Provided by: grass-doc_6.4.3-3_all bug


       r.resamp.rst   -  Reinterpolates  and  optionally computes topographic analysis from input
       raster map to a new raster map (possibly  with  different  resolution)  using  regularized
       spline with tension and smoothing.


       raster, resample


       r.resamp.rst help
       r.resamp.rst  [-td]  input=name  ew_res=float ns_res=float  [elev=string]   [slope=string]
       [aspect=string]    [pcurv=string]    [tcurv=string]     [mcurv=string]     [smooth=string]
       [maskmap=string]    [overlap=integer]    [zmult=float]    [tension=float]    [theta=float]
       [scalex=float]   [--overwrite]  [--verbose]  [--quiet]

           Use dnorm independent tension

           Output partial derivatives instead of topographic parameters

           Allow output files to overwrite existing files

           Verbose module output

           Quiet module output

           Name of input raster map

           Desired east-west resolution

           Desired north-south resolution

           Output z-file (elevation) map

           Output slope map (or fx)

           Output aspect map (or fy)

           Output profile curvature map (or fxx)

           Output tangential curvature map (or fyy)

           Output mean curvature map (or fxy)

           Name of raster map containing smoothing

           Name of raster map to be used as mask

           Rows/columns overlap for segmentation
           Default: 3

           Multiplier for z-values
           Default: 1.0

           Spline tension value
           Default: 40.

           Anisotropy angle (in degrees)

           Anisotropy scaling factor


       r.resamp.rst reinterpolates the values a from given raster map  (named  input)  to  a  new
       raster  map  (named elev).  This module is intended for reinterpolation of continuous data
       to a different resolution rather than for  interpolation  from  scattered  data  (use  the*  modules for that purpose).  Reinterpolation (resampling) is done to higher, same
       or lower resolution specified by the ew_res and ns_res parameters.

       All resulting raster maps are created using the settings of the current region (which  may
       be different from that of the input raster map).

       Optionally,  and  simultaneously  with  interpolation, topographic parameters are computed
       from an input raster map containing z-values of elevation/depth:  slope,  aspect,  profile
       curvature (measured in the direction of steepest slope), tangential curvature (measured in
       the direction of a tangent to contour line) and/or mean curvature are  computed  from  and
       saved  as  raster  maps  as  specified  by  the options slope, aspect, pcurv, tcurv, mcurv

       If the -d flag is set the program outputs partial derivatives fx, fy, fxx,  fxy,  and  fyy
       instead of slope, aspect and curvatures.

       For noisy data it is possible to define spatially variable smoothing by providing a raster
       map named by the smooth  option  containing  smoothing  parameters.   With  the  smoothing
       parameter  set  to zero (smooth is not given or contains zero data), the resulting surface
       passes exactly through the data points.

       The user can also define a raster map (named with maskmap) which will be used as  a  mask.
       The interpolation is skipped for cells which have zero or NULL value in the mask.

       Zero values will be assigned to these cells in all output raster maps.

       The zmult parameter allows the user to rescale the z-values which may be useful, e.g., for
       transformation of elevations given in feet to meters, so that the proper values of  slopes
       and curvatures can be computed.  The default value is 1.

       A  regularized  spline  with  tension  method  is used for the interpolation.  The tension
       parameter tunes the character of the resulting surface from thin plate to membrane. Higher
       values  of  tension parameter reduce the overshoots that can appear in surfaces with rapid
       change of gradient.

       The -t flag can be set to use "dnorm independent tension".

       The interpolation is performed for overlapping rectangular segments.  The user can  define
       the width of overlap (in number of cells) with the overlap option. The default value is 3.


       r.resamp.rst  uses  regularized  spline  with  tension  for interpolation (as described in
       Mitasova and Mitas, 1993).

       The region is temporarily changed while writing  output  files  with  desired  resolution.
       Topographic parameters are computed in the same way as in the module. (See also
       Mitasova and Hofierka, 1993)

       The raster map used with the smooth option should contain variable  smoothing  parameters.
       These can be derived from errors, slope, etc. using the r.mapcalc module.

       The  program gives warning when significant overshoots appear and higher tension should be
       used. However, with tension set too high the resulting surface changes its behavior  to  a
       membrane  (rubber  sheet stretched over the data points resulting in a peak or pit in each
       given point and everywhere else the surface goes rapidly to trend). Smoothing can be  used
       to  reduce  the  overshoots. When overshoots occur the resulting elev file will have white
       color in the locations of overshoots since the color table for the output file is the same
       as colortable for raster input file.

       The  program  checks  the numerical stability of the algorithm by computation of values at
       given points, and prints the maximum difference found into the history file of raster  map
       elev  (view  with   An  increase  in  tension  is suggested if the difference is
       unacceptable.  For computations with smoothing set to 0 this difference should be 0.  With
       a  smoothing parameter greater than zero the surface will not pass through the data points
       exactly, and the higher the parameter the closer the surface will be to the trend.

       The program writes the values of parameters used in computation into the comment  part  of
       the elev map history file. Additionally the following values are also written to assist in
       the evaluation of results and choosing of suitable parameters:

                     minimum and maximum z values in the data file (zmin_data, zmax_data) and  in
                     the interpolated raster map (zmin_int, zmax_int),

                     maximum  difference  between  the  given and interpolated z value at a given
                     point (errtotal),

                     rescaling parameter used for normalization  (dnorm),  which  influences  the

       The program gives a warning when the user wants to interpolate outside the region given by
       the input raster map's header data.  Zooming  into  the  area  where  the  points  are  is
       suggested in this case.

       When  a  mask  is used, the program uses all points in the given region for interpolation,
       including those in the area which is masked out, to ensure proper interpolation along  the
       border  of the mask. It therefore does not mask out the data points; if this is desirable,
       it must be done outside r.resamp.rst before processing.


       g.region,, r.resample, r.mapcalc,,


       Original version of program (in FORTRAN):
       Lubos Mitas, NCSA, University of Illinois at Urbana Champaign, Il
       Helena Mitasova, US Army CERL, Champaign, Illinois

       Modified program (translated to C, adapted for GRASS , segmentation procedure):
       Irina Kosinovsky, US Army CERL.
       Dave Gerdes, US Army CERL.


       Mitas, L., Mitasova, H., 1999, Spatial Interpolation. In: P.Longley, M.F.  Goodchild, D.J.
       Maguire,  D.W.Rhind  (Eds.),  Geographical  Information  Systems:  Principles, Techniques,
       Management and Applications, Wiley, 481-492.

       Mitasova, H. and Mitas, L., 1993. Interpolation by regularized  spline  with  tension:  I.
       Theory and implementation, Mathematical Geology No.25 p.641-656.

       Mitasova, H. and Hofierka, L., 1993. Interpolation by regularized spline with tension: II.
       Application to terrain modeling and surface geometry analysis, Mathematical Geology  No.25

       Talmi,  A.  and  Gilat,  G.,  1977.  Method  for  smooth approximation of data, Journal of
       Computational Physics , 23, pp 93-123.

       Wahba, G., 1990. Spline models for observational data, CNMS-NSF Regional Conference series
       in applied mathematics, 59, SIAM, Philadelphia, Pennsylvania.

       Last changed: $Date: 2008-05-16 12:09:06 -0700 (Fri, 16 May 2008) $

       Full index

       © 2003-2013 GRASS Development Team