NAME

       r.resamp.interp  - Resamples raster map to a finer grid using interpolation.

KEYWORDS

       raster, resample, interpolation, nearest neighbor, bilinear, bicubic, lanczos, parallel

SYNOPSIS

       r.resamp.interp
       r.resamp.interp --help
       r.resamp.interp  input=name  output=name   [method=string]    [nprocs=integer]    [memory=memory  in  MB]
       [--overwrite]  [--help]  [--verbose]  [--quiet]  [--ui]

   Flags:
       --overwrite
           Allow output files to overwrite existing files

       --help
           Print usage summary

       --verbose
           Verbose module output

       --quiet
           Quiet module output

       --ui
           Force launching GUI dialog

   Parameters:
       input=name [required]
           Name of input raster map

       output=name [required]
           Name for output raster map

       method=string
           Sampling interpolation method
           Options: nearest, bilinear, bicubic, lanczos
           Default: bilinear
           nearest: Nearest-neighbor interpolation
           bilinear: Bilinear interpolation
           bicubic: Bicubic interpolation

       nprocs=integer
           Number of threads for parallel computing
           Default: 1

       memory=memory in MB
           Maximum memory to be used (in MB)
           Cache size for raster rows
           Default: 300

DESCRIPTION

       r.resamp.interp resamples an input raster map by  interpolating  between  the  neighboring  cells  via  a
       selectable  resampling  algorithm. All cells present in the neighborhood of the input raster cell must be
       non-null to generate a non-null cell in the output raster map. A choice of four interpolation methods  is
       available;  each  uses  the  weighted  values of a different number of adjacent cells in the input map to
       determine the value of each cell in the output map as follows:

           •   nearest neighbour (1 cell)

           •   bilinear (4 cells)

           •   bicubic (16 cells)

           •   lanczos (25 cells)

       This module is intended for reinterpolation of continuous data to a different resolution rather than  for
       interpolation from scattered data (use the v.surf.* modules for that purpose).

NOTES

       Resampling  modules (r.resample, r.resamp.stats, r.resamp.interp, r.resamp.rst) resample the map to match
       the current region settings.

       Note that for bilinear, bicubic and lanczos interpolation, cells of the  output  raster  that  cannot  be
       bounded  by  the  appropriate number of input cell centers are set to NULL (NULL propagation). This could
       occur due to the input cells being outside the current region, being NULL or MASKed.

       For longitude-latitude coordinate reference systems, 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.

   PERFORMANCE
       By  specifying the number of parallel processes with nprocs option, r.resamp.interp can run significantly
       faster, see benchmarks below.
       Figure: Benchmark shows execution time for different number of cells. See  benchmark  scripts  in  source
       code.

       To  reduce  the  memory  requirements  to  minimum,  set option memory to zero.  To take advantage of the
       parallelization, GRASS GIS needs to compiled with OpenMP enabled.

EXAMPLE

       Resample elevation raster map to a higher resolution (from 500m to 250m; North Carolina sample dataset):
       g.region raster=elev_state_500m -p
       g.region res=250 -ap
       r.resamp.interp input=elev_state_500m output=elev_state_250m \
                       method=bilinear
       Original 500m resolution elevation map

       Resampled (bilinear) 250m resolution elevation map

SEE ALSO

        g.region, r.resample, r.resamp.filter, r.resamp.rst, r.resamp.stats

       Overview: Interpolation and Resampling in GRASS GIS

AUTHOR

       Glynn Clements

SOURCE CODE

       Available at: r.resamp.interp source code (history)

       Accessed: Friday Apr 04 01:19:29 2025

       Main index | Raster index | Topics index | Keywords index | Graphical index | Full index

       © 2003-2025 GRASS Development Team, GRASS GIS 8.4.1 Reference Manual

GRASS 8.4.1                                                                              r.resamp.interp(1grass)