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 dis-
tance from the nearest data point. If the distance speci-
fied 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 registra-
tion].
-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(l), grdlandmask(l), grdmath(l), grdclip(l), psmask(l),
psclip(l)