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<HTML>
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<TITLE>triangulate</TITLE>
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<BODY>
<H1>triangulate</H1>
<HR>
<PRE>
<!-- Manpage converted by man2html 3.0.1 -->
triangulate - Perform optimal Delauney triangulation and
gridding
</PRE>
<H2>SYNOPSIS</H2><PRE>
<B>triangulate</B> <I>infiles</I> [ <B>-Dx|y</B> ] [ <B>-E</B><I>empty</I> ] [ <B>-G</B><I>grdfile</I> ] [
<B>-H</B>[<I>nrec</I>] ] [ <B>-I</B><I>x</I><B>_</B><I>inc</I>[<B>m|c</B>][/<I>y</I><B>_</B><I>inc</I>[<B>m|c</B>]] ] [ <B>-J</B><I>parameters</I> ]
[ <B>-L</B> ] [ <B>-M</B>[<I>flag</I>] ] [ <B>-R</B><I>west/east/south/north</I>[<B>r</B>] ] [ <B>-V</B> ]
[ <B>-Z</B> ] [ <B>-:</B> ] [ <B>-bi</B>[<B>s</B>][<I>n</I>] ] [ <B>-bo</B>[<B>s</B>] ]
</PRE>
<H2>DESCRIPTION</H2><PRE>
<B>triangulate</B> reads one or more ASCII [or binary] files (or
standard input) containing x,y[,z] and performs Delauney
triangulation, i.e., it find how the points should be con
nected to give the most equilateral triangulation possi
ble. If a map projection is chosen then it is applied
before the triangulation is calculated. By default, the
output is triplets of point id numbers that make up each
triangle and is written to standard output. The id num
bers refer to the points position in the input file. As
an option, you may choose to create a multiple segment
file that can be piped through <B><A HREF="psxy.html">psxy</A></B> to draw the triangula
tion network. If <B>-G</B> <B>-I</B> are set a grid will be calculated
based on the surface defined by the planar triangles. The
actual algorithm used in the triangulations is either that
of Watson [1982] [Default] or Shewchuck [1996] (if
installed). This choice is made during the GMT installa
tion.
<I>infiles</I>
Data files with the point coordinates in ASCII (or
binary; see <B>-b</B>). If no files are given the standard
input is read.
</PRE>
<H2>OPTIONS</H2><PRE>
<B>-D</B> Take either the <I>x</I>- or <I>y</I>-derivatives of surface rep
resented by the planar facets (only used when <B>-G</B> is
set).
<B>-E</B> Set the value assigned to empty nodes when <B>-G</B> is
set [NaN].
<B>-G</B> Use triangulation to grid the data onto an even
grid (specified with <B>-I,</B> <B>-R</B>). Append the name of
the output grid file. The interpolation is per
formed in the original coordinates, so if your tri
angles are close to the poles you are better off
projecting all data to a local coordinate system
before using triangulate (this is true of all grid
ding routines).
<B>-H</B> Input file(s) has Header record(s). Number of
header records can be changed by editing your .gmt
<B>-I</B> <I>x</I><B>_</B><I>inc</I> [and optionally <I>y</I><B>_</B><I>inc</I>] sets the grid size for
optional grid output (see <B>-G</B>). Append <B>m</B> to indi
cate minutes or <B>c</B> to indicate seconds.
<B>-J</B> Selects the map projection. Scale is UNIT/degree,
1:xxxxx, or width in UNIT (upper case modifier).
UNIT is cm, inch, or m, depending on the MEA
SURE_UNIT setting in .<A HREF="gmtdefaults.html">gmtdefaults</A>, but this can be
overridden on the command line by appending the c,
i, or m to the scale/width value.
<B>CYLINDRICAL</B> <B>PROJECTIONS:</B>
<B>-Jc</B><I>lon0/lat0/scale</I> (Cassini)
<B>-Jj</B><I>lon0/scale</I> (Miller)
<B>-Jm</B><I>scale</I> (Mercator - Greenwich and Equator as ori
gin)
<B>-Jm</B><I>lon0/lat0/scale</I> (Mercator - Give meridian and
standard parallel)
<B>-Joa</B><I>lon0/lat0/azimuth/scale</I> (Oblique Mercator -
point and azimuth)
<B>-Job</B><I>lon0/lat0/lon1/lat1/scale</I> (Oblique Mercator -
two points)
<B>-Joc</B><I>lon0/lat0/lonp/latp/scale</I> (Oblique Mercator -
point and pole)
<B>-Jq</B><I>lon0/scale</I> (Equidistant Cylindrical Projection
(Plate Carree))
<B>-Jt</B><I>lon0/scale</I> (TM - Transverse Mercator, with Equa
tor as y = 0)
<B>-Jt</B><I>lon0/lat0/scale</I> (TM - Transverse Mercator, set
origin)
<B>-Ju</B><I>zone/scale</I> (UTM - Universal Transverse Mercator)
<B>-Jy</B><I>lon0/lats/scale</I> (Basic Cylindrical Projection)
<B>AZIMUTHAL</B> <B>PROJECTIONS:</B>
<B>-Ja</B><I>lon0/lat0/scale</I> (Lambert).
<B>-Je</B><I>lon0/lat0/scale</I> (Equidistant).
<B>-Jf</B><I>lon0/lat0/horizon/scale</I> (Gnomonic).
<B>-Jg</B><I>lon0/lat0/scale</I> (Orthographic).
<B>-Js</B><I>lon0/lat0/</I>[<I>slat/</I>]<I>scale</I> (General Stereographic)
<B>CONIC</B> <B>PROJECTIONS:</B>
<B>-Jb</B><I>lon0/lat0/lat1/lat2/scale</I> (Albers)
<B>-Jd</B><I>lon0/lat0/lat1/lat2/scale</I> (Equidistant)
<B>-Jl</B><I>lon0/lat0/lat1/lat2/scale</I> (Lambert)
<B>MISCELLANEOUS</B> <B>PROJECTIONS:</B>
<B>-Jh</B><I>lon0/scale</I> (Hammer)
<B>-Jn</B><I>lon0/scale</I> (Robinson)
<B>-Jr</B><I>lon0/scale</I> (Winkel Tripel)
<B>-Jv</B><I>lon0/scale</I> (Van der Grinten)
<B>-Jw</B><I>lon0/scale</I> (Mollweide)
<B>NON-GEOGRAPHICAL</B> <B>PROJECTIONS:</B>
<B>-Jp</B>[<B>a</B>]<I>scale</I>[<I>/origin</I>] (polar (theta,r) coordinates,
optional <B>a</B> for azimuths and offset theta [0])
<B>-Jx</B><I>x-scale</I>[<B>l|p</B><I>pow</I>][<I>/y-scale</I>[<B>l|p</B><I>pow</I>]] (Linear, log,
and power scaling)
More details can be found in the <B><A HREF="psbasemap.html">psbasemap</A></B> man
pages.
<B>-L</B> Indicates that the x column contains longitudes,
which may differ from the region in <B>-R</B> by [multi
ples of] 360 degrees [Default assumes no periodic
ity].
<B>-M</B> Output triangulation network as multiple line seg
ments separated by a record whose first character
is <I>flag</I> [>]. To plot, use <B><A HREF="psxy.html">psxy</A></B> with the <B>-M</B> option
(see Examples).
<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.
<B>-V</B> Selects verbose mode, which will send progress
reports to stderr [Default runs "silently"].
<B>-Z</B> Controls whether binary data file has two or three
columns [2]. Ignored if <B>-b</B> is not set.
<B>-:</B> Toggles between (longitude,latitude) and (lati
tude,longitude) input/output. [Default is (longi
tude,latitude)]. Applies to geographic coordinates
only.
<B>-bi</B> Selects binary input. Append <B>s</B> for single precision
[Default is double]. Append <I>n</I> for the number of
columns in the binary file(s). [Default is 2 input
columns].
<B>-bo</B> Selects binary output. Append <B>s</B> for single preci
sion [Default is double]. Node ids are stored as
binary 4-byte integer triplets. <B>-bo</B> is ignored if
<B>-M</B> is selected.
</PRE>
<H2>EXAMPLES</H2><PRE>
for the given area and spacing, try
triangulate samples.xyz <B>-bo</B> <B>-R</B>0/30/0/30 <B>-I</B>2 <B>-G</B>surf.grd >
samples.ijk
To draw the optimal Delauney triangulation network based
on the same file using a 15-cm-wide Mercator map, try
triangulate samples.xyz <B>-M</B> <B>-R</B>-100/-90/30/34 <B>-JM</B>15<B>c</B> | <A HREF="psxy.html">psxy</A>
<B>-M</B> <B>-R</B>-100/-90/30/34 <B>-JM</B>15<B>c</B> <B>-W</B>0.5<B>p</B> <B>-B</B>1 > network.ps
</PRE>
<H2>SEE ALSO</H2><PRE>
<I>gmt</I>(l), <I><A HREF="pscontour.html">pscontour</A></I>(l)
</PRE>
<H2>REFERENCES</H2><PRE>
Watson, D. F., 1982, Acord: Automatic contouring of raw
data, <I>Comp.</I> <I>&</I> <I>Geosci.,</I> <I>8</I>, 97-101.
Shewchuck, J. R., 1996, Triangle: Engineering a 2D Quality
Mesh Generator and Delaunay Triangulator, First Workshop
on Applied Computational Geometry (Philadelphia, PA),
124-133, ACM, May 1996.
www.cs.cmu.edu/~quake/triangle.html
</PRE>
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