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       triangulate - Perform optimal Delauney triangulation and gridding


       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] ]


       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.

              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 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.


              -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)


              -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)


              -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)


              -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

       -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.


       To triangulate the points in the file, store the  triangle  information  in  a
       binary file, and make a grid for the given area and spacing, try

       triangulate -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 -M -R-100/-90/30/34  -JM15c  |  psxy  -M  -R-100/-90/30/34  -JM15c
       -W0.5p -B1 >


       gmt(1gmt), pscontour(1gmt)


       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.

                                            1 Jan 2004                             TRIANGULATE(l)