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Fixed #14141: docs now use the :doc: construct for links between documents.

Browse source 
Thanks, Ramiro Morales.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@13608 bcc190cf-cafb-0310-a4f2-bffc1f526a37
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Jacob Kaplan-Moss 2010-08-19 19:27:44 +00:00
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docs/ref/contrib/gis/tutorial.txt
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@ -15,8 +15,8 @@ geographic web applications, like location-based services. Some features includ
data formats.
* Editing of geometry fields inside the admin.
This tutorial assumes a familiarity with Django; thus, if you're brand new to
Django please read through the :ref:`regular tutorial <intro-tutorial01>` to introduce
This tutorial assumes a familiarity with Django; thus, if you're brand new to
Django please read through the :doc:`regular tutorial </intro/tutorial01>` to introduce
yourself with basic Django concepts.
.. note::
@ -27,12 +27,12 @@ yourself with basic Django concepts.
This tutorial is going to guide you through guide the user through the creation
of a geographic web application for viewing the `world borders`_. [#]_ Some of
the code used in this tutorial is taken from and/or inspired by the
the code used in this tutorial is taken from and/or inspired by the
`GeoDjango basic apps`_ project. [#]_
.. note::
Proceed through the tutorial sections sequentially for step-by-step
Proceed through the tutorial sections sequentially for step-by-step
instructions.
.. _OGC: http://www.opengeospatial.org/
@ -51,11 +51,11 @@ Create a Spatial Database
are already built into the database.
First, a spatial database needs to be created for our project. If using
PostgreSQL and PostGIS, then the following commands will
PostgreSQL and PostGIS, then the following commands will
create the database from a :ref:`spatial database template <spatialdb_template>`::
$ createdb -T template_postgis geodjango
.. note::
This command must be issued by a database user that has permissions to
@ -65,9 +65,9 @@ create the database from a :ref:`spatial database template <spatialdb_template>`
$ sudo su - postgres
$ createuser --createdb geo
$ exit
Replace ``geo`` to correspond to the system login user name will be
connecting to the database. For example, ``johndoe`` if that is the
connecting to the database. For example, ``johndoe`` if that is the
system user that will be running GeoDjango.
Users of SQLite and SpatiaLite should consult the instructions on how
@ -92,7 +92,7 @@ Configure ``settings.py``
The ``geodjango`` project settings are stored in the ``settings.py`` file. Edit
the database connection settings appropriately::
DATABASES = {
DATABASES = {
'default': {
'ENGINE': 'django.contrib.gis.db.backends.postgis',
'NAME': 'geodjango',
@ -104,7 +104,7 @@ the database connection settings appropriately::
These database settings are for Django 1.2 and above.
In addition, modify the :setting:`INSTALLED_APPS` setting to include
In addition, modify the :setting:`INSTALLED_APPS` setting to include
:mod:`django.contrib.admin`, :mod:`django.contrib.gis`,
and ``world`` (our newly created application)::
@ -142,8 +142,8 @@ unzipped the world borders data set includes files with the following extensions
* ``.shp``: Holds the vector data for the world borders geometries.
* ``.shx``: Spatial index file for geometries stored in the ``.shp``.
* ``.dbf``: Database file for holding non-geometric attribute data
(e.g., integer and character fields).
* ``.dbf``: Database file for holding non-geometric attribute data
(e.g., integer and character fields).
* ``.prj``: Contains the spatial reference information for the geographic
data stored in the shapefile.
@ -153,7 +153,7 @@ __ http://en.wikipedia.org/wiki/Shapefile
Use ``ogrinfo`` to examine spatial data
---------------------------------------
The GDAL ``ogrinfo`` utility is excellent for examining metadata about
The GDAL ``ogrinfo`` utility is excellent for examining metadata about
shapefiles (or other vector data sources)::
$ ogrinfo world/data/TM_WORLD_BORDERS-0.3.shp
@ -192,13 +192,13 @@ and use the ``-so`` option to get only important summary information::
LAT: Real (7.3)
This detailed summary information tells us the number of features in the layer
(246), the geographical extent, the spatial reference system ("SRS WKT"),
(246), the geographical extent, the spatial reference system ("SRS WKT"),
as well as detailed information for each attribute field. For example,
``FIPS: String (2.0)`` indicates that there's a ``FIPS`` character field
with a maximum length of 2; similarly, ``LON: Real (8.3)`` is a floating-point
field that holds a maximum of 8 digits up to three decimal places. Although
this information may be found right on the `world borders`_ website, this shows
you how to determine this information yourself when such metadata is not
you how to determine this information yourself when such metadata is not
provided.
Geographic Models
@ -213,7 +213,7 @@ create a GeoDjango model to represent this data::
from django.contrib.gis.db import models
class WorldBorders(models.Model):
# Regular Django fields corresponding to the attributes in the
# Regular Django fields corresponding to the attributes in the
# world borders shapefile.
name = models.CharField(max_length=50)
area = models.IntegerField()
@ -227,7 +227,7 @@ create a GeoDjango model to represent this data::
lon = models.FloatField()
lat = models.FloatField()
# GeoDjango-specific: a geometry field (MultiPolygonField), and
# GeoDjango-specific: a geometry field (MultiPolygonField), and
# overriding the default manager with a GeoManager instance.
mpoly = models.MultiPolygonField()
objects = models.GeoManager()
@ -235,23 +235,23 @@ create a GeoDjango model to represent this data::
# So the model is pluralized correctly in the admin.
class Meta:
verbose_name_plural = "World Borders"
# Returns the string representation of the model.
# Returns the string representation of the model.
def __unicode__(self):
return self.name
Two important things to note:
1. The ``models`` module is imported from :mod:`django.contrib.gis.db`.
2. The model overrides its default manager with
2. The model overrides its default manager with
:class:`~django.contrib.gis.db.models.GeoManager`; this is *required*
to perform spatial queries.
to perform spatial queries.
When declaring a geometry field on your model the default spatial reference system
is WGS84 (meaning the `SRID`__ is 4326) -- in other words, the field coordinates are in
longitude/latitude pairs in units of degrees. If you want the coordinate system to be
different, then SRID of the geometry field may be customized by setting the ``srid``
with an integer corresponding to the coordinate system of your choice.
with an integer corresponding to the coordinate system of your choice.
__ http://en.wikipedia.org/wiki/SRID
@ -259,7 +259,7 @@ Run ``syncdb``
--------------
After you've defined your model, it needs to be synced with the spatial database.
First, let's look at the SQL that will generate the table for the ``WorldBorders``
First, let's look at the SQL that will generate the table for the ``WorldBorders``
model::
$ python manage.py sqlall world
@ -295,7 +295,7 @@ If satisfied, you may then create this table in the database by running the
Installing custom SQL for world.WorldBorders model
The ``syncdb`` command may also prompt you to create an admin user; go ahead and
do so (not required now, may be done at any point in the future using the
do so (not required now, may be done at any point in the future using the
``createsuperuser`` management command).
Importing Spatial Data
@ -303,11 +303,11 @@ Importing Spatial Data
This section will show you how to take the data from the world borders
shapefile and import it into GeoDjango models using the :ref:`ref-layermapping`.
There are many different different ways to import data in to a
There are many different different ways to import data in to a
spatial database -- besides the tools included within GeoDjango, you
may also use the following to populate your spatial database:
* `ogr2ogr`_: Command-line utility, included with GDAL, that
* `ogr2ogr`_: Command-line utility, included with GDAL, that
supports loading a multitude of vector data formats into
the PostGIS, MySQL, and Oracle spatial databases.
* `shp2pgsql`_: This utility is included with PostGIS and only supports
@ -339,7 +339,7 @@ tutorial, then we can determine the path using Python's built-in
>>> world_shp = os.path.abspath(os.path.join(os.path.dirname(world.__file__),
... 'data/TM_WORLD_BORDERS-0.3.shp'))
Now, the world borders shapefile may be opened using GeoDjango's
Now, the world borders shapefile may be opened using GeoDjango's
:class:`~django.contrib.gis.gdal.DataSource` interface::
>>> from django.contrib.gis.gdal import *
@ -347,7 +347,7 @@ Now, the world borders shapefile may be opened using GeoDjango's
>>> print ds
/ ... /geodjango/world/data/TM_WORLD_BORDERS-0.3.shp (ESRI Shapefile)
Data source objects can have different layers of geospatial features; however,
Data source objects can have different layers of geospatial features; however,
shapefiles are only allowed to have one layer::
>>> print len(ds)
@ -367,10 +367,10 @@ contains::
.. note::
Unfortunately the shapefile data format does not allow for greater
specificity with regards to geometry types. This shapefile, like
specificity with regards to geometry types. This shapefile, like
many others, actually includes ``MultiPolygon`` geometries in its
features. You need to watch out for this when creating your models
as a GeoDjango ``PolygonField`` will not accept a ``MultiPolygon``
as a GeoDjango ``PolygonField`` will not accept a ``MultiPolygon``
type geometry -- thus a ``MultiPolygonField`` is used in our model's
definition instead.
@ -391,7 +391,7 @@ system associated with it -- if it does, the ``srs`` attribute will return a
Here we've noticed that the shapefile is in the popular WGS84 spatial reference
system -- in other words, the data uses units of degrees longitude and latitude.
In addition, shapefiles also support attribute fields that may contain
In addition, shapefiles also support attribute fields that may contain
additional data. Here are the fields on the World Borders layer:
>>> print lyr.fields
@ -403,8 +403,8 @@ a string) associated with each of the fields:
>>> [fld.__name__ for fld in lyr.field_types]
['OFTString', 'OFTString', 'OFTString', 'OFTInteger', 'OFTString', 'OFTInteger', 'OFTInteger', 'OFTInteger', 'OFTInteger', 'OFTReal', 'OFTReal']
You can iterate over each feature in the layer and extract information from both
the feature's geometry (accessed via the ``geom`` attribute) as well as the
You can iterate over each feature in the layer and extract information from both
the feature's geometry (accessed via the ``geom`` attribute) as well as the
feature's attribute fields (whose **values** are accessed via ``get()``
method)::
@ -427,7 +427,7 @@ And individual features may be retrieved by their feature ID::
>>> print feat.get('NAME')
San Marino
Here the boundary geometry for San Marino is extracted and looking
Here the boundary geometry for San Marino is extracted and looking
exported to WKT and GeoJSON::
>>> geom = feat.geom
@ -465,7 +465,7 @@ We're going to dive right in -- create a file called ``load.py`` inside the
world_shp = os.path.abspath(os.path.join(os.path.dirname(__file__), 'data/TM_WORLD_BORDERS-0.3.shp'))
def run(verbose=True):
lm = LayerMapping(WorldBorders, world_shp, world_mapping,
lm = LayerMapping(WorldBorders, world_shp, world_mapping,
transform=False, encoding='iso-8859-1')
lm.save(strict=True, verbose=verbose)
@ -473,8 +473,8 @@ We're going to dive right in -- create a file called ``load.py`` inside the
A few notes about what's going on:
* Each key in the ``world_mapping`` dictionary corresponds to a field in the
``WorldBorders`` model, and the value is the name of the shapefile field
that data will be loaded from.
``WorldBorders`` model, and the value is the name of the shapefile field
that data will be loaded from.
* The key ``mpoly`` for the geometry field is ``MULTIPOLYGON``, the
geometry type we wish to import as. Even if simple polygons are encountered
in the shapefile they will automatically be converted into collections prior
@ -503,10 +503,10 @@ do the work::
Try ``ogrinspect``
------------------
Now that you've seen how to define geographic models and import data with the
Now that you've seen how to define geographic models and import data with the
:ref:`ref-layermapping`, it's possible to further automate this process with
use of the :djadmin:`ogrinspect` management command. The :djadmin:`ogrinspect`
command introspects a GDAL-supported vector data source (e.g., a shapefile) and
command introspects a GDAL-supported vector data source (e.g., a shapefile) and
generates a model definition and ``LayerMapping`` dictionary automatically.
The general usage of the command goes as follows::
@ -525,13 +525,13 @@ and mapping dictionary created above, automatically::
A few notes about the command-line options given above:
* The ``--srid=4326`` option sets the SRID for the geographic field.
* The ``--mapping`` option tells ``ogrinspect`` to also generate a
* The ``--mapping`` option tells ``ogrinspect`` to also generate a
mapping dictionary for use with :class:`~django.contrib.gis.utils.LayerMapping`.
* The ``--multi`` option is specified so that the geographic field is a
:class:`~django.contrib.gis.db.models.MultiPolygonField` instead of just a
:class:`~django.contrib.gis.db.models.PolygonField`.
The command produces the following output, which may be copied
The command produces the following output, which may be copied
directly into the ``models.py`` of a GeoDjango application::
# This is an auto-generated Django model module created by ogrinspect.
@ -584,7 +584,7 @@ Now, define a point of interest [#]_::
>>> pnt_wkt = 'POINT(-95.3385 29.7245)'
The ``pnt_wkt`` string represents the point at -95.3385 degrees longitude,
and 29.7245 degrees latitude. The geometry is in a format known as
and 29.7245 degrees latitude. The geometry is in a format known as
Well Known Text (WKT), an open standard issued by the Open Geospatial
Consortium (OGC). [#]_ Import the ``WorldBorders`` model, and perform
a ``contains`` lookup using the ``pnt_wkt`` as the parameter::
@ -611,7 +611,7 @@ available -- the :ref:`ref-gis-db-api` documentation has more.
Automatic Spatial Transformations
---------------------------------
When querying the spatial database GeoDjango automatically transforms
When querying the spatial database GeoDjango automatically transforms
geometries if they're in a different coordinate system. In the following
example, the coordinate will be expressed in terms of `EPSG SRID 32140`__,
a coordinate system specific to south Texas **only** and in units of
@ -634,26 +634,26 @@ of abstraction::
('SELECT "world_worldborders"."id", "world_worldborders"."name", "world_worldborders"."area",
"world_worldborders"."pop2005", "world_worldborders"."fips", "world_worldborders"."iso2",
"world_worldborders"."iso3", "world_worldborders"."un", "world_worldborders"."region",
"world_worldborders"."subregion", "world_worldborders"."lon", "world_worldborders"."lat",
"world_worldborders"."mpoly" FROM "world_worldborders"
"world_worldborders"."subregion", "world_worldborders"."lon", "world_worldborders"."lat",
"world_worldborders"."mpoly" FROM "world_worldborders"
WHERE ST_Intersects("world_worldborders"."mpoly", ST_Transform(%s, 4326))',
(<django.contrib.gis.db.backend.postgis.adaptor.PostGISAdaptor object at 0x25641b0>,))
>>> qs # printing evaluates the queryset
[<WorldBorders: United States>]
[<WorldBorders: United States>]
__ http://spatialreference.org/ref/epsg/32140/
Lazy Geometries
---------------
Geometries come to GeoDjango in a standardized textual representation. Upon
access of the geometry field, GeoDjango creates a `GEOS geometry object <ref-geos>`,
exposing powerful functionality, such as serialization properties for
access of the geometry field, GeoDjango creates a `GEOS geometry object <ref-geos>`,
exposing powerful functionality, such as serialization properties for
popular geospatial formats::
>>> sm = WorldBorders.objects.get(name='San Marino')
>>> sm.mpoly
<MultiPolygon object at 0x24c6798>
>>> sm.mpoly.wkt # WKT
>>> sm.mpoly.wkt # WKT
MULTIPOLYGON (((12.4157980000000006 43.9579540000000009, 12.4505540000000003 43.9797209999999978, ...
>>> sm.mpoly.wkb # WKB (as Python binary buffer)
<read-only buffer for 0x1fe2c70, size -1, offset 0 at 0x2564c40>
@ -682,16 +682,16 @@ Google
Geographic Admin
----------------
GeoDjango extends :ref:`Django's admin application <ref-contrib-admin>` to
enable support for editing geometry fields.
GeoDjango extends :doc:`Django's admin application </ref/contrib/admin/index>`
to enable support for editing geometry fields.
Basics
^^^^^^
GeoDjango also supplements the Django admin by allowing users to create
GeoDjango also supplements the Django admin by allowing users to create
and modify geometries on a JavaScript slippy map (powered by `OpenLayers`_).
Let's dive in again -- create a file called ``admin.py`` inside the
Let's dive in again -- create a file called ``admin.py`` inside the
``world`` application, and insert the following::
from django.contrib.gis import admin