1r.bilinear(1) Grass User's Manual r.bilinear(1)
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6 r.bilinear - Bilinear interpolation utility for raster map layers.
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9 raster
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12 r.bilinear
13 r.bilinear help
14 r.bilinear input=name output=name [north=float] [east=float]
15 [--overwrite] [--verbose] [--quiet]
16 Flags:
18 --overwrite
19 Allow output files to overwrite existing files
20 --verbose
22 Verbose module output
23 --quiet
25 Quiet module output
26 Parameters:
28 input=name
29 Name of input raster map
30 output=name
32 Name for output raster map
33 north=float
35 Specific input value to be assigned to the north and/or south poles
36 for longitude-latitude grids
37 east=float
39 Specific input value to be assigned to the north and/or south poles
40 for longitude-latitude grids
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43 This module is deprecated and scheduled for demolition.
44 Please use "r.resamp.interp" instead. r.bilinear fills a grid cell
45 (raster) matrix with interpolated values generated from a set of input
46 layer data points. It uses the bilinear interpolation method, a simple
47 algorithm usually applied only to completely defined raster areas
48 (input data void of null data values). Here the values of 4 input
49 cells are used to define an interpolation function of constant gradient
50 within each rectangular area defined by the cell centers. User should
51 be aware that the gradient of the interpolation functions changes dis‐
52 continuously across lines intersecting the cell centers of the input
53 raster.
54 If there is a current working mask, it applies to the output raster
56 map. Only those cells falling within the mask will be assigned inter‐
57 polated values. The procedure for selection of input data will con‐
58 sider all input data relevant to interpolating values at the cell cen‐
59 ters of the current geographic region, ignoring the curent mask. Note
60 that cells of the output raster that cannot be bounded by 4 input cell
61 centers are set to null.
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64 The north and south parameters have been included to allow for specific
65 input values to be assigned to the north and/or south poles for longi‐
66 tude-latitude grids. These data, if included, are used to interpolate
67 values for cells that are north or south of a line intersecting the
68 cell centers of the first or last row of input, respectively. When
69 utilized, the interpolation procedure will be continuous from the north
70 and/or south boundary of the current geographic region. This option is
71 necessary, since the data structure defining a raster will not allow
72 for data to be assigned to a cell centered at 90N or 90S. By including
73 the option, the user can create output surfaces that are continuous
74 between the poles. The interpolation will be "wrap-around" from west
75 to east (across latitude) only if the input raster has an east edge
76 identical to its west edge.
77 For longitude-latitude databases, the interpolation algorithm is based
79 on degree fractions, not on the absolute distances between cell cen‐
80 ters. Any attempt to implement the latter would violate the integrity
81 of the interpolation method.
82 r.bilinear may be used in some instances as an alternative to the near‐
84 est neighbor approach inherent to r.resample. Note, however, that the
85 extent of non-null data area of the output raster must be less than
86 that of the input raster. The only exception to this occurs in the
87 case where the north and south parameters are utilized for longitude-
88 latitude rasters.
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91 r.surf.idw, r.surf.idw2, g.region, r.resample, r.resamp.interp,
92 r.resamp.stats
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95 Greg Koerper
96 ManTech Environmental Technology, Inc.
97 Global Climate Research Project
98 U.S. EPA Environmental Research Laboratory
99 Last changed: $Date: 2006-12-13 15:21:43 +0100 (Wed, 13 Dec 2006) $
101 Full index
103 © 2003-2008 GRASS Development Team
105GRASS 6.3.0 r.bilinear(1)