatial Integrators, Inc.
http://www.SpatialGIS.com

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