NAME
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 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
-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 reso-
lution 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 dif-
ferent resolution is selected.
-F Force pixel registration. [Default is grid registra-
tion].
-N Sets the values that will be assigned to nodes. Values
can be any number, including the textstring 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 lev-
els 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)