pscontour - Contour table data by direct triangulation [method]
pscontour [ table ] -C[+]cpt -Jparameters -Rwest/east/south/north[/zmin/zmax][r] [ -A[-|[+]annot_int][labelinfo] ] [ -B[p|s]parameters ] [ -D[template] ] [ -Eindexfile ] [ -G[d|f|n|l|L|x|X]params ] [ -I ] [ -Jz|Zparameters ] [ -K ] [ -Lpen ] [ -N ] [ -O ] [ -P ] [ -Qcut ] [ -S[p|t] ] [ -T[+|-][+dgap[/length]][+l[labels]] ] [ -U[just/dx/dy/][c|label] ] [ -V[level] ] [ -W[+]pen ] [ -Xx_offset ] [ -Yy_offset ] [ -b<binary> ] [ -ccopies ] [ -h<headers> ] [ -i<flags> ] [ -p<flags> ] [ -t<transp> ] [ -:[i|o] ]
Note: No space is allowed between the option flag and the associated arguments.
pscontour reads an ASCII [or binary] table and produces a raw contour plot by triangulation. By default, the optimal Delaunay triangulation is performed (using either Shewchuk’s [1996] or Watson’s [1982] method as selected during GMT installation; type pscontour - to see which method is selected), but the user may optionally provide a second file with network information, such as a triangular mesh used for finite element modeling. In addition to contours, the area between contours may be painted according to the CPT file. Alternatively, the x/y/z positions of the contour lines may be saved to one or more output files (or stdout) and no plot is produced.
The contours to be drawn may be specified in one of three possible ways:
If a file is given and -T is set, then only contours marked with upper case C or A will have tick-marks. In all cases the contour values have the same units as the file.
For perspective view p, optionally append /zmin/zmax. (more ...)
- +aangle
- For annotations at a fixed angle, +an for contour-normal, or +ap for contour-parallel [Default]. For +ap, you may optionally append u for up-hill and d for down-hill cartographic annotations.
- +cdx[/dy]
- Sets the clearance between label and optional text box. Append c|i|p to specify the unit or % to indicate a percentage of the label font size [15%].
- +d
- Turns on debug which will draw helper points and lines to illustrate the workings of the contour line setup.
- +e
- Delay the plotting of the text. This is used to build a clip path based on the text, then lay down other overlays while that clip path is in effect, then turning of clipping with psclip -Cs which finally plots the original text.
- +ffont
- Sets the desired font [Default FONT_ANNOT_PRIMARY with its size changed to 9p].
- +g[color]
- Selects opaque text boxes [Default is transparent]; optionally specify the color [Default is PS_PAGE_COLOR].
- +jjust
- Sets label justification [Default is MC].
- +ndx[/dy]
- Nudges the placement of labels by the specified amount (append c|i|p to specify the units). Increments are considered in the coordinate system defined by the orientation of the contour; use +N to force increments in the plot x/y coordinates system [no nudging]. Not allowed with +v.
- +o
- Selects rounded rectangular text box [Default is rectangular]. Not applicable for curved text (+v) and only makes sense for opaque text boxes.
- +p[pen]
- Draws the outline of text boxes [Default is no outline]; optionally specify pen for outline [Default is width = 0.25p, color = black, style = solid].
- +rmin_rad
- Will not place labels where the contours’s radius of curvature is less than min_rad [Default is 0].
- +t[file]
- Saves contour label x, y, and text to file [Contour_labels.txt]. Use +T to save x, y, angle, text instead.
- +uunit
- Appends unit to all contour labels. [Default is no unit]. If z is appended we use the z-unit from the grdfile.
- +v
- Specifies curved labels following the contour [Default is straight labels].
- +w
- Specifies how many (x,y) points will be used to estimate label angles [automatic].
- +=prefix
- Prepends prefix to all contour labels. [Default is no prefix].
-D[template]
Dump the (x,y,z) coordinates of each contour to one or more output files (or stdout if template is not given). No plotting will take place. If template contains one or more of the C-format specifiers %d, %f, %c then line segments will be written to different files; otherwise all lines are written to the specified file (template). The use of the C-format specifiers controls how many files are created and how the contours are organized. If the float format %f is present (standard modifications to width and precision are allowed, e.g., %f7.3f), then the filenames will contain the contour value and lines are thus separated into files based on a common contour value. If the integer format %d is present (including modifications like %05d), then all contours are written to individual segment files; if any of the other specifiers are present they just affect the file names. Finally, if the character format %c is present it is replaced with the letters C (for closed) or O (for open), reflecting the nature of each contour. Any combination of one, two, or all three modifiers are valid, resulting in different filenames and number of files. For instance, if %c appears by itself, then only two files are created, separating the open from the closed contours (assuming both kinds are present). If just %f is used, then all segments for the same contour level will be written to the same file, resulting in N multi-segment files. If both %f and %c were combined then each contour level would be further subdivided into closed and open contours. Any combination involving %d will result in one individual file for each segment; %c, %f only modifies the file names. The files are ASCII unless -bo is used.
-G
The required argument controls the placement of labels along the quoted lines. Choose among five controlling algorithms:
- ddist[c|i|p] or Ddist[d|e|f|k|m|M|n|s]
- For lower case d, give distances between labels on the plot in your preferred measurement unit c (cm), i (inch), or p (points), while for upper case D, specify distances in map units and append the unit; choose among e (m), f (foot), k (km), M (mile), n (nautical mile) or u (US survey foot), and d (arc degree), m (arc minute), or s (arc second). [Default is 10c or 4i]. As an option, you can append /fraction which is used to place the very first label for each contour when the cumulative along-contour distance equals fraction * dist [0.25].
- fffile.d
- Reads the ASCII file ffile.d and places labels at locations in the file that matches locations along the quoted lines. Inexact matches and points outside the region are skipped.
- l|Lline1[,line2,...]
- Give start and stop coordinates for one or more comma-separated straight line segments. Labels will be placed where these lines intersect the quoted lines. The format of each line specification is start/stop, where start and stop are either a specified point lon/lat or a 2-character XY key that uses the justification format employed in pstext to indicate a point on the map, given as [LCR][BMT]. In addition, you can use Z-, Z+ to mean the global minimum and maximum locations in the grid. L will interpret the point pairs as defining great circles [Default is straight line].
- nn_label
- Specifies the number of equidistant labels for quoted lines line [1]. Upper case N starts labeling exactly at the start of the line [Default centers them along the line]. N-1 places one justified label at start, while N+1 places one justified label at the end of quoted lines. Optionally, append /min_dist[c|i|p] to enforce that a minimum distance separation between successive labels is enforced.
- x|Xxfile.d
- Reads the multisegment file xfile.d and places labels at the intersections between the quoted lines and the lines in xfile.d. X will resample the lines first along great-circle arcs.
In addition, you may optionally append +rradius[c|i|p] to set a minimum label separation in the x-y plane [no limitation].
-X[a|c|f|r][x-shift[u]]
To make a raw contour plot from the file topo.xyz and drawing the contours (pen = 2) given in the CPT file topo.cpt on a Lambert map at 0.5 inch/degree along the standard parallels 18 and 24, use
gmt pscontour topo.xyz -R320/330/20/30 -Jl18/24/0.5i -Ctopo.cpt -W0.5p > topo.ps
To create a color PostScript plot of the numerical temperature solution obtained on a triangular mesh whose node coordinates and temperatures are stored in temp.xyz and mesh arrangement is given by the file mesh.ijk, using the colors in temp.cpt, run
gmt pscontour temp.xyz -R0/150/0/100 -Jx0.1i -Ctemp.cpt -G -W0.25p > temp.ps
To save the triangulated 100-m contour lines in topo.txt and separate them into multisegment files (one for each contour level), try
gmt pscontour topo.txt -C100 -Dcontours_%.0f.txt
gmt, gmt.conf, gmtcolors, grdcontour, grdimage, nearneighbor, psbasemap, psscale, surface, triangulate
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.