Hi Jan, That sounds interesting and promising.
For the mentioned file it takes about 2 minutes with "-et 5" (low accuracy), and 12 minutes without this switch. Without -tps it takes less than 0.5 seconds.
The machine is quite decent with 16 GB memory and SSD disk. Best regards from Knut-Frode On 12. des. 2012 13:24, Jan Hartmann wrote:
Hi Knut, What do you mean by "very slow"? I regularly use gdalwarp -tps on much larger rasters with a few thousand gcp-s, and never noticed unacceptable delays. Do you have very little physical memory, or many parallel processes running? Jan On 12/12/2012 01:12 PM, Knut-Frode Dagestad wrote:Hi list, When warping images with many GCPs, the -tps switch (Thin Plate Spline) is found to be necessary to get decent accuracy. This makes however warping very slow. The only method I found to increase speed is the -et switch, but at cost of spatial accuracy. Below some comments about the other tries which did not help: - compiling GDAL with armadillo support had no effect on speed. Btw, to compile with armadillo I had to manually insert -llapack in the following line in configure: if test -z "`${CXX} testarmadillo.cpp -o testarmadillo -larmadillo 2>&1`" ; then ..... Perhaps ${LIBS} should be added permanently to this line in trunk? - compiling GDAL with OpenCL had also no effect. At first surprising, but looking at the opencl warp kernel it seems that it only makes a difference for other resampling algorithms than nearest neighbour? - Increasing memory with -wm had no effect - Using several threads (-multi -wo NUM_THREADS=ALL_CPUS) actually increased computing time significantly (my proj version is 4.7.1). From the debug output, a lot of the time is apparently spent on: "WARP: Copying metadata from first source to destination dataset" Is this an indication that much time is simply spent on reading and writing the GCPs to/from file? If so, we could perhaps expect improved performance if Geolocation Arrays could be used instead (not possible due to http://trac.osgeo.org/gdal/ticket/4907). The tests are made with the following file and command on Ubuntu: http://dl.dropbox.com/u/15885758/testgcp.tif (3212 GCPs and 2048x2511 pixels covering Southern Europe) time gdalwarp --debug on -et 5 -tps -t_srs '+proj=merc' testgcp.tif out.tif (+ other swithces mentioned above) Best regards from Knut-Frode _______________________________________________ gdal-dev mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/gdal-dev_______________________________________________ gdal-dev mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/gdal-dev
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