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]
15       [--verbose]  [--quiet]
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17   Flags:
18       --overwrite
19           Allow output files to overwrite existing files
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21       --verbose
22           Verbose module output
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24       --quiet
25           Quiet module output
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27   Parameters:
28       input=name
29           Name of input raster map
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31       output=name
32           Name for output raster map
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34       npoints=count
35           Number of interpolation points
36           Default: 12
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DESCRIPTION

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

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

76       r.surf.contour,  r.surf.idw,  r.surf.gauss, r.surf.fractal, r.surf.ran‐
77       dom, r.surf.idw2, v.surf.rst
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AUTHOR

80       Michael Shapiro, U.S.Army Construction Engineering Research Laboratory
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82       Last changed: $Date: 2006-04-13 21:01:38 +0200 (Thu, 13 Apr 2006) $
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84       Full index
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86       © 2003-2008 GRASS Development Team
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90GRASS 6.3.0                                                     r.surf.idw2(1)
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