.. index:: ! gmt.conf

********
gmt.conf
********

.. only:: not man

    Configuration for GMT

Description
-----------

The following is a list of the parameters that are user-definable in
GMT. The parameter names are always given in UPPER CASE. The
parameter values are case-insensitive unless otherwise noted. The system
defaults are given in brackets [ for SI (and US) ]. Those marked **\***
can be set on the command line as well (the corresponding option is
given in parentheses). Note that default distances and lengths below are
given in both cm or inch; the chosen default depends on your choice of
default unit (see :ref:`PROJ_LENGTH_UNIT <PROJ_LENGTH_UNIT>`). You can explicitly specify
the unit used for distances and lengths by appending **c** (cm), **i**
(inch), or **p** (points). When no unit is indicated the value will be
assumed to be in the unit set by :ref:`PROJ_LENGTH_UNIT <PROJ_LENGTH_UNIT>`. Several
parameters take only **true** or **false**. Finally, most of these
parameters can be changed on-the-fly via the **-**\ **-PARAMETER**\ =\ *VALUE*
option to any GMT program. However, a few are static and are only
read via the **gmt.conf** file; these are labeled (static).

Common Specifications
---------------------

The full explanation for how to specify pens, pattern fills, colors, and
fonts can be found in the :doc:`gmt` man page.


+---------------------------------+----------------+
| THEMATIC SUB-SECTIONS           | *prefix*       |
+=================================+================+
| `COLOR Parameters`_             | **COLOR_**     |
+---------------------------------+----------------+
| `DIR Parameters`_               | **DIR_**       |
+---------------------------------+----------------+
| `FONT Parameters`_              | **FONT_**      |
+---------------------------------+----------------+
| `FORMAT Parameters`_            | **FORMAT_**    |
+---------------------------------+----------------+
| `GMT Miscellaneous Parameters`_ | **GMT_**       |
+---------------------------------+----------------+
| `I/O Parameters`_               | **IO_**        |
+---------------------------------+----------------+
| `MAP Parameters`_               | **MAP_**       |
+---------------------------------+----------------+
| `Projection Parameters`_        | **PROJ_**      |
+---------------------------------+----------------+
| `PostScript Parameters`_        | **PS_**        |
+---------------------------------+----------------+
| `Calendar/Time Parameters`_     | **TIME_**      |
+---------------------------------+----------------+

.. _COLOR Parameters:

.. _COLOR_BACKGROUND:

**COLOR_BACKGROUND**
    Color used for the background of images (i.e., when z < lowest color
    table entry) [black].

.. _COLOR_FOREGROUND:

**COLOR_FOREGROUND**
    Color used for the foreground of images (i.e., when z > highest
    color table entry) [white].

.. _COLOR_HSV_MAX_S:

**COLOR_HSV_MAX_S**
    Maximum saturation (0-1) assigned for most positive intensity value [0.1].

.. _COLOR_HSV_MIN_S:

**COLOR_HSV_MIN_S**
    Minimum saturation (0-1) assigned for most negative intensity value [1.0].

.. _COLOR_HSV_MAX_V:

**COLOR_HSV_MAX_V**
    Maximum value (0-1) assigned for most positive intensity value [1.0].

.. _COLOR_HSV_MIN_V:

**COLOR_HSV_MIN_V**
    Minimum value (0-1) assigned for most negative intensity value [0.3].

.. _COLOR_MODEL:

**COLOR_MODEL**
    Selects in which color space a CPT should be interpolated.
    By default, color interpolation takes place directly on the RGB
    values which can produce some unexpected hues, whereas interpolation
    directly on the HSV values better preserves those hues. The choices
    are: **none** (default: use whatever the COLOR_MODEL setting in the
    CPT demands), **rgb** (force interpolation in RGB),
    **hsv** (force interpolation in HSV), **cmyk** (assumes colors are
    in CMYK but interpolates in RGB).

.. _COLOR_NAN:

**COLOR_NAN**
    Color used for the non-defined areas of images (i.e., where z == NaN) [127.5].

.. _DIR Parameters:

.. _DIR_CACHE:

**DIR_CACHE**
    Cache directory where we save files downloaded when using external URL addresses, the
    files called **@earth_relief_**\ *res*\ **.grd** or other remote filenames starting
    in @ (e.g., @hotspots.txt) [~/.gmt].

.. _DIR_DATA:

**DIR_DATA**
    Session data dir. Overrides the value of the environment variable **$GMT_DATADIR**
    (see :ref:`Directory parameters` in the CookBook).

.. _DIR_DCW:

**DIR_DCW**
    Path to optional Digital Chart of the World polygon files.

.. _DIR_GSHHG:

**DIR_GSHHG**
    Path to GSHHG files. Defaults to **$GMT_SHAREDIR**/coast if empty.

.. _FONT Parameters:

.. _FONT:

**FONT**
    Sets the default for all fonts, except **FONT_LOGO**. This setting is
    not included in the **gmt.conf** file.

.. _FONT_ANNOT:

**FONT_ANNOT**
    Sets both **FONT_ANNOT_PRIMARY** and **FONT_ANNOT_SECONDARY** to the value specified.
    This setting is not included in the **gmt.conf** file.

.. _FONT_ANNOT_PRIMARY:

**FONT_ANNOT_PRIMARY**
    Font used for primary annotations, etc. [12p,Helvetica,black]. When
    **+** is prepended, scale fonts, offsets and tick-lengths relative
    to **FONT_ANNOT_PRIMARY**.

.. _FONT_ANNOT_SECONDARY:

**FONT_ANNOT_SECONDARY**
    Font to use for time axis secondary annotations
    [14p,Helvetica,black].

.. _FONT_HEADING:

**FONT_HEADING**
    Font to use when plotting headings above subplots [32p,Helvetica,black].

.. _FONT_LABEL:

**FONT_LABEL**
    Font to use when plotting labels below axes [16p,Helvetica,black].

.. _FONT_LOGO:

**FONT_LOGO**
    Font to use for text plotted as part of the GMT time logo
    [8p,Helvetica,black].

.. _FONT_TAG:

**FONT_TAG**
    Font to use for subplot panel tags such as a), ii)
    [20p,Helvetica,black].

.. _FONT_TITLE:

**FONT_TITLE**
    Font to use when plotting titles over graphs [24p,Helvetica,black].

.. _FORMAT Parameters:

.. _FORMAT_CLOCK_IN:

**FORMAT_CLOCK_IN**
    Formatting template that indicates how an input clock string is
    formatted. This template is then used to guide the reading of clock
    strings in data fields. To properly decode 12-hour clocks, append am
    or pm (or upper case) to match your data records. As examples, try
    hh:mm, hh:mm:ssAM, etc. [hh:mm:ss].

.. _FORMAT_CLOCK_MAP:

**FORMAT_CLOCK_MAP**
    Formatting template that indicates how an output clock string is to
    be plotted. This template is then used to guide the formatting of
    clock strings in plot annotations. See **FORMAT_CLOCK_OUT** for
    details. [hh:mm:ss].

.. _FORMAT_CLOCK_OUT:

**FORMAT_CLOCK_OUT**
    Formatting template that indicates how an output clock string is to
    be formatted. This template is then used to guide the writing of
    clock strings in data fields. To use a floating point format for the
    smallest unit (e.g., seconds), append .xxx, where the number of x
    indicates the desired precision. If no floating point is indicated
    then the smallest specified unit will be rounded off to nearest
    integer. For 12-hour clocks, append am, AM, a.m., or A.M. (GMT
    will replace a\|A with p\|P for pm). If your template starts with a
    leading hyphen (-) then each integer item (y,m,d) will be printed
    without leading zeros (default uses fixed width formats). As
    examples, try hh:mm, hh.mm.ss, hh:mm:ss.xxxx, hha.m., etc.
    [hh:mm:ss]. If the format is simply - then no clock is output and
    the ISO T divider between date and clock is omitted.

.. _FORMAT_DATE_IN:

**FORMAT_DATE_IN**
    Formatting template that indicates how an input date string is
    formatted. This template is then used to guide the reading of date
    strings in data fields. You may specify either Gregorian calendar
    format or ISO week calendar format. Gregorian calendar: Use any
    combination of yyyy (or yy for 2-digit years; if so see
    **TIME_Y2K_OFFSET_YEAR**), mm (or o for abbreviated month name in
    the current time language), and dd, with or without delimiters. For
    day-of-year data, use jjj instead of mm and/or dd. Examples can be
    ddmmyyyy, yy-mm-dd, dd-o-yyyy, yyyy/dd/mm, yyyy-jjj, etc. ISO
    Calendar: Expected template is yyyy[-]W[-]ww[-]d, where ww is ISO
    week and d is ISO week day. Either template must be consistent,
    e.g., you cannot specify months if you do not specify years.
    Examples are yyyyWwwd, yyyy-Www, etc. [yyyy-mm-dd].

.. _FORMAT_DATE_MAP:

**FORMAT_DATE_MAP**
    Formatting template that indicates how an output date string is to
    be plotted. This template is then used to guide the plotting of date
    strings in data fields. See **FORMAT_DATE_OUT** for details. In
    addition, you may use a single o instead of mm (to plot month name)
    and u instead of W[-]ww to plot "Week ##". Both of these text
    strings will be affected by the **GMT_LANGUAGE**,
    **FORMAT_TIME_PRIMARY_MAP** and **FORMAT_TIME_SECONDARY_MAP**
    setting. [yyyy-mm-dd].

.. _FORMAT_DATE_OUT:

**FORMAT_DATE_OUT**
    Formatting template that indicates how an output date string is to
    be formatted. This template is then used to guide the writing of
    date strings in data fields. You may specify either Gregorian
    calendar format or ISO week calendar format. Gregorian calendar: Use
    any combination of yyyy (or yy for 2-digit years; if so see
    **TIME_Y2K_OFFSET_YEAR**), mm (or o for abbreviated month name in
    the current time language), and dd, with or without delimiters. For
    day-of-year data, use jjj instead of mm and/or dd. As examples, try
    yy/mm/dd, yyyy=jjj, dd-o-yyyy, dd-mm-yy, yy-mm, etc. ISO Calendar:
    Expected template is yyyy[-]W[-]ww[-]d, where ww is ISO week and d
    is ISO week day. Either template must be consistent, e.g., you
    cannot specify months if you do not specify years. As examples, try
    yyyyWww, yy-W-ww-d, etc. If your template starts with a leading
    hyphen (-) then each integer item (y,m,d) will be printed without
    leading zeros (default uses fixed width formats) [yyyy-mm-dd]. If
    the format is simply - then no date is output and the ISO T divider
    between date and clock is omitted.

.. _FORMAT_GEO_MAP:

**FORMAT_GEO_MAP**
    Formatting template that indicates how an output geographical
    coordinate is to be plotted. This template is then used to guide the
    plotting of geographical coordinates in data fields. See
    **FORMAT_GEO_OUT** for details. In addition, you can append A
    which plots the absolute value of the coordinate. The default is
    ddd:mm:ss. Not all items may be plotted as this depends on the
    annotation interval.

.. _FORMAT_GEO_OUT:

**FORMAT_GEO_OUT**
    Formatting template that indicates how an output geographical
    coordinate is to be formatted. This template is then used to guide
    the writing of geographical coordinates in data fields. The template
    is in general of the form [±]D or [±]ddd[:mm[:ss]][.xxx][F].
    By default, longitudes will be reported in the range [-180,180]. The
    various terms have the following purpose:

    +D Output longitude in the range [0,360]

    -D Output longitude in the range [-360,0]

    D Use **FORMAT_FLOAT_OUT** for floating point degrees.

    ddd Fixed format integer degrees

    : delimiter used

    mm Fixed format integer arc minutes

    ss Fixed format integer arc seconds

    .xxx Floating fraction of previous integer field, fixed width.

    F Encode sign using WESN suffix

    G Same as F but with a leading space before suffix

    The default is D.

.. _FORMAT_FLOAT_MAP:

**FORMAT_FLOAT_MAP**
    Format (C language printf syntax) to be used when plotting double
    precision floating point numbers along plot frames and contours.
    For geographic coordinates, see **FORMAT_GEO_MAP**. [%.12lg].

.. _FORMAT_FLOAT_OUT:

**FORMAT_FLOAT_OUT**
    Format (C language printf syntax) to be used when printing double
    precision floating point numbers to output files. For geographic
    coordinates, see **FORMAT_GEO_OUT**. [%.12lg]. To give some
    columns a separate format, supply one or more comma-separated
    *cols*:*format* specifications, where *cols* can be specific columns
    (e.g., 5 for 6th since 0 is the first) or a range of columns (e.g.,
    3-7). The last specification without column information will
    override the format for all other columns.  Alternatively, you can
    list N space-separated formats and these apply to the first N
    columns.

.. _FORMAT_TIME_MAP:

**FORMAT_TIME_MAP**
    Sets both **FORMAT_TIME_PRIMARY_MAP** and **FORMAT_TIME_SECONDARY_MAP** to the value specified.
    This setting is not included in the **gmt.conf** file.

.. _FORMAT_TIME_PRIMARY_MAP:

**FORMAT_TIME_PRIMARY_MAP**
    Controls how primary month-, week-, and weekday-names are formatted.
    Choose among **full**, **abbreviated**, and **character**. If the
    leading **f**, **a**, or **c** are replaced with **F**, **A**, and
    **C** the entire annotation will be in upper case [full].

.. _FORMAT_TIME_SECONDARY_MAP:

**FORMAT_TIME_SECONDARY_MAP**
    Controls how secondary month-, week-, and weekday-names are
    formatted. Choose among **full**, **abbreviated**, and
    **character**. If the leading **f**, **a**, or **c** are replaced
    with **F**, **A**, and **C** the entire annotation will be in upper case [full].

.. _FORMAT_TIME_STAMP:

**FORMAT_TIME_STAMP**
    Defines the format of the time information in the UNIX time stamp.
    This format is parsed by the C function **strftime**, so that
    virtually any text can be used (even not containing any time
    information) [%Y %b %d %H:%M:%S].

.. _GMT Miscellaneous Parameters:

.. _GMT_AUTO_DOWNLOAD:

**GMT_AUTO_DOWNLOAD**
    Determines if GMT is allowed to automatically download datasets and
    files from the remote server selected via **GMT_DATA_URL**.  Default
    is *on* but you can turn this off by setting it to *off*.

.. _GMT_DATA_URL:

**GMT_DATA_URL**
    Address of the data directory on the remote server [The SOEST server].

.. _GMT_DATA_URL_LIMIT:

**GMT_DATA_URL_LIMIT**
    Upper limit on the size of remote file to download [unlimited].  Give
    the maximum file size in bytes, or append k, m, or g for kilo-, mega-,
    or giga-bytes.

.. _GMT_COMPATIBILITY:

**GMT_COMPATIBILITY**
    Determines if this GMT version should be able to parse command-line
    options for a prior major release.  Specify either 4 or 5. If 4 is
    set we will parse obsolete GMT 4 options and issue warnings; if 5
    is set then parsing GMT 4 only syntax will result in errors [4].

.. _GMT_EXPORT_TYPE:

**GMT_EXPORT_TYPE**
    This setting is only used by external interfaces and controls the
    data type used for table entries.  Choose from double,
    single, [u]long, [u]int, [u]short, and [u]char [Default is double].

.. _GMT_EXTRAPOLATE_VAL:

**GMT_EXTRAPOLATE_VAL**
    Determines what to do if extrapolating beyond the data domain.
    Choose among 'NaN', 'extrap' or 'extrapval,val' (without quotes). In
    the first case return NaN for any element of x that is outside range
    [Default]. Second case lets the selected algorithm compute the
    extrapolation values. Third case sets the extrapolation values to
    the constant value passed in 'val' (this value must off course be
    numeric).

.. _GMT_CUSTOM_LIBS:

**GMT_CUSTOM_LIBS**
    Comma-separated list of GMT-compliant shared libraries that extend
    the capability of GMT with additional custom modules [none]. Alternatively,
    provide a directory name, that MUST end with a slash (or back slash),
    to use all shared libraries in that directory. On Windows, if the dir
    name is made up only of a single slash ('/') search inside a subdirectory
    called 'gmt_plugins' of the directory that contains the 'gmt' executable.
    See the API documentation for how to build your own shared modules.

.. _GMT_FFT:

**GMT_FFT**
    Determines which Fast Fourier Transform (FFT) should be used among
    those that have been configured during installation. Choose from
    **auto** (pick the most suitable for the task among available
    algorithms), **fftw**\ [,\ *planner_flag*] (The Fastest Fourier
    Transform in the West), **accelerate** (Use the Accelerate Framework
    under OS X; Note, that the number of samples to be processed must be
    a base 2 exponent), **kiss**, (Kiss FFT), **brenner** Brenner Legacy
    FFT [auto].
    FFTW can "learn" how to optimally compute Fourier transforms on the
    current hardware and OS by computing several FFTs and measuring
    their execution time. This so gained "Wisdom" will be stored in and
    reloaded from the file fftw_wisdom_<hostname> in $GMT_USERDIR or, if
    $GMT_USERDIR is not writable, in the current directory. To use this
    feature append *planner_flag*, which can be one of *measure*,
    *patient*, and *exhaustive*; see FFTW reference for details. The
    default FFTW planner flag is *estimate*, i.e., pick a (probably
    sub-optimal) plan quickly. Note: if you need a single transform of a
    given size only, the one-time cost of the smart planner becomes
    significant. In that case, stick to the default planner, *estimate*,
    based on heuristics.

.. _GMT_HISTORY:

**GMT_HISTORY**
    Passes the history of past common command options via the
    gmt.history file. The different values for this setting are:
    **true**, **readonly**, **false**, to either read and write to the
    gmt.history file, only read, or not use the file at all [true].

.. _GMT_INTERPOLANT:

**GMT_INTERPOLANT**
    Determines if linear (linear), Akima's spline (akima), natural cubic
    spline (cubic) or no interpolation (none) should be used for 1-D
    interpolations in various programs [akima].

.. _GMT_LANGUAGE:

**GMT_LANGUAGE**
    Language to use when plotting calendar and map items such as months and
    days, map annotations and cardinal points. Select from:

    * CN1 Simplified Chinese
    * CN2 Traditional Chinese
    * DE German
    * DK Danish
    * EH Basque
    * ES Spanish
    * FI Finnish
    * FR French
    * GR Greek
    * HI Hawaiian
    * HU Hungarian
    * IE Irish
    * IL Hebrew
    * IS Icelandic
    * IT Italian
    * JP Japanese
    * KR Korean
    * NL Dutch
    * NO Norwegian
    * PL Polish
    * PT Portuguese
    * RU Russian
    * SE Swedish
    * SG Scottish Gaelic
    * TO Tongan
    * TR Turkish
    * UK British English
    * US US English

    If your language is not supported, please examine the
    **$GMT_SHAREDIR**/localization/gmt_us.locale file and make a similar file. Please
    submit it to the GMT Developers for official inclusion. Custom
    language files can be placed in directories **$GMT_SHAREDIR**/localization
    or ~/.gmt. Note: Some of these languages may require you to also
    change the **PS_CHAR_ENCODING** setting.

.. _GMT_TRIANGULATE:

**GMT_TRIANGULATE**
    Determines if we use the **Watson** [Default] or **Shewchuk**
    algorithm (if configured during installation) for triangulation.
    Note that Shewchuk is required for operations involving Voronoi
    constructions.

.. _GMT_VERBOSE:

**GMT_VERBOSE**
    (**-V**) Determines the level of verbosity used by GMT
    programs. Choose among 6 levels; each level adds to the verbosity of
    the lower levels: **q**\ uiet, **n**\ normal (errors and warnings),
    **c**\ ompatibility warnings, **v**\ erbose progress reports, **l**\ ong
    verbose progress reports, **d**\ ebugging messages [c].

.. _I/O Parameters:

.. _IO_COL_SEPARATOR:

**IO_COL_SEPARATOR**
    This setting determines what character will separate ASCII output
    data columns written by GMT. Choose from tab, space, comma, and
    none [tab].

.. _IO_FIRST_HEADER:

**IO_FIRST_HEADER**
    This setting determines if the first segment header is written when
    there is only a single segment (for multiple segment it must be written).
    By default, such single-segment headers are only written if the header
    has contents. Choose from always, never, or maybe [maybe].

.. _IO_GRIDFILE_FORMAT:

**IO_GRIDFILE_FORMAT**
    Default file format for grids, with optional scale, offset and
    invalid value, written as *ff*\ [**+s**\ *scale*][**+o**\ *offset*][**+n**\ *invalid*]. The
    2-letter format indicator can be one of [**abcegnrs**][**bsifd**]. See
    :doc:`grdconvert` and Section :ref:`grid-file-format` of the
    GMT Technical Reference and Cookbook for more information.
    You may the scale as *a* for auto-adjusting the scale and/or offset of
    packed integer grids (=\ *ID*\ **+s**\ *a* is a shorthand for
    =\ *ID*\ **+s**\ *a*\ **+o**\ *a*).  When *invalid* is omitted
    the appropriate value for the given format is used (NaN or largest negative). [nf].

.. _IO_GRIDFILE_SHORTHAND:

**IO_GRIDFILE_SHORTHAND**
    If true, all grid file names are examined to see if they use the
    file extension shorthand discussed in Section :ref:`grid-file-format` of the GMT
    Technical Reference and Cookbook. If false, no filename expansion is done [false].

.. _IO_HEADER:

**IO_HEADER**
    (**-h**) Specifies whether input/output ASCII files have header record(s) or not [false].

.. _IO_HEADER_MARKER:

**IO_HEADER_MARKER**
    This holds the character we expect to indicate a header record in
    an incoming ASCII data or text table [#]. If this marker should be
    different for output then append another character for the output
    header record marker. The two characters must be separated by a comma.

.. _IO_LONLAT_TOGGLE:

**IO_LONLAT_TOGGLE**
    (**-:**) Set if the first two columns of input and output files
    contain (latitude,longitude) or (y,x) rather than the expected
    (longitude,latitude) or (x,y). false means we have (x,y) both on
    input and output. true means both input and output should be (y,x).
    IN means only input has (y,x), while OUT means only output should be (y,x). [false].

.. _IO_N_HEADER_RECS:

**IO_N_HEADER_RECS**
    Specifies how many header records to expect if **-h** is used [0].
    Note: This will skip the specified number of records regardless of
    what they are.  Since any records starting with # is automatically
    considered a header you will only specify a non-zero number in order
    to skip headers that do not conform to that convention.

.. _IO_NAN_RECORDS:

**IO_NAN_RECORDS**
    Determines what happens when input records containing NaNs for *x*
    or *y* (and in some cases *z*) are read. This may happen, for instance,
    when there is text or other junk present instead of data coordinates, and
    the conversion to a data value fails and yields a NaN.  Choose between **skip**,
    which will report how many bad records were skipped, and **pass** [Default],
    which will quietly pass these records on to the calling
    programs. For most programs this will result in output records with
    NaNs as well, but some will interpret these NaN records to indicate
    gaps in a series; programs may then use that information to detect
    segmentation (if applicable).

.. _IO_NC4_CHUNK_SIZE:

**IO_NC4_CHUNK_SIZE**
    Sets the default chunk size for the vertical (**lat**, **y**) and
    horizontal (**lon**, **x**) dimensions of
    the **z** variable. Very large chunk sizes and sizes smaller than
    128 should be avoided because they can lead to unexpectedly bad
    performance. Note that a chunk of a single precision floating point
    variable of size 2896x2896 completely fills the chunk cache of
    32 MiB. Specify the chunk size for each dimension separated by a
    comma, or **a**\ uto for optimally chosen chunk sizes in the range
    [128,256). Setting **IO_NC4_CHUNK_SIZE** will produce netCDF version 4
    files, which can only be read with the netCDF 4 library, unless all
    dimensions are less than 128 or **c**\ lassic is specified for
    classic netCDF. [auto]

.. _IO_NC4_DEFLATION_LEVEL:

**IO_NC4_DEFLATION_LEVEL**
    Sets the compression level for netCDF4 files upon output. Values
    allowed are integers from 0 (no compression) to 9 (maximum
    compression). Enabling a low compression level can dramatically
    improve performance and reduce the size of certain data. While
    higher compression levels further reduce the data size, they do so
    at the cost of extra processing time. This parameter does not
    apply to classic netCDF files. [3]

.. _IO_SEGMENT_BINARY:

**IO_SEGMENT_BINARY**
    Determines how binary data records with all values set to NaN are
    interpreted.  Such records are considered to be encoded segment
    headers in binary files provided the number of columns equals or
    exceeds the current setting of IO_SEGMENT_BINARY [2].  Specify 0
    or "off" to deactivate the segment header determination.

.. _IO_SEGMENT_MARKER:

**IO_SEGMENT_MARKER**
    This holds the character we expect to indicate a segment header in
    an incoming ASCII data or text table [>]. If this marker should be
    different for output then append another character for the output
    segment marker. The two characters must be separated by a comma. Two
    marker characters have special meaning: B means "blank line" and
    will treat blank lines as initiating a new segment, whereas N means
    "NaN record" and will treat records with all NaNs as initiating a
    new segment. If you choose B or N for the output marker then the
    normal GMT segment header is replaced by a blank or NaN record,
    respectively, and no segment header information is written. To use B
    or N as regular segment markers you must escape them with a leading
    backslash.

.. _MAP Parameters:

.. _MAP_ANNOT_MIN_ANGLE:

**MAP_ANNOT_MIN_ANGLE**
    If the angle between the map boundary and the annotation baseline is
    less than this minimum value (in degrees), the annotation is not
    plotted (this may occur for certain oblique projections.) Give a
    value in the range [0,90]. [20]

.. _MAP_ANNOT_MIN_SPACING:

**MAP_ANNOT_MIN_SPACING**
    If an annotation would be plotted less than this minimum distance
    from its closest neighbor, the annotation is not plotted (this may
    occur for certain oblique projections.) [0p]

.. _MAP_ANNOT_OBLIQUE:

**MAP_ANNOT_OBLIQUE**
    This integer is a sum of 6 bit flags (most of which only are
    relevant for oblique projections): If bit 1 is set (1),
    annotations will occur wherever a gridline crosses the map
    boundaries, else longitudes will be annotated on the lower and upper
    boundaries only, and latitudes will be annotated on the left and
    right boundaries only. If bit 2 is set (2), then
    longitude annotations will be plotted horizontally. If bit 3 is set
    (4), then latitude annotations will be plotted
    horizontally. If bit 4 is set (8), then oblique
    tick-marks are extended to give a projection equal to the specified
    tick length. If bit 5 is set (16), tick-marks will be drawn normal
    to the border regardless of gridline angle. If bit 6 is set (32),
    then latitude annotations will be plotted parallel to the border. To
    set a combination of these, add up the values in parentheses. [1].

.. _MAP_ANNOT_OFFSET:

**MAP_ANNOT_OFFSET**
    Sets both **MAP_ANNOT_OFFSET_PRIMARY** and **MAP_ANNOT_OFFSET_SECONDARY** to the value specified.
    This setting is not included in the **gmt.conf** file.

.. _MAP_ANNOT_OFFSET_PRIMARY:

**MAP_ANNOT_OFFSET_PRIMARY**
    Distance from end of tick-mark to start of annotation [5p].

.. _MAP_ANNOT_OFFSET_SECONDARY:

**MAP_ANNOT_OFFSET_SECONDARY**
    Distance from base of primary annotation to the top of the secondary
    annotation [5p] (Only applies to time axes with both primary and
    secondary annotations).

.. _MAP_ANNOT_ORTHO:

**MAP_ANNOT_ORTHO**
    Determines which axes will get their annotations (for Cartesian
    projections) plotted orthogonally to the axes. Combine any **w**,
    **e**, **s**, **n**, **z** (uppercase allowed as well). [we] (if nothing specified).
    Note that this setting can be overridden via the **+a** modifier in **-B**.

.. _MAP_DEFAULT_PEN:

**MAP_DEFAULT_PEN**
    Sets the default of all pens related to **-W** options. Prepend
    **+** to overrule the color of the parameters
    **MAP_GRID_PEN_PRIMARY**, **MAP_GRID_PEN_SECONDARY**,
    **MAP_FRAME_PEN**, **MAP_TICK_PEN_PRIMARY**, and
    **MAP_TICK_PEN_SECONDARY** by the color of **MAP_DEFAULT_PEN**
    [default,black].

.. _MAP_DEGREE_SYMBOL:

**MAP_DEGREE_SYMBOL**
    Determines what symbol is used to plot the degree symbol on
    geographic map annotations. Choose between ring, degree, colon, or
    none [ring].

.. _MAP_FRAME_AXES:

**MAP_FRAME_AXES**
    Sets which axes to draw and annotate. Combine any uppercase **W**,
    **E**, **S**, **N**, **Z** to draw and annotate west, east, south,
    north and/or vertical (perspective view only) axis. Use lower case
    to draw the axis only, but not annotate. Add an optional **+** to
    draw a cube of axes in perspective view. [WESN].

.. _MAP_FRAME_PEN:

**MAP_FRAME_PEN**
    Pen attributes used to draw plain map frame [thicker,black].

.. _MAP_FRAME_TYPE:

**MAP_FRAME_TYPE**
    Choose between **inside**, **plain** and **fancy** (thick boundary,
    alternating black/white frame; append **+** for rounded corners)
    [fancy]. For some map projections (e.g., Oblique Mercator), plain is
    the only option even if fancy is set as default. In general, fancy
    only applies to situations where the projected x and y directions
    parallel the longitude and latitude directions (e.g., rectangular
    projections, polar projections). For situations where all boundary
    ticks and annotations must be inside the maps (e.g., for preparing
    geotiffs), chose **inside**.  Finally, for Cartesian plots you can
    also choose **graph**\ , which adds a vector to the end of each axis.
    This works best when you reduce the number of axes plotted to one
    per dimension.  By default, the vector tip extends the length of each
    axis by 7.5%. Alternatively, append ,\ *length*\ [**u**], where **u**
    can be % (then *length* is the alternate extension in percent) or one
    of **c**, **i**, or **p** (then *length* is the absolute extension
    of the axis to the start of the vector base instead).  The vector stem
    is set to match :ref:`MAP_FRAME_WIDTH <MAP_FRAME_WIDTH>`, while the vector
    head length and width are 10 and 5 times this width, respectively.  You
    may control its shape via :ref:`MAP_VECTOR_SHAPE <MAP_VECTOR_SHAPE>`.

.. _MAP_FRAME_WIDTH:

**MAP_FRAME_WIDTH**
    Width (> 0) of map borders for fancy map frame [5p]. Note: For fancy
    frames, **MAP_FRAME_PEN** is automatically set to 0.1 times the
    **MAP_FRAME_WIDTH** setting.

.. _MAP_GRID_CROSS_SIZE:

**MAP_GRID_CROSS_SIZE**
    Sets both **MAP_GRID_CROSS_SIZE_PRIMARY** and **MAP_GRID_CROSS_SIZE_SECONDARY** to the value specified.
    This setting is not included in the **gmt.conf** file.

.. _MAP_GRID_CROSS_SIZE_PRIMARY:

**MAP_GRID_CROSS_SIZE_PRIMARY**
    Size (>= 0) of grid cross at lon-lat intersections. 0 means draw
    continuous gridlines instead [0p].

.. _MAP_GRID_CROSS_SIZE_SECONDARY:

**MAP_GRID_CROSS_SIZE_SECONDARY**
    Size (>= 0) of grid cross at secondary lon-lat intersections. 0
    means draw continuous gridlines instead [0p].

.. _MAP_GRID_PEN_PRIMARY:

**MAP_GRID_PEN_PRIMARY**
    Pen attributes used to draw primary grid lines in dpi units or
    points (append p) [default,black].

.. _MAP_GRID_PEN_SECONDARY:

**MAP_GRID_PEN_SECONDARY**
    Pen attributes used to draw secondary grid lines in dpi units or
    points (append p) [thinner,black].

.. _MAP_HEADING_OFFSET:

**MAP_HEADING_OFFSET**
    Distance from top of subplot panel titles to the base of the heading [18p].

.. _MAP_LABEL_OFFSET:

**MAP_LABEL_OFFSET**
    Distance from base of axis annotations to the top of the axis label [8p].

.. _MAP_LINE_STEP:

**MAP_LINE_STEP**
    Determines the maximum length (> 0) of individual straight
    line-segments when drawing arcuate lines [0.75p]

.. _MAP_LOGO:

**MAP_LOGO**
    (**-U**) Specifies if a GMT logo with system timestamp should be
    plotted at the lower left corner of the plot [false].

.. _MAP_LOGO_POS:

**MAP_LOGO_POS**
    (**-U**) Sets the justification and the position of the
    logo/timestamp box relative to the current plots lower left corner
    of the plot [+jBL+o-54p/-54p].

.. _MAP_ORIGIN_X:

**MAP_ORIGIN_X**
    (**-X**) Sets the x-coordinate of the origin on the paper for a
    new plot [1i]. For an overlay, the default offset is 0.

.. _MAP_ORIGIN_Y:

**MAP_ORIGIN_Y**
    (**-Y**) Sets the y-coordinate of the origin on the paper for a
    new plot [1i]. For an overlay, the default offset is 0.

.. _MAP_POLAR_CAP:

**MAP_POLAR_CAP**
    Controls the appearance of gridlines near the poles for all
    azimuthal projections and a few others in which the geographic poles
    are plotted as points (Lambert Conic, Oblique Mercator, Hammer, Mollweide,
    Sinusoidal and van der Grinten). Specify either none (in which case there
    is no special handling) or *pc_lat*/*pc_dlon*. In that case, normal
    gridlines are only drawn between the latitudes
    -*pc_lat*/+\ *pc_lat*, and above those latitudes the gridlines are
    spaced at the (presumably coarser) *pc_dlon* interval; the two
    domains are separated by a small circle drawn at the *pc_lat*
    latitude [85/90]. Note for r-theta (polar) projection where r = 0 is
    at the center of the plot the meaning of the cap is reversed, i.e.,
    the default 85/90 will draw a r = 5 radius circle at the center of
    the map with less frequent radial lines there.

.. _MAP_SCALE_HEIGHT:

**MAP_SCALE_HEIGHT**
    Sets the height (> 0) on the map of the map scale bars drawn by
    various programs [5p].

.. _MAP_TICK_LENGTH:

**MAP_TICK_LENGTH**
    Sets both **MAP_TICK_LENGTH_PRIMARY** and **MAP_TICK_LENGTH_SECONDARY** to the value specified.
    This setting is not included in the **gmt.conf** file.

.. _MAP_TICK_LENGTH_PRIMARY:

**MAP_TICK_LENGTH_PRIMARY**
    The length of a primary major/minor tick-marks [5p/2.5p]. If only
    the first value is set, the second is assumed to be 50% of the first.

.. _MAP_TICK_LENGTH_SECONDARY:

**MAP_TICK_LENGTH_SECONDARY**
    The length of a secondary major/minor tick-marks [15p/3.75p]. If
    only the first value is set, the second is assumed to be 25% of the first.

.. _MAP_TICK_PEN:

**MAP_TICK_PEN**
    Sets both **MAP_TICK_PEN_PRIMARY** and **MAP_TICK_PEN_SECONDARY** to the value specified.
    This setting is not included in the **gmt.conf** file.

.. _MAP_TICK_PEN_PRIMARY:

**MAP_TICK_PEN_PRIMARY**
    Pen attributes to be used for primary tick-marks in dpi units or
    points (append p) [thinner,black].

.. _MAP_TICK_PEN_SECONDARY:

**MAP_TICK_PEN_SECONDARY**
    Pen attributes to be used for secondary tick-marks in dpi units or
    points (append p) [thinner,black].

.. _MAP_TITLE_OFFSET:

**MAP_TITLE_OFFSET**
    Distance from top of axis annotations (or axis label, if present) to
    base of plot title [14p].

.. _MAP_VECTOR_SHAPE:

**MAP_VECTOR_SHAPE**
    Determines the shape of the head of a vector. Normally (i.e., for
    vector_shape = 0), the head will be triangular, but can be changed
    to an arrow (1) or an open V (2).
    Intermediate settings give something in between. Negative values (up
    to -2) are allowed as well [0].

.. _PROJ_AUX_LATITUDE:

**PROJ_AUX_LATITUDE**
    Only applies when geodesics are approximated by great circle
    distances on an equivalent sphere. Select from authalic, geocentric,
    conformal, meridional, parametric, or none [authalic]. When not none
    we convert any latitude used in the great circle calculation to the
    chosen auxiliary latitude before doing the distance calculation. See
    also **PROJ_MEAN_RADIUS**.

.. _Projection Parameters:

.. _PROJ_ELLIPSOID:

**PROJ_ELLIPSOID**
    The (case sensitive) name of the ellipsoid used for the map projections [WGS-84]. Choose among:

|
|     *Airy*: Applies to Great Britain (1830)
|     *Airy-Ireland*: Applies to Ireland in 1965 (1830)
|     *Andrae*: Applies to Denmark and Iceland (1876)
|     *APL4.9*: Appl. Physics (1965)
|     *ATS77*: Average Terrestrial System, Canada Maritime provinces (1977)
|     *Australian*: Applies to Australia (1965)
|     *Bessel*: Applies to Central Europe, Chile, Indonesia (1841)
|     *Bessel-Namibia*: Same as Bessel-Schwazeck (1841)
|     *Bessel-NGO1948*: Modified Bessel for NGO 1948 (1841)
|     *Bessel-Schwazeck*: Applies to Namibia (1841)
|     *Clarke-1858*: Clarke's early ellipsoid (1858)
|     *Clarke-1866*: Applies to North America, the Philippines (1866)
|     *Clarke-1866-Michigan*: Modified Clarke-1866 for Michigan (1866)
|     *Clarke-1880*: Applies to most of Africa, France (1880)
|     *Clarke-1880-Arc1950*: Modified Clarke-1880 for Arc 1950 (1880)
|     *Clarke-1880-IGN*: Modified Clarke-1880 for IGN (1880)
|     *Clarke-1880-Jamaica*: Modified Clarke-1880 for Jamaica (1880)
|     *Clarke-1880-Merchich*: Modified Clarke-1880 for Merchich (1880)
|     *Clarke-1880-Palestine*: Modified Clarke-1880 for Palestine (1880)
|     *CPM*: Comm. des Poids et Mesures, France (1799)
|     *Delambre*: Applies to Belgium (1810)
|     *Engelis*: Goddard Earth Models (1985)
|     *Everest-1830*: India, Burma, Pakistan, Afghanistan, Thailand (1830)
|     *Everest-1830-Kalianpur*: Modified Everest for Kalianpur (1956) (1830)
|     *Everest-1830-Kertau*: Modified Everest for Kertau, Malaysia & Singapore (1830)
|     *Everest-1830-Pakistan*: Modified Everest for Pakistan (1830)
|     *Everest-1830-Timbalai*: Modified Everest for Timbalai, Sabah Sarawak (1830)
|     *Fischer-1960*: Used by NASA for Mercury program (1960)
|     *Fischer-1960-SouthAsia*: Same as Modified-Fischer-1960 (1960)
|     *Fischer-1968*: Used by NASA for Mercury program (1968)
|     *FlatEarth*: As Sphere, but implies fast "Flat Earth" distance calculations (1984)
|     *GRS-67*: International Geodetic Reference System (1967)
|     *GRS-80*: International Geodetic Reference System (1980)
|     *Hayford-1909*: Same as the International 1924 (1909)
|     *Helmert-1906*: Applies to Egypt (1906)
|     *Hough*: Applies to the Marshall Islands (1960)
|     *Hughes-1980*: Hughes Aircraft Company for DMSP SSM/I grid products (1980)
|     *IAG-75*: International Association of Geodesy (1975)
|     *Indonesian*: Applies to Indonesia (1974)
|     *International-1924*: Worldwide use (1924)
|     *International-1967*: Worldwide use (1967)
|     *Kaula*: From satellite tracking (1961)
|     *Krassovsky*: Used in the (now former) Soviet Union (1940)
|     *Lerch*: For geoid modeling (1979)
|     *Maupertius*: Really old ellipsoid used in France (1738)
|     *Mercury-1960*: Same as Fischer-1960 (1960)
|     *MERIT-83*: United States Naval Observatory (1983)
|     *Modified-Airy*: Same as Airy-Ireland (1830)
|     *Modified-Fischer-1960*: Applies to Singapore (1960)
|     *Modified-Mercury-1968*: Same as Fischer-1968 (1968)
|     *NWL-10D*: Naval Weapons Lab (Same as WGS-72) (1972)
|     *NWL-9D*: Naval Weapons Lab (Same as WGS-66) (1966)
|     *OSU86F*: Ohio State University (1986)
|     *OSU91A*: Ohio State University (1991)
|     *Plessis*: Old ellipsoid used in France (1817)
|     *SGS-85*: Soviet Geodetic System (1985)
|     *South-American*: Applies to South America (1969)
|     *Sphere*: The mean radius in WGS-84 (for spherical/plate tectonics applications) (1984)
|     *Struve*: Friedrich Georg Wilhelm Struve (1860)
|     *TOPEX*: Used commonly for altimetry (1990)
|     *Walbeck*: First least squares solution by Finnish astronomer (1819)
|     *War-Office*: Developed by G. T. McCaw (1926)
|     *WGS-60*: World Geodetic System (1960)
|     *WGS-66*: World Geodetic System (1966)
|     *WGS-72*: World Geodetic System (1972)
|     *WGS-84*: World Geodetic System [Default] (1984)
|     *Moon*: Moon (IAU2000) (2000)
|     *Mercury*: Mercury (IAU2000) (2000)
|     *Venus*: Venus (IAU2000) (2000)
|     *Mars*: Mars (IAU2000) (2000)
|     *Jupiter*: Jupiter (IAU2000) (2000)
|     *Saturn*: Saturn (IAU2000) (2000)
|     *Uranus*: Uranus (IAU2000) (2000)
|     *Neptune*: Neptune (IAU2000) (2000)
|     *Pluto*: Pluto (IAU2000) (2000)

    Note that for some global projections, GMT may use a spherical
    approximation of the ellipsoid chosen, setting the flattening to
    zero, and using a mean radius. A warning will be given when this
    happens. If a different ellipsoid name than those mentioned here is
    given, GMT will attempt to parse the name to extract the
    semi-major axis (*a* in m) and the flattening. Formats allowed are:

    *a* implies a zero flattening

    *a*,\ *inv_f* where *inv_f* is the inverse flattening

    *a*,\ **b=**\ *b* where *b* is the semi-minor axis (in m)

    *a*,\ **f=**\ *f* where *f* is the flattening

    This way a custom ellipsoid (e.g., those used for other planets) may
    be used. Further note that coordinate transformations in
    **mapproject** can also specify specific datums; see the
    :doc:`mapproject` man page for further details and how to view
    ellipsoid and datum parameters.

.. _PROJ_GEODESIC:

**PROJ_GEODESIC**
    Selects the algorithm to use for geodesic calculations. Choose between
    **Vincenty** [Default], **Rudoe**, or **Andoyer**. The **Andoyer**
    algorithm is only approximate (to within a few tens of meters) but is
    up to 5 times faster.  The **Rudoe** is given for legacy purposes.
    The default **Vincenty** is accurate to about 0.5 mm.

.. _PROJ_LENGTH_UNIT:

**PROJ_LENGTH_UNIT**
    Sets the unit length. Choose between **c**\ m, **i**\ nch, or
    **p**\ oint [c (or i)]. Note that, in GMT, one point is defined
    as 1/72 inch (the PostScript definition), while it is often
    defined as 1/72.27 inch in the typesetting industry. There is no
    universal definition.

.. _PROJ_MEAN_RADIUS:

**PROJ_MEAN_RADIUS**
    Applies when geodesics are approximated by great circle distances on
    an equivalent sphere or when surface areas are computed. Select from
    mean (R_1), authalic (R_2), volumetric (R_3), meridional, or
    quadratic [authalic].

.. _PROJ_SCALE_FACTOR:

**PROJ_SCALE_FACTOR**
    Changes the default map scale factor used for the Polar
    Stereographic [0.9996], UTM [0.9996], and Transverse Mercator [1]
    projections in order to minimize areal distortion. Provide a new
    scale-factor or leave as default.

.. _PostScript Parameters:

.. _PS_CHAR_ENCODING:

**PS_CHAR_ENCODING**
    (static) Names the eight bit character set being used for text in
    files and in command line parameters. This allows GMT to ensure
    that the PostScript output generates the correct characters on the
    plot. Choose from Standard, Standard+, ISOLatin1, ISOLatin1+, and
    ISO-8859-x (where x is in the ranges [1,10] or [13,15]). See
    Appendix F for details [ISOLatin1+ (or Standard+)].  Note: Normally
    the character set is written as part of the PostScript header.  If
    you need to switch to another character set for a later overlay then
    you must use --PS_CHAR_ENCODING=\ *encoding* on the command line and
    not via gmt set.

.. _PS_COLOR_MODEL:

**PS_COLOR_MODEL**
    Determines whether PostScript output should use RGB, HSV, CMYK, or
    GRAY when specifying color [rgb]. Note if HSV is selected it does
    not apply to images which in that case uses RGB. When selecting
    GRAY, all colors will be converted to gray scale using YIQ
    (television) conversion.

.. _PS_COMMENTS:

**PS_COMMENTS**
    (static) If true we will issue comments in the PostScript file
    that explain the logic of operations. These are useful if you need
    to edit the file and make changes; otherwise you can set it to false
    which yields a somewhat slimmer PostScript file [false].

.. _PS_CONVERT:

**PS_CONVERT**
    Comma-separated list of optional module arguments that we should
    supply when :doc:`psconvert` is called implicitly under modern mode [**A**].
    Ignored when psconvert is called on the command line explicitly.
    The option arguments must be listed without their leading option hyphen.

.. _PS_IMAGE_COMPRESS:

**PS_IMAGE_COMPRESS**
    Determines if PostScript images are compressed using the Run-Length
    Encoding scheme (rle), Lempel-Ziv-Welch compression (lzw), DEFLATE
    compression (deflate[,level]), or not at all (none) [deflate,5]. When
    specifying deflate, the compression level (1–9) may optionally be
    appended.

.. _PS_LINE_CAP:

**PS_LINE_CAP**
    Determines how the ends of a line segment will be drawn. Choose
    among a *butt* cap (default) where there is no projection beyond the
    end of the path, a *round* cap where a semicircular arc with
    diameter equal to the line-width is drawn around the end points, and
    *square* cap where a half square of size equal to the line-width
    extends beyond the end of the path [butt].

.. _PS_LINE_JOIN:

**PS_LINE_JOIN**
    Determines what happens at kinks in line segments. Choose among a
    *miter* join where the outer edges of the strokes for the two
    segments are extended until they meet at an angle (as in a picture
    frame; if the angle is too acute, a bevel join is used instead, with
    threshold set by **PS_MITER_LIMIT**), *round* join where a
    circular arc is used to fill in the cracks at the kinks, and *bevel*
    join which is a miter join that is cut off so kinks are triangular in shape [miter].

.. _PS_MEDIA:

**PS_MEDIA**
    Sets the physical format of the current plot paper [a4 (or letter)].
    The following formats (and their widths and heights in points) are
    recognized:

    Media width height

    * A0 2380 3368
    * A1 1684 2380
    * A2 1190 1684
    * A3 842 1190
    * A4 595 842
    * A5 421 595
    * A6 297 421
    * A7 210 297
    * A8 148 210
    * A9 105 148
    * A10 74 105
    * B0 2836 4008
    * B1 2004 2836
    * B2 1418 2004
    * B3 1002 1418
    * B4 709 1002
    * B5 501 709
    * archA 648 864
    * archB 864 1296
    * archC 1296 1728
    * archD 1728 2592
    * archE 2592 3456
    * flsa 612 936
    * halfletter 396 612
    * statement 396 612
    * note 540 720
    * letter 612 792
    * legal 612 1008
    * 11x17 792 1224
    * tabloid 792 1224
    * ledger 1224 792

    For a completely custom format (e.g., for large format plotters) you
    may also specify WxH, where W and H are in points unless you append
    a unit to each dimension (**c**, **i**, **m** or **p** [Default]).
    Additional user-specific formats may be saved as separate line in a
    gmt_custom_media.conf file stored in ~/.gmt.  Each record would have a
    format name followed by width and height of your media in points.  For
    infinitely long paper rolls (e.g., plotters you can set height = 0).

.. _PS_MITER_LIMIT:

**PS_MITER_LIMIT**
    Sets the threshold angle in degrees (integer in range [0,180]) used
    for mitered joins only. When the angle between joining line segments
    is smaller than the threshold the corner will be bevelled instead of
    mitered. The default threshold is 35 degrees. Setting the threshold
    angle to 0 implies the PostScript default of about 11 degrees.
    Setting the threshold angle to 180 causes all joins to be beveled.

.. _PS_PAGE_COLOR:

**PS_PAGE_COLOR**
    Sets the color of the imaging background, i.e., the paper [white].

.. _PS_PAGE_ORIENTATION:

**PS_PAGE_ORIENTATION**
    (**-P**) Sets the orientation of the page. Choose portrait or
    landscape [landscape].  Only available in GMT classic mode.

.. _PS_SCALE_X:

**PS_SCALE_X**
    Global x-scale (> 0) to apply to plot-coordinates before plotting.
    Normally used to shrink the entire output down to fit a specific
    height/width [1.0].

.. _PS_SCALE_Y:

**PS_SCALE_Y**
    Global y-scale (> 0) to apply to plot-coordinates before plotting.
    Normally used to shrink the entire output down to fit a specific
    height/width [1.0].

.. _PS_TRANSPARENCY:

**PS_TRANSPARENCY**
    Sets the transparency mode to use when preparing PS for rendering to
    PDF. Choose from Color, ColorBurn, ColorDodge, Darken, Difference,
    Exclusion, HardLight, Hue, Lighten, Luminosity, Multiply, Normal,
    Overlay, Saturation, SoftLight, and Screen [Normal].

.. _Calendar/Time Parameters:

.. _TIME_EPOCH:

**TIME_EPOCH**
    Specifies the value of the calendar and clock at the origin (zero
    point) of relative time units (see **TIME_UNIT**). It is a string
    of the form yyyy-mm-ddT[hh:mm:ss] (Gregorian) or
    yyyy-Www-ddT[hh:mm:ss] (ISO) Default is 1970-01-01T00:00:00, the
    origin of the UNIX time epoch.

.. _TIME_INTERVAL_FRACTION:

**TIME_INTERVAL_FRACTION**
    Determines if partial intervals at the start and end of an axis
    should be annotated. If the range of the partial interval exceeds
    the specified fraction of the normal interval stride we will place
    the annotation centered on the partial interval [0.5].

.. _TIME_IS_INTERVAL:

**TIME_IS_INTERVAL**
    Used when input calendar data should be truncated and adjusted to
    the middle of the relevant interval. In the following discussion,
    the unit **u** can be one of these time units: (**y** year, **o**
    month, **u** ISO week, **d** day, **h** hour, **m** minute, and
    **s** second). **TIME_IS_INTERVAL** can have any of the following
    three values: (1) OFF [Default]. No adjustment, time is decoded as
    given. (2) +\ *n*\ **u**. Activate interval adjustment for input by
    truncate to previous whole number of *n* units and then center time
    on the following interval. (3) -*n*\ **u**. Same, but center time on
    the previous interval. For example, with **TIME_IS_INTERVAL** =
    +1o, an input data string like 1999-12 will be interpreted to mean
    1999-12-15T12:00:00.0 (exactly middle of December), while if
    **TIME_IS_INTERVAL** = off then that date is interpreted to mean
    1999-12-01T00:00:00.0 (start of December) [off].

.. _TIME_REPORT:

**TIME_REPORT**
    Controls if a time-stamp should be issued at start of all progress
    reports.  Choose among **clock** (absolute time stamp),
    **elapsed** (time since start of session), or **none**
    [none].

.. _TIME_SYSTEM:

**TIME_SYSTEM**
    Shorthand for a combination of **TIME_EPOCH** and **TIME_UNIT**,
    specifying which time epoch the relative time refers to and what the
    units are. Choose from one of the preset systems below (epoch and
    units are indicated):

    JD -4713-11-25T12:00:00 d (Julian Date)

    MJD 1858-11-17T00:00:00 d (Modified Julian Date)

    J2000 2000-01-01T12:00:00 d (Astronomical time)

    S1985 1985-01-01T00:00:00 s (Altimetric time)

    UNIX 1970-01-01T00:00:00 s (UNIX time)

    RD0001 0001-01-01T00:00:00 s

    RATA 0000-12-31T00:00:00 d

    This parameter is not stored in the **gmt.conf** file but is
    translated to the respective values of **TIME_EPOCH** and
    **TIME_UNIT**.

.. _TIME_UNIT:

**TIME_UNIT**
    Specifies the units of relative time data since epoch (see
    **TIME_EPOCH**). Choose **y** (year - assumes all years are 365.2425
    days), **o** (month - assumes all months are of equal length y/12), **d**
    (day), **h** (hour), **m** (minute), or **s** (second) [**s**].

.. _TIME_WEEK_START:

**TIME_WEEK_START**
    When weeks are indicated on time axes, this parameter determines the
    first day of the week for Gregorian calendars. (The ISO weekly
    calendar always begins weeks with Monday.) [Monday (or Sunday)].

.. _TIME_Y2K_OFFSET_YEAR:

**TIME_Y2K_OFFSET_YEAR**
    When 2-digit years are used to represent 4-digit years (see various
    **FORMAT_DATE**\ s), **TIME_Y2K_OFFSET_YEAR** gives the first
    year in a 100-year sequence. For example, if
    **TIME_Y2K_OFFSET_YEAR** is 1729, then numbers 29 through 99
    correspond to 1729 through 1799, while numbers 00 through 28
    correspond to 1800 through 1828. [1950].

See Also
--------

:doc:`gmt` , :doc:`gmtdefaults` ,
:doc:`gmtcolors` , :doc:`gmtget` ,
:doc:`gmtset`
