On Fri, Aug 6, 2010 at 11:34 AM, Jason Beverage <jasonbever...@gmail.com> wrote: > Hi all, > > I have quite a few MrSid files that are in UTM that I want to mosaic > together into some epsg:4326 tiles. I've written some python scripts > to produce the appropriate gdal_warp commands to create the tiles, but > they are running extremely slow. > > I've read various mailing list posts and blogs about different options > for MrSid like this one: > http://priour.wordpress.com/2007/01/09/massive-performance-improvements-in-converting-mrsid-files/ > which highlights using GDAL_FORCE_CACHING = YES to speed up a > gdal_translate when using MrSids. I've also read about using > GDAL_ONE_BIG_READREAD to speed things up in MapServer. Which option, > or any other options, would be helpful for gdal_warp?
Jason, Generally speaking gdalwarp tries to read in big chunks, and it would be beneficial to enable GDAL_ONE_BIG_READ to on and avoid caching. Caching is more beneficial when doing lots of little reads. > Also, my MrSids are wrapped in VRTs to provide coordinate system info. > If I use the VRTs will the GDAL_FORCE_CACHING and GDAL_ONE_BIGREAD > options be used? When access is done through a VRT it forces access at a smaller chunk size which can be at least somewhat painful for formats like mrsid for which each read is quite expensive. You might want to consider ways of associating the coordinate system without using the VRT. Note that gdalwarp does have a -s_srs switch to set the source coordinate system if it is missing or wrong on the source file. Best regards, -- ---------------------------------------+-------------------------------------- I set the clouds in motion - turn up | Frank Warmerdam, warmer...@pobox.com light and sound - activate the windows | http://pobox.com/~warmerdam and watch the world go round - Rush | Geospatial Programmer for Rent _______________________________________________ gdal-dev mailing list gdal-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/gdal-dev
