Provided by: grass-doc_8.3.0-1_all bug

NAME

       r.import   - Imports raster data into a GRASS raster map using GDAL library and reprojects
       on the fly.

KEYWORDS

       raster, import, projection

SYNOPSIS

       r.import
       r.import --help
       r.import  [-enlo]  input=name   [band=integer[,integer,...]]     [memory=memory   in   MB]
       [output=name]         [resample=string]         [extent=string]        [resolution=string]
       [resolution_value=float]     [title=phrase]     [--overwrite]     [--help]     [--verbose]
       [--quiet]  [--ui]

   Flags:
       -e
           Estimate resolution only

       -n
           Do not perform region cropping optimization

       -l
           Force Lat/Lon maps to fit into geographic coordinates (90N,S; 180E,W)

       -o
           Override projection check (use current location’s projection)
           Assume that the dataset has the same projection as the current location

       --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 GDAL dataset to be imported

       band=integer[,integer,...]
           Input band(s) to select (default is all bands)

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

       output=name
           Name for output raster map

       resample=string
           Resampling method to use for reprojection
           Options: nearest, bilinear, bicubic, lanczos, bilinear_f, bicubic_f, lanczos_f
           Default: nearest
           nearest: nearest neighbor
           bilinear: bilinear interpolation
           bicubic: bicubic interpolation
           lanczos: lanczos filter
           bilinear_f: bilinear interpolation with fallback
           bicubic_f: bicubic interpolation with fallback
           lanczos_f: lanczos filter with fallback

       extent=string
           Output raster map extent
           Options: input, region
           Default: input
           input: extent of input map
           region: extent of current region

       resolution=string
           Resolution of output raster map (default: estimated)
           Options: estimated, value, region
           Default: estimated
           estimated: estimated resolution
           value: user-specified resolution
           region: current region resolution

       resolution_value=float
           Resolution of output raster map (use with option resolution=value)

       title=phrase
           Title for resultant raster map

DESCRIPTION

       r.import  imports  a  map or selected bands from a GDAL raster datasource into the current
       location and mapset. If the projection of the input does not match the projection  of  the
       location,  the  input  is  reprojected into the current location. If the projection of the
       input does match the projection of the location,  the  input  is  imported  directly  with
       r.in.gdal.

NOTES

       r.import  checks the projection metadata of the dataset to be imported against the current
       location’s projection. If not identical a related error message is shown.
       To override this projection check (i.e. to use current location’s projection) by  assuming
       that  the dataset has the same projection as the current location the -o flag can be used.
       This is also useful when geodata to be imported do not contain any projection metadata  at
       all. The user must be sure that the projection is identical in order to avoid to introduce
       data errors.

   Resolution
       r.import reports the estimated target  resolution  for  each  input  band.  The  estimated
       resolution  will  usually  be  some  floating  point  number, e.g. 271.301. In case option
       resolution is set to estimated (default), this floating  point  number  will  be  used  as
       target  resolution.  Since the target resolution should be typically the rounded estimated
       resolution, e.g. 250 or 300 instead of 271.301, flag -e can be used first  to  obtain  the
       estimate  without  importing  the  raster  bands.  Then the desired resolution is set with
       option  resolution_value  and  option  resolution=value.   For  latlong   locations,   the
       resolution  might  be  set  to  arc  seconds,  e.g.  1, 3, 7.5, 15, and 30 arc seconds are
       commonly used resolutions.

   Resampling methods
       When reprojecting a map to a new spatial reference system, the projected data is resampled
       with  one  of four different methods: nearest neighbor, bilinear, bicubic interpolation or
       lanczos.

       In the following, common use cases are:

       nearest is the simplest method and the only possible method for categorical data.

       bilinear does linear interpolation and provides smoother output than nearest. bilinear  is
       recommended  when  reprojecting  a  DEM  for  hydrological  analysis or for surfaces where
       overshoots must be avoided, e.g. precipitation should not become negative.

       bicubic produces smoother output than bilinear, at the cost  of  overshoots.  Here,  valid
       pixels that are adjacent to NULL pixels or edge pixels are set to NULL.

       lanczos  produces the smoothest output of all methods and preserves contrast best. lanczos
       is recommended for imagery.  Both bicubic  and  lanczos  preserve  linear  features.  With
       nearest or bilinear, linear features can become zigzag features after reprojection.

       In  the  bilinear,  bicubic  and  lanczos methods, if any of the surrounding cells used to
       interpolate the new cell value are NULL, the resulting cell will  be  NULL,  even  if  the
       nearest  cell  is  not NULL. This will cause some thinning along NULL borders, such as the
       coasts of land areas in a DEM.  The  bilinear_f,  bicubic_f  and  lanczos_f  interpolation
       methods  can  be  used  if  thinning along NULL edges is not desired.  These methods "fall
       back" to simpler interpolation methods along NULL  borders.   That  is,  from  lanczos  to
       bicubic to bilinear to nearest.

       For explanation of the -l flag, please refer to the r.in.gdal manual.

       When importing whole-world maps the user should disable map-trimming with the -n flag. For
       further explanations of -n flag, please refer the to r.proj manual.

EXAMPLES

   Import of SRTM V3 global data at 1 arc-seconds resolution
       The SRTM  V3  1  arc-second  global  data  (~30  meters  resolution)  are  available  from
       EarthExplorer  (http://earthexplorer.usgs.gov/).   The  SRTM collections are located under
       the "Digital Elevation" category.

       Example for North Carolina sample dataset (the tile name is "n35_w079_1arc_v3.tif"):
       # set computational region to e.g. 10m elevation model:
       g.region raster=elevation -p
       # Import with reprojection on the fly. Recommended parameters:
       # resample   Resampling method to use for reprojection - bilinear
       # extent     Output raster map extent - region: extent of current region
       # resolution Resolution of output raster map
       #  - region: current region resolution - limit to g.region setting from above
       r.import input=n35_w079_1arc_v3.tif output=srtmv3_resamp10m resample=bilinear \
         extent=region resolution=region title="SRTM V3 resampled to 10m resolution"
       # beautify colors:
       r.colors srtmv3_resamp10m color=elevation

   Import of WorldClim data
       Import of a subset from WorldClim Bioclim data set, to be reprojected to current  location
       projection  (North Carolina sample dataset).  Different resolutions are available, in this
       example we use the 2.5 arc-minutes resolution data. During import, we spatially subset the
       world data to the North Carolina region using the extent parameter:
       # download selected Bioclim data (2.5 arc-minutes resolution)
       # optionally tiles are available for the 30 arc-sec resolution
       wget http://biogeo.ucdavis.edu/data/climate/worldclim/1_4/grid/cur/bio_2-5m_bil.zip
       # extract BIO1 from package (BIO1 = Annual Mean Temperature):
       unzip bio_2-5m_bil.zip bio1.bil bio1.hdr
       # prior to import, fix broken WorldClim extent using GDAL tool
       gdal_translate -a_ullr -180 90 180 -60 bio1.bil bio1_fixed.tif
       # set computational region to North Carolina, 4000 m target pixel resolution
       g.region -d res=4000 -ap
       # subset to current region and reproject on the fly to current location projection,
       # using -n since whole-world map is imported:
       r.import input=bio1_fixed.tif output=bioclim01 resample=bilinear \
                extent=region resolution=region -n
       # temperature data are in °C * 10
       r.info bioclim01
       r.univar -e bioclim01

SEE ALSO

        r.in.gdal, r.proj

AUTHORS

       Markus Metz
       Improvements: Martin Landa, Anna Petrasova

SOURCE CODE

       Available at: r.import source code (history)

       Accessed: Tuesday Jun 27 11:14:33 2023

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

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