---
title: "Geographic Database Functions"
version: 1.9
locale: ja
source: https://docs.djangoproject.com/ja/1.9/ref/contrib/gis/functions/
canonical: https://djangodocs.dev/ja/1.9/ref/contrib/gis/functions/
---
# Geographic Database Functions

> **New in Django 1.9**

The functions documented on this page allow users to access geographic database
functions to be used in annotations, aggregations, or filters in Django.

Example:

```
>>> from django.contrib.gis.db.models.functions import Length
>>> Track.objects.annotate(length=Length('line')).filter(length__gt=100)
```

Not all backends support all functions, so refer to the documentation of each
function to see if your database backend supports the function you want to use.
If you call a geographic function on a backend that doesn't support it, you'll
get a `NotImplementedError` exception.

Function's summary:

| Measurement | Relationships | Operations | Editors | Output format | Miscellaneous |
| --- | --- | --- | --- | --- | --- |
| [`Area`](#django.contrib.gis.db.models.functions.Area) | [`BoundingCircle`](#django.contrib.gis.db.models.functions.BoundingCircle) | [`Difference`](#django.contrib.gis.db.models.functions.Difference) | [`ForceRHR`](#django.contrib.gis.db.models.functions.ForceRHR) | [`AsGeoJSON`](#django.contrib.gis.db.models.functions.AsGeoJSON) | [`MemSize`](#django.contrib.gis.db.models.functions.MemSize) |
| [`Distance`](#django.contrib.gis.db.models.functions.Distance) | [`Centroid`](#django.contrib.gis.db.models.functions.Centroid) | [`Intersection`](#django.contrib.gis.db.models.functions.Intersection) | [`Reverse`](#django.contrib.gis.db.models.functions.Reverse) | [`AsGML`](#django.contrib.gis.db.models.functions.AsGML) | [`NumGeometries`](#django.contrib.gis.db.models.functions.NumGeometries) |
| [`Length`](#django.contrib.gis.db.models.functions.Length) | [`Envelope`](#django.contrib.gis.db.models.functions.Envelope) | [`SymDifference`](#django.contrib.gis.db.models.functions.SymDifference) | [`Scale`](#django.contrib.gis.db.models.functions.Scale) | [`AsKML`](#django.contrib.gis.db.models.functions.AsKML) | [`NumPoints`](#django.contrib.gis.db.models.functions.NumPoints) |
| [`Perimeter`](#django.contrib.gis.db.models.functions.Perimeter) | [`PointOnSurface`](#django.contrib.gis.db.models.functions.PointOnSurface) | [`Union`](#django.contrib.gis.db.models.functions.Union) | [`SnapToGrid`](#django.contrib.gis.db.models.functions.SnapToGrid) | [`AsSVG`](#django.contrib.gis.db.models.functions.AsSVG) |  |
|  |  |  | [`Transform`](#django.contrib.gis.db.models.functions.Transform) | [`GeoHash`](#django.contrib.gis.db.models.functions.GeoHash) |  |
|  |  |  | [`Translate`](#django.contrib.gis.db.models.functions.Translate) |  |  |

## `Area`

#### `class Area(expression, **extra)`

*Availability*: MySQL, Oracle, PostGIS, SpatiaLite

Accepts a single geographic field or expression and returns the area of the
field as an [`Area`](/ja/1.9/ref/contrib/gis/measure/#django.contrib.gis.measure.Area) measure. On MySQL, a raw
float value is returned, as it's not possible to automatically determine the
unit of the field.

## `AsGeoJSON`

#### `class AsGeoJSON(expression, bbox=False, crs=False, precision=8, **extra)`

*Availability*: PostGIS, SpatiaLite (≥ 3.0)

Accepts a single geographic field or expression and returns a [GeoJSON](http://geojson.org/) representation of the geometry. Note that the result is
not a complete GeoJSON structure but only the `geometry` key content of a
GeoJSON structure. See also [GeoJSON Serializer](/ja/1.9/ref/contrib/gis/serializers/).

Example:

```
>>> City.objects.annotate(json=AsGeoJSON('point')).get(name='Chicago').json
{"type":"Point","coordinates":[-87.65018,41.85039]}
```

| Keyword Argument | Description |
| --- | --- |
| `bbox` | Set this to `True` if you want the bounding box<br>to be included in the returned GeoJSON. |
| `crs` | Set this to `True` if you want the coordinate<br>reference system to be included in the returned<br>GeoJSON. |
| `precision` | It may be used to specify the number of significant<br>digits for the coordinates in the GeoJSON<br>representation -- the default value is 8. |

## `AsGML`

#### `class AsGML(expression, version=2, precision=8, **extra)`

*Availability*: PostGIS, SpatiaLite (≥ 2.4.0-RC4)

Accepts a single geographic field or expression and returns a [Geographic Markup
Language (GML)](https://en.wikipedia.org/wiki/Geography_Markup_Language) representation of the geometry.

Example:

```
>>> qs = Zipcode.objects.annotate(gml=AsGML('poly'))
>>> 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` | It may be used to specify the number of significant<br>digits for the coordinates in the GML representation --<br>the default value is 8. |
| `version` | It may be used to specify the GML version used, and may<br>only be values of 2 or 3.  The default value is 2. |

## `AsKML`

#### `class AsKML(expression, precision=8, **extra)`

*Availability*: PostGIS, SpatiaLite (≥ 2.4.0-RC4)

Accepts a single geographic field or expression and returns a [Keyhole Markup
Language (KML)](https://developers.google.com/kml/documentation/) representation of the geometry.

Example:

```
>>> qs = Zipcode.objects.annotate(kml=AsKML('poly'))
>>> 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<br>significant digits for the coordinates in the KML<br>representation -- the default value is 8. |

## `AsSVG`

#### `class AsSVG(expression, relative=False, precision=8, **extra)`

*Availability*: PostGIS, SpatiaLite

Accepts a single geographic field or expression and returns a [Scalable Vector
Graphics (SVG)](http://www.w3.org/Graphics/SVG/) representation of the geometry.

| Keyword Argument | Description |
| --- | --- |
| `relative` | If set to `True`, the path data will be implemented<br>in terms of relative moves. Defaults to `False`,<br>meaning that absolute moves are used instead. |
| `precision` | This keyword may be used to specify the number of<br>significant digits for the coordinates in the SVG<br>representation -- the default value is 8. |

## `BoundingCircle`

#### `class BoundingCircle(expression, num_seg=48, **extra)`

*Availability*: [PostGIS](http://postgis.net/docs/ST_MinimumBoundingCircle.html)

Accepts a single geographic field or expression and returns the smallest circle
polygon that can fully contain the geometry.

## `Centroid`

#### `class Centroid(expression, **extra)`

*Availability*: MySQL, PostGIS, Oracle, SpatiaLite

Accepts a single geographic field or expression and returns the `centroid`
value of the geometry.

## `Difference`

#### `class Difference(expr1, expr2, **extra)`

*Availability*: PostGIS, Oracle, SpatiaLite

Accepts two geographic fields or expressions and returns the geometric
difference, that is the part of geometry A that does not intersect with
geometry B.

## `Distance`

#### `class Distance(expr1, expr2, spheroid=None, **extra)`

*Availability*: MySQL (≥ 5.6.1), PostGIS, Oracle, SpatiaLite

Accepts two geographic fields or expressions and returns the distance between
them, as a [`Distance`](/ja/1.9/ref/contrib/gis/measure/#django.contrib.gis.measure.Distance) object. On MySQL, a raw
float value is returned, as it's not possible to automatically determine the
unit of the field.

On backends that support distance calculation on geodetic coordinates, the
proper backend function is automatically chosen depending on the SRID value of
the geometries (e.g. `ST_Distance_Sphere` on PostGIS).

When distances are calculated with geodetic (angular) coordinates, as is the
case with the default WGS84 (4326) SRID, you can set the `spheroid` keyword
argument to decide if the calculation should be based on a simple sphere (less
accurate, less resource-intensive) or on a spheroid (more accurate, more
resource-intensive).

In the following example, the distance from the city of Hobart to every other
[`PointField`](/ja/1.9/ref/contrib/gis/model-api/#django.contrib.gis.db.models.PointField) in the `AustraliaCity`
queryset is calculated:

```
>>> from django.contrib.gis.db.models.functions import Distance
>>> pnt = AustraliaCity.objects.get(name='Hobart').point
>>> for city in AustraliaCity.objects.annotate(distance=Distance('point', pnt)):
...     print(city.name, city.distance)
Wollongong 990071.220408 m
Shellharbour 972804.613941 m
Thirroul 1002334.36351 m
...
```

> **Note**
>
> Because the `distance` attribute is a
> [`Distance`](/ja/1.9/ref/contrib/gis/measure/#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 [Measurement Objects](/ja/1.9/ref/contrib/gis/measure/) for usage details and the list of
> [Supported units](/ja/1.9/ref/contrib/gis/measure/#supported-units).

## `Envelope`

#### `class Envelope(expression, **extra)`

*Availability*: MySQL, PostGIS, SpatiaLite

Accepts a single geographic field or expression and returns the geometry
representing the bounding box of the geometry.

## `ForceRHR`

#### `class ForceRHR(expression, **extra)`

*Availability*: [PostGIS](http://postgis.net/docs/ST_ForceRHR.html)

Accepts a single geographic field or expression and returns a modified version
of the polygon/multipolygon in which all of the vertices follow the
right-hand rule.

## `GeoHash`

#### `class GeoHash(expression, **extra)`

*Availability*: PostGIS

Accepts a single geographic field or expression and returns a [GeoHash](https://en.wikipedia.org/wiki/Geohash)
representation of the geometry.

## `Intersection`

#### `class Intersection(expr1, expr2, **extra)`

*Availability*: PostGIS, Oracle, SpatiaLite

Accepts two geographic fields or expressions and returns the geometric
intersection between them.

## `Length`

#### `class Length(expression, spheroid=True, **extra)`

*Availability*: MySQL, Oracle, PostGIS, SpatiaLite

Accepts a single geographic linestring or multilinestring field or expression
and returns its length as an [`Distance`](/ja/1.9/ref/contrib/gis/measure/#django.contrib.gis.measure.Distance)
measure. On MySQL, a raw float value is returned, as it's not possible to
automatically determine the unit of the field.

On PostGIS and SpatiaLite, when the coordinates are geodetic (angular), you can
specify if the calculation should be based on a simple sphere (less
accurate, less resource-intensive) or on a spheroid (more accurate, more
resource-intensive) with the `spheroid` keyword argument.

## `MemSize`

#### `class MemSize(expression, **extra)`

*Availability*: PostGIS

Accepts a single geographic field or expression and returns the memory size
(number of bytes) that the geometry field takes.

## `NumGeometries`

#### `class NumGeometries(expression, **extra)`

*Availability*: MySQL, PostGIS, Oracle, SpatiaLite

Accepts a single geographic field or expression and returns the number of
geometries if the geometry field is a collection (e.g., a `GEOMETRYCOLLECTION`
or `MULTI*` field); otherwise returns `None`.

## `NumPoints`

#### `class NumPoints(expression, **extra)`

*Availability*: MySQL, PostGIS, Oracle, SpatiaLite

Accepts a single geographic field or expression and returns the number of points
in the first linestring in the geometry field; otherwise returns `None`.

## `Perimeter`

#### `class Perimeter(expression, **extra)`

*Availability*: PostGIS, Oracle, SpatiaLite (≥ 4.0)

Accepts a single geographic field or expression and returns the perimeter of the
geometry field as a [`Distance`](/ja/1.9/ref/contrib/gis/measure/#django.contrib.gis.measure.Distance) object. On
MySQL, a raw float value is returned, as it's not possible to automatically
determine the unit of the field.

## `PointOnSurface`

#### `class PointOnSurface(expression, **extra)`

*Availability*: PostGIS, Oracle, SpatiaLite

Accepts a single geographic field or expression and returns a `Point` geometry
guaranteed to lie on the surface of the field; otherwise returns `None`.

## `Reverse`

#### `class Reverse(expression, **extra)`

*Availability*: PostGIS, Oracle, SpatiaLite (≥ 4.0)

Accepts a single geographic field or expression and returns a geometry with
reversed coordinates.

## `Scale`

#### `class Scale(expression, x, y, z=0.0, **extra)`

*Availability*: PostGIS, SpatiaLite

Accepts a single geographic field or expression and returns a geometry with
scaled coordinates by multiplying them with the `x`, `y`, and optionally
`z` parameters.

## `SnapToGrid`

#### `class SnapToGrid(expression, *args, **extra)`

*Availability*: PostGIS, SpatiaLite (≥ 3.1)

Accepts a single geographic field or expression and returns a geometry with all
points snapped to the given 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 both 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. |

## `SymDifference`

#### `class SymDifference(expr1, expr2, **extra)`

*Availability*: PostGIS, Oracle, SpatiaLite

Accepts two geographic fields or expressions and returns the geometric
symmetric difference (union without the intersection) between the given
parameters.

## `Transform`

#### `class Transform(expression, srid, **extra)`

*Availability*: PostGIS, Oracle, SpatiaLite

Accepts a geographic field or expression and a SRID integer code, and returns
the transformed geometry to the spatial reference system specified by the
`srid` parameter.

> **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.

## `Translate`

#### `class Translate(expression, x, y, z=0.0, **extra)`

*Availability*: PostGIS, SpatiaLite

Accepts a single geographic field or expression and returns a geometry with
its coordinates offset by the `x`, `y`, and optionally `z` numeric
parameters.

## `Union`

#### `class Union(expr1, expr2, **extra)`

*Availability*: MySQL (≥ 5.6.1), PostGIS, Oracle, SpatiaLite

Accepts two geographic fields or expressions and returns the union of both
geometries.