Move 'Coordinate operations' to top level of docs [skip ci]

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diff --git a/docs/source/operations/projections/fouc_s.rst b/docs/source/operations/projections/fouc_s.rst
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+.. _fouc_s:
+
+********************************************************************************
+Foucaut Sinusoidal
+********************************************************************************
+
+.. image:: ./images/fouc_s.png
+   :scale: 50%
+   :alt:   Foucaut Sinusoidal
+
+
+The `y`-axis is based upon a weighted mean of the cylindrical equal-area and
+the sinusoidal projections. Parameter :math:`n=n` is the weighting factor where
+:math:`0 <= n <= 1`.
+
+.. math::
+
+    x &= \lambda \cos \phi / (n + (1 - n) \ cos \phi)
+
+    y &= n \phi + (1 - n) \sin \phi
+
+For the inverse, the Newton-Raphson method can be used to determine
+:math:`\phi` from the equation for :math:`y` above. As :math:`n \rightarrow 0` and
+:math:`\phi \rightarrow \pi/2`, convergence is slow but for :math:`n = 0`, :math:`\phi =
+\sin^1y`