Provided by: gmt_4.5.11-1build1_amd64 bug

NAME

       triangulate  -  Perform  optimal  Delaunay  triangulation  and  gridding of Cartesian data
       [method]

SYNOPSIS

       triangulate infiles [ -Dx|y ] [ -Eempty ]  [  -F  ]  [  -Ggrdfile  ]  [  -H[i][nrec]  ]  [
       -Ixinc[unit][=|+][/yinc[unit][=|+]] ] [ -Jparameters ] [ -Q ] [ -Rwest/east/south/north[r]
       ] [ -V ] [ -Z ] [ -:[i|o] ] [ -b[i|o][s|S|d|D[ncol]|c[var1/...]] ] [  -f[i|o]colinfo  ]  [
       -m[i|o][flag] ]

DESCRIPTION

       triangulate  reads  one  or  more  ASCII  [or binary] files (or standard input) containing
       x,y[,z] and performs Delaunay triangulation, i.e.,  it  find  how  the  points  should  be
       connected  to give the most equilateral triangulation possible.  If a map projection (give
       -R and -J) 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  (line  number,
       starting  at  0  for  the  first line) 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 Shewchuk [1996] (if installed; type triangulate - to see which
       method is selected).  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].

       -F     Force  pixel  node  registration  [Default  is   gridline   registration].    (Node
              registrations  are  defined in GMT Cookbook Appendix B on grid file formats.)  Only
              valid with -G).

       -G     Use triangulation to grid the data onto  an  even  grid  (specified  with  -R  -I).
              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).  If used, the default number of header  records
              is  N_HEADER_RECS.   Use -Hi if only input data should have header records [Default
              will write out header records if the input data have them]. Blank lines  and  lines
              starting with # are always skipped.

       -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
              .gmtdefaults4, but this can be overridden on the command line by appending c, i, or
              m  to  the scale/width value.  When central meridian is optional, default is center
              of longitude range on -R option.  Default standard parallel is  the  equator.   For
              map  height,  max  dimension,  or  min  dimension,  append h, +, or - to the width,
              respectively.
              More details can be found in the psbasemap man pages.

              CYLINDRICAL PROJECTIONS:

              -Jclon0/lat0/scale (Cassini)
              -Jcyl_stere/[lon0/[lat0/]]scale (Cylindrical Stereographic)
              -Jj[lon0/]scale (Miller)
              -Jm[lon0/[lat0/]]scale (Mercator)
              -Jmlon0/lat0/scale (Mercator - Give meridian and standard parallel)
              -Jo[a]lon0/lat0/azimuth/scale (Oblique Mercator - point and azimuth)
              -Jo[b]lon0/lat0/lon1/lat1/scale (Oblique Mercator - two points)
              -Joclon0/lat0/lonp/latp/scale (Oblique Mercator - point and pole)
              -Jq[lon0/[lat0/]]scale (Cylindrical Equidistant)
              -Jtlon0/[lat0/]scale (TM - Transverse Mercator)
              -Juzone/scale (UTM - Universal Transverse Mercator)
              -Jy[lon0/[lat0/]]scale (Cylindrical Equal-Area)

              CONIC PROJECTIONS:

              -Jblon0/lat0/lat1/lat2/scale (Albers)
              -Jdlon0/lat0/lat1/lat2/scale (Conic Equidistant)
              -Jllon0/lat0/lat1/lat2/scale (Lambert Conic Conformal)
              -Jpoly/[lon0/[lat0/]]scale ((American) Polyconic)

              AZIMUTHAL PROJECTIONS:

              -Jalon0/lat0[/horizon]/scale (Lambert Azimuthal Equal-Area)
              -Jelon0/lat0[/horizon]/scale (Azimuthal Equidistant)
              -Jflon0/lat0[/horizon]/scale (Gnomonic)
              -Jglon0/lat0[/horizon]/scale (Orthographic)
              -Jglon0/lat0/altitude/azimuth/tilt/twist/Width/Height/scale (General Perspective).
              -Jslon0/lat0[/horizon]/scale (General Stereographic)

              MISCELLANEOUS PROJECTIONS:

              -Jh[lon0/]scale (Hammer)
              -Ji[lon0/]scale (Sinusoidal)
              -Jkf[lon0/]scale (Eckert IV)
              -Jk[s][lon0/]scale (Eckert VI)
              -Jn[lon0/]scale (Robinson)
              -Jr[lon0/]scale (Winkel Tripel)
              -Jv[lon0/]scale (Van der Grinten)
              -Jw[lon0/]scale (Mollweide)

              NON-GEOGRAPHICAL PROJECTIONS:

              -Jp[a]scale[/origin][r|z] (Polar coordinates (theta,r))
              -Jxx-scale[d|l|ppow|t|T][/y-scale[d|l|ppow|t|T]] (Linear, log, and power scaling)

       -Q     Output the edges of the Voronoi cells instead [Default is Delaunay triangle edges].
              Requires  both  -m  and -R and is only available if linked with the Shewchuk [1996]
              library.

       -R     xmin, xmax, ymin, and ymax specify the Region of interest.  For geographic regions,
              these limits correspond to west, east, south, and north and you may specify them in
              decimal degrees or in [+-]dd:mm[:ss.xxx][W|E|S|N] format.  Append r if  lower  left
              and  upper  right map coordinates are given instead of w/e/s/n.  The two shorthands
              -Rg and -Rd stand for global domain (0/360 and -180/+180 in longitude respectively,
              with  -90/+90  in  latitude).   Alternatively, specify the name of an existing grid
              file and the -R settings (and grid spacing, if  applicable)  are  copied  from  the
              grid.   For  calendar  time  coordinates  you  may  either  give  (a) relative time
              (relative to the selected TIME_EPOCH and in the selected  TIME_UNIT;  append  t  to
              -JX|x),  or  (b)  absolute time of the form [date]T[clock] (append T to -JX|x).  At
              least one of date and clock must be present; the T is always  required.   The  date
              string must be of the form [-]yyyy[-mm[-dd]] (Gregorian calendar) or yyyy[-Www[-d]]
              (ISO week calendar), while the clock string must be  of  the  form  hh:mm:ss[.xxx].
              The  use  of  delimiters  and their type and positions must be exactly as indicated
              (however, input, output and plot formats are customizable; see gmtdefaults).

       -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 and/or  output.
              [Default  is  (longitude,latitude)].   Append i to select input only or o to select
              output only.  [Default affects both].

       -bi    Selects binary input.  Append s for  single  precision  [Default  is  d  (double)].
              Uppercase  S or D will force byte-swapping.  Optionally, append ncol, the number of
              columns in your binary input file if it exceeds the columns needed by the  program.
              Or  append  c  if  the  input  file  is netCDF. Optionally, append var1/var2/... to
              specify the variables to be read.  [Default is 2 input columns].

       -bo    Selects binary output.  Append s for single  precision  [Default  is  d  (double)].
              Uppercase  S or D will force byte-swapping.  Optionally, append ncol, the number of
              desired columns in your binary output file.  [Default is same as input].  Node  ids
              are stored as binary 4-byte integer triplets.  -bo is ignored if -m is selected.

       -f     Special  formatting  of  input  and/or  output columns (time or geographical data).
              Specify i or o to make this apply only to  input  or  output  [Default  applies  to
              both].   Give one or more columns (or column ranges) separated by commas.  Append T
              (absolute calendar time), t (relative time in chosen TIME_UNIT since TIME_EPOCH), x
              (longitude),  y  (latitude),  or  f (floating point) to each column or column range
              item.  Shorthand -f[i|o]g means -f[i|o]0x,1y (geographic coordinates).

       -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).

ASCII FORMAT PRECISION

       The  ASCII  output  formats  of  numerical  data  are  controlled  by  parameters  in your
       .gmtdefaults4   file.    Longitude   and   latitude    are    formatted    according    to
       OUTPUT_DEGREE_FORMAT,  whereas other values are formatted according to D_FORMAT.  Be aware
       that the format in effect can lead to loss of precision in the output, which can  lead  to
       various problems downstream.  If you find the output is not written with enough precision,
       consider switching to binary output (-bo if available) or specify more decimals using  the
       D_FORMAT setting.

GRID VALUES PRECISION

       Regardless  of  the  precision of the input data, GMT programs that create grid files will
       internally hold the grids in 4-byte floating point  arrays.   This  is  done  to  conserve
       memory and furthermore most if not all real data can be stored using 4-byte floating point
       values.  Data with higher  precision  (i.e.,  double  precision  values)  will  lose  that
       precision  once  GMT  operates  on  the  grid  or  writes out new grids.  To limit loss of
       precision when processing data you should always consider normalizing the  data  prior  to
       processing.

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, use

       triangulate samples.xyz -bo -R 0/30/0/30 -I 2 -G surf.grd > samples.ijk

       To draw the optimal Delaunay triangulation network based on the same file using a 15  -cm-
       wide Mercator map, use

       triangulate  samples.xyz -m -R-100/-90/30/34 -JM 15c | psxy -m -R-100/-90/30/34 -JM 15c -W
       0.5p -B 1 > network.ps

       To instead plot the Voronoi cell outlines, try
       triangulate samples.xyz -m -Q -R-100/-90/30/34 -JM 15c | psxy -m -R-100/-90/30/34 -JM  15c
       -W 0.5p -B 1 > cells.ps

SEE ALSO

       GMT(1), pscontour(1)

REFERENCES

       Watson, D. F., 1982, Acord: Automatic contouring of raw data, Comp. & Geosci., 8, 97-101.
       Shewchuk,  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