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<HTML>
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<TITLE>grdlandmask</TITLE>
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<H1>grdlandmask</H1>
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<PRE>
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grdlandmask - Create "wet-dry" mask grdfile from shoreline
data base.
</PRE>
<H2>SYNOPSIS</H2><PRE>
<B>grdlandmask</B> <B>-G</B><I>mask</I><B>_</B><I>grd</I><B>_</B><I>file</I>] <B>-I</B><I>xinc</I>[<B>m|c</B>][/<I>yinc</I>[<B>m|c</B>]]
<B>-R</B><I>west/east/south/north</I>[<B>r</B>] [
<B>-A</B><I>min</I><B>_</B><I>area</I>[/<I>min</I><B>_</B><I>level/max</I><B>_</B><I>level</I>] ] [ <B>-D</B><I>resolution</I> ] [ <B>-F</B> ]
[ <B>-N</B><I>maskvalues</I>[<B>o</B>] ] [ <B>-V</B> ]
</PRE>
<H2>DESCRIPTION</H2><PRE>
<B>grdlandmask</B> 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 <B><A HREF="grdmath.html">grdmath</A></B> to mask out data
from land [or water] areas.
<B>-G</B> Name of resulting output mask grd file.
<B>-I</B> <I>x</I><B>_</B><I>inc</I> [and optionally <I>y</I><B>_</B><I>inc</I>] is the grid spacing.
Append <B>m</B> to indicate minutes or <B>c</B> to indicate sec
onds.
<B>-R</B> <I>west,</I> <I>east,</I> <I>south,</I> and <I>north</I> specify the Region of
interest. To specify boundaries in degrees and min
utes [and seconds], use the dd:mm[:ss] format.
Append <B>r</B> if lower left and upper right map coordi
nates are given instead of wesn.
</PRE>
<H2>OPTIONS</H2><PRE>
<B>-A</B> Features with an area smaller than <I>min</I><B>_</B><I>area</I> in km^2
or of hierarchical level that is lower than
<I>min</I><B>_</B><I>level</I> or higher than <I>max</I><B>_</B><I>level</I> will be ignored
[Default is 0/4 (all features)]. See DATABASE
INFORMATION in the <B><A HREF="pscoast.html">pscoast</A></B> man-pages for more
details.
<B>-D</B> Selects the resolution of the data set to use
((<B>f</B>)ull, (<B>h</B>)igh, (<B>i</B>)ntermediate, (<B>l</B>)ow, or
(<B>c</B>)rude). The resolution drops off by ~80% between
data sets. [Default is <B>l</B>]. 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.
<B>-F</B> Force pixel registration. [Default is grid regis
tration].
NaN. Append <B>o</B> to let nodes exactly on feature
boundaries be considered outside [Default is
inside]. Specify this information using 1 of 2
formats:
<B>-N</B><I>wet/dry</I>.
<B>-N</B><I>ocean/land/lake/island/pond</I>.
[Default is 0/1/0/1/0 (i.e., 0/1)].
<B>-V</B> Selects verbose mode, which will send progress
reports to stderr [Default runs "silently"].
</PRE>
<H2>EXAMPLES</H2><PRE>
To set all nodes on land to NaN, and nodes over water to
1, using the high resolution data set, do
grdlandmask <B>-R</B>-60/-40/-40/-30 <B>-Dh</B> <B>-I</B>5<B>m</B> <B>-N</B>1/NaN
<B>-G</B>land_mask.grd <B>-V</B>
To make a 1x1 degree global grid with the hierarchical
levels of the nodes based on the low resolution data, try
grdlandmask <B>-R</B>0/360/-90/90 <B>-Dl</B> <B>-I</B>1 <B>-N</B>0/1/2/3/4
<B>-G</B>levels.grd <B>-V</B>
</PRE>
<H2>SEE ALSO</H2><PRE>
<I>gmt</I>(l), <I><A HREF="grdmath.html">grdmath</A></I>(l), <I><A HREF="grdclip.html">grdclip</A></I>(l), <I><A HREF="psmask.html">psmask</A></I>(l), <I><A HREF="psclip.html">psclip</A></I>(l),
<I><A HREF="pscoast.html">pscoast</A></I>(l)
</PRE>
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