Hi all I am experiencing problems using a VRT dataset built from a large directory of .tif files.
While if a build the VRT from just one of these datasets, gdalwarp will work very fast with it, if I use the VRT will all of these images, it becomes undefinite times slower. Debugging the gdalwarp command, it seems that gdalwarp accesses every single raster composing the vrt datasource, even if that single raster is not within the extent defined by the -te gdalwarp option. Here is the output for a vrt composed by just one single .tif file: $ time gdalwarp -te -88.88 20.28 -87.88 21.28 single.vrt single.tiff ... Src=1344,4463,1201x1201 Dst=0,0,1200x1200 0...10...20...30...40...50...60...70...80...90...100 - done. GDAL: GDALClose(single.vrt, this=0x8ca6ef8) GDAL: GDALClose(/home/capooti/training/vrt/srtm_19_08.tif, this=0x8ca9aa8) GDAL: GDALClose(/home/capooti/training/vrt/srtm_19_08.tif, this=0x8ca7208) GDAL: GDALClose(single.tiff, this=0x8ca7e98) GDAL: In GDALDestroy - unloading GDAL shared library. real 0m0.137s user 0m0.076s sys 0m0.052s and here is the output for a vrt composed of all of the .tif files: capooti@ubuntu:~/training/vrt$ time gdalwarp -te -88.88 20.28 -87.88 21.28 all.vrt all.tiff ... Src=7344,16464,1201x1201 Dst=0,0,1200x1200 0...10...20...30...40...50...60...70...80...90...100 - done. GDAL: GDALClose(all.vrt, this=0x9d332b0) GDAL: GDALClose(/home/capooti/training/vrt/srtm_18_09.tif, this=0x9d46618) GDAL: GDALClose(/home/capooti/training/vrt/srtm_19_08.tif, this=0x9d467c8) ... GDAL: GDALClose(/home/capooti/training/vrt/srtm_35_09.tif, this=0x9d4c1b8) GDAL: GDALClose(/home/capooti/training/vrt/srtm_35_10.tif, this=0x9d4c3a8) GDAL: GDALClose(/home/capooti/training/vrt/srtm_19_08.tif, this=0x9d30800) GDAL: GDALClose(/home/capooti/training/vrt/srtm_35_11.tif, this=0x9d4c630) GDAL: GDALClose(all.tiff, this=0x9d33990) GDAL: In GDALDestroy - unloading GDAL shared library. real 61m12.130s user 0m6.076s sys 0m18.052s Any hint here to prevent gdalwarp to access the unneeded source raster files - the defined extent in -te should just hit a couple of ones? thanks in advance p -- Paolo Corti Geospatial software developer web: http://www.paolocorti.net twitter: @capooti skype: capooti
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