NAME

       r.surf.idw2  - Surface generation program.

KEYWORDS

       raster, interpolation

SYNOPSIS

       r.surf.idw2
       r.surf.idw2 help
       r.surf.idw2 input=name output=name  [npoints=count]   [--overwrite]  [--verbose]  [--quiet]

   Flags:
       --overwrite
           Allow output files to overwrite existing files

       --verbose
           Verbose module output

       --quiet
           Quiet module output

   Parameters:
       input=name
           Name of input raster map

       output=name
           Name for output raster map

       npoints=count
           Number of interpolation points
           Default: 12

DESCRIPTION

       r.surf.idw2  fills  a  raster  matrix with interpolated values generated from a set of irregularly spaced
       data points using numerical approximation (weighted averaging) techniques.  The interpolated value  of  a
       cell  is determined by values of nearby data points and the distance of the cell from those input points.
       In comparison with other methods, numerical approximation allows representation of more complex  surfaces
       (particularly  those  with  anomalous  features),  restricts  the  spatial  influence  of any errors, and
       generates the interpolated surface from the data points.  It is the most appropriate method to  apply  to
       most  spatial  data.   The  npoints parameter defines the number of points to use for interpolation.  The
       default is to use the 12 nearest points when interpolating the value for a particular cell.

NOTES

       The amount of memory used by this program is related to the number of non-zero data values in  the  input
       map  layer.   If the input raster map layer is very dense (i.e., contains many non-zero data points), the
       program may not be able to get all the memory it needs from the system.  The  time  required  to  execute
       increases with the number of input data points.

       If  the  user  has a mask set, then interpolation is only done for those cells that fall within the mask.
       However, all non-zero data points in the input layer are used even if they fall outside the mask.

       This program does not work with latitude/longitude data bases.  Another surface generation program, named
       r.surf.idw, should be used with latitude/longitude data bases.

       The user should refer to the manual entries for
       r.surf.idw
       r.surf.contour
       v.surf.rst
       to compare this surface generation program with others available in GRASS.

SEE ALSO

       r.surf.contour, r.surf.idw, r.surf.gauss, r.surf.fractal, r.surf.random, r.surf.idw2, v.surf.rst

AUTHOR

       Michael Shapiro, U.S.Army Construction Engineering Research Laboratory

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

       Full index

       © 2003-2013 GRASS Development Team

GRASS 6.4.3                                                                                  r.surf.idw2(1grass)