Provided by: gmt-common_5.2.1+dfsg-3build1_all bug

NAME

       grdraster - Extract subregion from a binary raster and save as a GMT grid

SYNOPSIS

       grdraster  [ filenumber | "text pattern" ] region [ grdfile ] [ increment ] [ parameters ]
       [ [level] ] [ -bo<binary> ] [ -do<nodata> ] [ -o<flags> ]

       Note: No space is allowed between the option flag and the associated arguments.

DESCRIPTION

       grdraster reads a file called grdraster.info  from  the  current  working  directory,  the
       directories  pointed  to by the environment variables $GMT_USERDIR and $GMT_DATADIR, or in
       $GMT_SHAREDIR/dbase (in that order). The file grdraster.info defines binary arrays of data
       stored  in  scan-line  format  in data files.  Each file is given a filenumber in the info
       file. grdraster figures out how to load the raster data into a grid file spanning a region
       defined by -R. By default the grid spacing equals the raster spacing. The -I option may be
       used to sub-sample the raster data. No filtering or interpolating is  done,  however;  the
       x_inc  and  y_inc  of  the grid must be multiples of the increments of the raster file and
       grdraster simply takes every n'th point. The output of grdraster is either grid  or  pixel
       registered  depending  on  the registration of the raster used. It is up to the GMT system
       person to maintain the grdraster.info file in accordance with  the  available  rasters  at
       each site. Raster data sets are not supplied with GMT but can be obtained by anonymous ftp
       and on CD-ROM (see README page in dbase directory).  grdraster  will  list  the  available
       files  if no arguments are given.  Finally, grdraster will write xyz-triplets to stdout if
       no output gridfile name is given

REQUIRED ARGUMENTS

       filenumber
              If an integer matching one of the files listed in the grdraster.info file is  given
              we  will use that data set, else we will match the given text pattern with the data
              set description in order to determine the data set.

       -R[unit]west/east/south/north[/zmin/zmax][r]
              west, east, south, and north specify the region of interest, and  you  may  specify
              them in decimal degrees or in [+-]dd:mm[:ss.xxx][W|E|S|N] format. Append r if lower
              left and upper right  map  coordinates  are  given  instead  of  w/e/s/n.  The  two
              shorthands  -Rg  and  -Rd stand for global domain (0/360 and -180/+180 in longitude
              respectively, with -90/+90 in latitude).  Alternatively  for  grid  creation,  give
              Rcodelon/lat/nx/ny,  where  code is a 2-character combination of L, C, R (for left,
              center, or right) and T, M, B for top, middle, or bottom. e.g., BL for lower  left.
              This  indicates  which  point on a rectangular region the lon/lat coordinate refers
              to, and the grid dimensions nx and ny with grid spacings via -I is used  to  create
              the corresponding region.  Alternatively, specify the name of an existing grid file
              and the -R settings (and grid spacing, if applicable) are  copied  from  the  grid.
              Using  -Runit  expects  projected (Cartesian) coordinates compatible with chosen -J
              and we inversely project to determine actual rectangular  geographic  region.   For
              perspective  view  (-p), optionally append /zmin/zmax.  In case of perspective view
              (-p), a z-range (zmin, zmax) can be appended to indicate the third dimension.  This
              needs to be done only when using the -Jz option, not when using only the -p option.
              In the latter case a perspective view of  the  plane  is  plotted,  with  no  third
              dimension.  If  r  is appended, you may also specify a map projection to define the
              shape of your region. The output region will be rounded off to  the  nearest  whole
              grid-step in both dimensions.

OPTIONAL ARGUMENTS

       -Ggrdfile
              Name of output grid file. If not set, the grid will be written as ASCII (or binary;
              see -bo) xyz-triplets to stdout instead.

       -Ixinc[unit][=|+][/yinc[unit][=|+]]
              x_inc [and optionally y_inc] is the  grid  spacing.  Optionally,  append  a  suffix
              modifier. Geographical (degrees) coordinates: Append m to indicate arc minutes or s
              to indicate arc seconds. If one of the units e,  f,  k,  M,  n  or  u  is  appended
              instead,  the  increment  is assumed to be given in meter, foot, km, Mile, nautical
              mile or US survey foot, respectively, and  will  be  converted  to  the  equivalent
              degrees  longitude  at the middle latitude of the region (the conversion depends on
              PROJ_ELLIPSOID). If /y_inc is given but set to 0 it will be reset equal  to  x_inc;
              otherwise  it  will  be  converted  to  degrees  latitude. All coordinates: If = is
              appended then the corresponding max x (east) or y (north) may be slightly  adjusted
              to  fit  exactly  the  given  increment  [by  default the increment may be adjusted
              slightly to fit the given domain]. Finally, instead of giving an increment you  may
              specify  the  number  of  nodes  desired  by  appending  +  to the supplied integer
              argument; the increment is then recalculated from  the  number  of  nodes  and  the
              domain.  The  resulting  increment  value  depends  on  whether you have selected a
              gridline-registered or pixel-registered grid;  see  App-file-formats  for  details.
              Note:  if -Rgrdfile is used then the grid spacing has already been initialized; use
              -I to override the values.

       -Jparameters (more ...)
              Select map projection.

       -V[level] (more ...)
              Select verbosity level [c].

       -bo[ncols][type] (more ...)
              Select native binary output.

       -donodata (more ...)
              Replace output columns that equal NaN with nodata.

       -ocols[,...] (more ...)
              Select output columns (0 is first column).

         This option applies only if no -G option has been set.

       -^ or just -
              Print a short message about the syntax of the command, then exits (NOTE: on Windows
              use just -).

       -+ or just +
              Print  an  extensive  usage  (help)  message,  including  the  explanation  of  any
              module-specific option (but not the GMT common options), then exits.

       -? or no arguments
              Print a complete usage (help) message, including the explanation of  options,  then
              exits.

       --version
              Print GMT version and exit.

       --show-datadir
              Print full path to GMT share directory and exit.

EXAMPLES

       To  extract  data  from  raster  1, taking one point every 30 minutes, in an area extended
       beyond 360 degrees to allow later filtering, run

              gmt grdraster 1 -R-4/364/-62/62 -I30m -Gdata.nc

       To obtain data for an oblique Mercator projection we need to extract  more  data  that  is
       actually  used.  This  is  necessary  because the output of grdraster has edges defined by
       parallels and meridians, while the oblique map in general does not. Hence, to get all  the
       data from the ETOPO2 data needed to make a contour map for the region defined by its lower
       left and upper right corners and the desired projection, use

              gmt grdraster ETOPO2 -R160/20/220/30r -Joc190/25.5/292/69/1 -Gdata.nc

       To extract data from the 2 min  Geoware  relief  blend  and  write  it  as  binary  double
       precision xyz-triplets to standard output:

              gmt grdraster "2 min Geoware" -R20/25/-10/5 -bo > triplets.b

SEE ALSO

       gmtdefaults, gmt, grdsample, grdfilter

COPYRIGHT

       2015, P. Wessel, W. H. F. Smith, R. Scharroo, J. Luis, and F. Wobbe