## NAME

          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] ] [ -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 depending on whether the node is outside, on the
          polygon perimeter, 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 represent 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 seconds.

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

## OPTIONS

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

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

          -M   Multiple segment file.  Segments are separated by a 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 indicate 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, grdlandmask, grdmath, grdclip, psmask, psclip