NAME

     grdcontour - contouring of 2-D gridded data sets


SYNOPSIS

     grdcontour   grdfile   -Ccont_int   -Jparameters   [    -A[-
     ][anot_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] ]


DESCRIPTION

     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 available.
          No space between the option  flag  and  the  associated
     arguments.   Use  upper  case for the option flags and lower
     case for modifiers.

     grdfile
          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  all
          contours  are  labeled;  use  -A- to disable all anota-
          tions.
          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  UNIT/degree,
          1:xxxxx,  or width in UNIT (upper case modifier).  UNIT
          is cm, inch, or m, depending on the  MEASURE_UNIT  set-
          ting in .gmtdefaults, but this can be overridden on the
          command line by  appending  the  c,  i,  or  m  to  the
          scale/width value.

          CYLINDRICAL PROJECTIONS:

          -Jclon0/lat0/scale (Cassini)
          -Jjlon0/scale (Miller)
          -Jmscale (Mercator - Greenwich and Equator as origin)
          -Jmlon0/lat0/scale (Mercator - Give meridian and  stan-
          dard 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  ori-
          gin)
          -Juzone/scale (UTM - Universal Transverse Mercator)
          -Jylon0/lats/scale (Basic Cylindrical Projection)

          AZIMUTHAL PROJECTIONS:

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

          CONIC PROJECTIONS:

          -Jblon0/lat0/lat1/lat2/scale (Albers)
          -Jdlon0/lat0/lat1/lat2/scale (Equidistant)
          -Jllon0/lat0/lat1/lat2/scale (Lambert)

          MISCELLANEOUS PROJECTIONS:

          -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-GEOGRAPHICAL PROJECTIONS:
          -Jpscale[/origin] (polar (theta,r) coordinates, option-
          ally 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.


OPTIONS

     No space between the option flag and  the  associated  argu-
     ments.

     -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.  Give - to disable all anota-
          tions.  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 out-
          line].

     -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  mul-
          tisegment file is created instead.

     -E   Sets the viewpoint's azimuth and elevation for perspec-
          tive view [180/90]

     -G   gap is distance between each annotation along the  same
          contour.  width is number of points over which to esti-
          mate  the  best  fitting  slope  for   contour   labels
          [Default is 10c/10 or 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 system].

     -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 or use defaults  [0.5c/0.1c  or
          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.
          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).   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  scal-
          ing 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 spe-
          cial 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 double].


EXAMPLES

     To contour the file hawaii_grav.grd every 25 mGal on a  Mer-
     cator  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  >
     hawaii_grav.ps

     To contour the file image.grd using the levels in  the  file
     cont.d  on a linear projection at 0.1 cm/x-unit and 50 cm/y-
     unit, using 20 (x) and 0.1 (y) tickmarks,  smooth  the  con-
     tours 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    -Jx0.1c/50.0c    -Ccont.d     -S4
     -B20/0.1:."RMS Misfit":  -Wa5/255/0/0 -Wc1/0/0/255ta | lp


BUGS

     The text-outline box has not been implemented  for  perspec-
     tive  view  plots.  Anotations will plot correctly, but con-
     tours 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.


SEE ALSO

     gmt(l), psbasemap(l), grdimage(l), grdview(l), pscontour(l)