Provided by: gmt-manpages_3.4.4-1_all 
NAME
triangulate - Perform optimal Delauney triangulation and gridding
SYNOPSIS
triangulate infiles [ -Dx|y ] [ -Eempty ] [ -Ggrdfile ] [ -H[nrec] ] [
-Ix_inc[m|c][/y_inc[m|c]] ] [ -Jparameters ] [ -L ] [ -M[flag] ] [
-Rwest/east/south/north[r] ] [ -V ] [ -Z ] [ -: ] [ -bi[s][n] ] [ -bo[s][n] ]
DESCRIPTION
triangulate 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
connected to give the most equilateral triangulation possible. 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 numbers 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 psxy to draw the
triangulation network. If -G -I 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 installation.
infiles
Data files with the point coordinates in ASCII (or binary; see -b). If no files are
given the standard input is read.
OPTIONS
-D Take either the x- or y-derivatives of surface represented by the planar facets
(only used when -G is set).
-E Set the value assigned to empty nodes when -G is set [NaN].
-G Use triangulation to grid the data onto an even grid (specified with -I, -R).
Append the name of the output grid file. The interpolation is performed in the
original coordinates, so if your triangles 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 gridding routines).
-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.
-I x_inc [and optionally y_inc] sets the grid size for optional grid output (see -G).
Append m to indicate minutes or c to indicate seconds.
-J 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 MEASURE_UNIT setting in
.gmtdefaults, but this can be overridden on the command line by appending the c, i,
or m to the scale/width value.
CYLINDRICAL PROJECTIONS:
-Jclon0/lat0/scale (Cassini)
-Jjlon0/scale (Miller)
-Jmscale (Mercator - Greenwich and Equator as origin)
-Jmlon0/lat0/scale (Mercator - Give meridian and standard parallel)
-Joalon0/lat0/azimuth/scale (Oblique Mercator - point and azimuth)
-Joblon0/lat0/lon1/lat1/scale (Oblique Mercator - two points)
-Joclon0/lat0/lonp/latp/scale (Oblique Mercator - point and pole)
-Jqlon0/scale (Equidistant Cylindrical Projection (Plate Carree))
-Jtlon0/scale (TM - Transverse Mercator, with Equator as y = 0)
-Jtlon0/lat0/scale (TM - Transverse Mercator, set origin)
-Juzone/scale (UTM - Universal Transverse Mercator)
-Jylon0/lats/scale (Basic Cylindrical Projection)
AZIMUTHAL PROJECTIONS:
-Jalon0/lat0/scale (Lambert).
-Jelon0/lat0/scale (Equidistant).
-Jflon0/lat0/horizon/scale (Gnomonic).
-Jglon0/lat0/scale (Orthographic).
-Jslon0/lat0/[slat/]scale (General Stereographic)
CONIC PROJECTIONS:
-Jblon0/lat0/lat1/lat2/scale (Albers)
-Jdlon0/lat0/lat1/lat2/scale (Equidistant)
-Jllon0/lat0/lat1/lat2/scale (Lambert)
MISCELLANEOUS PROJECTIONS:
-Jhlon0/scale (Hammer)
-Jilon0/scale (Sinusoidal)
-Jk[f|s]lon0/scale (Eckert IV (f) and VI (s))
-Jnlon0/scale (Robinson)
-Jrlon0/scale (Winkel Tripel)
-Jvlon0/scale (Van der Grinten)
-Jwlon0/scale (Mollweide)
NON-GEOGRAPHICAL PROJECTIONS:
-Jp[a]scale[/origin] (polar (theta,r) coordinates, optional a for azimuths and
offset theta [0])
-Jxx-scale[l|ppow][/y-scale[l|ppow]] (Linear, log, and power scaling)
More details can be found in the psbasemap manpages.
-L Indicates that the x column contains longitudes, which may differ from the region
in -R by [multiples of] 360 degrees [Default assumes no periodicity].
-M Output triangulation network as multiple line segments separated by a record whose
first character is flag [>]. To plot, use psxy with the -M option (see Examples).
-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.
-V Selects verbose mode, which will send progress reports to stderr [Default runs
"silently"].
-Z Controls whether binary data file has two or three columns [2]. Ignored if -b is
not set.
-: Toggles between (longitude,latitude) and (latitude,longitude) input/output.
[Default is (longitude,latitude)]. Applies to geographic coordinates only.
-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].
-bo Selects binary output. Append s for single precision [Default is double]. Node ids
are stored as binary 4-byte integer triplets. -bo is ignored if -M is selected.
EXAMPLES
To triangulate the points in the file samples.xyz, store the triangle information in a
binary file, and make a grid for the given area and spacing, try
triangulate samples.xyz -bo -R0/30/0/30 -I2 -Gsurf.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 -M -R-100/-90/30/34 -JM15c | psxy -M -R-100/-90/30/34 -JM15c
-W0.5p -B1 > network.ps
SEE ALSO
gmt(1gmt), pscontour(1gmt)
REFERENCES
Watson, D. F., 1982, Acord: Automatic contouring of raw data, Comp. & Geosci., 8, 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
1 Jan 2004 TRIANGULATE(l)