triangulate - Perform optimal Delauney triangulation and gridding

triangulateinfiles[-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] ] [-bo[s][n] ] [-f[i|o]colinfo]

triangulatereads 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 writ- ten 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 seg- ment file that can be piped throughpsxyto draw the triangulation net- work. If-G-Iare set a grid will be calculated based on the surface defined by the planar triangles. The actual algorithm used in the tri- angulations is either that of Watson [1982] [Default] or Shewchuk [1996] (if installed). This choice is made during theGMTinstalla- tion.infilesData files with the point coordinates in ASCII (or binary; see-b). If no files are given the standard input is read.

-DTake either thex- ory-derivatives of surface represented by the planar facets (only used when-Gis set).-ESet the value assigned to empty nodes when-Gis set [NaN].-GUse 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 pro- jecting all data to a local coordinate system before usingtri-angulate(this is true of all gridding routines).-HInput file(s) has Header record(s). Number of header records can be changed by editing your .gmtdefaults4 file. If used,GMTdefault is 1 header record. Use-Hiif only input data should have header records [Default will write out header records if the input data have them].-Ix_inc[and optionallyy_inc] sets the grid size for optional grid output (see-G). Appendmto indicate minutes orcto indicate seconds.-JSelects 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 appendingc,i, ormto the scale/width value. For map height, max dimension, or min dimension, appendh,+, or-to the width, respectively.CYLINDRICALPROJECTIONS:-Jclon0/lat0/scale(Cassini)-Jjlon0/scale(Miller)-Jmscale(Mercator - Greenwich and Equator as origin)-Jmlon0/lat0/scale(Mercator - Give meridian and standard paral- lel)-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 Car- ree))-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)AZIMUTHALPROJECTIONS:-Jalon0/lat0/scale(Lambert).-Jelon0/lat0/scale(Equidistant).-Jflon0/lat0/horizon/scale(Gnomonic).-Jglon0/lat0/scale(Orthographic).-Jslon0/lat0/[slat/]scale(General Stereographic)CONICPROJECTIONS:-Jblon0/lat0/lat1/lat2/scale(Albers)-Jdlon0/lat0/lat1/lat2/scale(Equidistant)-Jllon0/lat0/lat1/lat2/scale(Lambert)MISCELLANEOUSPROJECTIONS:-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-GEOGRAPHICALPROJECTIONS:-Jp[a]scale[/origin] (polar (theta,r) coordinates, optionalafor azimuths and offset theta [0])-Jxx-scale[l|ppow][/y-scale[l|ppow]][d] (Linear, log, and power scaling) More details can be found in thepsbasemapman pages.-MOutput triangulation network as multiple line segments separated by a record whose first character isflag[>]. To plot, usepsxywith the-Moption (see Examples).-Rxmin,xmax,ymin,andymaxspecify the Region of interest. For geographic regions, these limits correspond towest,east,south,andnorthand you may specify them in decimal degrees or in [+-]dd:mm[:ss.xxx][W|E|S|N] format. Appendrif lower left and upper right map coordinates are given instead of wesn. The two shorthands-Rg-Rdstand for global domain (0/360 or -180/+180 in longitude respectively, with -90/+90 in latitude). For calendar time coordinates you may either give relative time (relative to the selected TIME_EPOCH and in the selected TIME_UNIT; appendtto-JX|x), or absolute time of the form [date]T[clock] (appendTto-JX|x). At least one ofdateandclockmust be present; theTis always required. Thedatestring must be of the form [-]yyyy[-mm[-dd]] (Gregorian calendar) or yyyy[-Www[-d]] (ISO week calendar), while theclockstring must be of the form hh:mm:ss[.xxx]. The use of delimiters and their type and positions must be as indicated (however, input/output and plotting formats are flexible).-VSelects verbose mode, which will send progress reports to stderr [Default runs "silently"].-ZControls whether binary data file has two or three columns [2]. Ignored if-bis not set.-:Toggles between (longitude,latitude) and (latitude,longitude) input and/or output. [Default is (longitude,latitude)]. Appendito select input only oroto select output only. [Default affects both].-biSelects binary input. Appendsfor single precision [Default is double]. Appendnfor the number of columns in the binary file(s). [Default is 2 input columns].-boSelects binary output. Appendsfor single precision [Default is double]. Appendnfor the number of columns in the binary file(s). Node ids are stored as binary 4-byte integer triplets.-bois ignored if-Mis selected.-fSpecial formatting of input and output columns (time or geo- graphical data) Specifyi(nput) oro(utput) [Default is both input and output]. Give one or more columns (or column ranges) separated by commas. AppendT(Absolute calendar time),t(time relative to chosen TIME_EPOCH),x(longitude),y(latitude),g(geographic coordinate), orf(floating point) to each column or column range item.

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, usetriangulatesamples.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, usetriangulatesamples.xyz-M-R-100/-90/30/34-JM15c| psxy-M-R-100/-90/30/34-JM15c-W0.5p-B1 > network.ps

gmt(l),pscontour(l)

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 Genera- tor and Delaunay Triangulator, First Workshop on Applied Computational Geometry (Philadelphia, PA), 124-133, ACM, May 1996. www.cs.cmu.edu/~quake/triangle.html GMT4.0 1 Oct 2004 TRIANGULATE(l)

Man(1) output converted with man2html