grdcontour - contouring of 2-D gridded data sets
grdcontour grdfile -Ccont_int -Jparameters [ -A[-|annot_int][labelinfo]
] [ -Btickinfo ] [ -Ddumpfile ] [ -Eazimuth/elevation ] [
-G[d|f|n|l|L|x|X]info ] [ -K ] [ -Llow/high ] [ -M[flag] ] [ -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][n] ]
grdcontour reads a 2-D gridded file and produces a contour map by trac-
ing 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 out-
put. 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.
2-D gridded data set to be contoured
-C The contours to be drawn may be specified in one of three possi-
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 annotation
flags in the last column then those contours will be annotated.
By default all contours are labeled; use -A- to disable all
If cont_int is a file but not a cpt-file, it is expected to con-
tain 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 annotation 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 annotation interval.
If a file is given and -T is set, then only contours marked with
upper case C or A will have tickmarks. In all cases the contour
values have the same units as the grid.
-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. For map height, max dimension, or min
dimension, append h, +, or - to the width, respectively.
-Jmscale (Mercator - Greenwich and Equator as origin)
-Jmlon0/lat0/scale (Mercator - Give meridian and standard paral-
-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
-Jqlon0/scale (Equidistant Cylindrical Projection (Plate Car-
-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)
-Jslon0/lat0/[slat/]scale (General Stereographic)
-Jk[f|s]lon0/scale (Eckert IV (f) and VI (s))
-Jrlon0/scale (Winkel Tripel)
-Jvlon0/scale (Van der Grinten)
-Jp[a]scale[/origin] (polar (theta,r) coordinates, optional a
for azimuths and offset theta )
-Jxx-scale[l|ppow][/y-scale[l|ppow]][d] (Linear, log, and power
More details can be found in the psbasemap man pages.
No space between the option flag and the associated arguments.
-A annot_int is annotation interval in data units. Ignored if con-
tour levels are given in a file. [Default is no annotations].
Give - to disable all annotations implied by -C. The optional
labelinfo controls the specifics of the label formatting and
consists of a concatenated string made up of any of the follow-
ing control arguments:
+aangle for annotations at a fixed angle, +an for line-normal,
or +ap for line-parallel [Default].
+cdx[/dy] sets the clearance between label and optional text
box. Append c|i|m|p to specify the unit or % to indicate a per-
centage of the label font size [15%].
+ffont sets the desired font [Default ANNOT_FONT_PRIMARY].
+g[color] selects opaque text boxes [Default is transparent];
optionally specify the color [Default is PAGE_COLOR].
+jjust sets label justification [Default is CM].
+kcolor sets color of text labels [Default is COLOR_BACKGROUND].
+llabel sets the constant label text.
+Llflag sets the label text according to the specified flag:
flag is h: Take the label from the current multisegment header
(first scan for an embedded -Llabel option, if not use the first
word following the segment flag).
flag is d: Take the Cartesian plot distances along the line as
the label; append c|i|m|p as the unit [Default is MEASURE_UNIT].
flag is D: Calculate actual map distances; append d|e|k|m|n as
the unit [Default is d(egrees), unless label placement was based
on map distances along the lines in which case we use the same
unit specified for that algorithm]. Requires a map projection
to be used.
flag is f: Use text after the 2nd column in the fixed label
location file as the label. Requires the fixed label location
flag is x: As h but use the headers in the xfile.d instead.
Requires the crossing file option.
+o selects rounded rectangular text box [Default is rectangu-
lar]. Not applicable for curved text (+v) and only makes sense
for opaque text boxes.
+p[pen] draws the outline of text boxsets [Default is no out-
line]; optionally specify pen for outline [Default is width =
0.25p, color = black, texture = solid].
+rmin_rad will not place labels where the line’s radius of cur-
vature is less than min_rad [Default is 0].
+ssize sets the desired font size in points [Default is 9].
+uunit appends unit to all line labels. If unit starts with a
leading hypen (-) then there will be no space between label
value and the unit. [Default is no unit].
+v specifies curved labels following the path [Default is
+w specifies how many (x, y) points will be used to estimate
label angles [Default is 10].
+=prefix prepends prefix to all line labels. If prefix starts
with a leading hypen (-) then there will be no space between
label value and the prefix. [Default is no prefix]. If no name
is specified, the unit given in the grdfile will be used.
-B Sets map boundary annotation and tickmark intervals; see the
psbasemap man page for all the details.
-D Dump the (x,y,z) coordinates of each contour to separate files,
one for each contour segment. The files will be named dump-
file_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.) If the
prefix is given as ’-’ the file names are instead C#_i (inte-
rior) or C#_e (external) plus extension, and # is just a running
number. This allows us to make short file names that will work
with GNU utilities under DOS. However, when -M is used in con-
junction with -D a single multisegment file is created instead.
-E Sets the viewpoint’s azimuth and elevation for perspective view
-G Controls the placement of labels along the contours. Choose
among five controlling algorithms:
-Gddist[c|i|m|p] or -GDdist[d|e|k|m|n]. For lower case d, give
distances between labels on the plot in your preferred measure-
ment unit c (cm), i (inch), m (meter), or p (points), while for
upper case D, specify distances in map units and append the
unit; choose among e (m), k (km), m (mile), n (nautical mile),
or d (spherical degree). [Default is 10c or 4i].
-Gfffile.d reads the ascii file ffile.d and places labels at
locations in the file that matches locations along the contours.
Inexact mathces and points outside the region are skipped.
-Gl|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 contours. 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 may use
Z+ and Z- which correspond to the locations of the global max
and min locations in the grid, respectively. -GL will interpret
the point pairs as defining great circles [Default is straight
-Gnn_label specifies the number of equidistant labels for con-
tours line . Upper case -GN starts labeling exactly at the
start of the line [Default centers them along the line]. -GN-1
places one justified label at start, while -GN+1 places one jus-
tified label at the end of contours. Optionally, append
/min_dist[c|i|m|p] to enforce that a minimum distance separation
between successive labels is enforced.
-Gx|Xxfile.d reads the multi-segment file xfile.d and places
labels at the intersections between the contours and the lines
inxfile.d. -GX will resample the lines first along great-circle
-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
-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.
-O Selects Overlay plot mode [Default initializes a new plot sys-
-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
-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 wesn. The
two shorthands -Rg -Rd stand 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; append t to -JX|x), or 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 as indicated (however, input/output
and plotting formats are flexible). [Default is region defined
in the grd file].
-S Used to resample the contour lines at roughly every (grid-
-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 annota-
-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.). The GMT parameters
UNIX_TIME and UNIX_TIME_POS can affect the appearance; see the
gmtdefaults man page for details.
-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 con-
tour lines are taken from the cpt file (see -C).
-X -Y Shift origin of plot by (x-shift,y-shift). Prepend a for abso-
lute coordinates; the default (r) will reset plot origin. Give
c to center plot using current page size.
-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-con-
-c Specifies the number of plot copies. [Default is 1].
-bo Selects binary output. Append s for single precision [Default is
double]. Append n for the number of columns in the binary
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:
grdcontour hawaii_grav.grd -Jm0.5i -C25 -A50+f10 -B1g30m >
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 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, and send the output to the default printer:
grdcontour image.grd -Jx0.1c/50.0c -Ccont.d -S4 -B20/0.1:."RMS Misfit":
-Wa5/255/0/0 -Wc1/0/0/255ta | lp 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.
gmt(l), gmtdefaults(l), psbasemap(l), grdimage(l), grdview(l), pscon-
GMT4.0 1 Oct 2004 GRDCONTOUR(l)
Man(1) output converted with