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 supplements 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-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-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 user’s ~/.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
distribution, you may still need to source the gmt completion file from
~/.bash_completion or ~/.bashrc.  For more information see Section
Command-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
-crow,col|index
-dnodata
-eregexp
-fflags
-ggaps
-hheaders
-iflags
-jflags
-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.
-B[p|s]parameters
Set map Frame and Axes parameters. The Frame parameters are specified by
-B[axes][+b][+gfill][+i[val]][+n][+olon/lat][+ttitle]
where axes selects which axes to plot. By default, all 4 map boundaries
(or plot axes) are plotted (named W, E, S, N). To customize,
append the codes for those you want (e.g., WSn). Upper case means plot
and annotate while lower case just plots and ticks the specified axes.
To just draw an axis without annotation and ticks you can use the l(eft),
r(ight), b(ottom), t(opt) and (for 3-D) u(p) codes. If a 3-D basemap
is selected with -p and -Jz, append Z, z, or u to control the
appearance of the vertical axis. By default a single vertical axes will be
plotted at the most suitable map corner. Override the default by appending
any combination of corner ids 1234, where 1 represents the lower left
corner and the order goes counter-clockwise. Append +b to draw the outline of the 3-D
cube defined by -R; this modifier is also needed to display gridlines in
the x-z, y-z planes. Note that for 3-D views the title, if given, will be
suppressed. You can paint the interior of the canvas with +gfill.
Use +i to annotate an internal meridian or parallel when the axis that normally
would be drawn and annotated does not exist (e.g., azimuthal map with 360-degree range
has no latitude axis, and a global Hammer map has no longitude axis); optionally append the parallel or meridian [0].
Append +n to have no frame and annotations at all [Default is controlled by the codes].
Optionally append +oplon/plat to draw oblique gridlines about
specified pole [regular gridlines]. Ignored if gridlines are not
requested (below) and disallowed for the oblique Mercator projection.
To add a plot title, append +ttitle. The Frame setting is optional but
can be invoked once to override the above defaults.
The Axes parameters are specified by
-B[p|s][x|y|z]intervals[+aangle|n|p][+f][+l|Llabel][+pprefix][+s|Sseclabel][+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 first optional flag following -B selects p (rimary) [Default] or
s (econdary) axes information (mostly used for time axes annotations but
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 [x|y|z] flags specify which axes you are providing information for.
If none are given then we default to 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 (If a 3-D basemap is selected with -p and -Jz, use -Bz
to give settings for the vertical axis.).  To add a label to an axis,
just append +llabel (Cartesian projections only). Use +L (or +S) to
force a horizontal label for y-axes (useful for very short labels).
For Cartesian axes you may specify an alternate via +s which is used for
right or upper axis axis label (with any +l label used for left and bottom axes).
If the axis annotation should have a leading text prefix (e.g., dollar sign for those
plots of your net worth) you can append +pprefix. For geographic maps
the addition of degree symbols, etc. is automatic (and controlled by the GMT
default setting FORMAT_GEO_MAP). However, for other plots you can add
specific units by adding +uunit.  If any of these text strings contain
spaces or special characters you will need to enclose them in quotes.
Cartesian x-axes also allow for the optional +aangle, which
will plot slanted annotations; angle is measured with respect to the horizontal
and must be in the -90 <= angle <= 90 range only.  Also, +an is a shorthand
for normal (i.e., +a90) and +ap for parallel (i.e., +a0) annotations
[Default].  For the y- and z-axes, arbitrary angles are not allowed but +an and +ap
specify annotations normal [Default] and parallel to the axis, respectively. Note that
these defaults can be changed via MAP_ANNOT_ORTHO. Geographic axes can
take +f which will give fancy annotations with W|E|S|N suffices encoding the sign.
The intervals specification is a concatenated string made up of substrings
of the form
[a|f|g]stride[±phase][unit].
The leading a is used to specify the annotation and major tick
spacing [Default], f for minor tick spacing, and g for
gridline spacing. stride is the desired stride interval. The
optional phase shifts the annotation interval by that amount
(positive or negative). The optional unit indicates the unit of
the stride and are particularly important for time-axes as they
can be any of the ones listed below:
Y (year, plot with 4 digits)
y (year, plot with 2 digits)
O (month, plot using FORMAT_DATE_MAP)
o (month, plot with 2 digits)
U (ISO week, plot using FORMAT_DATE_MAP)
u (ISO week, plot using 2 digits)
r (Gregorian week, 7-day stride from start of week TIME_WEEK_START)
K (ISO weekday, plot name of weekdays in selected language)
k (weekday, plot number of day in the week (1–7) (see TIME_WEEK_START))
D (date, plot using FORMAT_DATE_MAP)
d (day, plot day of month 0-31 or year 1-366, via FORMAT_DATE_MAP)
R (day, same as d, aligned with TIME_WEEK_START)
H (hour, plot using FORMAT_CLOCK_MAP)
h (hour, plot with 2 digits)
M (minute, plot using FORMAT_CLOCK_MAP)
m (minute, plot with 2 digits)
S (second, plot using FORMAT_CLOCK_MAP)
s (second, plot with 2 digits).
For geographic axes d, m and s instead mean arc degrees, minutes and seconds,
while for Cartesian axes no unit is given.
All entities that are language-specific are under control
of GMT_LANGUAGE. Alternatively, we can omit stride, thus setting
xinfo, yinfo, or zinfo to a plots annotations at automatically determined intervals,
ag plots both annotations and grid lines with the same spacing,
afg adds suitable minor tick intervals,
g plots grid lines with the same interval as if -Bf was used.
For custom annotations and intervals, let intervals be given as
cintfile, where intfile contains any number of
records with coord type [label]. Here, type is one or more
letters from a|i, f, and g. For
a|i you must supply a label that will be plotted at
the coord location. 

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). 

For log10 axes: Annotations can be specified in one of three ways:
stride can be 1, 2, 3, or -n. Annotations will then occur at 1,
1-2-5, or 1-2-3-4-…-9, respectively; for -n we annotate every
n‘t magnitude. This option can also be used for the frame and
grid intervals.
An l is appended to the tickinfo string. Then, log10 of the
tick value is plotted at every integer log10 value.
A p is appended to the tickinfo string. Then,
annotations appear as 10 raised to log10 of the tick value.
For power axes: Annotations can be specified in one of two ways:
stride sets the regular annotation interval.
A p is appended to the tickinfo string. Then, the annotation interval is
expected to be in transformed units, but the annotation value will
be plotted as untransformed units. E.g., if stride = 1 and power
= 0.5 (i.e., sqrt), then equidistant annotations labeled 1-4-9…  will appear.
Finally, 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.
These GMT parameters can affect the appearance of the map boundary:
MAP_ANNOT_MIN_ANGLE, MAP_ANNOT_MIN_SPACING,
FONT_ANNOT_PRIMARY, FONT_ANNOT_SECONDARY,
MAP_ANNOT_OFFSET_PRIMARY,
MAP_ANNOT_OFFSET_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,
FORMAT_CLOCK_MAP, FORMAT_DATE_MAP,
FORMAT_TIME_PRIMARY_MAP, FORMAT_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.
-Jparameters
Select map projection. The first character of parameters determines the
projection. If the character is upper case then the argument(s) supplied
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)
dimension, 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:
-Jclon0/lat0/scale or -JClon0/lat0/width (Cassini).
Give projection center lon0/lat0 and scale (1:xxxx or UNIT/degree).
-Jcyl_stere/[lon0/[lat0/]]scale or
-JCyl_stere/[lon0/[lat0/]]width (Cylindrical Stereographic).
Give central meridian lon0 (optional), standard parallel lat0
(optional), and scale along parallel (1:xxxx or
UNIT/degree). The standard parallel is typically one of these (but
can be any value):
66.159467 - Miller’s modified Gall
55 - Kamenetskiy’s First
45 - Gall’s Stereographic
30 - Bolshoi Sovietskii Atlas Mira or Kamenetskiy’s Second
0 - Braun’s Cylindrical
-Jj[lon0/]scale or -JJ[lon0/]width (Miller Cylindrical Projection).
Give the central meridian lon0 (optional) and scale
(1:xxxx or UNIT/degree).
-Jm[lon0/[lat0/]]scale or -JM[lon0/[lat0/]]width (Mercator [C])
Give central meridian lon0 (optional), standard parallel lat0
(optional), and scale along parallel (1:xxxx or UNIT/degree).
-Joparameters[+v] (Oblique Mercator [C]).
Typically used with -RLLx/LLy/URx/URy+r or with projected coordinates.  Specify one of:





    
-Jo[a|A]lon0/lat0/azimuth/scale or -JO[a|A]lon0/lat0/azimuth/width
Set projection center lon0/lat0, azimuth of oblique equator, and scale.
-Jo[b|B]lon0/lat0/lon1/lat1/scale or -JO[b|B]lon0/lat0/lon1/lat1/width
Set projection center lon0/lat0, another point on the oblique
equator lon1/lat1, and scale.
-Joc|Clon0/lat0/lonp/latp/scale or -JOc|Clon0/lat0/lonp/latp/width
Set projection center lon0/lat0, pole of oblique projection
lonp/latp, and scale.
Give scale along oblique equator (1:xxxx or UNIT/degree).
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 modifier then the arguments are considered oblique
degrees relative to the projection center and not longitude/latitude bounds.
-Jq[lon0/[lat0/]]scale or
-JQ[lon0/[lat0/]]width (Cylindrical Equidistant).
Give the central meridian lon0 (optional), standard parallel
lat0 (optional), and scale (1:xxxx or UNIT/degree). The
standard parallel is typically one of these (but can be any value):
61.7 - Grafarend and Niermann, minimum linear distortion
50.5 - Ronald Miller Equirectangular
43.5 - Ronald Miller, minimum continental distortion
42 - Grafarend and Niermann
37.5 - Ronald Miller, minimum overall distortion
0 - Plate Carree, Simple Cylindrical, Plain/Plane Chart
-JTlon0/[lat0/]width (Transverse Mercator [C])

Give the central meridian lon0, central parallel lat0
(optional), and scale (1:xxxx or UNIT/degree).
-Juzone/scale or -JUzone/width (UTM - Universal Transverse Mercator [C]).
Give the UTM zone (A,B,1-60[C-X],Y,Z)) and scale (1:xxxx or UNIT/degree).
Zones: If C-X not given, prepend - or + to enforce southern or
northern hemisphere conventions [northern if south > 0].
-Jy[lon0/[lat0/]]scale or -JY[lon0/[lat0/]]width (Cylindrical Equal-Area [E]).
Give the central meridian lon0 (optional), standard parallel
lat0 (optional), and scale (1:xxxx or UNIT/degree). The
standard parallel is typically one of these (but can be any value):
50 - Balthasart
45 - Gall
37.0666 - Caster
37.4 - Trystan Edwards
37.5 - Hobo-Dyer
30 - Behrman
0 - Lambert (default)
CONIC PROJECTIONS:





    
-Jblon0/lat0/lat1/lat2/scale or -JBlon0/lat0/lat1/lat2/width (Albers [E]).
Give projection center lon0/lat0, two standard parallels
lat1/lat2, and scale (1:xxxx or UNIT/degree).
-Jdlon0/lat0/lat1/lat2/scale or -JDlon0/lat0/lat1/lat2/width (Conic Equidistant)
Give projection center lon0/lat0, two standard parallels
lat1/lat2, and scale (1:xxxx or UNIT/degree).
-Jllon0/lat0/lat1/lat2/scale or -JLlon0/lat0/lat1/lat2/width (Lambert [C])
Give origin lon0/lat0, two standard parallels lat1/lat2, and
scale along these (1:xxxx or UNIT/degree).
-Jpoly/[lon0/[lat0/]]scale or -JPoly/[lon0/[lat0/]]width ((American) Polyconic).
Give the central meridian lon0 (optional), reference parallel
lat0 (optional, default = equator), and scale along central
meridian (1:xxxx or UNIT/degree).
AZIMUTHAL PROJECTIONS:
Except for polar aspects, -Rw/e/s/n will be reset to -Rg.
Use -R<…>+r for smaller regions.
-Jalon0/lat0[/horizon]/scale or -JAlon0/lat0[/horizon]/width (Lambert [E]).
lon0/lat0 specifies the projection center. horizon specifies
the max distance from projection center (in degrees, <= 180,
default 90). Give scale as 1:xxxx or radius/lat,
where radius is distance in UNIT from origin to the oblique
latitude lat.
-Jelon0/lat0[/horizon]/scale or -JElon0/lat0[/horizon]/width (Azimuthal Equidistant).
lon0/lat0 specifies the projection center. horizon specifies
the max distance from projection center (in degrees, <= 180,
default 180). Give scale as 1:xxxx or radius/lat,
where radius is distance in UNIT from origin to the oblique
latitude lat.
-Jflon0/lat0[/horizon]/scale or -JFlon0/lat0[/horizon]/width (Gnomonic).
lon0/lat0 specifies the projection center. horizon specifies
the max distance from projection center (in degrees, < 90,
default 60). Give scale as 1:xxxx or radius/lat,
where radius is distance in UNIT from origin to the oblique
latitude lat.
-Jglon0/lat0[/horizon]/scale or -JGlon0/lat0[/horizon]/width (Orthographic).
lon0/lat0 specifies the projection center. horizon specifies
the max distance from projection center (in degrees, <= 90,
default 90). Give scale as 1:xxxx or radius/lat,
where radius is distance in UNIT from origin to the oblique
latitude lat.
-Jglon0/lat0/altitude/azimuth/tilt/twist/Width/Height/scale or -JGlon0/lat0/altitude/azimuth/tilt/twist/Width/Height/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
altitude 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
projection. 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
as 1:xxxx or radius/lat, where radius is distance in
UNIT from origin to the oblique latitude lat.
-Jslon0/lat0[/horizon]/scale or -JSlon0/lat0[/horizon]/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 as 1:xxxx (true at pole) or
lat0/1:xxxx (true at standard parallel lat) or
radius/lat (radius in UNIT 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.
MISCELLANEOUS PROJECTIONS:
-Jh[lon0/]scale or -JH[lon0/]width (Hammer [E]).
Give the central meridian lon0 (optional) and scale along
equator (1:xxxx or UNIT/degree).
-Ji[lon0/]scale or -JI[lon0/]width (Sinusoidal [E]).
Give the central meridian lon0 (optional) and scale along
equator (1:xxxx or UNIT/degree).
-Jkf[lon0/]scale or -JKf[lon0/]width (Eckert IV) [E]).
Give the central meridian lon0 (optional) and scale along
equator (1:xxxx or UNIT/degree).
-Jk[s][lon0/]scale or -JK[s][lon0/]width (Eckert VI) [E]).
Give the central meridian lon0 (optional) and scale along
equator (1:xxxx or UNIT/degree).
-Jn[lon0/]scale or -JN[lon0/]width (Robinson).
Give the central meridian lon0 (optional) and scale along
equator (1:xxxx or UNIT/degree).
-Jr[lon0/]scale -JR[lon0/]width (Winkel Tripel).
Give the central meridian lon0 (optional) and scale along
equator (1:xxxx or UNIT/degree).
-Jv[lon0/]scale or -JV[lon0/]width (Van der Grinten).
Give the central meridian lon0 (optional) and scale along
equator (1:xxxx or UNIT/degree).
-Jw[lon0/]scale or -JW[lon0/]width (Mollweide [E]).
Give the central meridian lon0 (optional) and scale along
equator (1:xxxx or UNIT/degree).
NON-GEOGRAPHICAL PROJECTIONS:
-Jpscale[+a][+f[e|p|radius]][+roffset][+torigin][+z[p|radius]]] or -JPwidth[+a][+f[e|p|radius]][+roffset][+torigin][+z[p|radius]]
(Polar coordinates (theta, r))
Give scale in UNIT/r-unit.  Optionally add +a if theta is azimuth CW
from North instead of direction CCW from East [Default].
Append +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.
Append +roffset to include a radial offset in measurement units [0].
Append +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) [0].
Finally, append +z if you want to annotate depth rather than radius [Default].
Alternatively, if your r data are actually depths then you can append p or radius to get
radial annotations (r = radius - z) instead.
-Jxx-scale[/y-scale] or -JXwidth[/height] (Linear, log, and power scaling)
Give x-scale (1:xxxx or UNIT/x-unit) and/or y-scale
(1:xxxx or UNIT/y-unit); or specify width and/or height
in UNIT. 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. Optionally,
append to x-scale, y-scale, width or height one of the
following:
d
Data are geographical coordinates (in degrees).
l
Take log10 of values before scaling.
ppower
Raise values to power before scaling.
t
Input coordinates are time relative to TIME_EPOCH.
T
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
projection 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
-J“+proj=merc +ellps=WGS84 +units=m” 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 GDAL’s data sub-directory). For example -JEPSG:4326 sets
the WGS-84 system.
For mapproject and grdproject we can go directly from the
referencing 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 grdproject we can use all PROJ projections, the situations is, however, 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 it’s 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 “/1:xxx” to the end of the projection parameters.
-Rxmin/xmax/ymin/ymax[+r][+uunit]
xmin, xmax, ymin, and ymax specify the region of interest.
For geographic regions, these limits correspond to west, east,
south, and north and you may specify them in decimal degrees or
in [±]dd:mm[:ss.xxx][W|E|S|N]
format. Append +r if lower left
and upper right map coordinates are given instead of west/east/south/north. The
two shorthands -Rg and -Rd stand for global domain (0/360
and -180/+180 in longitude respectively, with -90/+90 in latitude).
Set geographic regions by specifying ISO country codes from the Digital Chart of the World using
-Rcode1,code2,…[+e|r|R[incs]] instead:
Append one or more comma-separated countries using the 2-character
ISO 3166-1 alpha-2 convention.  To select a state of a country
(if available), append .state, e.g, US.TX for Texas.  To specify a
whole continent, prepend = to any of the continent codes AF (Africa),
AN (Antarctica), AS (Asia), EU (Europe), OC (Oceania),
NA (North America), or SA (South America).  Use +r to modify the bounding box coordinates from the polygon(s):
Append inc, xinc/yinc, or winc/einc/sinc/ninc to adjust the
region to be a multiple of these steps [no adjustment]. Alternatively, use +R to extend the region
outward by adding these increments instead, or +e which is like +r but
it ensures that the bounding box extends by at least 0.25 times the increment [no extension].
Alternatively for grid creation, give -Rcodex0/y0/nx/ny, where
code 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.  This
indicates which point on a rectangular region the x0/y0 coordinate
refers to, and the grid dimensions nx and ny with grid spacings via
-I is used to create the corresponding region.
Alternatively, specify the name of an existing grid file and the
-R settings (and grid spacing and registration, if applicable) are copied from
the grid. When -R is used without any further arguments, the
values from the last use of -R in a previous GMT command
will be used.
For calendar time coordinates you may either give (a) relative time
(relative to the selected TIME_EPOCH and in the selected
TIME_UNIT; append t to -JX|x), or (b) absolute
time of the form [date]T[clock] (append T to
-JX|x). At least one of date and clock must be
present; the T is always required. The date string must be of
the form [-]yyyy[-mm[-dd]]
(Gregorian calendar) or yyyy[-Www[-d]]
(ISO week calendar), while the clock string must be of the form
hh:mm:ss[.xxx]. The use of delimiters and their type and positions
must be exactly as indicated (however, input, output and plot
formats are customizable; see gmt.conf).
You can also use Cartesian projected coordinates compatible with the
chosen projection.  Append the length unit via the +u modifier, (e.g.,
-R-200/200/-300/300+uk for a 400 by 600 km rectangular area centered
on the projection center (0, 0). These coordinates are internally
converted to the corresponding geographic (longitude, latitude)
coordinates for the lower left and upper right corners. This form is
convenient when you want to specify a region directly in the
projected units (e.g., UTM meters).  For Cartesian data in radians you
can also use [±][s]pi[f], for optional integer
scales s and fractions f.




    

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.
-U[label][+c][+jjust][+odx/dy]
Draw the GMT system time stamp on the plot.
By appending +jjust [BL] and/or +odx/dy [-54p/-54p], the
user may specify the justification of the stamp and where the stamp
should fall on the page relative to lower left corner of the plot.
For example, +jBL+o0/0 will align the lower left corner of the time
stamp with the bottom left corner of the plot. Optionally, append a
label, or give +c which will plot the module command string. The GMT
parameters MAP_LOGO, MAP_LOGO_POS,
FONT_LOGO and FORMAT_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 environment variable
TZ (generally local time).
-V[level]
Select verbose mode, which modulates the messages written to stderr.
Choose among 7 levels of verbosity; each level adds more messages:
q - Quiet, not even fatal error messages are produced,
e - Error messages only,
w - Warnings [Default],
t - Timings (report runtimes for time-intensive algorithms),
i - Informational messages (same as -V only),
c - Compatibility warnings, or
d - Debugging messages.
-X[a|c|f|r][xshift]
-Y[a|c|f|r][yshift]
Shift plot origin relative to the current origin by
(xshift,yshift) and optionally append the length unit
(c, i, or p). You can prepend a to shift the origin
back to the original position after plotting, prepend c to
center the plot on the center of the paper (optionally add shift),
prepend f to shift the origin relative to the fixed lower left
corner of the page, or prepend r [Default] to move the origin
relative to its current location. For overlays the default
(xshift,yshift) is (r0), otherwise it is (r72p). 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 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.
-a[col=]name[,…]
Control how aspatial data are handled in GMT during input and output.
Reading OGR/GMT-formatted files: To assign certain aspatial data
items to GMT data columns, give 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 use as data input for column col. In addition, to assign an
aspatial value to non-column data, you may specify col as D
for distance, G for fill, I for ID, L for label,
T for text, W for pen, and Z for value [e.g., used
to look up color via a CPT].  If you skip the leading “col=” in
the argument then we supply (and automatically increment) a column
value starting at 2.  Give just -a to select all aspatial items
to be added to the input record.
Writing OGR/GMT-formatted files: To write OGR/GMT-formatted
files, give one or more comma-separated associations
col=name[:type], with an optional data type from DOUBLE,
FLOAT, INTEGER, CHAR, STRING, DATETIME, or LOGICAL [DOUBLE]. To
extract information from GMT multisegment headers encoded in the
-Ddistance, -Gfill, -IID, -Llabel,
-Ttext, -Wpen, or -Zvalue settings, specify
COL as D, G, I, L, T, W or Z,
respectively; type will be set automatically. Finally, you must
append +ggeometry, where geometry is either POINT, LINE,
or POLY. Optionally, prepend M for multi-versions of these
geometries. To force the clipping of features crossing the Dateline,
use upper-case +G instead. See The GMT Vector Data Format for OGR Compatibility
for details of the OGR/GMT file format.
-bi[ncols][type][w][+l|b]
Select native binary format for primary input (secondary inputs are always ASCII).
Here, ncols is the number of data columns of
given type, which must be one of c (int8_t, aka char), u
(uint8_t, aka unsigned char), h (int16_t, 2-byte signed int),
H (uint16_t, 2-byte unsigned int), i (int32_t, 4-byte
signed int), I ((capital i) uint32_t, 4-byte unsigned int), l
((lower case el) int64_t, 8-byte signed int), L (uint64_t, 8-byte unsigned
int), f (4-byte single-precision float), and d (8-byte
double-precision float). In addition, use x to skip ncols
bytes anywhere in the record.
For records with mixed types, simply append additional comma-separated
combinations of ncols type (no space). Append w to any item to force
byte-swapping. Alternatively, append +l|b to indicate
that the entire data file should be read as little- 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 program. If the input file is netCDF, no
-b is needed; simply append ?var1/var2/…
to the filename to specify the variables to be read. (Example)
     
-bio example
     # Write a binary file, and read it back, with 3 columns in which the first
     # is a 4 bytes float, second a 8 bytes long int and third a 8 bytes double.
     echo 1.5 2 2.5 | gmt convert -bo1f,1l,1d > lixo.bin
     gmt convert lixo.bin -bi1f,1l,1d
-bo[ncols][type][w][+l|b]
Select native binary output. Here, ncols is the actual number
of data columns of type type, which must be one of c, u, h,
H, i, I (capital i), l (lower case ell), L, f, and d (see -bi).
For a mixed-type output record, append additional comma-separated
combinations of ncols type (no space).
Append w to any item to force byte-swapping or +l|b
for byte-swapping of the entire record. 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.
-c[row,col|index]
Used to advance to the selected subplot panel.  Only allowed when in
subplot mode.  Available to all plot modules.  If no arguments are
given then we advance to the next panel in the selected order. If
no -c is given and we just entered subplot mode then the first
panel (top, left) is selected.  Instead of row, col you may give
the one-dimensional index which depends on the order you set via -A
when the subplot was defined. Note: row, col, and index all start at 0.
-d[i|o]nodata
Control how user-coded missing data values are translated to official
NaN values in GMT.  For input data we replace any value that equals
nodata with NaN. For output data we replace any NaN with the chosen
nodata value.  Use -di or -do to only affect input or output.
-dinodata
Examine all input columns and if any item equals nodata we interpret
this value as a missing data item and substitute the value NaN.
-donodata
Examine all output columns and if any item equals NaN we substitute
it with the chosen missing data value nodata.
-e[~]“pattern” | -e[~]/regexp/[i]
Only accept ASCII data records that contain the specified pattern.
To reverse the search, i.e., to only accept data records that do not
contain the specified pattern, use -e~. 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 patterns, give +ffile with one pattern per line.
To give a single pattern starting with +f, escape it with a backslash.
-f[i|o]colinfo
Specify the data types of input and/or output columns (time or
geographical data). Specify i or o to make this apply only
to input or output [Default applies to both]. Give one or more
columns (or column ranges) separated by commas, or use -f
multiple times (column ranges must be given
in the format start[:inc]:stop, where inc defaults to 1 if
not specified).  Append T (absolute calendar time), t
(relative time in chosen TIME_UNIT since TIME_EPOCH),
x (longitude), y (latitude), p[unit] (projected
x,y map coordinates in given unit [meter]) or f (floating point)
to each column or column range item. Shorthands
-f[i|o]g means
-f[i|o]0x,1y (geographic coordinates)
and -f[i|o]c means
-f[i|o]0:1f (Cartesian coordinates)
-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. Append x|X or
y|Y to define a gap when there is a large enough change
in the x or y coordinates, respectively, or d|D for
distance gaps; use upper case to calculate gaps from projected
coordinates. For gap-testing on other columns use [col]z;
if col is not prepended the it defaults to 2 (i.e., 3rd column).
Append gap and optionally a unit u and modifiers +n or +p.
Here, +n means previous minus current column value must exceed
gap to be a gap and +p means current minus previous column value
must exceed gap. Otherwise the absolute value of the
difference must exceed gap. For geographic data
(x|y|d), the unit u may be arc
degree, minute, or second, or meter
[Default], foot, kilometer, Mile, nautical
mile, or survey foot. For projected data
(X|Y|D), choose from inch,
centimeter, or point [Default unit set by
PROJ_LENGTH_UNIT]. Note: For x|y|z with
time data the unit is instead controlled by TIME_UNIT. Repeat
the option to specify multiple criteria, of which any can be met to
produce a line break. Issue an additional -ga to indicate that
all criteria must be met instead.
-h[i|o][n][+c][+d][+msegheader][+rremark][+ttitle]
Primary input file(s) has n extra header record(s). If used, the default number of
header records is IO_N_HEADER_RECS [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]. Blank lines and lines starting
with # are always skipped; to use another leading character for indicating header records,
please see IO_HEADER_MARKER. Note that with -h in effect
the first n records are taken verbatim as headers and not skipped even if any is starting with #.
For output you may request additional headers
to be written via the option modifiers, and use +d to remove existing
header records. Append +c to issue a header comment with column names to the output [none].
Append +m to add a new segment header with a segheader to the output after the header block [none].
Append +r to add a remark comment to the output [none].
Append +t to add a title comment to the output [none].
These optional remark and title strings may contain n to indicate line-breaks).
If used with native binary data we interpret n to instead mean the
number of bytes to skip on input or pad on output.




    

-icols[+l][+sscale][+ooffset][,…][,t[word]]
Select specific data columns for primary input, in arbitrary order. Columns
not listed will be skipped. Give 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 (0)]. Columns may be repeated.  To each
column, optionally add any of  the following: +l takes log10 of
the input values first; +sscale, subsequently multiplies by a
given  scale factor [1]; +ooffset, finally adds a given offset [0].
To read from a given column until the end of the record, leave off stop.
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.
-je|f|g
Determine how spherical distances are calculated in modules that support this.
By default (-jg), we perform great circle distance calculations and parameters such
as distance increments or radii will be compared against calculated great
circle distances. To simplify and speed up calculations you can select Flat
Earth mode (-jf) which gives an approximate but faster result.  Alternatively,
you can select ellipsoidal (-je; or geodesic) mode for the highest precision
(and slowest calculation time).  All spherical distance calculations depend on
the current ellipsoid (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).
-l[label][+Dpen][+Ggap][+Hheader][+L[code/]txt][+Ncols][+Ssize][+V[pen]][+ffont][+gfill][+jjust][+ooff][+ppen][+sscale][+wwidth]
Add a map legend entry to the session legend information file for the
current plot.  Optionally append a text label to describe the entry.
Several modifiers allow further changes to the legend (to be built
when legend is called): Use +D to draw a horizontal line before the
legend entry is placed [no line], +G to add some vertical space [0],
+H to add a legend header [no header], +L to set a line text; prepend
a horizontal justification code L, C, or R [C], +N
to change the number of columns used to set the following legend items [1],
+S to override the size of the current symbol for the legend or set a
length if plotting a line or contour [same as plotted], and
+V to start and +vpen to stop drawing vertical line from
previous to current horizontal line [no vertical line].  In addition, several
lower-case modifiers can be set to affect the legend: Use
+f to set the font used for the legend header [FONT_TITLE],
+g to set the fill used for the legend frame [white],
+j to set placement of the legend [TR],
+o to set the offset from legend frame to anchor point [0.2c],
+p to set the pen used for the legend frame [1p],
+sscale to resize all symbol and length sizes in the legend, and
+wwidth to set legend frame width [auto].
Default pen is given by MAP_DEFAULT_PEN.
Note that +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 subdivides the available width among the specified columns.
The upper-case modifiers reflect legend codes described in legend, which provide more details and
customization.  If legend is not called explicitly we will call it implicitly when finishing the plot
via end.
-n[b|c|l|n][+a][+bBC][+c][+tthreshold]
Select grid interpolation mode by adding b for B-spline
smoothing, c for bicubic interpolation, l for bilinear
interpolation, or n for nearest-neighbor value (for example to
plot categorical data). Optionally, append +a to switch off
antialiasing (where supported). Append +bBC to override the
boundary conditions used, adding g for geographic, 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. Append +c to clip the interpolated
grid to input z-min/max [Default may exceed limits]. Append +tthreshold to
control how close to nodes with NaNs the interpolation will go. A
threshold of 1.0 requires all (4 or 16) nodes involved in
interpolation to be non-NaN. 0.5 will interpolate about half way
from a non-NaN value; 0.1 will go about 90% of the way, etc.
[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].
-ocols[,…][,t[word]]
Select specific data columns for primary output, in arbitrary order. Columns
not listed will be skipped. Give columns (or column ranges
in the format start[:inc]:stop, where inc defaults to 1 if
not specified) separated by commas.  Columns may be repeated.
To write from a given column until the end the columns, leave off stop.
[Default writes all columns in order].
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.
-p[x|y|z]azim[/elev[/zlevel]][+wlon0/lat0[/z0]][+vx0/y0]
Select perspective view and set the azimuth and elevation of the
viewpoint [180/90]. When -p is used in consort with -Jz or
-JZ, a third value can be appended which indicates at which
z-level all 2D material, like the plot frame, is plotted (in
perspective). [Default is at the bottom of the z-axis]. Use -px
or -py to plot against the “wall” x = level or y = level
(default is on the horizontal plane, which is the same as using
-pz). For frames used for animation, note we fix the center of your
data domain.  Specify another center using a particular
world coordinate point with +wlon0/lat0[/z0]) which will
project to the center of your page size, or specify the coordinates
of the projected 2-D view point with +vx0/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).  Alternatively, you
can perform a simple rotation about the z-axis by just giving the
rotation angle.  Optionally, use +v or +w to select another
axis location than the plot origin.
-q[i|o][~]rows[+ccol][+a|f|s]
Select specific data rows to be read (-qi [Default]) or written (-qo) [all].
Give individual rows (or row ranges in the format start[:inc]:stop, where
inc defaults to 1 if not specified) separated by commas [Default reads/writes all rows,
starting with the first row (0)]. By default (+a) we count rows in the data set;
append +f or +s to reset the count at the start of each file or segment, respectively.
Alternatively, use +ccol to indicate that the arguments instead
are min/max data limits for the values in column col.
Note: Because arguments may contain colons or be negative, your must specify start/stop instead.
To read (or write) from a given row until the end of the data, leave off stop.
To reverse the tests, prepend ~ before giving your first range.
-qi[~]rows[+ccol][+a|f|s]
Select specific data rows to be read during input [all].
Give individual rows (or row ranges in the format start[:inc]:stop, where
inc defaults to 1 if not specified) separated by commas [Default reads all rows,
starting with the first row (0)]. By default (+a) we count rows in the data set;
append +f or +s to reset the count at the start of each file or segment.
Alternatively, use +ccol to indicate that the arguments instead
are min/max data limits for the values in column col.
Note: Because data limits may contain colons or be negative, your must specify start/stop instead.
To read from a given row until the end of the data, leave off stop.
To reverse the tests, prepend ~ before giving your first range.
-qo[~]rows[+ccol][+a|f|s]
Select specific data rows to be writing during output [all].
Give individual rows (or row ranges in the format start[:inc]:stop, where
inc defaults to 1 if not specified) separated by commas [Default writes all rows,
starting with the first row (0)]. By default (+a) we count rows in the data set;
append +f or +s to reset the count at the start of each file or segment, respectively.
Alternatively, use +ccol to indicate that the arguments instead
are min/max data limits for the values in column col.
Note: Because data limits may contain colons or be negative, your must specify start/stop instead.
To write from a given row until the end of the data, leave off stop.
To reverse the tests, prepend ~ before giving your first range.
-r[g|p]
Force gridline or pixel node registration [gridline]. Just -r sets pixel registration.
If no -r is given then gridline registration is selected.
(Node registrations are defined in Section Grid registration: The -r option
of the GMT Technical Reference and Cookbook.)
-s[cols][+a][+r]
Suppress output of data records whose z-value(s) equal NaN [Default
outputs all records]. By default, we only consider the third data column
(cols = 2).  However, you can append a comma-separated list of all columns
or column ranges to include in the NaN test (column ranges must be given
in the format start[:inc]:stop, where inc defaults to 1 if
not specified).  All the selected data columns must be NaN to skip the record.
Append +a to skip the record if just one or more of the columns equal NaN.
Append +r to reverse the decision, i.e., only output records that failed the test.
-t[transp]
Set transparency level for an overlay, in (0-100] percent range. [Default
is 0, i.e., opaque].  Only visible when PDF or raster format output is selected.
Only the PNG format selection adds a transparency layer in the image (for further processing).
-x[[-]n]
Limit the number of cores to be used in any OpenMP-enabled
multi-threaded algorithms. By default we try
to use all available 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.
-:[i|o]
Swap 1st and 2nd column on input and/or 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
-icols[+l][+sscale][+ooffset][,…][,t[word]].
-^ 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 explanation 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
code (r/g/b, each in range 0-255; h-s-v, ranges 0-360, 0-1, 0-1; or
c/m/y/k, each in range 0-1), or by a hexadecimal color code
(#rrggbb, as used in HTML). For transparency, append
@transparency in the 0-100 percent range [0 or opaque]
(Only visible when PDF or raster format output is selected.).
See gmtcolors for more information and a full list of color
names.
fill
The attribute fill specifies the solid shade or solid color (see
Specifying Color above) or the pattern used for filling polygons.
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 Predefined Bit and Hachure Patterns in GMT for information on
individual built-in patterns.
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
outline. 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:
Helvetica
Helvetica-Bold
Helvetica-Oblique
Helvetica-BoldOblique
Times-Roman
Times-Bold
Times-Italic
Times-BoldItalic
Courier
Courier-Bold
Courier-Oblique
Courier-BoldOblique
Symbol
AvantGarde-Book
AvantGarde-BookOblique
AvantGarde-Demi
AvantGarde-DemiOblique
Bookman-Demi
Bookman-DemiItalic
Bookman-Light
Bookman-LightItalic
Helvetica-Narrow
Helvetica-Narrow-Bold
Helvetica-Narrow-Oblique
Helvetica-Narrow-BoldOblique
NewCenturySchlbk-Roman
NewCenturySchlbk-Italic
NewCenturySchlbk-Bold
NewCenturySchlbk-BoldItalic
Palatino-Roman
Palatino-Italic
Palatino-Bold
Palatino-BoldItalic
ZapfChancery-MediumItalic
ZapfDingbats
Ryumin-Light-EUC-H
Ryumin-Light-EUC-V
GothicBBB-Medium-EUC-H
GothicBBB-Medium-EUC-V
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 obese. color specifies a gray shade or color (see
Specifying Color above). style can be any of ‘solid’, ‘dashed’
‘dotted’, ‘dashdot’, or ‘dotdash’, or a custom combination of dashes ‘-‘ and
dots ‘.’. 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 FORMAT_DATE_OUT and
FORMAT_CLOCK_OUT, whereas general floating point values are formatted
according to FORMAT_FLOAT_OUT. Be aware that the format 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 setting.
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 “packing” 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][+ooffset][+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 provided, as in +sscale
than 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 specifications
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: “z”. See
grdconvert and Sections Modifiers for COARDS-compliant netCDF files and Grid file format specifications
of the GMT Technical Reference and Cookbook for more information, particularly on
how to read slices of 3-, 4-, or 5-dimensional grids.
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 system].
Required for all but the first plot command when building
multi-layer plots.
-P
Select “Portrait” plot orientation [Default is “Landscape”; see
gmt.conf or gmtset to change the PS_PAGE_ORIENTATION
parameter, or supply --PS_PAGE_ORIENTATION=orientation on the
command line].
See Also¶
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
directories. 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¶