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