Confirmed GEOS 3.4 support

        ref_union = GEOSGeometry(ref_ewkt)

        union = City3D.objects.aggregate(Union('point'))['point__union']

        self.assertTrue(union.hasz)

        self.assertEqual(ref_union, union)

        # Ordering of points in the resulting geometry may vary between implementations

        self.assertSetEqual(set([p.ewkt for p in ref_union]), set([p.ewkt for p in union]))

    def test_extent(self):

        """

        p4 = Point(-96.801611, 32.782057)

        p5 = Point(-95.363151, 29.763374)

        # Creating the reference union geometry depending on the spatial backend,

        # as Oracle will have a different internal ordering of the component

        # geometries than PostGIS.  The second union aggregate is for a union

        # The second union aggregate is for a union

        # query that includes limiting information in the WHERE clause (in other

        # words a `.filter()` precedes the call to `.unionagg()`).

        if oracle:

            ref_u1 = MultiPoint(p4, p5, p3, p1, p2, srid=4326)

            ref_u2 = MultiPoint(p3, p2, srid=4326)

        else:

            # Looks like PostGIS points by longitude value.

        ref_u1 = MultiPoint(p1, p2, p4, p5, p3, srid=4326)

        ref_u2 = MultiPoint(p2, p3, srid=4326)

        u1 = City.objects.unionagg(field_name='location__point')

        u2 = City.objects.exclude(name__in=('Roswell', 'Houston', 'Dallas', 'Fort Worth')).unionagg(field_name='location__point')

        u3 = aggs['location__point__union']

        self.assertEqual(ref_u1, u1)

        self.assertEqual(ref_u2, u2)

        self.assertEqual(ref_u1, u3)

        self.assertEqual(type(u1), MultiPoint)

        self.assertEqual(type(u3), MultiPoint)

        # Ordering of points in the result of the union is not defined and

        # implementation-dependent (DB backend, GEOS version)

        self.assertSetEqual(set([p.ewkt for p in ref_u1]), set([p.ewkt for p in u1]))

        self.assertSetEqual(set([p.ewkt for p in ref_u2]), set([p.ewkt for p in u2]))

        self.assertSetEqual(set([p.ewkt for p in ref_u1]), set([p.ewkt for p in u3]))

    def test05_select_related_fk_to_subclass(self):

        "Testing that calling select_related on a query over a model with an FK to a model subclass works"

========================  ====================================  ================================  ==========================

Program                   Description                           Required                          Supported Versions

========================  ====================================  ================================  ==========================

:ref:`GEOS <ref-geos>`    Geometry Engine Open Source           Yes                               3.3, 3.2, 3.1

:ref:`GEOS <ref-geos>`    Geometry Engine Open Source           Yes                               3.4, 3.3, 3.2, 3.1

`PROJ.4`_                 Cartographic Projections library      Yes (PostgreSQL and SQLite only)  4.8, 4.7, 4.6, 4.5, 4.4

:ref:`GDAL <ref-gdal>`    Geospatial Data Abstraction Library   No (but, required for SQLite)     1.9, 1.8, 1.7, 1.6

:ref:`GeoIP <ref-geoip>`  IP-based geolocation library          No                                1.4

    GEOS 3.1.0 2009-03-11

    GEOS 3.2.0 2009-12-14

    GEOS 3.3.0 2011-05-30

    GEOS 3.4.0 2013-08-11

    GDAL 1.6.0 2008-12-04

    GDAL 1.7.1 2010-02-08

    GDAL 1.8.0 2011-01-13