grdmask

       grdmask - Create mask grdfiles from xy paths.

SYNOPSIS

       grdmask pathfiles -Gmask_grd_file] -Ixinc[m|c][/yinc[m|c]]
       -Rwest/east/south/north[r] [ -F ] [ -H[nrec] ] [  -L  ]  [
       -M[flag] ] [ -Nout/edge/in ] [ -S[radius][k] ] [ -V ] [ -:
       ] [ -bi[s][n] ]

DESCRIPTION

       grdmask can operate in 2 different modes. 1. It reads  one
       or  more  xy-files that each define a closed polygon.  The
       nodes defined by the specified region and lattice  spacing
       will  be set equal to one of three possible values depend­
       ing on whether the node is outside, on the polygon perime­
       ter, or inside the polygon. The resulting mask grdfile may
       be used in subsequent operations involving grdmath to mask
       out data from polygonal areas. 2. The xy-files simply rep­
       resent data point locations and the mask  is  set  to  the
       inside  or  outside  value  depending on whether a node is
       within a maximum distance from the nearest data point.  If
       the distance specified is zero then only the nodes nearest
       each data point are considered "inside".

       pathfiles
              The name of 1 or more ASCII  [or  binary,  see  -b]
              files holding the polygon(s) or data points.

       -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

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

       -H     Input  file(s)  has  Header  record(s).  Number  of
              header records can be changed by editing your .gmt­
              defaults file. If used, GMT  default  is  1  header
              record.

       -L     Indicates  that  the  x column contains longitudes,
              which may differ from the regions in -R by  [multi­
              ples  of] 360 degrees [Default assumes no periodic­
              ity].
              record  whose first character is flag.  [Default is
              '>'].

       -N     Sets the values that will be assigned to nodes that
              are  outside  the polygons, on the edge, or inside.
              Values can be any number, including the  textstring
              NaN [Default is 0/0/1].

       -S     Set  nodes  depending  on  their  distance from the
              nearest data point. Nodes within radius [0] from  a
              data point are considered inside. Append k to indi­
              cate map units (e.g., -R -I in degrees  and  radius
              in km).

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

       -bi    Selects binary input. Append s for single precision
              [Default  is  double].   Append n for the number of
              columns in the binary file(s).  [Default is 2 input
              columns].

EXAMPLES

       To set all nodes inside and on the polygons coastline_*.xy
       to 0, and outside points to 1, do

       grdmask  coastline_*.xy  -R-60/-40/-40/-30  -I5m   -N1/0/0
       -Gland_mask.grd -V

       To  set  nodes  within 50 km of data points to 1 and other
       nodes to NaN, do

       grdmask data.xyz -R-60/-40/-40/-30  -I5m  -NNaN/1/1  -S50k
       -Gdata_mask.grd -V

SEE ALSO

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