gmt-fork/doc/rst/source/explain_symbols_only.rst_

**-S**\ [*symbol*][*size*]
    Plot individual symbols.
    If present, *size* is symbol size in the unit set in
    :doc:`gmt.conf` (unless **c**, **i**, or **p** is appended). If the symbol
    code (see below) is not given it will be read from the last column in
    the input data; this cannot be used in conjunction with binary input.
    Optionally, append **c**, **i**, or
    **p** to indicate that the size information in the input data is in
    units of cm, inch, or point, respectively [Default is
    :term:`PROJ_LENGTH_UNIT`]. **Note**: If you provide *both* size and symbol via the
    input file you must use :term:`PROJ_LENGTH_UNIT` to indicate the unit
    used for the symbol size or append the units to the sizes in the file.
    If symbol sizes are expected via the third data column then you may convert
    those values to suitable symbol sizes via the **-i** mechanism. The general
    input expectations are::

    *x y* [ *z* ] [ *size* ] [ *symbol-parameters* ] [ *symbol* ]

    where the optional *z* is required when **-C** is used, the optional
    *size* is required when no symbol size is specified, and the trailing
    text with the symbol code is required when symbol code is not specified
    on the command line.  The *symbol-parameters* may vary in numbers; see
    specifics below.
    

    The uppercase symbols **A**, **C**, **D**, **G**, **H**, **I**, **N**,
    **S**, **T** are normalized to have the same area as a circle with
    diameter *size*, while the size of the corresponding lowercase symbols
    refers to the diameter of a circumscribed circle.

    You can change symbols by adding the required **-S** option to any of
    your multisegment headers.

    Choose between these symbol codes:

    **-S-**
        x-dash (-). *size* is the length of a short horizontal (x-dir) line segment.

    **-S+**
        plus (+). *size* is diameter of circumscribing circle.

    **-Sa**
        st\ **a**\ r. *size* is diameter of circumscribing circle.

    **-Sb**\ [*size*\ [**c**\|\ **i**\|\ **p**\|\ **u**]][**+b**\ [*base*]]
        Vertical **b**\ ar extending from *base* to y. The *size* is bar width.
        Append **u** if *size* is in x-units [Default is plot-distance units].
        By default, *base* = 0. Append **+b**\ [*base*] to change this
        value. If *base* is not appended then we read it from the last input
        data column.  Use **+B**\ [*base*] if the bar height is measured relative
        to *base* [Relative to origin].

    **-SB**\ [*size*\ [**c**\|\ **i**\|\ **p**\|\ **u**]][**+b**\ [*base*]]
        Horizontal **b**\ ar extending from *base* to x. The *size* is bar width.
        Append **u** if *size* is in y-units [Default is plot-distance units].
        By default, *base* = 0. Append **+b**\ [*base*] to change this
        value. If *base* is not appended then we read it from the last input
        data column.  Use **+B**\ [*base*] if the bar length is measured relative
        to *base* [Relative to origin].

    **-Sc**
        **c**\ ircle. *size* is diameter of circle.

    **-Sd**
        **d**\ iamond. *size* is diameter of circumscribing circle.

    **-Se**
        **e**\ llipse. Direction (in degrees counter-clockwise from horizontal),
        major_axis, and minor_axis must be found in columns 3, 4, and 5.

    **-Sg**
        octa\ **g**\ on. *size* is diameter of circumscribing circle.

    **-Sh**
        **h**\ exagon. *size* is diameter of circumscribing circle.

    **-Si**
        **i**\ nverted triangle. *size* is diameter of circumscribing circle.

    **-Sj**
        Rotated rectangle. Direction (in degrees counter-clockwise from
        horizontal), x-dimension, and y-dimension must be found in columns 3, 4, and 5.

    **-Sk**
        **k**\ ustom symbol. Append *name*\ /\ *size*, and we will look for a
        definition file called *name*\ .def in (1) the current
        directory or (2) in ~/.gmt or (3) in
        **$GMT_SHAREDIR**/custom. The symbol as defined in that file is of size
        1.0 by default; the appended *size* will scale symbol accordingly. Users
        may add their own custom \*.def files; see CUSTOM SYMBOLS below.

    **-Sl**
        **l**\ etter or text string (less than 256 characters). Give size, and
        append **+t**\ *string* after the size. Note that the size is only approximate;
        no individual scaling is done for different characters. Remember to
        escape special characters like \*. Optionally, you may append **+f**\ *font*
        to select a particular font [Default is :term:`FONT_ANNOT_PRIMARY`] and
        **+j**\ *justify* to change justification [CM].

    **-Sn**
        pe\ **n**\ tagon. *size* is diameter of circumscribing circle.

    **-Sp**
        **p**\ oint. No size needs to be specified (1 pixel is used).

    **-Sr**
        **r**\ ectangle. No size needs to be specified, but the x- and
        y-dimensions must be found in columns 3 and 4.

    **-SR**
        **R**\ ounded rectangle. No size needs to be specified, but the x-
        and y-dimensions and corner radius must be found in columns 3, 4, and 5.

    **-Ss**
        **s**\ quare. *size* is diameter of circumscribing circle.

    **-St**
        **t**\ riangle. *size* is diameter of circumscribing circle.

    **-Sw**
        pie **w**\ edge. Start and stop directions (in degrees
        counter-clockwise from horizontal) for pie slice must be found in
        columns 3 and 4.  Append /*inner* to select a separate inner diameter [0].
        Append **+a**\ [*dr*] to draw the arc line (at inner and outer diameter);
        if *dr* is appended then we draw all arc lines separated radially by *dr*.
        Append **+r**\ [*da*] to draw radial lines (at start and stop directions)
        if *da* is appended then we draw all radial lines separated angularly by *da*.
        These spider-web lines are drawn using the current pen unless **+p**\ *pen* is added.

    **-SW**
        Same as **-Sw**, except azimuths (in degrees east of north) should
        be given instead of the two directions. The azimuths will be mapped
        into angles based on the chosen map projection (**-Sw** leaves the
        directions unchanged).
        Append /*inner* to select a separate inner diameter [0].
        Append **+a**\ [*dr*] to draw the arc line (at inner and outer diameter);
        if *dr* is appended then we draw all arc lines separated radially by *dr*.
        Append **+r**\ [*da*] to draw radial lines (at start and stop directions)
        if *da* is appended then we draw all radial lines separated angularly by *da*.
        These spider-web lines are drawn using the current pen unless **+p**\ *pen* is added.

    **-Sx**
        cross (x). *size* is diameter of circumscribing circle.

    **-Sy**
        y-dash (\|). *size* is the length of a short vertical (y-dir) line segment.