django/docs/ref/contrib/gis/geoquerysets.txt

.. _ref-geoquerysets:

=========================
GeoQuerySet API Reference
=========================

.. currentmodule:: django.contrib.gis.db.models

.. class:: GeoQuerySet([model=None])


.. _spatial-lookups:

Spatial Lookups
===============

Just like when using the the :ref:`queryset-api`, interaction 
with ``GeoQuerySet`` by :ref:`chaining filters <chaining-filters>`.
Instead of the regular Django :ref:`field-lookups`, the
spatial lookups in this section are available for :class:`GeometryField`.

For an introduction, see the :ref:`spatial lookups introduction 
<spatial-lookups-intro>`.  For an overview of what lookups are
compatible with a particular spatial backend, refer to the
:ref:`spatial lookup compatibility table <spatial-lookup-compatibility>`.

.. fieldlookup:: bbcontains

bbcontains
----------

*Availability*: PostGIS, MySQL, SpatiaLite

Tests if the geometry field's bounding box completely contains the lookup 
geometry's bounding box.

Example::

    Zipcode.objects.filter(poly__bbcontains=geom)

==========  ==========================
Backend     SQL Equivalent
==========  ==========================
PostGIS     ``poly ~ geom``
MySQL       ``MBRContains(poly, geom)``
SpatiaLite  ``MbrContains(poly, geom)``
==========  ==========================

.. fieldlookup:: bboverlaps

bboverlaps
----------

*Availability*: PostGIS, MySQL, SpatiaLite

Tests if the geometry field's bounding box overlaps the lookup geometry's 
bounding box.

Example::

    Zipcode.objects.filter(poly__bboverlaps=geom)

==========  ==========================
Backend     SQL Equivalent
==========  ==========================
PostGIS     ``poly && geom``
MySQL       ``MBROverlaps(poly, geom)``
SpatiaLite  ``MbrOverlaps(poly, geom)``
==========  ==========================

.. fieldlookup:: contained

contained
---------

*Availability*: PostGIS, MySQL, SpatiaLite

Tests if the geometry field's bounding box is completely contained by the
lookup geometry's bounding box.

Example::

    Zipcode.objects.filter(poly__contained=geom)

==========  ==========================
Backend     SQL Equivalent
==========  ==========================
PostGIS     ``poly @ geom``
MySQL       ``MBRWithin(poly, geom)``
SpatiaLite  ``MbrWithin(poly, geom)``
==========  ==========================

.. fieldlookup:: gis-contains

contains
--------

*Availability*: PostGIS, Oracle, MySQL, SpatiaLite

Tests if the geometry field spatially contains the lookup geometry.

Example::

    Zipcode.objects.filter(poly__contains=geom)

==========  ============================
Backend     SQL Equivalent
==========  ============================
PostGIS     ``ST_Contains(poly, geom)``
Oracle      ``SDO_CONTAINS(poly, geom)``
MySQL       ``MBRContains(poly, geom)``
SpatiaLite  ``Contains(poly, geom)``
==========  ============================

.. fieldlookup:: contains_properly

contains_properly
-----------------

.. versionadded:: 1.2

*Availability*: PostGIS

Returns true if the lookup geometry intersects the interior of the
geometry field, but not the boundary (or exterior). [#fncontainsproperly]_

.. note::

    Requires PostGIS 1.4 and above.

Example::

    Zipcode.objects.filter(poly__contains_properly=geom)

==========  ===================================
Backend     SQL Equivalent
==========  ===================================
PostGIS     ``ST_ContainsProperly(poly, geom)``
==========  ===================================

.. fieldlookup:: coveredby

coveredby
---------

*Availability*: PostGIS, Oracle

Tests if no point in the geometry field is outside the lookup geometry.
[#fncovers]_

Example::

    Zipcode.objects.filter(poly__coveredby=geom)

==========  =============================
Backend     SQL Equivalent
==========  =============================
PostGIS     ``ST_CoveredBy(poly, geom)``
Oracle      ``SDO_COVEREDBY(poly, geom)``
==========  =============================

.. fieldlookup:: covers

covers
------

*Availability*: PostGIS, Oracle

Tests if no point in the lookup geometry is outside the geometry field.
[#fncovers]_

Example::

    Zipcode.objects.filter(poly__covers=geom)

==========  ==========================
Backend     SQL Equivalent
==========  ==========================
PostGIS     ``ST_Covers(poly, geom)``
Oracle      ``SDO_COVERS(poly, geom)``
==========  ==========================

.. fieldlookup:: crosses

crosses
-------

*Availability*: PostGIS, SpatiaLite

Tests if the geometry field spatially crosses the lookup geometry.

Example::

    Zipcode.objects.filter(poly__crosses=geom)

==========  ==========================
Backend     SQL Equivalent
==========  ==========================
PostGIS     ``ST_Crosses(poly, geom)``
SpatiaLite  ``Crosses(poly, geom)``
==========  ==========================

.. fieldlookup:: disjoint

disjoint
--------

*Availability*: PostGIS, Oracle, MySQL, SpatiaLite

Tests if the geometry field is spatially disjoint from the lookup geometry.

Example::

    Zipcode.objects.filter(poly__disjoint=geom)

==========  =================================================
Backend     SQL Equivalent
==========  =================================================
PostGIS     ``ST_Disjoint(poly, geom)``
Oracle      ``SDO_GEOM.RELATE(poly, 'DISJOINT', geom, 0.05)``
MySQL       ``MBRDisjoint(poly, geom)``
SpatiaLite  ``Disjoint(poly, geom)``
==========  =================================================

equals
------

*Availability*: PostGIS, Oracle, MySQL, SpatiaLite

.. fieldlookup:: exact
.. fieldlookup:: same_as

exact, same_as
--------------

*Availability*: PostGIS, Oracle, MySQL, SpatiaLite

.. fieldlookup:: intersects

intersects
----------

*Availability*: PostGIS, Oracle, MySQL, SpatiaLite

Tests if the geometry field spatially intersects the lookup geometry.

Example::

    Zipcode.objects.filter(poly__intersects=geom)

==========  =================================================
Backend     SQL Equivalent
==========  =================================================
PostGIS     ``ST_Intersects(poly, geom)``
Oracle      ``SDO_OVERLAPBDYINTERSECT(poly, geom)``
MySQL       ``MBRIntersects(poly, geom)``
SpatiaLite  ``Intersects(poly, geom)``
==========  =================================================

.. fieldlookup:: overlaps

overlaps
--------

*Availability*: PostGIS, Oracle, MySQL, SpatiaLite

.. fieldlookup:: relate

relate
------

*Availability*: PostGIS, Oracle, SpatiaLite

Tests if the geometry field is spatially related to the the lookup geometry by
the values given in the given pattern.  This lookup requires a tuple parameter,
``(geom, pattern)``; the form of ``pattern`` will depend on the spatial backend:

PostGIS & SpatiaLite
~~~~~~~~~~~~~~~~~~~~
On these spatial backends the intersection pattern is a string comprising 
nine characters, which  define intersections between  the interior, boundary, 
and exterior of the geometry field and the lookup geometry.  
The intersection pattern matrix may only use the following characters:
``1``, ``2``, ``T``, ``F``, or ``*``.  This lookup type allows users to "fine tune"
a specific geometric relationship consistent with the DE-9IM model. [#fnde9im]_

Example::

    # A tuple lookup parameter is used to specify the geometry and
    # the intersection pattern (the pattern here is for 'contains').
    Zipcode.objects.filter(poly__relate(geom, 'T*T***FF*'))

PostGIS SQL equivalent::

    SELECT ... WHERE ST_Relate(poly, geom, 'T*T***FF*')

SpatiaLite SQL equivalent::

    SELECT ... WHERE Relate(poly, geom, 'T*T***FF*')

Oracle
~~~~~~

Here the relation pattern is compreised at least one of the nine relation
strings: ``TOUCH``, ``OVERLAPBDYDISJOINT``, ``OVERLAPBDYINTERSECT``, 
``EQUAL``, ``INSIDE``, ``COVEREDBY``, ``CONTAINS``, ``COVERS``, ``ON``, and
``ANYINTERACT``.   Multiple strings may be combined with the logical Boolean
operator OR, for example, ``'inside+touch'``. [#fnsdorelate]_  The relation
strings are case-insensitive.

Example::

    Zipcode.objects.filter(poly__relate(geom, 'anyinteract'))

Oracle SQL equivalent:: 

    SELECT ... WHERE SDO_RELATE(poly, geom, 'anyinteract')

.. fieldlookup:: touches

touches
-------

*Availability*: PostGIS, Oracle, MySQL, SpatiaLite

Tests if the geometry field spatially touches the lookup geometry.

Example::

    Zipcode.objects.filter(poly__touches=geom)

==========  ==========================
Backend     SQL Equivalent
==========  ==========================
PostGIS     ``ST_Touches(poly, geom)``
MySQL       ``MBRTouches(poly, geom)``
Oracle      ``SDO_TOUCH(poly, geom)``
SpatiaLite  ``Touches(poly, geom)``
==========  ==========================

.. fieldlookup:: within

within
------

*Availability*: PostGIS, Oracle, MySQL, SpatiaLite

Tests if the geometry field is spatially within the lookup geometry.

Example::

    Zipcode.objects.filter(poly__within=geom)

==========  ==========================
Backend     SQL Equivalent
==========  ==========================
PostGIS     ``ST_Within(poly, geom)``
MySQL       ``MBRWithin(poly, geom)``
Oracle      ``SDO_INSIDE(poly, geom)``
SpatiaLite  ``Within(poly, geom)``
==========  ==========================

.. fieldlookup:: left

left
----

*Availability*: PostGIS

Tests if the geometry field's bounding box is strictly to the left of the
lookup geometry's bounding box.

Example::

    Zipcode.objects.filter(poly__left=geom)

PostGIS equivalent::

    SELECT ... WHERE poly << geom

.. fieldlookup:: right

right
-----

*Availability*: PostGIS

Tests if the geometry field's bounding box is strictly to the right of the
lookup geometry's bounding box.

Example::

    Zipcode.objects.filter(poly__right=geom)

PostGIS equivalent::

    SELECT ... WHERE poly >> geom

.. fieldlookup:: overlaps_left

overlaps_left
-------------

*Availability*: PostGIS

Tests if the geometry field's bounding box overlaps or is to the left of the lookup 
geometry's bounding box.

Example::

    Zipcode.objects.filter(poly__overlaps_left=geom)

PostGIS equivalent::

    SELECT ... WHERE poly &< geom


.. fieldlookup:: overlaps_right

overlaps_right
--------------

*Availability*: PostGIS

Tests if the geometry field's bounding box overlaps or is to the right of the lookup 
geometry's bounding box.

Example::

    Zipcode.objects.filter(poly__overlaps_right=geom)

PostGIS equivalent::

    SELECT ... WHERE poly &> geom

.. fieldlookup:: overlaps_above

overlaps_above
--------------

*Availability*: PostGIS

Tests if the geometry field's bounding box overlaps or is above the lookup 
geometry's bounding box.

Example::

    Zipcode.objects.filter(poly__overlaps_above=geom)

PostGIS equivalent::

    SELECT ... WHERE poly |&> geom

.. fieldlookup:: overlaps_below

overlaps_below
--------------

*Availability*: PostGIS

Tests if the geometry field's bounding box overlaps or is below the lookup 
geometry's bounding box.

Example::

    Zipcode.objects.filter(poly__overlaps_below=geom)

PostGIS equivalent::

    SELECT ... WHERE poly &<| geom

.. fieldlookup:: strictly_above

strictly_above
--------------

*Availability*: PostGIS

Tests if the geometry field's bounding box is strictly above the lookup 
geometry's bounding box.

Example::

    Zipcode.objects.filter(poly__strictly_above=geom)

PostGIS equivalent::

    SELECT ... WHERE poly |>> geom

.. fieldlookup:: strictly_below

strictly_below
--------------

*Availability*: PostGIS

Tests if the geometry field's bounding box is strictly above the lookup 
geometry's bounding box.

Example::

    Zipcode.objects.filter(poly__strictly_above=geom)

PostGIS equivalent::

    SELECT ... WHERE poly |>> geom


.. _distance-lookups:

Distance Lookups
================

*Availability*: PostGIS, Oracle, SpatiaLite

For an overview on performing distance queries, please refer to
the :ref:`distance queries introduction <distance-queries>`.

Distance lookups take the following form::

    <field>__<distance lookup>=(<geometry>, <distance value>[, 'spheroid'])

The value passed into a distance lookup is a tuple; the first two
values are mandatory, and are the geometry to calculate distances to,
and a distance value (either a number in units of the field or a
:class:`~django.contrib.gis.measure.Distance` object).  On every
distance lookup but :lookup:`dwithin`, an optional
third element, ``'spheroid'``, may be included to tell GeoDjango
to use the more accurate spheroid distance calculation functions on
fields with a geodetic coordinate system (e.g., ``ST_Distance_Spheroid``
would be used instead of ``ST_Distance_Sphere``).

.. fieldlookup:: distance_gt

distance_gt
-----------

Returns models where the distance to the geometry field from the lookup
geometry is greater than the given distance value.

Example::

    Zipcode.objects.filter(poly__distance_gt=(geom, D(m=5)))

==========  ===============================================
Backend     SQL Equivalent
==========  ===============================================
PostGIS     ``ST_Distance(poly, geom) > 5``
Oracle      ``SDO_GEOM.SDO_DISTANCE(poly, geom, 0.05) > 5``
SpatiaLite  ``Distance(poly, geom) > 5``
==========  ===============================================

.. fieldlookup:: distance_gte

distance_gte
------------

Returns models where the distance to the geometry field from the lookup
geometry is greater than or equal to the given distance value.

Example::

    Zipcode.objects.filter(poly__distance_gte=(geom, D(m=5)))

==========  ================================================
Backend     SQL Equivalent
==========  ================================================
PostGIS     ``ST_Distance(poly, geom) >= 5``
Oracle      ``SDO_GEOM.SDO_DISTANCE(poly, geom, 0.05) >= 5``
SpatiaLite  ``Distance(poly, geom) >= 5``
==========  ================================================

.. fieldlookup:: distance_lt

distance_lt
-----------

Returns models where the distance to the geometry field from the lookup
geometry is less than the given distance value.

Example::

    Zipcode.objects.filter(poly__distance_lt=(geom, D(m=5)))

==========  ===============================================
Backend     SQL Equivalent
==========  ===============================================
PostGIS     ``ST_Distance(poly, geom) < 5``
Oracle      ``SDO_GEOM.SDO_DISTANCE(poly, geom, 0.05) < 5``
SpatiaLite  ``Distance(poly, geom) < 5``
==========  ===============================================

.. fieldlookup:: distance_lte

distance_lte
------------

Returns models where the distance to the geometry field from the lookup
geometry is less than or equal to the given distance value.

Example::

    Zipcode.objects.filter(poly__distance_lte=(geom, D(m=5)))

==========  ================================================
Backend     SQL Equivalent
==========  ================================================
PostGIS     ``ST_Distance(poly, geom) <= 5``
Oracle      ``SDO_GEOM.SDO_DISTANCE(poly, geom, 0.05) <= 5``
SpatiaLite  ``Distance(poly, geom) <= 5``
==========  ================================================

.. fieldlookup:: dwithin

dwithin
-------

Returns models where the distance to the geometry field from the
lookup geometry are within the given distance from one another.

Example::

    Zipcode.objects.filter(poly__dwithin=(geom, D(m=5)))

==========  ======================================
Backend     SQL Equivalent
==========  ======================================
PostGIS     ``ST_DWithin(poly, geom, 5)``
Oracle      ``SDO_WITHIN_DISTANCE(poly, geom, 5)``
==========  ======================================

.. note::

    This lookup is not available on SpatiaLite.

.. fieldlookup:: equals


``GeoQuerySet`` Methods
=======================

``GeoQuerySet`` methods specify that a spatial operation be performed
on each patial operation on each geographic
field in the queryset and store its output in a new attribute on the model
(which is generally the name of the ``GeoQuerySet`` method).

There are also aggregate ``GeoQuerySet`` methods which return a single value
instead of a queryset.  This section will describe the API and availability
of every ``GeoQuerySet`` method available in GeoDjango.

.. note::

    What methods are available depend on your spatial backend.  See
    the :ref:`compatibility table <geoqueryset-method-compatibility>`
    for more details.

With a few exceptions, the following keyword arguments may be used with all
``GeoQuerySet`` methods:

=====================  =====================================================
Keyword Argument       Description
=====================  =====================================================
``field_name``         By default, ``GeoQuerySet`` methods use the first
                       geographic field encountered in the model.  This
                       keyword should be used to specify another 
                       geographic field (e.g., ``field_name='point2'``)
                       when there are multiple geographic fields in a model.

                       On PostGIS, the ``field_name`` keyword may also be
                       used on geometry fields in models that are related
                       via a ``ForeignKey`` relation (e.g.,
                       ``field_name='related__point'``).
    
``model_att``          By default, ``GeoQuerySet`` methods typically attach
                       their output in an attribute with the same name as
                       the ``GeoQuerySet`` method.  Setting this keyword
                       with the desired attribute name will override this
                       default behavior.  For example,
                       ``qs = Zipcode.objects.centroid(model_att='c')`` will
                       attach the centroid of the ``Zipcode`` geometry field
                       in a ``c`` attribute on every model rather than in a
                       ``centroid`` attribute.  

                       This keyword is required if 
                       a method name clashes with an existing 
                       ``GeoQuerySet`` method -- if you wanted to use the 
                       ``area()`` method on model with a ``PolygonField`` 
		       named ``area``, for example.
=====================  =====================================================

Measurement
-----------
*Availability*: PostGIS, Oracle, SpatiaLite

``area``
~~~~~~~~

.. method:: GeoQuerySet.area(**kwargs)

Returns the area of the geographic field in an ``area`` attribute on
each element of this GeoQuerySet.

``distance``
~~~~~~~~~~~~

.. method:: GeoQuerySet.distance(geom, **kwargs)

This method takes a geometry as a parameter, and attaches a ``distance`` 
attribute to every model in the returned queryset that contains the 
distance (as a :class:`~django.contrib.gis.measure.Distance` object) to the given geometry.

In the following example (taken from the `GeoDjango distance tests`__), 
the distance from the `Tasmanian`__ city of Hobart to every other 
:class:`PointField` in the ``AustraliaCity`` queryset is calculated::

    >>> pnt = AustraliaCity.objects.get(name='Hobart').point
    >>> for city in AustraliaCity.objects.distance(pnt): print city.name, city.distance
    Wollongong 990071.220408 m
    Shellharbour 972804.613941 m
    Thirroul 1002334.36351 m
    Mittagong 975691.632637 m
    Batemans Bay 834342.185561 m
    Canberra 598140.268959 m
    Melbourne 575337.765042 m
    Sydney 1056978.87363 m
    Hobart 0.0 m
    Adelaide 1162031.83522 m
    Hillsdale 1049200.46122 m

.. note::

    Because the ``distance`` attribute is a
    :class:`~django.contrib.gis.measure.Distance` object, you can easily express
    the value in the units of your choice.  For example, ``city.distance.mi`` is
    the distance value in miles and ``city.distance.km`` is the distance value 
    in kilometers.  See the :ref:`ref-measure` for usage details and the list of
    :ref:`supported_units`.

__ http://code.djangoproject.com/browser/django/trunk/django/contrib/gis/tests/distapp/models.py
__ http://en.wikipedia.org/wiki/Tasmania

``length``
~~~~~~~~~~

.. method:: GeoQuerySet.length(**kwargs)

Returns the length of the geometry field in a ``length`` attribute
(a :class:`~django.contrib.gis.measure.Distance` object) on each model in
the queryset.

``perimeter``
~~~~~~~~~~~~~

.. method:: GeoQuerySet.perimeter(**kwargs)

Returns the perimeter of the geometry field in a ``perimeter`` attribute
(a :class:`~django.contrib.gis.measure.Distance` object) on each model in
the queryset.

Geometry Relationships
----------------------

The following methods take no arguments, and attach geometry objects
each element of the :class:`GeoQuerySet` that is the result of relationship
function evaluated on the the geometry field.

``centroid``
~~~~~~~~~~~~

.. method:: GeoQuerySet.centroid(**kwargs)

*Availability*: PostGIS, Oracle, SpatiaLite

Returns the ``centroid`` value for the geographic field in a ``centroid``
attribute on each element of the ``GeoQuerySet``.

``envelope``
~~~~~~~~~~~~

.. method:: GeoQuerySet.envelope(**kwargs)

*Availability*: PostGIS, SpatiaLite

Returns a geometry representing the bounding box of the geometry field in
an ``envelope`` attribute on each element of the ``GeoQuerySet``.

``point_on_surface``
~~~~~~~~~~~~~~~~~~~~

.. method:: GeoQuerySet.point_on_surface(**kwargs)

*Availability*: PostGIS, Oracle, SpatiaLite

Returns a Point geometry guaranteed to lie on the surface of the
geometry field in a ``point_on_surface`` attribute on each element
of the queryset; otherwise sets with None.

Geometry Editors
----------------

``force_rhr``
~~~~~~~~~~~~~

.. method:: GeoQuerySet.force_rhr(**kwargs)

.. versionadded:: 1.2

*Availability*: PostGIS

Returns a modified version of the polygon/multipolygon in which all
of the vertices follow the Right-Hand-Rule, and attaches as a
``force_rhr`` attribute on each element of the queryset.

``reverse_geom``
~~~~~~~~~~~~~~~~

.. method:: GeoQuerySet.reverse_geom(**kwargs)

.. versionadded:: 1.2

*Availability*: PostGIS, Oracle

Reverse the coordinate order of the geometry field, and attaches as a
``reverse`` attribute on each element of the queryset.

``scale``
~~~~~~~~~

.. method:: GeoQuerySet.scale(x, y, z=0.0, **kwargs)

*Availability*: PostGIS, SpatiaLite

``snap_to_grid``
~~~~~~~~~~~~~~~~

.. method:: GeoQuerySet.snap_to_grid(*args, **kwargs)

.. versionadded:: 1.1

Snap all points of the input geometry to the grid.  How the
geometry is snapped to the grid depends on how many numeric
(either float, integer, or long) arguments are given.

===================  =====================================================
Number of Arguments  Description
===================  =====================================================
1                    A single size to snap bot the X and Y grids to.
2                    X and Y sizes to snap the grid to.
4                    X, Y sizes and the corresponding X, Y origins.
===================  =====================================================

``transform``
~~~~~~~~~~~~~

.. method:: GeoQuerySet.transform(srid=4326, **kwargs)

*Availability*: PostGIS, Oracle, SpatiaLite

The ``transform`` method transforms the geometry field of a model to the spatial
reference system specified by the ``srid`` parameter.  If no ``srid`` is given,
then 4326 (WGS84) is used by default.

.. note::

    Unlike other ``GeoQuerySet`` methods, ``transform`` stores its output
    "in-place".  In other words, no new attribute for the transformed
    geometry is placed on the models.

.. note::
    
    What spatial reference system an integer SRID corresponds to may depend on 
    the spatial database used.  In other words, the SRID numbers used for Oracle 
    are not necessarily the same as those used by PostGIS.

Example::

    >>> qs = Zipcode.objects.all().transform() # Transforms to WGS84
    >>> qs = Zipcode.objects.all().transform(32140) # Transforming to "NAD83 / Texas South Central"
    >>> print qs[0].poly.srid
    32140
    >>> print qs[0].poly
    POLYGON ((234055.1698884720099159 4937796.9232223574072123 ...

``translate``
~~~~~~~~~~~~~
.. method:: GeoQuerySet.translate(x, y, z=0.0, **kwargs)

*Availability*: PostGIS, SpatiaLite

Translates the geometry field to a new location using the given numeric
parameters as offsets.

Geometry Operations
-------------------
*Availability*: PostGIS, Oracle, SpatiaLite

The following methods all take a geometry as a parameter and attach a geometry
to each element of the ``GeoQuerySet`` that is the result of the operation.

``difference``
~~~~~~~~~~~~~~

.. method:: GeoQuerySet.difference(geom)

Returns the spatial difference of the geographic field with the given
geometry in a ``difference`` attribute on each element of the 
``GeoQuerySet``.


``intersection``
~~~~~~~~~~~~~~~~

.. method:: GeoQuerySet.intersection(geom)

Returns the spatial intersection of the geographic field with the
given geometry in an ``intersection`` attribute on each element of the 
``GeoQuerySet``.

``sym_difference``
~~~~~~~~~~~~~~~~~~

.. method:: GeoQuerySet.sym_difference(geom)

Returns the symmetric difference of the geographic field with the
given geometry in a ``sym_difference`` attribute on each element of the
``GeoQuerySet``.

``union``
~~~~~~~~~

.. method:: GeoQuerySet.union(geom)

Returns the union of the geographic field with the given
geometry in an ``union`` attribute on each element of the
``GeoQuerySet``.

Geometry Output
---------------

The following ``GeoQuerySet`` methods will return an attribute that has the value 
of the geometry field in each model converted to the requested output format.

``geohash``
~~~~~~~~~~~

.. method:: GeoQuerySet.geohash(preceision=20, **kwargs)

.. versionadded:: 1.2

Attaches a ``geohash`` attribute to every model the the queryset
containing the `GeoHash`__ representation of the geometry.

__ http://geohash.org/

``geojson``
~~~~~~~~~~~

.. method:: GeoQuerySet.geojson(**kwargs)

.. versionadded:: 1.1

*Availability*: PostGIS

Attaches a ``geojson`` attribute to every model in the queryset that contains the
`GeoJSON`__ representation of the geometry.

=====================  =====================================================
Keyword Argument       Description
=====================  =====================================================
``precision``          It may be used to specify the number of significant 
                       digits for the coordinates in the GeoJSON 
                       representation -- the default value is 8.

``crs``                Set this to ``True`` if you want the coordinate
                       reference system to be included in the returned
                       GeoJSON.

``bbox``               Set this to ``True`` if you want the bounding box
                       to be included in the returned GeoJSON.
=====================  =====================================================

__ http://geojson.org/

``gml``
~~~~~~~

.. method:: GeoQuerySet.gml(**kwargs)

*Availability*: PostGIS, Oracle

Attaches a ``gml`` attribute to every model in the queryset that contains the 
`Geographic Markup Language (GML)`__ representation of the geometry. 

Example::

    >>> qs = Zipcode.objects.all().gml()
    >>> print qs[0].gml
    <gml:Polygon srsName="EPSG:4326"><gml:OuterBoundaryIs>-147.78711,70.245363 ...  -147.78711,70.245363</gml:OuterBoundaryIs></gml:Polygon>

=====================  =====================================================
Keyword Argument       Description
=====================  =====================================================
``precision``          This keyword is for PostGIS only.  It may be used 
                       to specify the number of significant digits for the 
                       coordinates in the GML representation -- the default 
                       value is 8.

``version``            This keyword is for PostGIS only.  It may be used to
                       specify the GML version used, and may only be values
                       of 2 or 3.  The default value is 2.
=====================  =====================================================

__ http://en.wikipedia.org/wiki/Geography_Markup_Language

``kml``
~~~~~~~

.. method:: GeoQuerySet.kml(**kwargs)

*Availability*: PostGIS

Attaches a ``kml`` attribute to every model in the queryset that contains the 
`Keyhole Markup Language (KML)`__ representation of the geometry fields. It 
should be noted that the contents of the KML are transformed to WGS84 if 
necessary.

Example::

    >>> qs = Zipcode.objects.all().kml()
    >>> print qs[0].kml
    <Polygon><outerBoundaryIs><LinearRing><coordinates>-103.04135,36.217596,0 ... -103.04135,36.217596,0</coordinates></LinearRing></outerBoundaryIs></Polygon>

=====================  =====================================================
Keyword Argument       Description
=====================  =====================================================
``precision``          This keyword may be used to specify the number of 
                       significant digits for the coordinates in the KML 
                       representation -- the default value is 8.
=====================  =====================================================

__ http://code.google.com/apis/kml/documentation/

``svg``
~~~~~~~

.. method:: GeoQuerySet.svg(**kwargs)

*Availability*: PostGIS, SpatiaLite

Attaches a ``svg`` attribute to every model in the queryset that contains
the `Scalable Vector Graphics (SVG)`__ path data of the geometry fields.

=====================  =====================================================
Keyword Argument       Description
=====================  =====================================================
``relative``           If set to ``True``, the path data will be implemented
                       in terms of relative moves.  Defaults to ``False``, 
		       meaning that absolute moves are used instead.

``precision``          This keyword may be used to specify the number of 
                       significant digits for the coordinates in the SVG 
                       representation -- the default value is 8.
=====================  =====================================================

__ http://www.w3.org/Graphics/SVG/

Miscellaneous
-------------

``mem_size``
~~~~~~~~~~~~

.. method:: GeoQuerySet.mem_size(**kwargs)

*Availability*: PostGIS

Returns the memory size (number of bytes) that the geometry field takes
in a ``mem_size`` attribute  on each element of the ``GeoQuerySet``.

``num_geom``
~~~~~~~~~~~~

.. method:: GeoQuerySet.num_geom(**kwargs)

*Availability*: PostGIS, Oracle, SpatiaLite

Returns the number of geometries in a ``num_geom`` attribute on
each element of the ``GeoQuerySet`` if the geometry field is a
collection (e.g., a ``GEOMETRYCOLLECTION`` or ``MULTI*`` field);
otherwise sets with ``None``.

``num_points``
~~~~~~~~~~~~~~

.. method:: GeoQuerySet.num_points(**kwargs)

*Availability*: PostGIS, Oracle, SpatiaLite

Returns the number of points in the first linestring in the
geometry field in a ``num_points`` attribute on each element of
the ``GeoQuerySet``; otherwise sets with ``None``.

Spatial Aggregates
==================
.. versionadded:: 1.1

Aggregate Methods
-----------------

``collect``
~~~~~~~~~~~

.. method:: GeoQuerySet.collect(**kwargs)

.. versionadded:: 1.1

*Availability*: PostGIS

Returns a ``GEOMETRYCOLLECTION`` or a ``MULTI`` geometry object from the geometry
column.  This is analagous to a simplified version of the :meth:`GeoQuerySet.unionagg` method,
except it can be several orders of magnitude faster than peforming a union because
it simply rolls up geometries into a collection or multi object, not caring about
dissolving boundaries.

``extent``
~~~~~~~~~~

.. method:: GeoQuerySet.extent(**kwargs)

*Availability*: PostGIS, Oracle

Returns the extent of the ``GeoQuerySet`` as a four-tuple, comprising the 
lower left coordinate and the upper right coordinate.

Example::

    >>> qs = City.objects.filter(name__in=('Houston', 'Dallas'))
    >>> print qs.extent()
    (-96.8016128540039, 29.7633724212646, -95.3631439208984, 32.782058715820)

``extent3d``
~~~~~~~~~~~~

.. method:: GeoQuerySet.extent3d(**kwargs)

.. versionadded:: 1.2

*Availability*: PostGIS

Returns the 3D extent of the ``GeoQuerySet`` as a six-tuple, comprising
the lower left coordinate and upper right coordinate.

Example::

    >>> qs = City.objects.filter(name__in=('Houston', 'Dallas'))
    >>> print qs.extent3d()
    (-96.8016128540039, 29.7633724212646, 0, -95.3631439208984, 32.782058715820, 0)

``make_line``
~~~~~~~~~~~~~

.. method:: GeoQuerySet.make_line(**kwargs)

*Availability*: PostGIS

Returns a ``LineString`` constructed from the point field geometries in the 
``GeoQuerySet``.  Currently, ordering the queryset has no effect.

Example::

     >>> print City.objects.filter(name__in=('Houston', 'Dallas')).make_line()
     LINESTRING (-95.3631510000000020 29.7633739999999989, -96.8016109999999941 32.7820570000000018)

``unionagg``
~~~~~~~~~~~~

.. method:: GeoQuerySet.unionagg(**kwargs)

*Availability*: PostGIS, Oracle, SpatiaLite

This method returns a :class:`~django.contrib.gis.geos.GEOSGeometry` object
comprising the union of every geometry in the queryset.  Please note that
use of ``unionagg`` is processor intensive and may take a significant amount
of time on large querysets.

.. note::
  
    If the computation time for using this method is too expensive,
    consider using :meth:`GeoQuerySet.collect` instead.

Example::
    
    >>> u = Zipcode.objects.unionagg() # This may take a long time.
    >>> u = Zipcode.objects.filter(poly__within=bbox).unionagg() # A more sensible approach.

=====================  =====================================================
Keyword Argument       Description
=====================  =====================================================
``tolerance``          This keyword is for Oracle only.  It is for the 
                       tolerance value used by the ``SDOAGGRTYPE``
                       procedure; the  `Oracle documentation`__ has more 
                       details.
=====================  =====================================================

__ http://download.oracle.com/docs/html/B14255_01/sdo_intro.htm#sthref150 

Aggregate Functions
-------------------

Example::

    >>> from django.contrib.gis.db.models import Extent, Union
    >>> WorldBorders.objects.aggregate(Extent('mpoly'), Union('mpoly'))

``Collect``
~~~~~~~~~~~

.. class:: Collect(geo_field)

Returns the same as the :meth:`GeoQuerySet.collect` aggregate method.

``Extent``
~~~~~~~~~~
.. class:: Extent(geo_field)


Returns the same as the :meth:`GeoQuerySet.extent` aggregate method.

``Extent3D``
~~~~~~~~~~~~

.. class:: Extent3D(geo_field)

.. versionadded:: 1.2

Returns the same as the :meth:`GeoQuerySet.extent3d` aggregate method.

``MakeLine``
~~~~~~~~~~~~

.. class:: MakeLine(geo_field)

Returns the same as the :meth:`GeoQuerySet.make_line` aggregate method.

``Union``
~~~~~~~~~

.. class:: Union(geo_field)

Returns the same as the :meth:`GeoQuerySet.union` aggregate method.

.. rubric:: Footnotes
.. [#fnde9im] *See* `OpenGIS Simple Feature Specification For SQL <http://www.opengis.org/docs/99-049.pdf>`_, at Ch. 2.1.13.2, p. 2-13 (The Dimensionally Extended Nine-Intersection Model).
.. [#fnsdorelate] *See* `SDO_RELATE documentation <http://download.oracle.com/docs/cd/B19306_01/appdev.102/b14255/sdo_operat.htm#sthref845>`_, from Ch. 11 of the Oracle Spatial User's Guide and Manual.
.. [#fncovers] For an explanation of this routine, read `Quirks of the "Contains" Spatial Predicate <http://lin-ear-th-inking.blogspot.com/2007/06/subtleties-of-ogc-covers-spatial.html>`_ by Martin Davis (a PostGIS developer).
.. [#fncontainsproperly] Refer to the PostGIS ``ST_ContainsProperly`` `documentation <http://postgis.refractions.net/documentation/manual-1.4/ST_ContainsProperly.html>`_ for more details.