Even Rouault <mailto:even.roua...@spatialys.com>
January 28, 2015 at 9:28 PM
Le mercredi 28 janvier 2015 20:17:08, Jorge Arévalo a écrit :
Hi,
I'm working with a patched version of gdal2tiles, which makes use of
parallelization:
http://gis.stackexchange.com/questions/7743/performance-of-google-map-tile-
creation-processes/74446#74446
I want to create a complete TMS cache from raster imagery. No
assumptions about SRS of data type for input data.
I want the tiling process to be as fast as possible (gdal2tiles is
really heavy process), do you have any recomendations about the data or
the parameters used?
Right now, I'm doing this
Step 1: build vrt from input images
gdal_vrtmerge.py -o merged.vrt<list of input tif files>
Step 2: build tiles from vrt file
gdal2tiles.py -r cubic -s epsg:XXXX -z 0-19 -w all merged.vrt tms_dir
Even with parallelization, process still feels really slow. Would it be
faster if, for example, I convert all my input files to epsg:3857? Or if
I scale them to 8-bit? Or if I use near resampling method instead of
cubic? (I'm using cubic because I'm working with continuous data:
satellite images, am I doing it right?).
From a quick look at the source, it seems that there's an optimization if the
input SRS == output SRS that avoids going through the warped VRT path.
That said, we definitely need one or several maintainers for gdal2tiles. There
are quite a faw patches floating around in Trac that would need someone to
review, test, fix, apply them, as well as writing tests (no autotest for
gdal2tiles yet), etc...
Ok. But the applications is taking hours to generate a complete tile
cache (zoom levels 0-19) for a 3MB tiff file, in epsg:3857. A 4 cores
machine with 8GB of RAM. The file is this one
https://dl.dropboxusercontent.com/u/6599273/gis_data/katrina-3857.tif
Taking so much time for a 3MB file sounds ridiculous. I'm probably doing
something wrong. This is the line
gdal2tiles.py -s epsg:3857 -z 0-19 -r cubic katrina-3857.tif tiles_dir
Do you see something wrong in this approach?
Anyway, if this is a problem of gdal2tiles and it needs fine tunning or
maintenance, we could talk. I don't know if there's any other method to
generate a complete TMS cache using GDAL.
Any other tips?
Many thanks in advance
Best regards
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