Add the Spilhaus projection to the supported GMT projections

doc/techref/projections.md

@@ -12,7 +12,7 @@ myst:
 
 # GMT Map Projections
 
-The table below shows the projection codes for the 31 GMT map projections:
+The table below shows the projection codes for the 32 GMT map projections:
 
 | PyGMT Projection Argument | Projection Name |
 | --- | --- |
@@ -47,3 +47,4 @@ The table below shows the projection codes for the 31 GMT map projections:
 | **W**[{{ lon0 }}/]*width*                                   | [](/projections/misc/misc_mollweide.rst) |
 | **X***width*[**l**\|**p***exp*\|**T**\|**t**][/*height*[**l**\|**p***exp*\|**T**\|**t**]][**d**] | Cartesian [linear](/projections/nongeo/cartesian_linear.rst), [logarithmic](/projections/nongeo/cartesian_logarithmic.rst), [power](/projections/nongeo/cartesian_power.rst), and time |
 | **Y**{{ lon0 }}/{{ lat0 }}/*width*                          | [](/projections/cyl/cyl_equal_area.rst) |
+| **+proj=spilhaus+width=**_width_                            | [](/projections/misc/misc_spilhaus.rst) |

examples/projections/misc/misc_spilhaus.py

@@ -0,0 +1,32 @@
+r"""
+Spilhaus projection
+===================
+
+The Spilhaus projection is a world map projection that presents the world's
+oceans as one contiguous body of water, with Antarctica at the top. It was
+developed by Athelstan Spilhaus and is useful for oceanographic studies.
+
+**+proj=spilhaus+width=**\ *width*
+
+The projection is set as a PROJ string with ``+proj=spilhaus`` and the figure
+size is set with *width*.
+
+.. note::
+
+    This projection works well for coastlines but currently has issues for filling
+    land and water masses.
+"""
+
+# %%
+import pygmt
+from pygmt.params import Axis
+
+fig = pygmt.Figure()
+# Use the PROJ string to set the Spilhaus projection
+fig.coast(
+    region="d",
+    projection="+proj=spilhaus+width=12c",
+    frame=Axis(annot=True, tick=True, grid=True),
+    shorelines=True,
+)
+fig.show()