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  locations,  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: Tuesday Jun 27 11:13:07 2023

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       © 2003-2023 GRASS Development Team, GRASS GIS 8.3.0 Reference Manual