grdlandmask

       grdlandmask - Create "wet-dry" mask grdfile from shoreline
       data base.

SYNOPSIS

       grdlandmask    -Gmask_grd_file]    -Ixinc[m|c][/yinc[m|c]]
       -Rwest/east/south/north[r]                               [
       -Amin_area[/min_level/max_level] ] [ -Dresolution ] [ -F ]
       [ -Nmaskvalues[o] ] [ -V ]

DESCRIPTION

       grdlandmask reads the selected shoreline database and uses
       that information to decide which nodes  in  the  specified
       grid are over land or over water. The nodes defined by the
       selected region and lattice spacing will be set  according
       to  one  of  two  criteria: (1) Lands vs water, or (2) the
       more detailed (hierarchial)  ocean  vs  land  vs  lake  vs
       island  vs pond. The resulting mask grdfile may be used in
       subsequent operations involving grdmath to mask  out  data
       from land [or water] areas.

       -G     Name of resulting output mask grd file.

       -I     x_inc  [and  optionally y_inc] is the grid spacing.
              Append m to indicate minutes or c to indicate  sec­
              onds.

       -R     west,  east, south, and north specify the Region of
              interest. To specify boundaries in degrees and min­
              utes  [and  seconds],  use  the  dd:mm[:ss] format.
              Append r if lower left and upper right map  coordi­
              nates are given instead of wesn.

OPTIONS

       -A     Features with an area smaller than min_area in km^2
              or  of  hierarchical  level  that  is  lower   than
              min_level  or higher than max_level will be ignored
              [Default  is  0/4  (all  features)].  See  DATABASE
              INFORMATION  in  the  pscoast  man-pages  for  more
              details.

       -D     Selects the resolution  of  the  data  set  to  use
              ((f)ull,    (h)igh,   (i)ntermediate,   (l)ow,   or
              (c)rude). The resolution drops off by ~80%  between
              data  sets.  [Default  is l]. Note that because the
              coastlines differ in details a node in a mask  file
              using  one  resolution  is not guaranteed to remain
              inside [or outside] when a different resolution  is
              selected.

       -F     Force  pixel  registration. [Default is grid regis­
              tration].

              NaN. Append o  to  let  nodes  exactly  on  feature
              boundaries   be   considered  outside  [Default  is
              inside].  Specify this information  using  1  of  2
              formats:
                      -Nwet/dry.
                      -Nocean/land/lake/island/pond.
              [Default is 0/1/0/1/0 (i.e., 0/1)].

       -V     Selects  verbose  mode,  which  will  send progress
              reports to stderr [Default runs "silently"].

EXAMPLES

       To set all nodes on land to NaN, and nodes over  water  to
       1, using the high resolution data set, do

       grdlandmask    -R-60/-40/-40/-30    -Dh    -I5m    -N1/NaN
       -Gland_mask.grd -V

       To make a 1x1 degree global  grid  with  the  hierarchical
       levels of the nodes based on the low resolution data, try

       grdlandmask    -R0/360/-90/90    -Dl    -I1    -N0/1/2/3/4
       -Glevels.grd -V

SEE ALSO

       gmt(l),  grdmath(l),  grdclip(l),  psmask(l),   psclip(l),
       pscoast(l)