Coastlines and boarders
-----------------------

Plotting coastlines and boarders is handled by :gmt-module:`coast`.

Shorelines
~~~~~~~~~~

Use the :gmt-module:`-W <coast#w>` parameter to plot only the shorelines:

.. gmtplot::

   gmt begin shorelines png
      gmt coast -Rg -JW15c -B -W
   gmt end show

The shorelines are divided in 4 levels:

1. coastline
2. lakeshore
3. island-in-lake shore
4. lake-in-island-in-lake shore

You can specify which level you want to plot by appending the level number and a
GMT pen configuration to the :gmt-module:`-W <coast#w>` parameter. For example,
to plot just the coastlines with 0.5 thickness and black lines:

.. gmtplot::

   gmt begin shorelines_levels png
      gmt coast -Rg -JW15c -B -W1/0.5p,black
   gmt end show

You can specify multiple levels by using the :gmt-module:`-W <coast#w>`
parameter more than once:

.. gmtplot::

   gmt begin shorelines_levels png
      gmt coast -Rg -JW15c -B -W1/0.5p,black -W2/0.5,red
   gmt end show

Resolutions
~~~~~~~~~~~

The coastline database comes with 5 resolutions, which can be set using the
:gmt-module:`-D <coast#d>` parameter. The resolution drops by 80% between levels:

1. **c**: crude
2. **l**: low
3. **i**: intermediate
4. **h**: high
5. **f**: full

.. gmtplot::

   oahu="-158.3/-157.6/21.2/21.8"
   gmt begin shorelines_resolutions png
      for res in c, l, i, h, f
      do
          gmt coast -R${oahu} -JM5c -W1p -D${res} -X5c
      done
   gmt end show

Land and water
~~~~~~~~~~~~~~

Use the :gmt-module:`-G <coast#g>` and :gmt-module:`-S <coast#s>` parameters to
specify a fill color for land and water bodies. The colors can be given by name
or hex codes:

.. gmtplot::

   gmt begin land_water png
      gmt coast -Rg -JW15c -B -G#666666 -Sskyblue
   gmt end show