Provided by: gmt_6.0.0+dfsg-1build2_amd64 
NAME
gmt - The Generic Mapping Tools data processing and display software package
INTRODUCTION
GMT is a collection of public-domain Unix tools that allows you to manipulate x,y and
x,y,z data sets (filtering, trend fitting, gridding, projecting, etc.) and produce
PostScript illustrations 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 directories. Choose
between defaults (deletes the current gmt.conf file used for the current modern
session), cache (deletes the user’s cache directory and all of its content), data
(deletes the user’s 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 directory. The optional session-prefix
assigns a name to the session, and this may be used as figure name for
single-figure sessions [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 current 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 labeling and advancement.
gmt end [show]
Terminates a GMT modern mode session and automatically converts the registered
illustration(s) to the specified formats, then eliminates the temporary work
directory. The figures are placed in the current directory.
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).
--show-bindir
Show directory of executables and exit.
--show-citation
Show the citation for the latest GMT publication.
--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 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.
--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 form the GMT infrastructure
and extend GMT in specific ways.
THE COMMON GMT OPTIONS
-B[p|s]parameters -Jparameters -Jz|Zparameters -K -O
-Rwest/east/south/north[/zmin/zmax][+r][+uunit]
-U[stamp]
-V[level]
-X[a|c|f|r][xshift[u]]
-Y[a|c|f|r][yshift[u]] -aflags -bbinary -dnodata -eregexp -fflags -ggaps -hheaders -i‐
flags -jflags -nflags -oflags -pflags -rreg -sflags -ttransp -x[[-]n] -:[i|o]
DESCRIPTION
These are all the common GMT options that remain the same for all GMT programs. 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][+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. 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 (+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][+l|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][+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). 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 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-axis, 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.
The intervals specification is a concatenated string made up of substrings of the form
[a|f|g]stride[+|-phase][u].
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 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).
Note for geographic axes m and s instead mean arc minutes and arc seconds. All entities
that are language-specific are under control by GMT_LANGUAGE. Alternatively, for linear
maps, 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:
1. 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.
2. An l is appended to the tickinfo string. Then, log10 of the tick value is plotted at
every integer log10 value.
3. 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:
1. stride sets the regular annotation interval.
2. 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 [n]pi[m], for an optional integer n and optional m
fractions 2, 3, or 4.
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 following character 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). UNIT 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 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 the
map projections is user-definable by editing the gmt.conf file in your home directory. 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 (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 (Oblique Mercator [C]).
Typically used with -RLLx/LLy/URx/URyr 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/scale
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/scale
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.
-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/]scale or -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:
-Jp[a]scale[/origin][r|z] or -JP[a]width[/origin][r|z] (Polar coordinates (theta,r))
Optionally insert a after -Jp [ or -JP] for azimuths CW from North instead of
directions CCW from East [Default]. Optionally append /origin in degrees to indicate an
angular offset [0]). Finally, append r if r is elevations in degrees (requires s >= 0
and n <= 90) or z if you want to annotate depth rather than radius [Default]. Give
scale in UNIT/r-unit.
-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.
-J<proj4>|EPSG:n
Starting at GMT6 it is possible to use the PROJ.4 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.4 syntax (that is the syntax of the proj and cs2cs programs) so users are
referred to it http://proj4.org/apps/index.html for the details.
The usage of PROJ.4 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.4 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.4 projections, the situations is, however, rather more limited for mapping
purposes. Here, only the subset of the PROJ.4 projections that can be mapped into
the GMT projections syntax is available to use. Another aspect that is not present
in PROJ.4, 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,…[+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 [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, 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 Unix System time stamp on the plot. By appending +jjust and/or
+odx/dy, 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 [BL]. Optionally, append a label, or give +c which will plot the
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 will send progress reports to stderr. Choose among 6
levels of verbosity; each level adds more messages: q - Complete silence, not even
fatal error messages are produced. n - Normal verbosity: produce only fatal error
messages. c - Produce also compatibility warnings (same as when -V is omitted). v
- Produce also warnings and progress messages (same as -V only). l - Produce also
detailed progress messages. d - Produce also debugging messages.
-X[a|c|f|r][xshift[u]]
-Y[a|c|f|r][yshift[u]]
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 (r1i). 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 GMT Appendix Q 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.
-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 contains the specified pattern. To reverse the
search, i.e., to only accept data record that do not contain the specified pattern,
use -e~. Should your pattern happen to start with ~ you need to escape this
character with a backslash [Default accepts all data records]. For matching data
records against extended regular expressions enclose the expression in slashes.
Append i for case-insensitive matching. For 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[u][+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][+rremark][+ttitle]
Primary input file(s) has header record(s). If used, the default number of header
records is IO_N_HEADER_RECS [1]. 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. 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 +r to add a remark comment to the output
[none]. Append +t to add a title comment to the output [none]. These optional
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]. 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 and fast result. Alternatively, you can select
ellipsoidal (-je) or geodesic mode for the highest precision (and slowest
calculation time). All spherical distance calculations depends 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][+ffont][+ggap][+hheader][+jjust][+l[code/]txt][+ncols][+ssize][+v[pen]][+wwidth][+xscale]
[beta version] 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], use
+f to set the font used for the legend header [FONT_TITLE], use +g to add some
vertical space [0], use +h to add a legend header [no header], +j to set placement
of the legend [TR], use +l to set a line text; prepend a horizontal justification
code L, C, or R [C], use +n to change the number of columns used to set the
following legend items [1], use +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], use +v
to start and +vpen to stop drawing vertical line from previous to current
horizontal line [no vertical line], use +w to set legend width [auto], and use
+xscale to resize all symbol and length sizes in the legend. Default pen is given
by MAP_DEFAULT_PEN. Note that +h, +j, +w, and +x will only take effect if given on
the very first -l option for a plot. The +n modifier, if used on the first -l
option, affects the legend width (unless set via +w); otherwise it just subdivides
the available width among the specified columns. The automatic legend has a fixed
white background with a solid black pen outline and offset 0.2 cm from the map
frame. The modifiers largely 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. [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. 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]
Selects perspective view and sets 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. 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.
-r[g|p]
Force gridline or pixel node registration [Just -r sets pixel registration]. If no
-r is given then gridline registration is selected. (Node registrations are
defined in Section option_nodereg of the GMT Technical Reference and Cookbook.)
-s[cols][+a|+r]
Suppress output for records whose z-value equals NaN [Default outputs all records].
Append +a to skip records where at least one field equal NaN, or append +r to
reverse the suppression, i.e., only output the records whose z-value equals NaN.
Alternatively, indicate a comma-separated list of all columns or column ranges to
consider for this NaN test (Column ranges must be given in the format
start[:inc]:stop, where inc defaults to 1 if not specified).
-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.
-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][,…].
-^ or just -
Print a short message about the syntax of the command, then exits (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 exits.
-? or no arguments
Print a complete usage (help) message, including the explanation of all options,
then exits.
--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.
Specifying Fill
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 [1200].
For 1-bit rasters: use upper case P for inverse video, or append +fcolor and/or
+bcolor to specify fore- and background colors (use color = - for transparency).
See GMT Cookbook & Technical Reference Appendix E for information on individual
built-in patterns.
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
outline. If you want to avoid that the outline partially obscures the text, append
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 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 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 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-CF and grid-file-format of the GMT Technical
Reference and Cookbook for more information, particularly on how to read splices 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/
COPYRIGHT
2019, The GMT Team.