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)