triangulate - Perform optimal Delauney triangulation and gridding
triangulate infiles [ -Dx|y ] [ -Eempty ] [ -Ggrdfile ] [ -H[nrec] ] [
-Ix_inc[m|c][/y_inc[m|c]] ] [ -Jparameters ] [ -M[flag] ] [
-Rwest/east/south/north[r] ] [ -V ] [ -Z ] [ -: ] [ -bi[s][n] ] [
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
Shewchuck  or Watson . This choice is made during the GMT
Data files with the point coordinates in ASCII (or binary; see
-b). If no files are given the standard input is read.
-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
-J Selects the map projection. Scale is inch/degree, 1:xxxxx, or
width in inch (upper case modifier).
-Jmscale (Mercator - Greenwich and Equator as origin)
-Jmlon0/lat0/scale (Mercator - Give meridian and standard
-Joalon0/lat0/azimuth/scale (Oblique Mercator - point and
-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)
-Juzone/scale (UTM - Universal Transverse Mercator)
-Jylon0/lats/scale (Basic Cylindrical Projection)
-Jslon0/lat0/scale (General Stereographic)
-Jklon0/scale (Eckert VI)
-Jrlon0/scale (Winkel Tripel)
-Jpscale (Linear projection for polar (theta,r) coordinates)
-Jxx-scale[l|ppow][/y-scale[l|ppow]] (Linear, log, and power
More details can be found in the psbasemap manpages.
-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 .
Ignored if -b is not set.
-: Toggles between (longitude,latitude) and (latitude,longitude)
input/output. [Default is (longitude,latitude)].
-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.
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
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 6-inch-wide Mercator map, try
triangulate samples.xyz -M -R-100/-90/30/34 -JM6i | psxy -M -R-100/-
90/30/34 -JM6i -W0.5p -B1 > network.ps
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.
Man(1) output converted with