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..
****************************************************************************
pgRouting Manual
Copyright(c) pgRouting Contributors
This documentation is licensed under a Creative Commons Attribution-Share
Alike 3.0 License: https://creativecommons.org/licenses/by-sa/3.0/
****************************************************************************
|
* **Supported versions:**
`Latest <https://docs.pgrouting.org/latest/en/pgr_alphaShape.html>`__
(`3.4 <https://docs.pgrouting.org/3.4/en/pgr_alphaShape.html>`__)
`3.3 <https://docs.pgrouting.org/3.3/en/pgr_alphaShape.html>`__
`3.2 <https://docs.pgrouting.org/3.2/en/pgr_alphaShape.html>`__
`3.1 <https://docs.pgrouting.org/3.1/en/pgr_alphaShape.html>`__
`3.0 <https://docs.pgrouting.org/3.0/en/pgr_alphaShape.html>`__
* **Unsupported versions:**
`2.6 <https://docs.pgrouting.org/2.6/en/pgr_alphaShape.html>`__
`2.5 <https://docs.pgrouting.org/2.5/en/pgr_alphaShape.html>`__
`2.4 <https://docs.pgrouting.org/2.4/en/pgr_alphaShape.html>`__
`2.3 <https://docs.pgrouting.org/2.3/en/src/alpha_shape/doc/pgr_alphaShape.html>`__
`2.2 <https://docs.pgrouting.org/2.2/en/src/alpha_shape/doc/pgr_alphaShape.html>`__
`2.1 <https://docs.pgrouting.org/2.1/en/src/driving_distance/doc/dd_alphashape.html>`__
`2.0 <https://docs.pgrouting.org/2.0/en/src/driving_distance/doc/dd_alphashape.html>`__
``pgr_alphaShape``
===============================================================================
``pgr_alphaShape`` — Polygon part of an alpha shape.
.. rubric:: Availability
* Version 3.0.0
* Breaking change on signature
* Old signature no longer supported
* **Boost 1.54** & **Boost 1.55** are supported
* **Boost 1.56+** is preferable
* Boost Geometry is stable on Boost 1.56
* Version 2.1.0
* Added alpha argument with default 0 (use optimal value)
* Support to return multiple outer/inner ring
* Version 2.0.0
* **Official** function
* Renamed from version 1.x
.. rubric:: Support
Description
-------------------------------------------------------------------------------
Returns the polygon part of an alpha shape.
Characteristics
* Input is a *geometry* and returns a *geometry*
* Uses PostGis ST_DelaunyTriangles
* Instead of using CGAL's definition of `alpha` it use the ``spoon_radius``
* :math:`spoon\_radius = \sqrt alpha`
* A Triangle area is considered part of the alpha shape when
:math:`circumcenter\ radius < spoon\_radius`
* The ``alpha`` parameter is the **spoon radius**
* When the total number of points is less than 3, returns an EMPTY geometry
Signatures
-------------------------------------------------------------------------------
.. rubric:: Summary
.. index::
single: alphaShape
.. admonition:: \ \
:class: signatures
| pgr_alphaShape(**geometry**, [alpha])
| RETURNS ``geometry``
:Example: passing a geometry collection with spoon radius :math:`1.5` using the
return variable ``geom``
.. literalinclude:: doc-pgr_alphashape.queries
:start-after: -- q1
:end-before: -- q2
Parameters
-------------------------------------------------------------------------------
============= ============= ======== ========================================
Parameter Type Default Description
============= ============= ======== ========================================
**geometry** ``geometry`` Geometry with at least :math:`3` points
``alpha`` ``FLOAT`` 0 The radius of the spoon.
============= ============= ======== ========================================
Return Value
-------------------------------------------------------------------------------
==================== ========================
Kind of geometry Description
==================== ========================
GEOMETRY COLLECTION A Geometry collection of Polygons
==================== ========================
See Also
-------------------------------------------------------------------------------
* :doc:`pgr_drivingDistance`
* :doc:`sampledata` network.
* `ST_ConcaveHull <https://postgis.net/docs/ST_ConcaveHull.html>`__
.. rubric:: Indices and tables
* :ref:`genindex`
* :ref:`search`
|
