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grdcut(1)                             GMT                            grdcut(1)




NAME

       grdcut - Extract subregion from a grid


SYNOPSIS

       grdcut ingrid  -Goutgrid
        -Rregion [  -N[nodata] ] [  -S[n]lon/lat/radius[unit] ] [  -V[level] ]
       [  -Z[n|r]min/max ] [ -fflags ]

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


DESCRIPTION

       grdcut  will produce a new outgrid file which is a subregion of ingrid.
       The subregion is specified with -R as in other programs; the  specified
       range  must  not exceed the range of ingrid (but see -N).  If in doubt,
       run grdinfo to check range. Alternatively, define the  subregion  indi-
       rectly  via  a  range  check on the node values or via distances from a
       given point. Complementary to grdcut there is grdpaste, which will join
       together two grid files along a common edge.


REQUIRED ARGUMENTS

       ingrid This is the input grid file.

       -Goutgrid
              This is the output grid file.


OPTIONAL ARGUMENTS

       -N[nodata]
              Allow grid to be extended if new -R exceeds existing boundaries.
              Append nodata value to initialize nodes outside  current  region
              [Default is NaN].

       -Rxmin/xmax/ymin/ymax[+r][+uunit] (more a|)
              Specify the region of interest. This defines the subregion to be
              cut out.

       -S[n]lon/lat/radius[unit]
              Specify an origin and radius; append a distance unit (see UNITS)
              and  we  determine  the corresponding rectangular region so that
              all grid nodes on or inside the circle are contained in the sub-
              set.  If -Sn is used we set all nodes outside the circle to NaN.

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

       -Z[n|r]min/max
              Determine the new rectangular region so that all  nodes  outside
              this  region  are also outside the given z-range [-inf/+inf]. To
              indicate no limit on min or max, specify a hyphen (-). Normally,
              any  NaNs  encountered  are simply skipped and not considered in
              the decision.  Use -Zn to consider  a  NaN  to  be  outside  the
              z-range.  This  means  the new subset will be NaN-free. Alterna-
              tively, use -Zr to consider NaNs to be within the data range. In
              this  case  we stop shrinking the boundaries once a NaN is found
              [Default simply skips NaNs when making the range decision].

       -f[i|o]colinfo (more a|)
              Specify data types of input and/or output columns.

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

       -+ or just +
              Print  an extensive usage (help) message, including the explana-
              tion 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 all options, then exits.


UNITS

       For map distance unit, append unit d for arc degree, m for arc  minute,
       and s for arc second, or e for meter [Default], f for foot, k for km, M
       for statute mile, n for nautical mile, and u for  US  survey  foot.  By
       default  we compute such distances using a spherical approximation with
       great circles. Prepend - to a distance (or the unit is no  distance  is
       given) to perform aFlat Eartha calculations (quicker but less accurate)
       or prepend + to perform exact geodesic calculations  (slower  but  more
       accurate).


GRID FILE FORMATS

       By  default  GMT  writes  out  grid  as  single  precision  floats in a
       COARDS-complaint netCDF file format. However, GMT is  able  to  produce
       grid  files  in  many  other  commonly  used grid file formats and also
       facilitates so called apackinga of grids, writing  out  floating  point
       data as 1- or 2-byte integers. (more a|)


GEOGRAPHICAL AND TIME COORDINATES

       When  the  output  grid type is netCDF, the coordinates will be labeled
       alongitudea, alatitudea, or atimea based on the attributes of the input
       data  or  grid  (if  any) or on the -f or -R options. For example, both
       -f0x -f1t and -R90w/90e/0t/3t will result  in  a  longitude/time  grid.
       When  the  x, y, or z coordinate is time, it will be stored in the grid
       as relative time since epoch as specified by TIME_UNIT  and  TIME_EPOCH
       in  the  gmt.conf  file  or  on the command line. In addition, the unit
       attribute of the time variable will indicate both this unit and  epoch.


EXAMPLES

       Suppose  you  have  used  surface  to  grid  ship gravity in the region
       between 148E - 162E and 8N - 32N, and you do  not  trust  the  gridding
       near  the  edges, so you want to keep only the area between 150E - 160E
       and 10N - 30N, then:

              gmt grdcut grav_148_162_8_32.nc -Ggrav_150_160_10_30.nc -R150/160/10/30 -V

       To return the subregion of a grid such that any boundary  strips  where
       all values are entirely above 0 are excluded, try

              gmt grdcut bathy.nc -Gtrimmed_bathy.nc -Z-/0 -V

       To return the subregion of a grid that contains all nodes within a dis-
       tance of 500 km from the point 45,30 try

              gmt grdcut bathy.nc -Gsubset_bathy.nc -S45/30/500k -V


SEE ALSO

       gmt(1), grdclip(1), grdinfo(1), grdpaste(1), surface(1)


COPYRIGHT

       2017, P. Wessel, W. H. F. Smith, R. Scharroo, J. Luis, and F. Wobbe



5.4.2                            Jun 24, 2017                        grdcut(1)

gmt5 5.4.2 - Generated Wed Jun 28 18:17:16 CDT 2017
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