Le 01/09/2026 à 15:33, Robin Wilson via gdal-dev a écrit :
Hi,
I have a lot of COGs hosted online in HTTP RANGE compatible storage. I
want to create a catalog/index of them so that GDAL and tools that use
GDAL (like QGIS) can extract the relevant data from the COGs for
specific areas. For example, I’d like to use `gdal raster clip` to
clip this big ‘virtual raster’ to a specific bbox or polygon. Ideally
I’d also like to be able to view the big raster on-the-fly in QGIS,
but I’m aware that may be more difficult. My tiles are ’true tiles’ in
that they tessellate properly and each location is in a single file.
I’ve been looking at the GDAL Tile Index format, but have been getting
a bit confused, and some things haven’t been working quite how I
expect. A few questions below:
1. Is there an easy way to generate a GDAL Tile Index file from a file
containing a list of remote URLs? I couldn’t find the right way to
specify a file containing URLs on the command line, so I ended up
writing a short Python script that loads the list of URLs from a file
and then passes them to gdal.TileIndex. Is that the best way to do
this? One disadvantage of this method is that I can’t seem to get a
progress bar to display.
see
https://github.com/OSGeo/gdal/blob/master/autotest/utilities/test_gdalalg_driver_gti_create.py
. The input argument can be a list of paths, local or remote (/vsis3/ etc)
you can use gdal.alg.vsi.list to get a list of remove /vsis3/ files
2. My current way of doing that requires GDAL loading the bbox of each
file by requesting it over the network, which is fairly slow, and I
have thousands of files to do this for. Is there a way to get the GTI
creation to use local files on my hard disk for getting the extent of
each file, but save the location as a /vsicurl/ URL to the remote file?
Not directly, but if you save in a .gpkg your GTI index, you can easily
patch the 'location' field from local paths to remote URLs
3. Once I’ve created the file, I can do `gdal raster clip` operations
on the command-line quite quickly, but if I load the GTI raster into
QGIS then QGIS just hangs. I hoped it would just request the relevant
COGs for the area I was looking at. I’ve tried loading it in by
dragging and dropping the .gti.gpkg file and then selecting the raster
in the layers popup, and also adding it via Add Layer->Raster and
putting ‘GTI:<path>’. I have a web map working which loads these COG
files on the fly depending on where you’re looking (using a minimal
STAC catalog in a JSON file) and was hoping to have the same thing
working in QGIS, without the effort of setting up something like
titiler or titiler-pgstac, as I’m currently managing to get away
without running any servers (as opposed to static data stores) for
this data.
QGIS will try to gather statistics, hence this can be slow. One way to
speed up is to have overviews defined in the GTI.
--
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