grdlandmask - Create "wet-dry" mask grdfile from shoreline data base.
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 ]
grdlandmask reads the selected shoreline database and uses that infor-
mation to decide which nodes in the specified grid are over land or
over water. The nodes defined by the selected region and lattice spac-
ing will be set according to one of two criteria: (1) land vs water, or
(2) the more detailed (hierarchical) 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 xmin, xmax, ymin, and ymax specify the Region of interest. For
geographic regions, these limits correspond to west, east,
south, and north and you may specify them in decimal degrees or
in [+-]dd:mm[:ss.xxx][W|E|S|N] format. Append r if lower left
and upper right map coordinates are given instead of wesn. The
two shorthands -Rg -Rd stand for global domain (0/360 or
-180/+180 in longitude respectively, with -90/+90 in latitude).
For calendar time coordinates you may either give relative time
(relative to the selected TIME_EPOCH and in the selected
TIME_UNIT; append t to -JX|x), or absolute time of the form
[date]T[clock] (append T to -JX|x). At least one of date and
clock must be present; the T is always required. The date string
must be of the form [-]yyyy[-mm[-dd]] (Gregorian calendar) or
yyyy[-Www[-d]] (ISO week calendar), while the clock string must
be of the form hh:mm:ss[.xxx]. The use of delimiters and their
type and positions must be as indicated (however, input/output
and plotting formats are flexible).
-A Features with an area smaller than min_area in km^2 or of hier-
archical 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 registration].
-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:
[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"].
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:
grdlandmask -R0/360/-90/90 -Dl -I1 -N0/1/2/3/4 -Glevels.grd -V
gmt(l), grdmath(l), grdclip(l), psmask(l), psclip(l), pscoast(l)
GMT4.0 1 Oct 2004 GRDLANDMASK(l)
Man(1) output converted with