Ubuntu Manpage: r.bilinear - Bilinear interpolation utility for raster map layers.

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.

AUTHOR