1 files changed, 90 insertions, 1 deletions
diff --git a/docs/source/operations/projections/ob_tran.rst b/docs/source/operations/projections/ob_tran.rst
index 3c996336..08833323 100644
--- a/docs/source/operations/projections/ob_tran.rst
+++ b/docs/source/operations/projections/ob_tran.rst
@@ -6,5 +6,94 @@ General Oblique Transformation
 
 .. image:: ./images/ob_tran.png
    :scale: 50%
-   :alt:   General Oblique Transformation  
+   :alt:   General Oblique Transformation
 
+Usage
+################################################################################
+
+All of the projections of spherical library can be used as an
+oblique projection by means of the General Oblique Transformation. The user
+performs the oblique transformation by selecting the oblique projection
+``+proj=obt_ran``, specifying the translation factors, :option:`+o_lat_p`, and
+:option:`+o_lon_p`, and the projection to be used, :option:`+o_proj`. In the
+example of the Fairgrieve projection the latitude and longitude of the pole of
+the new coordinates, :math:`\alpha` and :math:`\beta` respectively, are to be placed
+at 45°N and 90°W and use the :ref:`moll` projection. Because the central meridian
+of the translated coordinates will follow the :math:`\beta` meridian it is
+necessary to translate the translated system so that the Greenwich meridian
+will pass through the center of the projection by offsetting the central meridian.
+
+The final control for this projection is::
+
+    +proj=ob_tran +o_proj=moll +o_lat_p=45 +o_lon_p=-90 +lon_0=-90
+
+Parameters
+################################################################################
+
+Required
+--------------------------------------------------------------------------------
+
+.. option:: +o_proj=<projection>
+
+    Oblique projection.
+
+In addition to specifying an oblique projection, *how* to rotate the projection
+should be specified. This is done in one of three ways: Define a new pole,
+rotate the projection about a given point or define a new "equator" spanned by
+two points on the sphere. See the details below.
+
+New pole
+................................................................................
+
+.. option:: +o_lat_p=<latitude>
+
+    Latitude of new pole for oblique projection.
+
+.. option:: +o_lon_p=<longitude>
+
+    Longitude of new pole for oblique projection.
+
+Rotate about point
+................................................................................
+
+.. option:: +o_alpha=<value>
+
+    Angle to rotate the projection with.
+
+.. option:: +o_lon_c=<value>
+
+    Longitude of the point the projection will be rotated about.
+
+.. option:: +o_lat_c=<value>
+
+    Latitude of the point the projection will be rotated about.
+
+New "equator" points
+................................................................................
+
+.. option:: +lon_1=<value>
+
+    Longitude of first point.
+
+.. option:: +lat_1=<value>
+
+    Latitude of first point.
+
+.. option:: +lon_2=<value>
+
+    Longitude of second point.
+
+.. option:: +lat_2=<value>
+
+    Latitude of second point.
+
+Optional
+--------------------------------------------------------------------------------
+
+.. include:: ../options/lon_0.rst
+
+.. include:: ../options/R.rst
+
+.. include:: ../options/x_0.rst
+
+.. include:: ../options/y_0.rst