78 lines
3.1 KiB
Python
78 lines
3.1 KiB
Python
from django.contrib.gis.gdal import SpatialReference
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from django.db import connections, DEFAULT_DB_ALIAS
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def add_srs_entry(srs, auth_name='EPSG', auth_srid=None, ref_sys_name=None,
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database=DEFAULT_DB_ALIAS):
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"""
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This function takes a GDAL SpatialReference system and adds its information
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to the `spatial_ref_sys` table of the spatial backend. Doing this enables
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database-level spatial transformations for the backend. Thus, this utility
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is useful for adding spatial reference systems not included by default with
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the backend -- for example, the so-called "Google Maps Mercator Projection"
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is excluded in PostGIS 1.3 and below, and the following adds it to the
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`spatial_ref_sys` table:
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>>> from django.contrib.gis.utils import add_srs_entry
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>>> add_srs_entry(900913)
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Keyword Arguments:
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auth_name:
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This keyword may be customized with the value of the `auth_name` field.
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Defaults to 'EPSG'.
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auth_srid:
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This keyword may be customized with the value of the `auth_srid` field.
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Defaults to the SRID determined by GDAL.
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ref_sys_name:
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For SpatiaLite users only, sets the value of the the `ref_sys_name` field.
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Defaults to the name determined by GDAL.
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database:
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The name of the database connection to use; the default is the value
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of `django.db.DEFAULT_DB_ALIAS` (at the time of this writing, it's value
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is 'default').
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"""
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connection = connections[database]
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if not hasattr(connection.ops, 'spatial_version'):
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raise Exception('The `add_srs_entry` utility only works '
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'with spatial backends.')
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if connection.ops.oracle or connection.ops.mysql:
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raise Exception('This utility does not support the '
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'Oracle or MySQL spatial backends.')
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SpatialRefSys = connection.ops.spatial_ref_sys()
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# If argument is not a `SpatialReference` instance, use it as parameter
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# to construct a `SpatialReference` instance.
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if not isinstance(srs, SpatialReference):
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srs = SpatialReference(srs)
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if srs.srid is None:
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raise Exception('Spatial reference requires an SRID to be '
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'compatible with the spatial backend.')
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# Initializing the keyword arguments dictionary for both PostGIS
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# and SpatiaLite.
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kwargs = {'srid' : srs.srid,
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'auth_name' : auth_name,
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'auth_srid' : auth_srid or srs.srid,
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'proj4text' : srs.proj4,
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}
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# Backend-specific fields for the SpatialRefSys model.
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if connection.ops.postgis:
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kwargs['srtext'] = srs.wkt
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if connection.ops.spatialite:
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kwargs['ref_sys_name'] = ref_sys_name or srs.name
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# Creating the spatial_ref_sys model.
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try:
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# Try getting via SRID only, because using all kwargs may
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# differ from exact wkt/proj in database.
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sr = SpatialRefSys.objects.get(srid=srs.srid)
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except SpatialRefSys.DoesNotExist:
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sr = SpatialRefSys.objects.create(**kwargs)
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# Alias is for backwards-compatibility purposes.
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add_postgis_srs = add_srs_entry
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