Selon Andrea Peri <[email protected]>: > Hi, > I have a huge set of tiffs rasters. > Any single tiff is a geotiff tiled (256x256) and as an internal overview. > > To can use this raster dataset to lower scales (full extension) I need to > create a single simplified tiff raster of all this dataset. > Now I need to create a single simplified tiff raster . > > I don't know how is the better way to produce this simplified raster. > This because the original huge set of rasters are about 2 TB. Every raster > is about 15000 x 15000 px. > > SO I start creating a catalog named "cat_fogli.vrt" using gdalbuildvrt. > And after this was create, I tryed to produce an external overview of this > catalog. > using this command: > > gdaladdo -r average -ro --config BIGTIFF_OVERVIEW YES cat_fogli.vrt 256 512 > 1024 2048 4096 > > Unfortunately gdaladdo seem to be lock. It is take really many time and is > always on 0%. > > I don't know if is only a bug time due to the huge size of original raster > dataset or I'm using the wrong way.
I might not be surprised that it would really take a lot of time. You might want to increase significatively the block cache to hopefully speed up things. You can do that by specifying --config GDAL_CACHEMAX some_value_in_megabytes. See http://trac.osgeo.org/gdal/wiki/ConfigOptions#GDAL_CACHEMAX for more details. Note that if you want to use more than 2 gigabytes of RAM, you need a 64-bit build of GDAL. Another factor which might explain the slowness is the value of 256 as the first overview level, which is really a huge value. Computing a block of 256x256 of that level requires processing 65536x65536 pixels of the base image ! So I would recommand specifying much lower values before reaching 256. For example 4 16 64. I'm also skeptical on the fact that computing such huge overview levels will lead to a visually acceptable result. Sometimes you want to use other source of data than the high resolution data when displaying low resolution overviews. (Ah, and using gdaltindex will not help for your use case. gdaltindex output is only used by MapServer AFAIK.) Best regards, Even _______________________________________________ gdal-dev mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/gdal-dev
