Quoted from:http://www.saga-gis.org/en/index.html

Creates a 'Thin Plate Spline' function for each grid point based on all of the scattered data points that are within a given distance. The number of points can be limited to a maximum number of closest points. References:- Donato G., Belongie S. (2002): 'Approximation Methods for Thin Plate Spline Mappings and Principal Warps', In Heyden, A., Sparr, G., Nielsen, M., Johansen, P. (Eds.): 'Computer Vision - ECCV 2002: 7th European Conference on Computer Vision, Copenhagen, Denmark, May 28-31, 2002', Proceedings, Part III, Lecture Notes in Computer Science. Springer-Verlag Heidelberg; pp.21-31.- Elonen, J. (2005): 'Thin Plate Spline editor - an example program in C++', http://elonen.iki.fi/code/tpsdemo/index.html.