Fungsi Basisdata Geografis

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

Contoh:

>>> 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.

Ringkasan fungsi:

Pengukuran Hubungan Operasi Penyunting Bentuk keluaran Bermacam-macam
Area BoundingCircle Difference ForceRHR AsGeoJSON IsValid
Distance Centroid Intersection MakeValid AsGML MemSize
Length Envelope SymDifference Reverse AsKML NumGeometries
Perimeter PointOnSurface Union Scale AsSVG NumPoints
    SnapToGrid GeoHash  
    Transform    
    Translate    

Area

class Area(expression, **extra)

Tersedia: MySQL, Oracle, PostGIS, SpatiaLite

Accepts a single geographic field or expression and returns the area of the field as an Area measure.

MySQL and SpatiaLite without LWGEOM don't support area calculations on geographic SRSes.

Changed in Django 1.11:

Dalam versi terlama, nilai mentah dikembalikan pada MySQL ketika digunakan pada SRS yang diproyeksikan.

AsGeoJSON

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

Tersedia: PostGIS, SpatiaLite

Accepts a single geographic field or expression and returns a GeoJSON 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 Penserial GeoJSON.

Contoh:

>>> City.objects.annotate(json=AsGeoJSON('point')).get(name='Chicago').json
{"type":"Point","coordinates":[-87.65018,41.85039]}
Argumen Katakunci Deskripsi
bbox Setel ini menjadi True jika anda ingin membatasi kotak untuk disertakan dalam GeoJSON yang dikembalikan.
crs Setel ini menjadi True jika anda ingin sistem acuan kordinat untuk disertakan dalam GeoJSON yang dikembalikan.
ketelitian It may be used to specify the number of significant digits for the coordinates in the GeoJSON representation -- the default value is 8.

AsGML

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

Tersedia: Oracle, PostGIS, SpatiaLite

Accepts a single geographic field or expression and returns a Geographic Markup Language (GML) representation of the geometry.

Contoh:

>>> 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>
Argumen Katakunci Deskripsi
ketelitian Specifies the number of significant digits for the coordinates in the GML representation -- the default value is 8. Ignored on Oracle.
versi Menentukan versi GML untuk menggunakan: 2 (awalan) atau 3.
Changed in Django 1.11:

Dukungan Oracle telah ditambahkan.

AsKML

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

Tersedia: PostGIS, SpatiaLite

Accepts a single geographic field or expression and returns a Keyhole Markup Language (KML) representation of the geometry.

Contoh:

>>> 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>
Argumen Katakunci Deskripsi
ketelitian This keyword may be used to specify the number of significant digits for the coordinates in the KML representation -- the default value is 8.

AsSVG

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

Tersedia: PostGIS, SpatiaLite

Accepts a single geographic field or expression and returns a Scalable Vector Graphics (SVG) representation of the geometry.

Argumen Katakunci Deskripsi
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.
ketelitian This keyword may be used to specify the number of significant digits for the coordinates in the SVG representation -- the default value is 8.

BoundingCircle

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

Tersedia: PostGIS, Oracle (≥ 12.1.0.2)

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

Parameter num_seg hanya digunakan pada PostGIS.

Changed in Django 1.11:

Dukungan Oracle telah ditambahkan.

Centroid

class Centroid(expression, **extra)

Tersedia: MySQL, PostGIS, Oracle, SpatiaLite

Menerima bidang geografis tunggal atau mengembalikan nilai centroid dari geometri.

Difference

class Difference(expr1, expr2, **extra)

Tersedia: MySQL (≥ 5.6.1), PostGIS, Oracle, SpatiaLite

Menerima dua bidang geografis atau pernyataan dan mengembalikan perbedaan geometri, yaitu bagian dari geometri A yang tidak berinteraksi dengan geometri B.

Changed in Django 1.10:

Dukungan MySQL telah ditambahkan.

Distance

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

Tersedia: MySQL (≥ 5.6.1), PostGIS, Oracle, SpatiaLite

Accepts two geographic fields or expressions and returns the distance between them, as a Distance object. On MySQL, a raw float value is returned when the coordinates are geodetic.

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_DistanceSphere on PostGIS).

Ketika jarak dihitung dengan kordinat (bersiku-siku) geodetic, seperti halnya dengan awalan SRID WGS84 (4326), anda dapat menyetel argumen kata kunci spheroid untuk memutuskan jika perhitungan harus berdasarkan pada bulatan sederhana (kurang akurat, kurang sumber daya-intensif) atau pada sebuah berbentuk bola (lebih akurat, lebih sumber daya-intensif)

In the following example, the distance from the city of Hobart to every other 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
...

Catatan

Because the distance attribute is a 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 Obyek Pengukuran for usage details and the list of Satuan Didukung.

Changed in Django 1.11:

Dalam versi terlama, nilai mentah dikembalikan pada MySQL ketika digunakan pada SRS yang diproyeksikan.

Envelope

class Envelope(expression, **extra)

Tersedia: 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)

Tersedia: PostGIS

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, precision=None, **extra)

Tersedia: PostGIS, SpatiaLite (LWGEOM)

Menerima bidang geografi tunggal atau pernyataan dan mengembalikan perwakilan GeoHash dari geometri.

Argumen kata kunci precision mengendalikan sejumlah karakter dalam hasilnya.

Changed in Django 1.10:

Dukungan SpatiaLite  telah ditambahkan.

Intersection

class Intersection(expr1, expr2, **extra)

Tersedia: MySQL (≥ 5.6.1), PostGIS, Oracle, SpatiaLite

Menerima dua bidang geografi dan pernyataan dan mengembalikan persimpangan geometri diantara mereka.

Changed in Django 1.10:

Dukungan MySQL telah ditambahkan.

IsValid

class IsValid(expr)
New in Django 1.10.

Tersedia: PostGIS, Oracle, SpatiaLite (LWGEOM)

Menerima sebuah bidang geografi atau pernyataan dan percobaan jika nilai berbentuk bagus. Mengembalikan True jika nilainya adalah geometri sah dan False sebaliknya.

Changed in Django 1.11:

Dukungan SpatiaLite dan Oracle telah ditambahkan.

Length

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

Tersedia: MySQL, Oracle, PostGIS, SpatiaLite

Accepts a single geographic linestring or multilinestring field or expression and returns its length as a Distance measure.

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.

MySQL tidak mendukung dukungan perhitungan panjang pada geografis SRS.

Changed in Django 1.11:

Dalam versi terlama, nilai mentah dikembalikan pada MySQL.

MakeValid

class MakeValid(expr)
New in Django 1.10.

Tersedia: PostGIS, SpatiaLite (LWGEOM)

Accepts a geographic field or expression and attempts to convert the value into a valid geometry without losing any of the input vertices. Geometries that are already valid are returned without changes. Simple polygons might become a multipolygon and the result might be of lower dimension than the input.

Changed in Django 1.11:

Dukungan SpatiaLite  telah ditambahkan.

MemSize

class MemSize(expression, **extra)

Tersedia: 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)

Tersedia: 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). Returns 1 for single geometries.

Pada MySQL, mengembalikan None untuk geometri tunggal.

NumPoints

class NumPoints(expression, **extra)

Tersedia: 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)

Tersedia: PostGIS, Oracle, SpatiaLite

Accepts a single geographic field or expression and returns the perimeter of the geometry field as a Distance object.

PointOnSurface

class PointOnSurface(expression, **extra)

Tersedia: 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)

Tersedia: PostGIS, Oracle, SpatiaLite

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

Scale

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

Tersedia: 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)

Tersedia: PostGIS, SpatiaLite

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.

Jumlah Argumen Deskripsi
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)

Tersedia: MySQL (≥ 5.6.1), PostGIS, Oracle, SpatiaLite

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

Changed in Django 1.10:

Dukungan MySQL telah ditambahkan.

Transform

class Transform(expression, srid, **extra)

Tersedia: 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.

Catatan

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)

Tersedia: 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)

Tersedia: MySQL (≥ 5.6.1), PostGIS, Oracle, SpatiaLite

Menerima dua bidang geografi atau pernyataan dan mengembalikan gabungan dari kedua geometri.