This is a GRASS 5.0 version of a program for interpolation by regularized spline with tension. The original version was implemented in GRASS4.1 as s.surf.tps. This version has been rewritten (see DESCRIPTION) and numerous enhancements were added (see S_SURF_RST.html). Original program was written by Lubos Mitas and Helena Mitasova. GRASS4.1 implementation by Irina Kosinovsky and Dave Gerdes Rewriting to floating point was done by Irina Kosinovsky 1995 Modification for new site format was done by Darrell McCauley 1995 Various enhancements including spatially variable smoothing were added by Lubos and Helena, 1997 Also, normalization of z was removed, so neither smoothing nor z is normalized. You must have the floating point patches, the new sites API, the datetime API, and the TimeStamp patches to install these programs. The methods are described in (use these papers as references in your publications): Mitasova, H., and Mitas, L., 1993, Interpolation by Regularized Spline with Tension: I. Theory and implementation. Mathematical Geology, 25, 641-55. Mitasova, H., and Hofierka, L., 1993 Interpolation by Regularized Spline with Tension: II. Application to terrain modeling and surface geometry analysis. Mathematical Geology, 25, 657-69. Mitasova, H., Mitas, L., Brown, W.M., Gerdes, D.P., Kosinovsky, I., Baker, T., 1995, Modeling spatially and temporally distributed phenomena: New methods and tools for GRASS GIS. International Journal of Geographic Information Systems,9(4), 433-46.