[gdal-dev] gdalwarp with the -tps option -performance issues

[Buchheit, Maximilian]

When you use "gdalwarp -tps" what is the practical limit to the number of GCPs useable in the thin plate spline algorithm before the program bogs down.
I would like to use it  with  over 1600 spline knots spread over the image.
Currently on a X86_64 smp linux system with 4 cores and 8 cpus and "-multi" turned on,  1600 knots takes about 30 min.  As far as I can gather from experimenting with the  # of knots, most of this time is spent with either solving for the spline weights or generating the spline kernel.
 
Who can shed some light on what is going on under the hood here?  Is the spline kernel being calculated on-the-fly for every pixel in the image? What method of solving for the weights is being used, and can it handle very large sparse matrices?
 
Thanks,
   Max
 
------------------
Max Buchheit
Canada Centre for Remote Sensing / Centre Canadien de Télédétection
Earth Sciences Sector / Secteur des Sciences de la Terre
Natural Resources Canada / Ressources Naturelles Canada
4th Floor, 588 Booth Street /  4-ieme étage, 588 rue Booth
Ottawa, Ontario, K1A 0Y7
Phone: (613) 943-7444/ Email: mbuchhei at nrcan.gc.ca

 

 
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