Hey Robin,
I would look into the GTI raster driver:
https://gdal.org/en/latest/programs/gdal_driver_gti_create.html#gdal-driver-gti-create
It creates a GPKG index of rasters for efficient access. Creating a GTI:
gdal driver gti create --resolution .0029,.0029 --output-layer dem30
ned10/cogs cogs.gti.gpkg
Using the new index:
gdal raster clip -i cogs.gti.gpkg --bbox -111,36,-110,37 --of COG -o
newCog.tif
QGIS will read the index as a vector file (since it's GPKG) displaying
bounding boxes for each raster in the index, but not as a raster as a whole.
Hope that helps!
On 9/1/26 06:33, Robin Wilson via gdal-dev wrote:
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.
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?
I’ve found --base-url in `gdal raster index` though I’m slightly
confused by the description of it ("Base URL for STAC-GeoParquet the
href property of the id property in a STAC-GeoParquet index.” - does
that do what I want and put a base URL in front of each file it finds?).
That option doesn’t seem to be present in `gdal driver gti create`
though, and seems like it may be STAC-GeoParquet specific.
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.
If there’s an alternative method I should be looking at for doing either
part of this (the clipping or the viewing in QGIS) then let me know -
I’m aware I may be pushing the boundaries of what can be sensibly done
with the GTI format.
Best regards,
Robin
Dr Robin Wilson
_______________________________________________
gdal-dev mailing list
[email protected]
https://lists.osgeo.org/mailman/listinfo/gdal-dev
_______________________________________________
gdal-dev mailing list
[email protected]
https://lists.osgeo.org/mailman/listinfo/gdal-dev
