1r.surf.idw2(1)                Grass User's Manual               r.surf.idw2(1)
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NAME

6       r.surf.idw2  - Surface generation program.
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KEYWORDS

9       raster
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SYNOPSIS

12       r.surf.idw2
13       r.surf.idw2 help
14       r.surf.idw2 input=name output=name  [npoints=count]   [--overwrite]
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16   Flags:
17       --overwrite
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19   Parameters:
20       input=name
21           Name of input raster map
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23       output=name
24           Name for output raster map
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26       npoints=count
27           Number of interpolation points Default: 12
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DESCRIPTION

30       r.surf.idw2  fills  a  raster matrix with interpolated values generated
31       from a set of irregularly spaced data points using numerical approxima‐
32       tion (weighted averaging) techniques.  The interpolated value of a cell
33       is determined by values of nearby data points and the distance  of  the
34       cell from those input points.  In comparison with other methods, numer‐
35       ical approximation allows representation of more complex surfaces (par‐
36       ticularly  those with anomalous features), restricts the spatial influ‐
37       ence of any errors, and generates the  interpolated  surface  from  the
38       data  points.   It is the most appropriate method to apply to most spa‐
39       tial data.  The npoints parameter defines the number of points  to  use
40       for  interpolation.   The  default is to use the 12 nearest points when
41       interpolating the value for a particular cell.
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NOTES

44       The amount of memory used by this program is related to the  number  of
45       non-zero  data  values in the input map layer.  If the input raster map
46       layer is very dense (i.e., contains many  non-zero  data  points),  the
47       program may not be able to get all the memory it needs from the system.
48       The time required to execute increases with the number  of  input  data
49       points.
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51       If  the  user has a mask set, then interpolation is only done for those
52       cells that fall within the mask.  However, all non-zero data points  in
53       the input layer are used even if they fall outside the mask.
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55       This program does not work with latitude/longitude data bases.  Another
56       surface generation program, named r.surf.idw, should be used with lati‐
57       tude/longitude data bases.
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59       The user should refer to the manual entries for
60       r.surf.idw
61       r.surf.contour
62       v.surf.rst
63       to  compare  this  surface  generation program with others available in
64       GRASS.
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SEE ALSO

67       r.surf.contour, r.surf.idw, r.surf.gauss,  r.surf.fractal,  r.surf.ran‐
68       dom, r.surf.idw2, v.surf.rst
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AUTHOR

71       Michael Shapiro, U.S.Army Construction Engineering Research Laboratory
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73       Last changed: $Date: 2006/04/13 19:01:38 $
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75       Full index
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79GRASS 6.2.2                                                     r.surf.idw2(1)
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