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.. _isea:
********************************************************************************
Icosahedral Snyder Equal Area
********************************************************************************
Snyder's Icosahedral Equal Area map projections on polyhedral globes for the
dodecahedron and truncated icosahedron offer relatively low scale and
angular distortion. The equations involved are relatively straight-forward,
and for certain instructional tools and databases, the projections are useful
for world maps. The interruptions remain a disadvantage, as with any low-error
projection system applied to the entire globe :cite:`Snyder1992`.
+---------------------+----------------------------------------------------------+
| **Classification** | Polyhedral, equal area |
+---------------------+----------------------------------------------------------+
| **Available forms** | Forward, spherical |
+---------------------+----------------------------------------------------------+
| **Defined area** | Global |
+---------------------+----------------------------------------------------------+
| **Alias** | isea |
+---------------------+----------------------------------------------------------+
| **Domain** | 2D |
+---------------------+----------------------------------------------------------+
| **Input type** | Geodetic coordinates |
+---------------------+----------------------------------------------------------+
| **Output type** | Projected coordinates |
+---------------------+----------------------------------------------------------+
.. figure:: ./images/isea.png
:width: 500 px
:align: center
:alt: Icosahedral Snyder Equal Area
proj-string: ``+proj=isea``
Parameters
################################################################################
.. note:: All parameters are optional for the projection.
.. option:: +orient=<string>
Can be set to either ``isea`` or ``pole``. See Snyder's Figure 12 for pole orientation :cite:`Snyder1992`.
*Defaults to isea*
.. option:: +azi=<value>
Azimuth.
*Defaults to 0.0*
.. option:: +aperture=<value>
*Defaults to 3.0*
.. option:: +resolution=<value>
*Defaults to 4.0*
.. option:: +mode=<string>
Can be either ``plane``, ``di``, ``dd`` or ``hex``.
*Defaults to plane*
.. include:: ../options/lon_0.rst
.. include:: ../options/lat_0.rst
.. include:: ../options/R.rst
.. include:: ../options/x_0.rst
.. include:: ../options/y_0.rst
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