Dear list, Im using the gdalwarp command-line utility on Windows and im running into some strange behavior. When reprojecting a large global grid to a subset, the output filesize is way too large. Its a lot larger than xsize*ysize*datatype, and when pulling the file through gdal_translate shrinks the filesize to normal proportions. This occurs only when i run gdalwarp with "COMPRESSION=PACKBITS", with no compression the results from gdalwarp seem fine.
The GDAL version im using is: GDAL 1.9.1, released 2012/05/16 I can reproduce the problem with the following example data: The GMTED elevation dataset from the USGS, which can be found at: http://topotools.cr.usgs.gov/GMTED_viewer/gmted2010_global_grids.php The "Mean Statistic, 30 arc-seconds" is about 270MB. The effect is much more prominent with the 7.5 arc second file, which is about 3.1 GB! The data is delivered as an Arc/Info Binary Grid. I have tested it with several projections and different regions, for example the United States, reprojecting with gdalwarp like this: gdalwarp -ot Float32 -co "COMPRESS=PACKBITS" -r bilinear -t_srs "+proj=lcc +lat_1=20 +lat_2=60 +lat_0=40 +lon_0=-96 +x_0=0 +y_0=0 +ellps=GRS80 +datum=NAD83 +units=m +no_defs" -ts 10400 5800 -te -2600000 -1600000 2600000 1300000 hdr.adf GMTED.tif After gdalwarp the output is 401 MB, for a float32, i would expect an upper limit of about 10400*5800*4 = 230MB. When running gdal_translate with no compression and no other settings whatsoever the file size reduces to 235MB, which seems ok. With packbits compression it reduces further to 154MB. So for the 30 arc second dataset, the initial gdalwarp result is about 2.5 times to large. When using the higher resolution 7.5 arc second input (but otherwise the same procedure), the file sizes are: after gdalwarp with packbits: 626MB after gdal_translate: 235MB after gdal_translate with packbits: 154MB Making the gdalwarp result 4 times 'too large'. The effect seems larger with the higher resolution input data, even with exactly the same output settings. I have also tried to first convert the Arc/Info binary grid to a Geotiff and then starting the entire procedure, this produces the same results. Has anyone else ever noticed this behavior? And is there something i can do to prevent it? Thanks in advance. Regards, Rutger -- View this message in context: http://osgeo-org.1560.n6.nabble.com/gdalwarp-with-packbits-compression-output-too-large-tp5001731.html Sent from the GDAL - Dev mailing list archive at Nabble.com. _______________________________________________ gdal-dev mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/gdal-dev
