grdcontour - contouring of 2-D gridded data sets


      grdcontour grdfile -Ccont_int -Jparameters [
      -Aanot_int[ffont_size][aangle][/r/g/b][o]] ] [ -Btickinfo ] [
      -Ddumpfile ] [ -Eazimuth/elevation ] [ -Ggap/width ] [ -K ] [
      -Llow/high ] [ -M[flag] ] [ -N[unit] ] [ -O ] [ -P ] [ -Qcut ] [
      -Rwest/east/south/north[r] ] [ -Ssmoothfactor ] [ -T[+|-
      ][gap/length][:LH] ] [ -U[/dx/dy/][label] ] [ -V  ] [ -W[+][type]pen ]
      [ -Xx-shift ] [ -Yy-shift ] [ -Z[factor[/shift]][p] ] [ -ccopies ] [
      -bo[s] ]


      grdcontour reads a 2-D gridded file and produces a contour map by
      tracing each contour through the grid.  As an option, the x/y/z
      positions of the contour lines may be dumped to a single multisegment
      file or many separate files.  PostScript code is generated and sent to
      standard output.  Various options that affect the plotting are
           No space between the option flag and the associated arguments.
      Use upper case for the option flags and lower case for modifiers.

           2-D gridded data set to be contoured

      -C   The contours to be drawn may be specified in one of three
           possible ways:
           If cont_int has the suffix ".cpt" and can be opened as a file, it
           is assumed to be a color palette table.  The color boundaries are
           then used as contour levels.  If the cpt-file has anotation flags
           in the last column then those contours will be anotated.  By
           default no contours are labeled; use -A to anotate all contours.
           If cont_int is a file but not a cpt-file, it is expected to
           contain contour levels in column 1 and a C(ontour) OR A(nnotate)
           in col 2. The levels marked C (or c) are contoured, the levels
           marked A (or a) are contoured and annotated.  Optionally, a third
           column may be present and contain the fixed anotation angle for
           this contour level.
           If no file is found, then cont_int is interpreted as a constant
           contour interval.  If -A is set and -C is not, then the contour
           interval is set equal to the specified anotation interval.
           If a file is given and -T is set, then only contours marked with
           upper case C or A will have tickmarks.

      -J   Selects the map projection. Scale is inch/degree, 1:xxxxx, or
           width in inch (upper case modifier).


           -Jclon0/lat0/scale (Cassini)
           -Jjlon0/scale (Miller)
           -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)


           -Jalon0/lat0/scale (Lambert).
           -Jelon0/lat0/scale (Equidistant).
           -Jflon0/lat0/horizon/scale (Gnomonic).
           -Jglon0/lat0/scale (Orthographic).
           -Jslon0/lat0/scale (General Stereographic)


           -Jblon0/lat0/lat1/lat2/scale (Albers)
           -Jllon0/lat0/lat1/lat2/scale (Lambert)


           -Jhlon0/scale (Hammer)
           -Jilon0/scale (Sinusoidal)
           -Jklon0/scale (Eckert VI)
           -Jnlon0/scale (Robinson)
           -Jrlon0/scale (Winkel Tripel)
           -Jwlon0/scale (Mollweide)


           -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.


      No space between the option flag and the associated arguments.

      -A   anot_int is annotation interval in data units.  Ignored if
           contour levels are given in a file.  [Default is no annotations].
           Several options can be set to modify the form of the annotation.
           Append ffont_size to change font size [9], append /r/g/b to
           change color of text fill box [PAGE_COLOR], append aangle to fix
           annotation angle [Default follows contour], and append o to draw
           the outline of the surrounding text box [Default is no outline].

      -B   Sets map boundary tickmark intervals. See psbasemap for details.

      -D   Dump the (x,y,z) coordinates of each contour to separate files,
           one for each contour segment. The files will be named
           dumpfile_cont_segment[_i].xyz (or .b is -b is selected), where
           cont is the contour value and segment is a running segment number
           for each contour interval (for closed contours we append _i.)
           However, when -M is used in conjunction with -D a single
           multisegment file is created instead.

      -E   Sets the viewpoint's azimuth and elevation for perspective view

      -G   gap is distance in inch between each annotation along the same
           contour.  width is number of points over which to estimate the
           best fitting slope for contour labels  [Default is 4i/10].

      -K   More PostScript code will be appended later [Default terminates
           the plot system].

      -L   Limit range: Do not draw contours for data values below low or
           above high.

      -M   When used in conjunction with -D a single multisegment file is
           created, and each contour section is preceeded by a header record
           whose first column is flag followed by the contour level.

      -N   Appends unit to all contour labels (assuming -A is set).  If no
           name is specified, the unit given in the grdfile will be used
           [Default is no unit].

      -O   Selects Overlay plot mode [Default initializes a new plot

      -P   Selects Portrait plotting mode [GMT Default is Landscape, see
           gmtdefaults to change this].

      -Q   Do not draw contours with less than cut number of points [Draw
           all contours].

      -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.  [Default is region
           defined in the grd file].

      -S   Used to resample the contour lines at roughly every
           (gridbox_size/smoothfactor) interval.

      -T   Will draw tickmarks pointing in the downward direction every gap
           along the innermost closed contours.  Append gap and tickmark
           length (in inch) or use defaults [0.2i/0.04i].  User may choose
           to tick only local highs or local lows by specifying -T+ or -T-,
           respectively.  Appending :LH will plot the characters L and H at
           the center of closed innermost contours (local lows and highs).
           L and H can be any single character (e.g., LH, -+, etc.) If a
           file is given by -C and -T is set, then only contours marked with
           upper case C or A will have tickmarks [and anotation].

      -U   Draw Unix System time stamp on plot.  User may specify where the
           lower left corner of the stamp should fall on the page relative
           to lower left corner of plot in inch [Default is (-0.75i/-
           0.75i)].  Optionally, append a label, or c (which will plot the
           command string.)

      -V   Selects verbose mode, which will send progress reports to stderr
           [Default runs "silently"].

      -W   type, if present, can be 'a' for annotated contours or 'c' for
           regular contours [Default].  pen sets the attributes for the
           particular line.  Default values for annotated contours: width =
           3, color = black, texture = solid.  Regular contours have default
           width = 1.  If the + flag is specified then the color of the
           contour lines are taken from the cpt file (see -C).

      -X -Y
           Shift origin of plot by (x-shift,y-shift) inch  [Default is
           (a1i,a1i) for new plots, (0,0) for overlays].  Prepend a for
           absolute coordinates; the default (r) will reset plot origin.

      -Z   Use to subtract shift from the data and multiply the results by
           factor before contouring starts [1/0].  (Numbers in A, -C, -L
           refer to values after this scaling has occurred.) Append p to
           indicate that this grid file contains z-values that are periodic
           in 360 degrees (e.g., phase data, angular distributions) and that
           special precautions must be taken when determining 0-contours.

      -c   Specifies the number of plot copies. [Default is 1]

      -bo  Selects binary output.  Append s for single precision [Default is


      To contour the file hawaii_grav.grd every 25 mGal on a Mercator map at
      0.5 inch/degree, annotate every 50 mGal (using fontsize = 10), using 1
      degree tickmarks, and draw 30 minute gridlines, try

      grdcontour hawaii_grav.grd -Jm0.5i -C25 -A50f10 -B1g30m >

      To contour the file image.grd using the levels in the file cont.d on a
      linear projection at 0.1 inch/x-unit and 50 inch/y-unit, using 20 (x)
      and 0.1 (y) tickmarks, smooth the contours a bit, use "RMS Misfit" as
      plot-title, use a thick red pen for annotated contours, and a thin,
      dashed, blue pen for the rest, try

      grdcontour image.grd -Jx0.1i/50.0i -Ccont.d -S4 -B20/0.1:."RMS
      Misfit": -Wa5/255/0/0 -Wc1/0/0/255ta | lpr


      The text-outline box has not been implemented for perspective view
      plots.  Anotations will plot correctly, but contours will go right
      through the text.
      The labeling of local highs and lows may plot outside the innermost
      contour since only the mean value of the contour coordinates is used
      to position the label.
      There are too many options.


      gmt, psbasemap, grdimage, grdview, pscontour

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