gmt(1) GMT gmt(1)
NAME
gmt - The Generic Mapping Tools data processing and display software
package
INTRODUCTION
GMT is a collection of freely available command-line tools under the
GNU LGPL that allows you to manipulate x,y and x,y,z data sets (filter-
ing, trend fitting, gridding, projecting, etc.) and produce illustra-
tions ranging from simple x-y plots, via contour maps, to artificially
illuminated surfaces and 3-D perspective views in black/white or full
color. Linear, log10, and power scaling is supported in addition to
over 30 common map projections. The processing and display routines
within GMT are completely general and will handle any (x,y) or (x,y,z)
data as input.
SYNOPSIS
gmt is the main program that can start any of the modules:
gmt module module-options
Starts a given GMT module with the module-options that pertain
to that particular module. A few special commands are also
available:
gmt clear items
Deletes current defaults, or the cache, data or sessions direc-
tories. Choose between defaults (deletes the current gmt.conf
file used for the current modern session), cache (deletes the
useras cache directory and all of its content), data (deletes
the useras data download directory and all of its content), or
all (does all of the above).
gmt begin [session-prefix] [format] [options]
Initializes a new GMT session under modern mode [Default is
classic mode]. All work is performed in a temporary work direc-
tory. The optional session-prefix assigns a name to the ses-
sion, and this may be used as figure name for single-figure ses-
sions [gmtsession]. Likewise, the optional format can be used
to override the default graphics format [PDF].
gmt figure prefix [format(s)] [options]
Specifies the desired name, output format(s) and any custom
arguments that should be passed to psconvert when producing this
figure. All subsequent plotting will be directed to this cur-
rent figure until another gmt figure command is issued or the
session ends. The prefix is used to build final figure names
when extensions are automatically appended. The format setting
is a comma-separated list of desired extensions (e.g., pdf,png).
gmt inset [arguments]
Allows users to place a map inset by temporarily changing where
plotting takes place as well as the region and projection, then
resets to previous stage.
gmt subplot [arguments]
Allows users to create a matrix of panels with automatic label-
ing and advancement.
gmt end [show]
Terminates a GMT modern mode session and automatically converts
the registered illustration(s) to their specified formats, then
eliminates the temporary work directory. The figures are placed
in the current directory.
For information on any module, load the module documentation in your
browser via gmt docs, e.g.:
gmt docs grdimage
If no module is given then several other options are available:
--help List and description of GMT modules.
--new-script[=L]
Write a GMT modern mode script template to stdout. Optionally
append the desired scripting language among bash, csh, or batch.
Default is the main shell closest to your current shell (e.g.,
bash for zsh, csh for tcsh).
--new-glue=name
Write the C code glue needed when building third-party supple-
ments as shared libraries. The name is the name of the shared
library. Run gmt in the directory of the supplement and the glue
code will be written to stdout. Including this C code when
building the shared library means gmt can list available modules
via the --show-modules, --help options. We recommend saving the
code to gmt_name_glue.c.
--show-bindir
Show directory of executables and exit.
--show-citation
Show the citation for the latest GMT publication.
--show-classic
List classic module names on stdout and exit.
--show-classic-core
List classic module names (core only) on stdout and exit.
--show-cores
Show number of available cores.
--show-datadir
Show data directory/ies and exit.
--show-dataserver
Show URL of the remote GMT data server.
--show-doi
Show the DOI of the current release.
--show-modules
List modern module names on stdout and exit.
--show-modules-core
List modern module names (core only) on stdout and exit.
--show-library
Show the path of the shared GMT library.
--show-plugindir
Show plugin directory and exit.
--show-sharedir
Show share directory and exit.
--show-userdir
Show full path of useras ~/.gmt dir and exit.
--version
Print version and exit.
= Check if that module exist and if so the program will exit with
status of 0; otherwise the status of exit will be non-zero.
COMMAND-LINE COMPLETION
GMT provides basic command-line completion (tab completion) for bash.
The completion rules are either installed in /etc/bash_completion.d/gmt
or <prefix>/share/tools/gmt_completion.bash. Depending on the distri-
bution, you may still need to source the gmt completion file from
~/.bash_completion or ~/.bashrc. For more information see Section com-
mand-line-completion in the CookBook.
GMT MODULES
Run gmt --help to print the list of all core and supplementals modules
within GMT, and a very short description of their purpose. Detailed
information about each program can be found in the separate manual
pages.
CUSTOM MODULES
The gmt program can also load custom modules from shared libraries
built as specified in the GMT API documentation. This way your modules
can benefit from the GMT infrastructure and extend GMT in specific
ways.
THE COMMON GMT OPTIONS
-B[p|s]parameters -Jparameters -Jz|Zparameters
-Rwest/east/south/north[/zmin/zmax][+r][+uunit] -U[stamp] -V[level]
-X[a|c|f|r][xshift] -Y[a|c|f|r][yshift] -aflags -bbinary -c-
row,col|index -dnodata -eregexp -fflags -ggaps -hheaders -iflags -j-
flags -lflags -nflags -oflags -pflags -qflags -rreg -sflags -ttransp
-x[[-]n] -:[i|o]
DESCRIPTION
These are all the common GMT options that remain the same for all GMT
modules. No space between the option flag and the associated arguments.
The -B option
Syntax
-B[p|s]parameters
Set map boundary frame and axes attributes. (See cookbook infor-
mation).
Description
This is potentially the most complicated option in GMT, but most exam-
ples of its usage are actually quite simple. We distinguish between two
sets of information: Frame settings and Axes settings. These are set
separately by their own -B invocations; hence multiple -B specifica-
tions may be specified. The Frame settings cover things such as which
axes should be plotted, canvas fill, plot title (and subtitle), and
what type of gridlines be drawn, whereas the Axes settings deal with
annotation, tick, and gridline intervals, axes labels, and annotation
units.
Frame settings
The Frame settings are specified by
-B[axes][+b][+gfill][+i[val]][+n][+olon/lat][+ssubtitle][+tti-
tle][+w[pen]][+xfill][+yfill][+zfill]
The frame setting is optional but can be invoked once to override the
defaults. The following modifiers can be appended to -B to control the
Frame settings:
o axes to set which of the axes should be drawn and possibly annotated
using a combination of the codes listed below [default is theme
dependent]. Borders omitted from the set of codes will not be drawn.
For example, WSn denotes that the awesterna (left) and asoutherna
(bottom) axes should be drawn with tick-marks and annotations by
using W and S; that the anortherna (top) edge of the plot should be
drawn with tick-marks and without annotations by using n; and that
the aeasterna (right) axes should not be drawn by not including one
of E|e|r.
o West, East, South, North, and/or (for 3-D plots) Z indicate axes
that should be drawn with both tick-marks and annotations.
o west, east, south, north, and/or (for 3-D plots) z indicate axes
that should be drawn with tick-marks but without annotations.
o l(eft), r(ight), b(ottom), t(op) and/or (for 3-D plots) u(p)
indicate axes that should be drawn without tick-marks or annota-
tions.
o Z|zcode (for 3-D plots) where code is any combination of the corner
ids 1, 2, 3, 4. By default, a single vertical axes will be plotted
for 3-D plots at the most suitable map corner. code can be used to
override this, where 1 represents the south-western (lower-left) cor-
ner, 2 the south-eastern (lower-right), 3 the north-eastern
(upper-right), and 4 the north-western (upper-left) corner.
o +w[pen] (for 3-D plots) to draw the outlines of the x-z and y-z
planes [default is no outlines]. Optionally, append pen to specify
different pen attributes [default is MAP_GRID_PEN_PRIMARY].
o +b (for 3-D plots) to draw the foreground lines of the 3-D cube
defined by -R.
o +gfill to paint the interior of the canvas with a color specified by
fill [default is no fill]. This also sets fill for the two back-walls
in 3-D plots.
o +xfill to paint the yz plane with a color specified by fill [default
is no fill].
o +yfill to paint the xz plane with a color specified by fill [default
is no fill].
o +zfill to paint the xy plane with a color specified by fill [default
is no fill].
o +i[val] to annotate an internal meridian or parallel when the axis
that normally would be drawn and annotated does not exist (e.g., for
an azimuthal map with 360-degree range that has no latitude axis or a
global Hammer map that has no longitude axis). val gives the meridian
or parallel that should be annotated [default is 0].
o +olon/lat to produce oblique gridlines about another pole specified
by lon/lat [default references to the North pole]. +o is ignored if
no gridlines are requested.
o +n to have no frame and annotations at all [default is contolled by
axes].
o +ttitle to place the string given in title centered above the plot
frame [default is no title].
o +ssubtitle (requires +ttitle) to place the string given in subtitle
beneath the title [default is no subtitle].
Note: Both +ttitle and +ssubtitle may be set over multiple lines by
breaking them up using the markers @^ or <break>. To include LaTeX
code as part of a single-line title or subtitle, enclose the expression
with @[ markers (or alternatively <math> a| </math>) (requires latex
and dvips to be installed). See the /cookbook/gmt-latex chapter for
more details.
Axes settings
The Axes settings are specified by
-B[p|s][x|y|z]intervals[+aangle|n|p][+f][+llabel][+pprefix][+uunit]
but you may also split this into two separate invocations for clarity,
i.e.,
-B[p|s][x|y|z][+aangle|n|p][+f][+l|Llabel][+pprefix][+s|Sseclabel][+uunit]
-B[p|s][x|y|z]intervals
The following modifiers can be appended to -B to control the Axes set-
tings:
o p|s to set whether the modifiers apply to the p(rimary) or
s(econdary) axes [Default is p]. These settings are mostly used for
time axes annotations but are available for geographic axes as well.
Note: Primary refers to annotations closest to the axis and secondary
to annotations further away. Hence, primary annotation-, tick-, and
gridline-intervals must be shorter than their secondary counterparts.
The terms aprimarya and asecondarya do not reflect any hierarchical
order of units: the aprimarya annotation interval is usually smaller
(e.g., days) while the asecondarya annotation interval typically is
larger (e.g., months).
o x|y|z to set which axes the modifiers apply to [default is xy]. If
you wish to give different annotation intervals or labels for the
various axes then you must repeat the B option for each axis. For a
3-D plot with the -p and -Jz options used, -Bz can be used to provide
settings for the verical axis.
o +f (for geographic axes only) to give fancy annotations with W|E|S|N
suffices encoding the sign.
o +l|+Llabel (for Cartesian plots only) to add a label to an axis. +l
uses the default label orientation; +L forces a horizontal label for
y-axes, which is useful for very short labels.
o +s|Sseclabel (for Cartesion plots only) to specify an alternate label
for the right or upper axes. +s uses the default label orientation;
+S forces a horizontal label for y-axes, which is useful for very
short labels.
o +pprefix (for Cartesion plots only) to define a leading text prefix
for the axis annotation (e.g., dollar sign for plots related to
money). For geographic maps the addition of degree symbols, etc. is
automatic and controlled by FORMAT_GEO_MAP.
o +uunit (for Cartesion plots only) to append specific units to the
annotations. For geographic maps the addition of degree symbols, etc.
is automatic and controlled by FORMAT_GEO_MAP.
o +aangle (for Cartesion plots only) to plot slanted annotations, where
angle is measured with respect to the horizontal and must be in the
-90 <= angle <= 90 range. +an can be used as a shorthand for normal
(i.e., +a90) [Default for y-axis] and +ap for parallel (i.e., +a0)
annotations [Default for x-axis]. These defaults can be changed via
MAP_ANNOT_ORTHO.
o intervals to define the intervals for annotations and major tick
spacing, minor tick spacing, and/or grid line spacing. See Intervals
Specification for the formatting associated with this modifier.
NOTE: To include LaTeX code as part of a label, enclose the expression
with @[ markers (or alternatively <math> a| </math>). (requires latex
and dvips to be installed). See the /cookbook/gmt-latex chapter for
more details.
NOTE: If any labels, prefixes, or units contain spaces or special char-
acters you will need to enclose them in quotes.
NOTE: Text items such as title, subtitle, label and seclabel are seen
by GMT as part of a long string containing everything passed to -B.
Therefore, they cannot contain substrings that look like other modi-
fiers. If you need to embed such sequences (e.g., +taSolving a+b=ca)
you need to replace those + symbols with their octal equivalent \053,
(e.g., +taSolving a\053b=ca).
NOTE: For non-geographical projections: Give negative scale (in -Jx) or
axis length (in -JX) to change the direction of increasing coordinates
(i.e., to make the y-axis positive down).
Intervals specification
The intervals specification is a concatenated string made up of substrings of the form
[a|f|g][stride][phase][unit].
The choice of a|f|g sets the axis item of interest, which are detailed
in the Table interval types. Optionally, append phase to shift the
annotations by that amount (positive or negative with the sign being
required). Optionally, append unit to specify the units of stride,
where unit is one of the 18 supported unit codes. For custom annota-
tions and intervals, intervals can be given as cintfile, where intfile
contains any number of records with coord type [label]. See the section
Custom axes for more details.
+-----+----------------------------+
|Flag | Description |
+-----+----------------------------+
|a | Annotation and major tick |
| | spacing |
+-----+----------------------------+
|f | Minor tick spacing |
+-----+----------------------------+
|g | Grid line spacing |
+-----+----------------------------+
NOTE: The appearance of certain time annotations (month-, week-, and
day-names) may be affected by the GMT_LANGUAGE, FORMAT_TIME_PRI-
MARY_MAP, and FORMAT_TIME_SECONDARY_MAP settings.
Automatic intervals: GMT will auto-select the spacing between the anno-
tations and major ticks, minor ticks, and grid lines if stride is not
provided after a|f|g. This can be useful for automated plots where the
region may not always be the same, making it difficult to determine the
appropriate stride in advance. For example, -Bafg will select all three
spacings automatically for both axes. In case of longitudealatitude
plots, this will keep the spacing the same on both axes. You can also
use -Bxafg -Byafg to auto-select them separately. Note that given the
myriad ways of specifying time-axis annotations, the automatic selec-
tions may need to be overridden with manual settings to achieve exactly
what you need. When stride is omitted after g, the grid line are spaced
the same as the minor ticks; unless g is used in consort with a, in
which case the grid lines are spaced the same as the annotations.
Stride units: The unit flag can take on one of 18 codes which are
listed in Table Units. Almost all of these units are time-axis spe-
cific. However, the d, m, and s units will be interpreted as arc
degrees, minutes, and arc seconds respectively when a map projection is
in effect.
+-----+----------------+---------------------+
|Flag | Unit | Description |
+-----+----------------+---------------------+
|Y | year | Plot using all 4 |
| | | digits |
+-----+----------------+---------------------+
|y | year | Plot using last 2 |
| | | digits |
+-----+----------------+---------------------+
|O | month | Format annotation |
| | | using FOR- |
| | | MAT_DATE_MAP |
+-----+----------------+---------------------+
|o | month | Plot as 2-digit |
| | | integer (1a12) |
+-----+----------------+---------------------+
|U | ISO week | Format annotation |
| | | using FOR- |
| | | MAT_DATE_MAP |
+-----+----------------+---------------------+
|u | ISO week | Plot as 2-digit |
| | | integer (1a53) |
+-----+----------------+---------------------+
|r | Gregorian week | 7-day stride from |
| | | start of week (see |
| | | TIME_WEEK_START) |
+-----+----------------+---------------------+
|K | ISO weekday | Plot name of week- |
| | | day in selected |
| | | language |
+-----+----------------+---------------------+
|k | weekday | Plot number of day |
| | | in the week (1a7) |
| | | (see |
| | | TIME_WEEK_START) |
+-----+----------------+---------------------+
|D | date | Format annotation |
| | | using FOR- |
| | | MAT_DATE_MAP |
+-----+----------------+---------------------+
|d | day | Plot day of month |
| | | (1a31) or day of |
| | | year (1a366) (see |
| | | FORMAT_DATE_MAP) |
+-----+----------------+---------------------+
|R | day | Same as d; annota- |
| | | tions aligned with |
| | | week (see |
| | | TIME_WEEK_START) |
+-----+----------------+---------------------+
|H | hour | Format annotation |
| | | using FOR- |
| | | MAT_CLOCK_MAP |
+-----+----------------+---------------------+
|h | hour | Plot as 2-digit |
| | | integer (0a24) |
+-----+----------------+---------------------+
|M | minute | Format annotation |
| | | using FOR- |
| | | MAT_CLOCK_MAP |
+-----+----------------+---------------------+
|m | minute | Plot as 2-digit |
| | | integer (0a60) |
+-----+----------------+---------------------+
|S | seconds | Format annotation |
| | | using FOR- |
| | | MAT_CLOCK_MAP |
+-----+----------------+---------------------+
|s | seconds | Plot as 2-digit |
| | | integer (0a60) |
+-----+----------------+---------------------+
NOTE: If your axis is in radians you can use multiples or fractions of
pi to set such annotation intervals. The format is [s]pi[f], for an
optional integer scale s and optional integer fraction f. When GMT
parses one of these forms we alert the labeling machinery to look for
certain combinations of pi, limited to npi, 3/2 pi (3pi2), and frac-
tions 3/4 (3pi4), 2/3 (2pi3), 1/2 (1pi2), 1/3 (1pi3), and 1/4 (1pi4) in
the interval given to the -B axes settings. When an annotated value is
within roundoff-error of these combinations we typeset the label using
the Greek letter \pi and required multiples or fractions.
NOTE: These GMT parameters can affect the appearance of the map bound-
ary:
MAP_ANNOT_MIN_ANGLE, MAP_ANNOT_MIN_SPACING, FONT_ANNOT_PRIMARY,
FONT_ANNOT_SECONDARY, MAP_ANNOT_OFFSET_PRIMARY, MAP_ANNOT_OFF-
SET_SECONDARY, MAP_ANNOT_ORTHO, MAP_FRAME_AXES, MAP_DEFAULT_PEN,
MAP_FRAME_TYPE, FORMAT_GEO_MAP, MAP_FRAME_PEN, MAP_FRAME_WIDTH,
MAP_GRID_CROSS_SIZE_PRIMARY, MAP_GRID_PEN_PRIMARY,
MAP_GRID_CROSS_SIZE_SECONDARY, MAP_GRID_PEN_SECONDARY,
FONT_TITLE, FONT_LABEL, MAP_LINE_STEP, MAP_ANNOT_OBLIQUE, FOR-
MAT_CLOCK_MAP, FORMAT_DATE_MAP, FORMAT_TIME_PRIMARY_MAP, FOR-
MAT_TIME_SECONDARY_MAP, GMT_LANGUAGE, TIME_WEEK_START,
MAP_TICK_LENGTH_PRIMARY, and MAP_TICK_PEN_PRIMARY; see the
/gmt.conf man page for details.
The -J option
Syntax
-Jparameters
Specify the projection. (See cookbook summary) (See projections
table).
Description
Select map projection. The first character of parameters determines the
projection. If the character is upper case then the argument(s) sup-
plied as scale(s) is interpreted to be the map width (or axis lengths),
else the scale argument(s) is the map scale (see its definition for
each projection). The measurement unit (called UNIT below) is cm, inch,
or point, depending on the PROJ_LENGTH_UNIT setting in gmt.conf, but
this can be overridden on the command line by appending c, i, or p to
the scale or width values. Append +dh, +du, or +dl to the given width
if you instead want to set the map height, the maximum (upper) dimen-
sion, or the minimum (lower) dimension, respectively [Default is +dw
for width]. In case the central meridian is an optional parameter and
it is being omitted, then the center of the longitude range given by
the -R option is used. The default standard parallel is the equator.
The ellipsoid used in map projections is user-definable. 73 commonly
used ellipsoids and spheroids are currently supported, and users may
also specify their own custom ellipsoid parameters [Default is WGS-84].
Several GMT parameters can affect the projection: PROJ_ELLIPSOID,
GMT_INTERPOLANT, PROJ_SCALE_FACTOR, and PROJ_LENGTH_UNIT; see the
gmt.conf man page for details. Choose one of the following projections
and append the required parameters (The E or C after projection names
stands for Equal-Area and Conformal, respectively):
CYLINDRICAL PROJECTIONS:
-Jc|Clon0/lat0/scale|width (Cassini).
Give projection center lon0/lat0 and either scale (with -Jc; as
1:xxxx or plot-units/degree) or width (with -JC; in plot-units).
-Jcyl_stere|Cyl_stere/[lon0/[lat0/]]scale|width (Cylindrical Stereo-
graphic)
Give central meridian lon0 (optional), standard parallel lat0
(optional), and either scale along parallel (with -Jcyl_stere;
as 1:xxxx or plot-units/degree) or width (with -JCyc_stere; in
plot-units). The standard parallel is typically one of these
(but can be any value):
o 66.159467 - Milleras modified Gall
o 55 - Kamenetskiyas First
o 45 - Gallas Stereographic
o 30 - Bolshoi Sovietskii Atlas Mira or Kamenetskiyas Second
o 0 - Braunas Cylindrical
-Jj|J[lon0/]scale|width (Miller Cylindrical Projection).
Give the central meridian lon0 (optional) and either scale (with
-Jj; as 1:xxxx or plot-units/degree) or width (with -JJ; in
plot-units).
-Jm|M[lon0/[lat0/]]scale|width (Mercator [C])
Give central meridian lon0 (optional), standard parallel lat0
(optional), and either scale along parallel (with -Jm; as 1:xxxx
or plot-units/degree) or width (with -JM; in plot-units).
-Joparameters[+v] (Oblique Mercator [C]).
Typically used with -RLLx/LLy/URx/URy+r or with projected coor-
dinates. Specify one of:
-Jo|O[a|A]lon0/lat0/azimuth/scale|width[+v]
Set projection center lon0/lat0, azimuth of oblique equa-
tor, and scale or width
-Jo|O[b|B]lon0/lat0/lon1/lat1/scale|width[+v]
Set projection center lon0/lat0, another point on the
oblique equator lon1/lat1, and scale or width
-Jo|O[c|C]lon0/lat0/lonp/latp/scale|width[+v]
Set projection center lon0/lat0, pole of oblique projec-
tion lonp/latp, and scale or width
Give scale along oblique equator (with -Ja|b|c; 1:xxxx or
plot-units/degree) or width (with -JA|B|C; in plot-units). Use
upper-case A|B|C to remove enforcement of a northern hemisphere
pole. Append +v to let the oblique Equator align with the y-axis
[x-axis]. Note: If the region (-R) is given without the +r mod-
ifier then the arguments are considered oblique degrees relative
to the projection center and not longitude/latitude bounds.
-Jq|Q[lon0/[lat0/]]scale|width (Cylindrical Equidistant).
Give the central meridian lon0 (optional), standard parallel
lat0 (optional), and either scale (with -Jq; as 1:xxxx or
plot-units/degree) or width (with -JQ; in plot-units) The stan-
dard parallel is typically one of these (but can be any value):
o 61.7 - Grafarend and Niermann, minimum linear distortion
o 50.5 - Ronald Miller Equirectangular
o 43.5 - Ronald Miller, minimum continental distortion
o 42 - Grafarend and Niermann
o 37.5 - Ronald Miller, minimum overall distortion
o 0 - Plate Carree, Simple Cylindrical, Plain/Plane Chart
-Jt|Tlon0/[lat0/]scale|width (Transverse Mercator [C])
Give the central meridian lon0, central parallel lat0
(optional), and either scale (with -Jt; as 1:xxxx or
plot-units/degree) or width (with -JT; in plot-units).
-Ju|Uzone/scale|width (UTM - Universal Transverse Mercator [C]).
Give the UTM zone (A,B,1-60[C-X],Y,Z)) and either scale (with
-Ju; as 1:xxxx or plot-units/degree) or width (with -JU; in
plot-units). Zones: If C-X not given, prepend - or + to enforce
southern or northern hemisphere conventions [default is northern
if south > 0].
-Jy|Y[lon0/[lat0/]]scale|width (Cylindrical Equal-Area [E]).
Give the central meridian lon0 (optional), standard parallel
lat0 (optional), and either scale (with -Jy; as 1:xxxx or
plot-units/degree) or width (with -JY; in plot-units). The stan-
dard parallel is typically one of these (but can be any value):
o 50 - Balthasart
o 45 - Gall
o 37.0666 - Caster
o 37.4 - Trystan Edwards
o 37.5 - Hobo-Dyer
o 30 - Behrman
o 0 - Lambert (default)
CONIC PROJECTIONS:
-Jb|Blon0/lat0/lat1/lat2/scale|width (Albers [E]).
Give projection center lon0/lat0, two standard parallels
lat1/lat2, and either scale (with -Jb; as 1:xxxx or
plot-units/degree) or width (with -JB; in plot-units).
-Jd|Dlon0/lat0/lat1/lat2/scale|width (Conic Equidistant)
Give projection center lon0/lat0, two standard parallels
lat1/lat2, and either scale (with -Jd; as 1:xxxx or
plot-units/degree) or width (with -JD; in plot-units).
-Jl|Llon0/lat0/lat1/lat2/scale|width (Lambert [C])
Give origin lon0/lat0, two standard parallels lat1/lat2, and
scale along these (with -Jl; as 1:xxxx or plot-units/degree)
or width (with -JL; in plot-units).
-Jpoly|Poly/[lon0/[lat0/]]scale|width ((American) Polyconic).
Give the central meridian lon0 (optional), reference parallel
lat0 (optional, default = equator), and either scale along
central meridian (with -Jpoly; as 1:xxxx or
plot-units/degree) or width (with -JPoly; in plot-units).
AZIMUTHAL PROJECTIONS:
Except for polar aspects, -Rw/e/s/n will be reset to -Rg. Use
-Rxlleft/ylleft/xuright/yuright+r for smaller regions.
-Ja|Alon0/lat0[/horizon]scale|width (Lambert [E]).
lon0/lat0 specifies the projection center. horizon specifies
the max distance from projection center (in degrees, <= 180,
default 90). Give either scale (with -Ja; as 1:xxxx or
radius/lat, where radius is distance in plot-units from ori-
gin to the oblique latitude lat) or width (with -JA; in
plot-units).
-Je|Elon0/lat0[/horizon]scale|width (Azimuthal Equidistant).
lon0/lat0 specifies the projection center. horizon specifies
the max distance from projection center (in degrees, <= 180,
default 180). Give scale (with -Je; as 1:xxxx or radius/lat,
where radius is distance in plot-units from origin to the
oblique latitude lat) or width (with -JE; in plot-units).
-Jf|Flon0/lat0[/horizon]scale|width (Gnomonic).
lon0/lat0 specifies the projection center. horizon specifies
the max distance from projection center (in degrees, < 90,
default 60). Give scale (with -Jf; as 1:xxxx or radius/lat,
where radius is distance in plot-units from origin to the
oblique latitude lat) or width (with -JF; in plot-units).
-Jg|Glon0/lat0[/horizon]/scale|width (Orthographic).
lon0/lat0 specifies the projection center. horizon specifies
the max distance from projection center (in degrees, <= 90,
default 90). Give scale (with -Jg; as 1:xxxx or radius/lat,
where radius is distance in plot-units from origin to the
oblique latitude lat.
-Jg|Glon0/lat0/altitude/azimuth/tilt/twist/Width/Height/scale|width
(General Perspective).
lon0/lat0 specifies the projection center. altitude is the
height (in km) of the viewpoint above local sea level. If
altitude is less than 10, then it is the distance from the
center of the earth to the viewpoint in earth radii. If alti-
tude has a suffix r then it is the radius from the center of
the earth in kilometers. azimuth is measured to the east of
north of view. tilt is the upward tilt of the plane of pro-
jection. If tilt is negative, then the viewpoint is centered
on the horizon. Further, specify the clockwise twist, Width,
and Height of the viewpoint in degrees. Give scale (with -Jg;
as 1:xxxx or radius/lat, where radius is distance in
plot-units from origin to the oblique latitude lat) or width
(with -JG; in plot-units).
-Js|Slon0/lat0[/horizon]/scale|width (General Stereographic [C]).
lon0/lat0 specifies the projection center. horizon specifies
the max distance from projection center (in degrees, < 180,
default 90). Give scale (with -Js; as 1:xxxx (true at pole)
or lat0/1:xxxx (true at standard parallel lat) or radius/lat
(radius in plot-units from origin to the oblique latitude
lat). Note if 1:xxxx is used then to specify horizon you must
also specify the lat as +-90 to avoid ambiguity.) or width
(with -JS; in plot-units).
MISCELLANEOUS PROJECTIONS:
-Jh|H[lon0/]scale|width (Hammer [E]).
Give the central meridian lon0 (optional) and either scale
along equator (with -Jh; as 1:xxxx or plot-units/degree) or
width (with -JH; in plot-units).
-Ji|I[lon0/]scale|width (Sinusoidal [E]).
Give the central meridian lon0 (optional) and either scale
along equator (with -Ji; as 1:xxxx or plot-units/degree) or
width (with -JI; in plot-units).
-Jk|Kf[lon0/]scale|width (Eckert IV [E]).
Give the central meridian lon0 (optional) and either scale
along equator (with -Jk; as 1:xxxx or plot-units/degree) or
width (with -JK; in plot-units).
-Jk|K[s][lon0/]scale|width (Eckert VI [E]).
Give the central meridian lon0 (optional) and either scale
along equator (with -Jk; as 1:xxxx or plot-units/degree) or
width (with -JK; in plot-units).
-Jn|N[lon0/]scale|width (Robinson).
Give the central meridian lon0 (optional) and either scale
along equator (with -Jn; as 1:xxxx or plot-units/degree) or
width (with -JN; in plot-units).
-Jr|R[lon0/]scale|width (Winkel Tripel).
Give the central meridian lon0 (optional) and either scale
along equator (with -Jr; as 1:xxxx or plot-units/degree) or
width (with -JR; in plot-units).
-Jv|V[lon0/]scale|width (Van der Grinten).
Give the central meridian lon0 (optional) and either scale
along equator (with -Jv; as 1:xxxx or plot-units/degree) or
width (with -JV; in plot-units).
-Jw|W[lon0/]scale|width (Mollweide [E]).
Give the central meridian lon0 (optional) and either scale
along equator (with -Jw; as 1:xxxx or plot-units/degree) or
width (with -JW; in plot-units).
NON-GEOGRAPHICAL PROJECTIONS:
-Jp|Pscale|width[+a][+f[e|p|radius]][+kkind][+roffset][+tori-
gin][+z[p|radius]]] (Polar coordinates (theta, r))
Give scale (with -Jp; in plot-units/r-unit) or width (with -JP; in
plot-units). The following modifiers are supported by -Jp|P:
o +a to indicate that theta is azimuth CW from North instead of
direction CCW from East [Default is CCW from East].
o +f to flip the radial direction to point inwards, and append e to
indicate that r represents elevations in degrees (requires south
>= 0 and north <= 90), p to select current planetary radius
(determined by PROJ_ELLIPSOID) as maximum radius [north], or
radius to specify a custom radius.
o +k sets the annotation kind to be longitudes (x) or latitudes (y)
[Default is unspecified angles].
o +roffset to include a radial offset in measurement units [default
is 0].
o +torigin in degrees so that this angular value is aligned with the
positive x-axis (or the azimuth to be aligned with the positive
y-axis if +a) [default is 0].
o +z to annotate depth rather than radius [default is radius].
Alternatively, if your r data are actually depths then you can
append p or radius to get radial annotations (r = radius - z)
instead.
-Jx|Xx-scale|width[l|ppower|T|t][/y-scale|height[l|ppower|T|t]][d|g]
(Linear, log, and power scaling)
Give x-scale (with -Jx; as 1:xxxx or plot-units/x-unit) and/or
y-scale (1:xxxx or plot-units/y-unit); or specify width and/or
height (with -JX; in plot-units). y-scale=x-scale if not specified
separately and using 1:xxxx implies that x-unit and y-unit are in
meters. Use negative scale(s) to reverse the direction of an axis
(e.g., to have y be positive down). Set height or width to 0 to have
it recomputed based on the implied scale of the other axis. Option-
ally, append to x-scale y-scale, width or height one of the follow-
ing:
o d to indicate that data are geographical coordinates (in degrees).
o g to indicate that data are geographical coordinates
o l to take log10 of values before scaling.
o ppower to raise values to power before scaling.
o t to indicate that input coordinates are time relative to
TIME_EPOCH.
o T to indicate that input coordinates are absolute time.
For mixed axes with only one geographic axis you may need to
set -f as well.
When -J is used without any further arguments, or just with the projec-
tion type, the arguments of the last used -J, or the last used -J with
that projection type, will be used.
-Jz|Zparameters
Set z-axis scaling; same syntax as -Jx.
-Jproj|EPSG:n
Starting at GMT6 it is possible to use the PROJ library to do
coordinate and datum transforms. This is achieved via GDAL so
it requires that GMT build is linked to that library. It is,
however, beyond the scope of this manual to document the PROJ
syntax (that is the syntax of the proj and cs2cs programs) so
users are referred to PROJ Applications for the details.
The usage of PROJ follows very closely the syntax of proj and
cs2cs. The projection parameters are encapsulated under the -J
option. Because there are normally several parameters defining a
referencing system separated by spaces (in PROJ or GDAL) we can
either use double quotes as in -Ja+proj=merc +ellps=WGS84
+units=ma or just glue all parameters like in
-J+proj=merc+ellps=WGS84+units=m.
Using EPSG codes is also possible (but need the setting of the
GDAL_DATA environment variable to point to the GDALas data
sub-directory). For example -JEPSG:4326 sets the WGS-84 system.
For mapproject and grdproject we can go directly from the refer-
encing system A to B without the intermediate step of converting
to geographic coordinates. That is obtained (like in cs2cs) by
using the +to keyword. Example:
-JEPSG:4326+to+proj=aeqd+ellps=WGS84+units=m. A much awaited
bonus is also that we now do not need to set -R to do point
coordinate conversions.
While for point and grid conversions done by mapproject and grd-
project we can use all PROJ projections, the situations is, how-
ever, rather more limited for mapping purposes. Here, only the
subset of the PROJ projections that can be mapped into the GMT
projections syntax is available to use. Another aspect that is
not present in PROJ, because itas not a mapping library, is how
to set the map scale or map dimension. We introduced the two
extensions +width=size and +scale=1:xxxx that work exactly like
the map width and scale in classical GMT. It is also allowed to
provide the scale (but NOT the width) by appending the string
a/1:xxxa to the end of the projection parameters.
The -R option
Syntax
-Rxmin/xmax/ymin/ymax[+r][+uunit]
Specify the region of interest. (See cookbook information).
Description
The -R option defines the map region or data domain of interest. It may
be specified in one of seven ways (options 1 and 2 are shown in panels
a) and b) respectively of the Figure Map region):
1. -Rxmin/xmax/ymin/ymax[+uunit]. This is the standard way to specify
Cartesian data domains and geographic regions when using map projec-
tions where meridians and parallels are rectilinear. Optionally,
append +uunit to specify a region in projected units (e.g., UTM
meters) where xmin/xmax/ymin/ymax are Cartesian projected coordi-
nates compatible with the chosen projection and unit is an allowable
distance unit.
2. -Rxlleft/ylleft/xuright/yuright+r. This form is useful for map pro-
jections that are oblique, making meridians and parallels poor
choices for map boundaries. Here, we instead specify the lower left
corner and upper right corner geographic coordinates, followed by
the modifier +r. This form guarantees a rectangular map even though
lines of equal longitude and latitude are not straight lines.
3. -Rg or -Rd. These forms can be used to quickly specify the global
domain (0/360 for -Rg and -180/+180 for -Rd in longitude, with
-90/+90 in latitude).
4. -Rgridfile. This will copy the domain settings found for the grid in
specified file. Note that depending on the nature of the calling
module, this mechanism will also set grid spacing and possibly the
grid registration (see cookbook/options:Grid registration: The
**-r** option).
5. -Rcode1,code2,^<i>a|[+e|r|Rincs]]. This indirectly supplies the region
by consulting the DCW (Digital Chart of the World) database and
derives the bounding regions for one or more countries given by the
codes. Simply append one or more comma-separated countries using the
two-character ISO 3166-1 alpha-2 convention. To select a state
within a country (if available), append .state, e.g, US.TX for
Texas. To specify a whole continent, prepend = to any of the conti-
nent codes AF (Africa), AN (Antarctica), AS (Asia), EU (Europe), OC
(Oceania), NA (North America), or SA (South America). The following
modifiers can be appended:
o +r to adjust the region boundaries to be multiples of the steps
indicated by inc, xinc/yinc, or winc/einc/sinc/ninc [default is no
adjustment]. For example, -RFR+r1 will select the national bound-
ing box of France rounded to nearest integer degree.
o +R to extend the region outward by adding the amounts specified by
inc, xinc/yinc, or winc/einc/sinc/ninc [default is no extension].
o +e to adjust the region boundaries to be multiples of the steps
indicated by inc, xinc/yinc, or winc/einc/sinc/ninc, while ensur-
ing that the bounding box extends by at least 0.25 times the
increment [default is no adjustment].
6. -Rjustifyx0/y0/nx/ny, where justify is a 2-character combination of
L|C|R (for left, center, or right) and T|M|B (for top, middle, or
bottom) (e.g., BL for lower left). The two character code justify
indicates which point on a rectangular grid region the x0/y0 coordi-
nates refer to and the grid dimensions nx and ny are used with grid
spacings given via -I to create the corresponding region. This
method can be used when creating grids. For example, -RCM25/25/50/50
specifies a 50x50 grid centered on 25,25.
7. -Rxmin/xmax/ymin/ymax/zmin/zmax. This method can be used for per-
spective views with the -Jz and the -p option, where the z-range
(zmin/zmax) is appended to the first method to indicate the third
dimension. This is not used for -p without -Jz, in which case a per-
spective view of the place is plotted with no third dimension
In case of perspective view -p, a z-range (zmin, zmax) can be
appended to indicate the third dimension. This needs to be done only
when using the -Jz option, not when using only the -p option. In the
latter case a perspective view of the plane is plotted, with no
third dimension.
The -U option
Syntax
-U[label|+c][+jjust][+odx/dy]
Draw GMT time stamp logo on plot. (See cookbook information).
Description
The -U option draws the GMT system time stamp on the plot. The follow-
ing modifiers are supported:
o label to append the text string given in label (which must be sur-
rounded by double quotes if it contains spaces).
o +c to plot the current command string.
o +jjustify to specify the justification of the time stamp, where jus-
tify is a two-character justification code that is a combination of a
horizontal (L(eft), C(enter), or R(ight)) and a vertical (T(op),
M(iddle), or B(ottom)) code [default is BL].
o +odx[/dy] to offset the anchor point for the time stamp by dx and
optionally dy (if different than dx).
The GMT parameters MAP_LOGO, MAP_LOGO_POS, FONT_LOGO and FOR-
MAT_TIME_STAMP can affect the appearance; see the /gmt.conf man page
for details. The time string will be in the locale set by the environ-
ment variable TZ (generally local time).
The -V option
Syntax
-V[level]
Select verbosity level [w]. (See cookbook information).
Description
The -V option controls the verbosity mode, which determines which mes-
sages are sent to standard error. Choose among 7 levels of verbosity;
each level adds more messages:
o q - Quiet, not even fatal error messages are produced.
o e - Error messages only.
o w - Warnings.
o t - Timings (report runtimes for time-intensive algorithms).
o i - Informational messages (same as -V only).
o c - Compatibility warnings (if compiled with backward-compatibility).
o d - Debugging messages.
This option can also be set by specifying the default GMT_VERBOSE as
quiet, error, warning, timing, compat, information, or debug, in order
of increased verbosity [default is warning].
The -X -Y options
Syntax
-X[a|c|f|r][xshift]
Shift plot origin. (See cookbook information).
-Y[a|c|f|r][yshift]
Shift plot origin. (See cookbook information).
Description
The -X and -Y options shift the plot origin relative to the current
origin by (xshift,yshift). Optionally, append the length unit (c, i, or
p). Default is (MAP_ORIGIN_X, MAP_ORIGIN_Y) for new plots, which
ensures that boundary annotations fit on the page. Subsequent overlays
will be co-registered with the previous plot unless the origin is
shifted using these options. The following modifiers are supported
[default is r]:
o Prepend a to shift the origin back to the original position after
plotting.
o Prepend c to center the plot on the center of the paper (optionally
add a shift).
o Prepend f to shift the origin relative to the fixed lower left.
o Prepend r to move the origin relative to its current location.
When -X or -Y are used without any further arguments, the values from
the last use of that option in a previous GMT command will be used.
Note that -X and -Y can also access the previous plot bounding box
dimensions w and h and construct offsets that involves them. For
instance, to move the origin up 2 cm beyond the height of the previous
plot, use -Yh+2c. To move the origin half the width to the right, use
-Xw/2.
The -a option
Syntax
-a[[col=]name][,^<i>a|]
Control how aspatial data are handled in GMT during input and
output.
Description
GMT relies on external tools to translate geospatial files such as
shapefiles into a format we can read. The tool ogr2ogr in the GDAL
package can do such translations and preserve the aspatial metadata via
a new OGR/GMT format specification (See the cookbook chapter /cook-
book/ogrgmt-format). For this to be useful we need a mechanism to asso-
ciate certain metadata values with required input and output columns
expected by GMT programs. The -a option allows you to supply one or
more comma-separated associations col=name, where name is the name of
an aspatial attribute field in a OGR/GMT file and whose value we wish
to as data input for column col. The given aspatial field thus replaces
any other value already set. Note: col = 0 is the first data column.
Note: If no aspatial attributes are needed then the -a option is not
needed a GMT will still process and read such data files.
OGR/GMT input with -a option
If you need to populate GMT data columns with (constant) values speci-
fied by aspatial attributes, use -a and append any number of comma-sep-
arated col=name associations. For example, -a2=depth will read the spa-
tial x,y columns from the file and add a third (z) column based on the
value of the aspatial field called depth. You can also associate aspa-
tial fields with other settings such as labels, fill colors, pens, and
values (for looking-up colors) by letting the col value be one of D
(for distance), G (for fill), I (for ID), L (for label), T (for text),
W (for pen), or Z (for value). This works analogously to how standard
multi-segment files can pass such options via its segment headers (See
the cookbook chapter /cookbook/file-formats). Note: If the leading col=
is omitted, the column value is automatically incremented starting at
2.
OGR/GMT output with -a option
GMT table-writing tools can also output the OGR/GMT format directly.
Specify if certain GMT data columns with constant values should be
stored as aspatial metadata using col=name[:type], where you can
optionally specify what data type it should be from the options double,
float, integer, char, string, logical, byte, or datetime [default is
double]. As for input, you can also use the special col entries of D
(for distance), G (for fill), I (for ID), L (for label), T (for text),
W (for pen), or Z (for value) to have values stored as options in seg-
ment headers be used as the source for the named aspatial field. The
type will be set automatically for these special col entries. Finally,
for output you must append +ggeometry, where geometry can be any of
[M]POINT|LINE|POLY; where M represents the multi-versions of these
three geometries. Use upper-case +G to signal that you want to split
any line or polygon features that straddle the Dateline.
The -bi option
Syntax
-bi[ncols][type][w][+l|b]
Select native binary format for primary input (secondary inputs
are always ASCII).
Description
Select native binary format for primary input, where ncols is the num-
ber of data columns of given type and type must be one of:
o c - int8_t (1-byte signed char)
o u - uint8_t (1-byte unsigned char)
o h - int16_t (2-byte signed int)
o H - uint16_t (2-byte unsigned int)
o i - int32_t (4-byte signed int)
o I - uint32_t (4-byte unsigned int)
o l - int64_t (8-byte signed int)
o L - uint64_t (8-byte unsigned int)
o f - 4-byte single-precision float
o d - 8-byte double-precision float
o x - use to skip ncols anywhere in the record
For records with mixed types, simply append additional comma-separated
combinations of ncols type (no space). The following modifiers are sup-
ported:
o w after any item to force byte-swapping
o +l|b to indicate that the entire data file should be read as lit-
tle- or big-endian, respectively.
The cumulative number of ncols may exceed the columns actually needed
by the program. If ncols is not specified we assume that type applies
to all columns and that ncols is implied by the expectation of the pro-
gram. When using native binary data the user must be aware of the fact
that GMT has no way of determining the actual number of columns in the
file. Native binary files may have a header section, where the -h
option can be used to skip the first n bytes. If the input file is
netCDF, no -b is needed; simply append ?var1/var2/^<i>a| to the filename to
specify the variables to be read (see /cookbook/file-formats and Modi-
fiers for COARDS-compliant netCDF files for more information). Here is
an example that writes a binary file and reads it back with the first
column 4 byte float, the second column 8 byte int, and the third column
8 byte double.
echo 1.5 2 2.5 | gmt convert -bo1f,1l,1d > lixo.bin
gmt convert lixo.bin -bi1f,1l,1d
The -bo option
Syntax
-bo[ncols][type][w][+l|b]
Select native binary output.
Description
Select native binary output, where ncols is the number of data columns
of type, which must be one of c, u, h, H, i, I, l, L, f, or d (see -bi
types for descriptions). For a mixed-type output record, append addi-
tional comma-separated combinations of ncols type (no space). The fol-
lowing modifiers are supported:
o w after any item to force byte-swapping
o +l|b to indicate that the entire data file should be read as lit-
tle- or big-endian, respectively.
If ncols is not specified we assume that type applies to all columns
and that ncols is implied by the default output of the program. Note:
NetCDF file output is not supported.
The -c option
Syntax
-c[row,col|index]
Advance to the selected subplot panel.
Description
The -c option can be used to either advance the focus of plotting to
the next panel in the sequence (either by row or by column as set by
subplotas -A option) or to specify directly the row,col or 1-D index of
the desired panel, when using /subplot to assemble multiple individual
panels in a matrix layout. The -c option is only allowed when in sub-
plot mode. If no -c option is given for the first subplot then we
default to row=col=index=0, i.e., the upper left panel. Note: row,
col, and index all start at 0.
The -d option
Syntax
-di|onodata
Substitute specific values with NaN.
Description
The -d option allows user-coded missing data values to be translated to
official NaN values in GMT. Within GMT, any missing values are repre-
sented by the IEEE NaN value. However, user data may occasionally
denote missing data with an unlikely value (e.g., -99999). Since GMT
cannot guess this special missing data value, you can use the -d option
to have such values replaced with NaNs. Similarly, the -d option can
replace all NaNs with the chosed nodata value should the GMT output
need to conform to such a requirement.
For input only, use -dinodata to examine all input columns. If any item
equals nodata, the value is interpreted as a missing data item and is
substituted with the value NaN.
For output only, use -donodata to examine all output columns. If any
item equals NaN, the NaN value is substituted with the chosen missing
data value nodata.
The -e option
Syntax
-e[~]^<i>apattern^<i>a | -e[~]/regexp/[i]
Only accept ASCII data records that contain the specified pat-
tern.
Description
The -e option offers a built-in pattern scanner that will only pass
records that match the given pattern or regular expressions, whereas
modules that read ASCII tables will normally process all the data
records that are read. The test can also be inverted to only pass data
records that do not match the pattern, by using -e~. The test is not
applied to header or segment headers. Should your pattern happen to
start with ~ you will need to escape this character with a backslash
[Default accepts all data records]. For matching data records against
extended regular expressions, please enclose the expression in slashes.
Append i for case-insensitive matching. To supply a list of such pat-
terns, give +ffile with one pattern per line. To give a single pattern
starting with +f, escape it with a backslash.
The -f option
Syntax
-f[i|o]colinfo
Specify the data types of input and/or output columns (time or
geographical data).
Description
The -f option specifies what kind of data each input or output column
contains when map projections are not required. Optionally, append i or
o to make this apply only to input or output, respectively [Default
applies to both]. Append a text string with information about each col-
umn (or range of columns) separated by commas. Each string starts with
the column number (0 is the first column) followed by either x (longi-
tude), y (latitude), T (absolute calendar time) or t (relative time in
chosen TIME_UNIT since TIME_EPOCH). If several consecutive columns have
the same format you may specify a range of columns rather than a single
column. Column ranges must be given in the format start[:inc]:stop,
where inc defaults to 1 if not specified. For example, if our input
file has geographic coordinates (latitude, longitude) with absolute
calendar coordinates in the columns 3 and 4, we would specify
fi0y,1x,3:4T. All other columns are assumed to have the default (float-
ing point) format and need not be set individually.
The shorthand -f[i|o]g means -f[i|o]0x,1y (i.e., geographic coordi-
nates). A special use of -f is to select -fp[unit], which requires -J
and lets you use projected map coordinates (e.g., UTM meters) as data
input. Such coordinates are automatically inverted to longitude, lati-
tude during the data import. Optionally, append a length unit (see ta-
ble distance units) [default is meter]. For more information, see Sec-
tions input-data-formats and output-data-formats.
The -g option
Syntax
-g[a]x|y|d|X|Y|D|[col]zgap[+n|p]
Examine the spacing between consecutive data points in order to
impose breaks in the line.
Description
The -g option is used to detect gaps based on one or more criteria.
Repeat the option to specify multiple criteria and prepend a to subse-
quent modifiers to specify that all the criteria must be met [default
imposes breaks if any one criteria is met]. The criteria is specified
using the x|y|d|X|Y|D|[col]z modifiers. The upper-case options specify
that the criteria should be applied to the projected coordinates for
modules that map data to map coordinates.
o x|X - define a gap when there is a large enough change in the x coor-
dinates (upper case to use projected coordinates).
o y|Y - define a gap when there is a large enough change in the y coor-
dinates (upper case to use projected coordinates).
o d|D - define a gap when there is a large enough distance between
coordinates (upper case to use projected coordinates).
o [col]z - define a gap when there is a large enough change in the data
in column col [default col is 2 (i.e., 3rd column)].
A unit u may be appended to the specified gap:
o For geographic data (x|y|d), the unit may be arc d(egree), m(inute),
and s(econd), or (m)e(ter), f(eet), k(ilometer), M(iles), or n(auti-
cal miles) [Default is (m)e(ter)].
o For projected data (X|Y|D), the unit may be i(nch), c(entimeter), or
p(oint) [Default unit is set by PROJ_LENGTH_UNIT].
One of the following modifiers can be appended to gap [default imposes
breaks based on the absolute value of the difference between the cur-
rent and previous value]:
o +n - specify that the previous value minus the current column value
must exceed gap for a break to be imposed.
o +p - specify that the current value minus the previous value must
exceed gap for a break to be imposed.
Note: For x|y|z with time data the unit is instead controlled by
TIME_UNIT. Note: GMT has other mechanisms that can determine line seg-
mentation, including segments defined by multiple segment header
records (see the cookbook chapter /cookbook/file-formats) or segments
defined by NaN values when IO_NAN_RECORDS is set to pass [default skips
NaN values].
The -h option
Syntax
-h[i|o][n][+c][+d][+msegheader][+rremark][+ttitle]
Specify that input and/or output file(s) have n header records
[default is 0].
Description
Specify that the primary input file(s) has n header record(s). The
default number of header records is set by IO_N_HEADER_RECS [default is
0]. Use -hi if only the primary input data should have header records
[Default will write out header records if the input data have them].
For output you may control the writing of header records using -h[o]
and the optional modifiers:
o +d to remove existing header records.
o +c to add a header comment with column names to the output [default
is no column names].
o +m to add a segment header segheader to the output after the header
block [default is no segment header].
o +r to add a remark comment to the output [default is no comment]. The
remark string may contain \n to indicate line-breaks.
o +t to add a title comment to the output [default is no title]. The
title string may contain \n to indicate line-breaks.
Note: Blank lines and lines starting with # are always skipped. To use
another leading character for indicating header records, set
IO_HEADER_MARKER. With -h in effect the first n records are taken ver-
batim as headers and not skipped even if any is starting with #. Note:
If used with native binary data (using -b) we interpret n to instead
mean the number of bytes to skip on input or pad on output.
The -i option
Syntax
-icols[+l][+ddivisor][+sscale][+ooffset][,^<i>a|][,t[word]]
Select specific data columns for primary input, in arbitrary
order.
Description
The -i option allows you to specify which input file physical data col-
umns to use and in what order. Specify individual columns or column
ranges in the format start[:inc]:stop, where inc defaults to 1 if not
specified, separated by commas [Default reads all columns in order,
starting with the first column (i.e., column 0)]. Columns can be
repeated. The chosen data columns will be used as given and columns not
listed will be skipped. Optionally, append one of the following modi-
fiers to any column or column range to transform the input columns:
o +l to take the log10 of the input values.
o +d to divide the input values by the factor divisor [default is 1].
o +s to multiply the input values by the factor scale [default is 1].
o +o to add the given offset to the input values [default is 0].
To read from a given column until the end of the record, leave off stop
when specifying the column range. Normally, any trailing text is read
but when -i is used you must explicitly add the column t to retain the
text. To only ingest a single word from the trailing text, append the
word number (first word is 0). Finally, -in will simply read the
numerical input and skip any trailing text.
The -j option (spherical distance calculations)
Syntax
-je|f|g
Determine how spherical distances are calculated in modules that
support this [Default is -jg].
Description
GMT has different ways to compute distances on planetary bodies:
o -jg to perform great circle distance calculations, with parameters
such as distance increments or radii compared against calculated
great circle distances [Default is -jg].
o -jf to select Flat Earth mode, which gives a more approximate but
faster result.
o -je to select ellipsoidal (or geodesic) mode for the highest preci-
sion and slowest calculation time.
Note: All spherical distance calculations depend on the current ellip-
soid (PROJ_ELLIPSOID), the definition of the mean radius
(PROJ_MEAN_RADIUS), and the specification of latitude type
(PROJ_AUX_LATITUDE). Geodesic distance calculations is also controlled
by method (PROJ_GEODESIC).
The -l option
Syntax
-l[label][+Dpen][+Ggap][+Hheader][+L[code/]text][+Ncols][+Ssize[/height]][+V[pen]][+ffont][+gfill][+jjus-
tify][+ooff][+ppen][+sscale][+wwidth]
Add a map legend entry to the session legend information file for
the current plot.
Description
The -l option is used to automatically build the specfile that is read
by the /legend module to create map or plot legends. This allows
detailed and complicated legends that mix a variety of items, such as
symbols, free text, colorbars, scales, images, and more. Yet, a simple
legend will suffice for the vast majority of plots displaying symbols
or lines. Optionally, append a text label to describe the entry. The
following modifiers are supported to allow further changes to the leg-
end that is built by /legend (upper-case modifiers reflect legend codes
described in /legend, which provides more details and customization):
o +D to draw a horizontal line in the given pen before the legend entry
is placed [default is no line].
o +G to add the vertical space specified by gap [default is no extra
space].
o +H to add the specified legend header [default is no header].
o +L to set a line text. Optionally, prepend a horizontal justification
code L(eft), C(enter), or R(ight) for text [default is C].
o +N to change the number of columns used to set the following legend
items to cols [default is 1].
o +S to override the size of the current symbol for the legend or set a
height if plotting a line or contour [default uses the same symbol as
plotted].
o +V to start and +vpen to stop drawing vertical line from previous to
current horizontal line [default is no vertical line].
o +f to set the font used for the legend header [default is
FONT_TITLE].
o +g to set the fill used for the legend frame [default is white].
o +j to set placement of the legend using the two-character justifica-
tion code justify [default is TR].
o +o to set the offset from legend frame to anchor point [default is
0.2c].
o +p to set the pen used for the legend frame [default is 1p].
o +s to resize all symbol and length sizes in the legend by scale
[default is no scaling].
o +w to set legend frame width [default is auto].
Note: Default pen is given by MAP_DEFAULT_PEN. Note: +H, +g, +j, +o,
+p, +w, and +s will only take effect if appended to the very first -l
option for a plot. The +N modifier, if appended to the first -l option,
affects the legend width (unless set via +w); otherwise it just subdi-
vides the available width among the specified columns. If legend is not
called explicitly we will call it implicitly when finishing the plot
via /end. Note: If auto-coloring is used for pens or fills and -l is
set then label may contain a C-format for integers (e.g., %3.3d) or
just # and we will use the sequence number with the format to build the
label entries. Alternatively, give a list of comma-separated labels,
or give no label if your segment headers contain label settings.
The -n option
Syntax
-n[b|c|l|n][+a][+bg|p|n][+c][+tthreshold]
Select grid interpolation mode.
Description
The -n option controls parameters used for 2-D grids resampling
[default is bicubic interpolation with antialiasing and a threshold of
0.5, using geographic (if grid is known to be geographic) or natural
boundary conditions]. Append one of the following to select the type of
spline used:
o b to use B-spline smoothing.
o c to use bicubic interpolation.
o l to use bilinear interpolation.
o n to use nearest-neighbor value (for example to plot categorical
data).
The following modifiers are supported:
o +a to switch off antialiasing (where supported) [default uses
antialiasing].
o +b to override boundary conditions used, by appending g for geo-
graphic, p for periodic, or n for natural boundary conditions. For
the latter two you may append x or y to specify just one direction,
otherwise both are assumed.
o +c to clip the interpolated grid to input z-min/z-max [default may
exceed limits].
o +t to control how close to nodes with NaNs the interpolation will go
based on threshold. A threshold of 1.0 requires all (4 or 16) nodes
involved in interpolation to be non-NaN. For example, 0.5 will inter-
polate about half way from a non-NaN value and 0.1 will go about 90%
of the way [default is 0.5].
The -o option
Syntax
-ocols[,a|][,t[word]]
Select specific data columns for primary output, in arbitrary
order.
Description
The -o option allows you to specify which output file physical data
columns to use and in what order. Specify individual columns or column
ranges in the format start[:inc]:stop, where inc defaults to 1 if not
specified, separated by commas [Default writes all columns in order,
starting with the first column (i.e., column 0)]. Columns can be
repeated. The chosen data columns will be used as given and columns not
listed will be skipped. To write from a given column until the end of
the record, leave off stop when specifying the column range.
Normally, any trailing text in the internal records will be written but
when -o is used you must explicitly add the column t. To only output a
single word from the trailing text, append the word number (first word
is 0). Finally, -on will simply write the numerical output only and
skip any trailing text, while -ot will only output the trailing text
(or selected word). Note: If -i is also used then columns given to -o
correspond to the order after the -i selection and not the columns in
the original record.
The -p option
Syntax
-p[x|y|z]azim[/elev[/zlevel]][+wlon0/lat0[/z0]][+vx0/y0]
Select perspective view and set the azimuth and elevation of the
viewpoint.
Description
All plotting programs that normally produce a flat, two-dimensional
illustration can be told to view this flat illustration from a particu-
lar vantage point, resulting in a perspective view. You can select per-
spective view with the -p option by setting the azimuth (azim) of the
viewpoint [Default is 180]. The following modifiers are supported:
o x|y|z to plot against the awalla x = level (using x) or y = level
(using y) or the horizontal plain (using z) [default is z].
o /elev to set the elevation of the viewport [Default is 90].
o /zlevel to indicate the z-level at which all 2D material, like the
plot frame, is plotted (only valid when -p is used in consort with
-Jz or -JZ) [Default is at the bottom of the z-axis].
For frames used for animation, we fix the center of your data domain.
Specify another center using one of the following modifiers:
o +w to project lon0/lat0 (and z0 if applicable) to the center of the
page size.
o +v to specify the coordinates of the projected 2-D view point as
x0/y0.
When -p is used without any further arguments, the values from the last
use of -p in a previous GMT command will be used (in modern mode this
also supplies the previous -Jz or -JZ if doing a 3-D region). Alterna-
tively, you can perform a simple rotation about the z-axis by just giv-
ing the rotation angle. Optionally, use +v or +w to select another axis
location than the plot origin.
The -q option
Syntax
-q[i|o][~]rows[+ccol][+a|f|s]
Select specific data rows to be read and/or written.
Description
The -q option is used to select specific data rows to be read (using -q
or -qi) or written (using -qo) [Default is all rows]. Specify individ-
ual rows or row ranges in the format start[:inc]:stop, where inc
defaults to 1 if not specified, separated by commas [Default reads and
writes all rows in order, starting with the first row (i.e., row 0)].
To read (or write) from a given row until the end of the data, leave
off stop. To select all the rows not specified by the given ranges,
prepend the selected rows with a leading ~. Append one of the following
modifiers to control how the rows are counted [Default is +a]:
o +a to count all rows in the data set.
o +f to reset the count at the start of each file.
o +s to reset the count at the start of each segment.
Alternatively, use +ccol to indicate that the arguments instead are
min/max data limits for the values in column col. With +ccol, only rows
whose data for the given column col are within the range(s) given by
the min/max limits are read (with -qi) or written (with -qo). Note:
Because arguments may contain colons or be negative, your must specify
start/stop instead of start[:inc]:stop.
Note: Header records do not increase the row counters; only data
records do.
The -r option (grid registration)
Syntax
-r[g|p]
Select gridline or pixel node registration.
Description
All 2-D grids in GMT have their nodes organized in one of two ways,
known as gridline and pixel registration. The GMT default is gridline
registration (-rg); programs that allow for the creation of grids can
use the -r option (or -rp) to select pixel registration instead.
Most observed data tend to be in gridline registration while processed
data sometime may be distributed in pixel registration. While you may
convert between the two registrations this conversion looses the
Nyquist frequency and dampens the other high frequencies. It is best to
avoid any registration conversion if you can help it. Planning ahead
may be important. (Node registrations are defined in Section
option_nodereg of the GMT Technical Reference and Cookbook.)
The -s option
Syntax
-s[cols][+a][+r]
Suppress output of data records whose z-value(s) equal NaN.
Description
The -s option can be used to suppress output for records whose z-value
equals NaN [default outputs all records]. Optionally, supply a
comma-separated list of all columns or column ranges to consider for
this NaN test [default only considers the third data column (i.e., cols
= 2)]. Column ranges must be given in the format start[:inc]:stop,
where inc defaults to 1 if not specified. The following modifiers are
supported:
o +r to reverse the suppression, i.e., only output the records whose
z-value equals NaN.
o +a to suppress the output of the record if just one or more of the
columns equal NaN [default skips record only if values in all speci-
fied cols equal NaN]
The -t option
Syntax
-ttransp[/transp2][+f|s]
Set transparency level(s) for an overlay.
Description
The -t option allows you to change the transparency level for the cur-
rent overlay by appending the transp percentage in the 0-100 range
[default is 0 (i.e., opaque)]. Normally, transp applies to both fill
and stroke, but you can limit the transparency to one of them by
appending +f or +s for fill or stroke, respectively. Alternatively,
append /transp2 to set separate transparencies for fills and strokes.
Transparency may also be controlled on a feature by feature basis when
setting color or fill (see the cookbook section -Gfill_attrib). Note:
The modules /plot, /plot3d, and /text can all change transparency on a
record-by-record basis if -t is given without argument and the input
file supplies variable transparencies as the last numerical column
value(s). Note: The transparency is only visible when PDF or raster
format output is selected because the PostScript language does not sup-
port transparency. Only the PNG format selection adds a transparency
layer in the image (for further processing).
The -w option
Syntax
-wy|a|w|d|h|m|s|cperiod[/phase][+ccol]
Convert input records to a cyclical coordinate.
Description
The -w option converts the input x-coordinate to a cyclical coordinate,
or a different input column if selected via the +c modifier. Temporal
data (i.e., regular time series) can be analyzed for periods via stan-
dard spectral analysis, such as offered by /spectrum1d and /grdfft.
However, it is often of interest to examine aspects of such periodici-
ties in the time domain. To enable such analyses we need to convert
our monotonically increasing time coordinates to periodic or cyclic
coordinates so that data from many cycles can be stacked, binned, dis-
played in histograms, etc. The conversion from input x, y, or z coordi-
nates to wrapped, periodic coordinates follows the simple equation
t' = (t - \tau) \;\mathrm{mod}\; T,
where t is the input coordinate, \tau is a phase-shift (typically
zero), and T is the desired period for the modulus operator, yielding
cyclic coordinates t'. GMT offers many standard time cycles in pre-
scribed units plus a custom cycle for other types of Cartesian coordi-
nates. The table below shows the values for units, phase and period
that are prescribed and only requires the user to specify the corre-
sponding wrapping code (y|a|w|d|h|m|s|cperiod):
+-----+---------------+----------+-------+-------+
|Code | Purpose | Period | Phase | Range |
| | (unit) | | | |
+-----+---------------+----------+-------+-------+
|y | Yearly cycle | 1 year | 0 | 0a1 |
| | (normalized) | | | |
+-----+---------------+----------+-------+-------+
|a | Annual cycle | 1 year | 0 | 0a12 |
| | (month) | | | |
+-----+---------------+----------+-------+-------+
|w | Weekly cycle | 1 week | 0 | 0a7 |
| | (day) | | | |
+-----+---------------+----------+-------+-------+
|d | Daily cycle | 1 day | 0 | 0a24 |
| | (hour) | | | |
+-----+---------------+----------+-------+-------+
|h | Hourly cycle | 1 hour | 0 | 0a60 |
| | (minute) | | | |
+-----+---------------+----------+-------+-------+
|m | Minute cycle | 1 minute | 0 | 0a60 |
| | (second) | | | |
+-----+---------------+----------+-------+-------+
|s | Second cycle | 1 second | 0 | 0a1 |
| | (second) | | | |
+-----+---------------+----------+-------+-------+
|c | Custom cycle | T | \tau | 0a1 |
| | (normalized) | | | |
+-----+---------------+----------+-------+-------+
Optionally, append +ccol to select the input column with the coordi-
nates to be wrapped, [default col is 0 (i.e., the first column)]. If
the custom cycle c is chosen then you must also supply the period and
optionally any phase [default is 0] in the same units of your data
(i.e., no units should be appended to -w).
Note: Coordinates for w in the range 0-1 correspond to the first day of
the week [Monday] but can be changed via TIME_WEEK_START. Note: If a
temporal cycle is indicated then we implicitly set -f to indicate abso-
lute time (unless already set separately). See the cookbook section
Examining data cycles: The -w option for examples.
The -x option
Syntax
-x[[-]n]
Specify the number of active cores to be used in any
OpenMP-enabled multi-threaded algorithms.
Description
The -x option limits the number of cores to be used in any
OpenMP-enabled multi-threaded algorithms [default is to use all avail-
able cores]. Append n to only use n cores (if too large it will be
truncated to the maximum cores available). Finally, give a negative n
to select (all - n) cores (or at least 1 if n equals or exceeds all).
The -x option is only available to GMT modules compiled with OpenMP
support, with the exception of /movie and /batch which handle their own
parallel execution.
The -: option
Syntax
-:[i|o]
Swap 1st and 2nd column on input and/or output.
Description The -: option swaps the 1st and 2nd column on input and
output [default is no swapping]. Append i to select input only or o to
select output only [default affects both]. This option is typically
used to handle (latitude, longitude) files; see also cook-
book/options:Input columns selection: The **-i** option. Note that com-
mand line arguments that may take geographic coordinates (e.g., -R)
always expect longitude before latitude. Also, geographical grids are
expected to have the longitude as first (minor) dimension.
Module help and configuration
-^ or just -
Print a short message about the syntax of the command, then exit
(NOTE: on Windows just use -).
-+ or just +
Print an extensive usage (help) message, including the explana-
tion of any module-specific option (but not the GMT common
options), then exit.
-? or no arguments
Print a complete usage (help) message, including the explanation
of all options, then exit.
--PAR=value
Temporarily override a GMT default setting; repeatable. See
/gmt.conf for parameters.
Specifying Color
color The color of lines, areas and patterns can be specified by a
valid color name, by a gray shade (in the range 0-255), by a
decimal color triplet RGB (r/g/b, each in the range 0a255), by
hue-saturation-value HSV (h-s-v, with ranges of 0-360, 0-1,
0-1), by cyan/magenta/yellow/black CMYK (c/m/y/k, each in the
range 0-1), or by a hexadecimal color code (#rrggbb, as used in
HTML). For a transparency effect, append @transparency in the
0a100 percent range [Default is 0 (opaque)] Note: Transparency
effects are only visible when PDF or a raster graphics format is
selected. See Explanation of color codes in GMT for more infor-
mation and a full list of color names.
Specifying Fill
fill The attribute fill specifies the solid shade or solid color (see
Specifying Color above) or the pattern used for filling poly-
gons. Patterns are specified as ppattern, where pattern set the
number of the built-in pattern (1-90) or the name of a raster
image file. The optional +rdpi sets the resolution of the image
[300]. For 1-bit rasters: use upper case P for inverse video,
or append +fcolor and/or +bcolor to specify fore- and background
colors (no color given means transparency). See /cookbook/pre-
defined-patterns for information on individual built-in pat-
terns.
Specifying Fonts
font The attributes of text fonts as defined by font is a comma
delimited list of size, fonttype and fill, each of which is
optional. size is the font size (usually in points) but c or i
can be added to indicate other units. fonttype is the name (case
sensitive!) of the font or its equivalent numerical ID (e.g.,
Helvetica-Bold or 1). fill specifies the gray shade, color or
pattern of the text (see Specifying Fill above). Optionally, you
may append =pen to the fill value in order to draw a text out-
line. If you want to avoid that the outline partially obscures
the text, append =~pen instead; in that case only half the
linewidth is plotted on the outside of the font only. If an
outline is requested, you may optionally skip the text fill by
setting it to -, in which case the full pen width is always
used. If any of the font attributes is omitted their default or
previous setting will be retained.
The 35 available fonts (plus 4 optional Japanese fonts) are:
0. Helvetica
1. Helvetica-Bold
2. Helvetica-Oblique
3. Helvetica-BoldOblique
4. Times-Roman
5. Times-Bold
6. Times-Italic
7. Times-BoldItalic
8. Courier
9. Courier-Bold
10. Courier-Oblique
11. Courier-BoldOblique
12. Symbol
13. AvantGarde-Book
14. AvantGarde-BookOblique
15. AvantGarde-Demi
16. AvantGarde-DemiOblique
17. Bookman-Demi
18. Bookman-DemiItalic
19. Bookman-Light
20. Bookman-LightItalic
21. Helvetica-Narrow
22. Helvetica-Narrow-Bold
23. Helvetica-Narrow-Oblique
24. Helvetica-Narrow-BoldOblique
25. NewCenturySchlbk-Roman
26. NewCenturySchlbk-Italic
27. NewCenturySchlbk-Bold
28. NewCenturySchlbk-BoldItalic
29. Palatino-Roman
30. Palatino-Italic
31. Palatino-Bold
32. Palatino-BoldItalic
33. ZapfChancery-MediumItalic
34. ZapfDingbats
35. Ryumin-Light-EUC-H
36. Ryumin-Light-EUC-V
37. GothicBBB-Medium-EUC-H
38. GothicBBB-Medium-EUC-V
Specifying Pens
pen The attributes of lines and symbol outlines as defined by pen is
a comma-delimited list of width, color and style, each of which
is optional. width can be indicated as a measure (in points
(this is the default), centimeters, or inches) or as faint,
default, thin[ner|nest], thick[er|est], fat[ter|test], or wide.
color specifies a gray shade or color (see Specifying Color
above). style can be any of asolida, adasheda adotteda, adash-
dota, or adotdasha, or a custom combination of dashes a-a and
dots a.a. If any of the attributes is omitted their default or
previous setting will be retained. See GMT Cookbook & Technical
Reference Specifying pen attributes for more information.
ASCII FORMAT PRECISION
The ASCII output formats of numerical data are controlled by parameters
in your gmt.conf file. Longitude and latitude are formatted according
to FORMAT_GEO_OUT, absolute time is under the control of FOR-
MAT_DATE_OUT and FORMAT_CLOCK_OUT, whereas general floating point val-
ues are formatted according to FORMAT_FLOAT_OUT. Be aware that the for-
mat in effect can lead to loss of precision in ASCII output, which can
lead to various problems downstream. If you find the output is not
written with enough precision, consider switching to binary output (-bo
if available) or specify more decimals using the FORMAT_FLOAT_OUT set-
ting.
GRID FILE FORMATS
By default GMT writes out grids as single precision floats in a
COARDS-complaint netCDF file format. However, GMT is able to produce
and read grid files in many other commonly used grid file formats and
also facilitates so called apackinga of grids, writing out floating
point data as 1- or 2-byte integers. To specify the precision, scale
and offset, the user should add the suffix [=id][+sscale][+ooff-
set][+ninvalid], where id is a two-letter identifier of the grid type
and precision, and the scale, offset and invalid are the arguments of
optional modifiers to be applied to all grid values, Here, invalid is
the value used to indicate missing data. In case the id is not pro-
vided, as in +sscale, then a id=nf is assumed. When reading grids, the
format is generally automatically recognized from almost all of those
formats that GMT and GDAL combined offer. If not, the same suffix can
be added to input grid file names. See grdconvert and Section
grid-file-format of the GMT Technical Reference and Cookbook for more
information.
When reading a netCDF file that contains multiple grids, GMT will read,
by default, the first 2-dimensional grid that it can find in that file.
To coax GMT into reading another multi-dimensional variable in the grid
file, append ?varname to the file name, where varname is the name of
the variable. Note that you may need to escape the special meaning of ?
in your shell program by putting a backslash in front of it, or by
placing the filename and suffix between quotes or double quotes. The
?varname suffix can also be used for output grids to specify a variable
name different from the default: aza. See grdconvert and Sections modi-
fiers-for-CF and grid-file-format of the GMT Technical Reference and
Cookbook for more information, particularly on how to read slices of
3-, 4-, or 5-dimensional grids.
When writing a netCDF file, the grid is stored by default with the
variable name aza. To specify another variable name varname, append
?varname to the file name. Note that you may need to escape the special
meaning of ? in your shell program by putting a backslash in front of
it, or by placing the filename and suffix between quotes or double
quotes.
CLASSIC MODE OPTIONS
These options are only used in classic mode and are listed here just
for reference.
-K More PostScript code will be appended later [Default terminates
the plot system]. Required for all but the last plot command
when building multi-layer plots.
-O Selects Overlay plot mode [Default initializes a new plot sys-
tem]. Required for all but the first plot command when building
multi-layer plots.
-P Select aPortraita plot orientation [Default is aLandscapea; see
gmt.conf or gmtset to change the PS_PAGE_ORIENTATION parameter,
or supply --PS_PAGE_ORIENTATION=orientation on the command
line].
MORE INFORMATION SOURCES
Look up the individual man pages for more details and full syntax. Run
gmt --help to list all GMT programs and to show all installation direc-
tories. For an explanation of the various GMT settings in this man page
(like FORMAT_FLOAT_OUT), see the man page of the GMT configuration file
gmt.conf. Information is also available on the GMT documentation site
https://docs.generic-mapping-tools.org/
SEE ALSO
docs
COPYRIGHT
2021, The GMT Team.
6.2 Jun 04, 2021 gmt(1)
gmt 6.2.0 - Generated Wed Jun 9 13:35:24 CDT 2021