grdcontour
grdcontour - contouring of 2-D gridded data sets
SYNOPSIS
grdcontour grdfile -Ccont_int -Jparameters [
-A[-][anot_int][ffont_size][aangle][/r/g/b][o|t]] ] [
-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[fac
tor[/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 associ
ated 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 con
tour levels. If the cpt-file has anotation flags
in the last column then those contours will be ano
tated. By default all contours are labeled; use -A-
to disable all anotations.
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 con
tours marked with upper case C or A will have tick
marks.
UNIT is cm, inch, or m, depending on the MEA
SURE_UNIT setting 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 ori
gin)
-Jmlon0/lat0/scale (Mercator - Give meridian and
standard 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 Equa
tor as y = 0)
-Jtlon0/lat0/scale (TM - Transverse Mercator, set
origin)
-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/[slat/]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)
optional a for azimuths and offset theta [0])
-Jxx-scale[l|ppow][/y-scale[l|ppow]] (Linear, log,
and power scaling)
More details can be found in the psbasemap man
pages.
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 anotations. 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], append
o to draw the outline of the surrounding text box
[Default is no outline], or append t to use a
transparent label box [Default is opaque].
-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 con
tour 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 (interior) or C#_e (exter
nal) plus extension, and # is just a running num
ber. This allows us to make short file names that
will work with GNU utilities under DOS. 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 per
spective view [180/90]'
-G gap is distance 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 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.
ment 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. If unit starts with a
leading - then there will be no space between con
tour value and the unit. [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 min
utes [and seconds], use the dd:mm[:ss] format.
Append r if lower left and upper right map coordi
nates 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 direc
tion 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 inner
most 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 con
tours marked with upper case C or A will have tick
marks [and anotation].
-U Draw Unix System time stamp on plot. User may spec
ify 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 appear
ance; see the gmtdefaults man page for details.
-V Selects verbose mode, which will send progress
reports to stderr [Default runs "silently"].
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 0 -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 distribu
tions) 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 preci
sion [Default is double].
EXAMPLES
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 >
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
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 -Jx0.1c/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.
ANOT_OFFSET, respectively. You must thus change this value
in .gmtdefaults to affect the box size.
There are too many options.
SEE ALSO
gmt(l), gmtdefaults(l), psbasemap(l), grdimage(l), grd
view(l), pscontour(l)
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