NAME¶
r.bilinear - Bilinear interpolation utility for raster map layers.
KEYWORDS¶
raster, resample
SYNOPSIS¶
r.bilinear
r.bilinear help
r.bilinear input=
name output=
name
[
north=
float] [
east=
float] [--
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
- north=float
-
Specific input value to be assigned to the north and/or south poles for
longitude-latitude grids
- east=float
-
Specific input value to be assigned to the north and/or south poles for
longitude-latitude grids
DESCRIPTION¶
This module is deprecated and scheduled for demolition.¶
Please use "
r.resamp.interp" instead.
r.bilinear fills
a grid cell (raster) matrix with interpolated values generated from a set of
input layer data points. It uses the bilinear interpolation method, a simple
algorithm usually applied only to completely defined raster areas (input data
void of null data values). Here the values of 4 input cells are used to define
an interpolation function of constant gradient within each rectangular area
defined by the cell centers. User should be aware that the gradient of the
interpolation functions changes discontinuously across lines intersecting the
cell centers of the input raster.
If there is a current working mask, it applies to the output raster map. Only
those cells falling within the mask will be assigned interpolated values. The
procedure for selection of input data will consider all input data relevant to
interpolating values at the cell centers of the current geographic region,
ignoring the curent mask. Note that cells of the output raster that cannot be
bounded by 4 input cell centers are set to null.
NOTES¶
The
north and
south parameters have been included to allow for
specific input values to be assigned to the north and/or south poles for
longitude-latitude grids. These data, if included, are used to interpolate
values for cells that are north or south of a line intersecting the cell
centers of the first or last row of input, respectively. When utilized, the
interpolation procedure will be continuous from the north and/or south
boundary of the current geographic region. This option is necessary, since the
data structure defining a raster will not allow for data to be assigned to a
cell centered at 90N or 90S. By including the option, the user can create
output surfaces that are continuous between the poles. The interpolation will
be "wrap-around" from west to east (across latitude) only if the
input raster has an east edge identical to its west edge.
For longitude-latitude databases, the interpolation algorithm is based on degree
fractions, not on the absolute distances between cell centers. Any attempt to
implement the latter would violate the integrity of the interpolation method.
r.bilinear may be used in some instances as an alternative to the nearest
neighbor approach inherent to
r.resample. Note, however, that the
extent of non-null data area of the output raster must be less than that of
the input raster. The only exception to this occurs in the case where the
north and
south parameters are utilized for longitude-latitude
rasters.
SEE ALSO¶
r.surf.idw,
r.surf.idw2,
g.region,
r.resample,
r.resamp.interp,
r.resamp.stats
AUTHOR¶
Greg Koerper
ManTech Environmental Technology, Inc.
Global Climate Research Project
U.S. EPA Environmental Research Laboratory
Last changed: $Date: 2010-01-20 14:26:08 +0100 (Wed, 20 Jan 2010) $
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