|
- from django.contrib.gis.gdal import SpatialReference
- from django.db import DEFAULT_DB_ALIAS, connections
-
-
- def add_srs_entry(srs, auth_name='EPSG', auth_srid=None, ref_sys_name=None,
- database=None):
- """
- This function takes a GDAL SpatialReference system and adds its information
- to the `spatial_ref_sys` table of the spatial backend. Doing this enables
- database-level spatial transformations for the backend. Thus, this utility
- is useful for adding spatial reference systems not included by default with
- the backend:
-
- >>> from django.contrib.gis.utils import add_srs_entry
- >>> add_srs_entry(3857)
-
- Keyword Arguments:
- auth_name:
- This keyword may be customized with the value of the `auth_name` field.
- Defaults to 'EPSG'.
-
- auth_srid:
- This keyword may be customized with the value of the `auth_srid` field.
- Defaults to the SRID determined by GDAL.
-
- ref_sys_name:
- For SpatiaLite users only, sets the value of the `ref_sys_name` field.
- Defaults to the name determined by GDAL.
-
- database:
- The name of the database connection to use; the default is the value
- of `django.db.DEFAULT_DB_ALIAS` (at the time of this writing, its value
- is 'default').
- """
- if not database:
- database = DEFAULT_DB_ALIAS
- connection = connections[database]
-
- if not hasattr(connection.ops, 'spatial_version'):
- raise Exception('The `add_srs_entry` utility only works '
- 'with spatial backends.')
- if not connection.features.supports_add_srs_entry:
- raise Exception('This utility does not support your database backend.')
- SpatialRefSys = connection.ops.spatial_ref_sys()
-
- # If argument is not a `SpatialReference` instance, use it as parameter
- # to construct a `SpatialReference` instance.
- if not isinstance(srs, SpatialReference):
- srs = SpatialReference(srs)
-
- if srs.srid is None:
- raise Exception('Spatial reference requires an SRID to be '
- 'compatible with the spatial backend.')
-
- # Initializing the keyword arguments dictionary for both PostGIS
- # and SpatiaLite.
- kwargs = {'srid': srs.srid,
- 'auth_name': auth_name,
- 'auth_srid': auth_srid or srs.srid,
- 'proj4text': srs.proj4,
- }
-
- # Backend-specific fields for the SpatialRefSys model.
- srs_field_names = {f.name for f in SpatialRefSys._meta.get_fields()}
- if 'srtext' in srs_field_names:
- kwargs['srtext'] = srs.wkt
- if 'ref_sys_name' in srs_field_names:
- # Spatialite specific
- kwargs['ref_sys_name'] = ref_sys_name or srs.name
-
- # Creating the spatial_ref_sys model.
- try:
- # Try getting via SRID only, because using all kwargs may
- # differ from exact wkt/proj in database.
- SpatialRefSys.objects.using(database).get(srid=srs.srid)
- except SpatialRefSys.DoesNotExist:
- SpatialRefSys.objects.using(database).create(**kwargs)
-
- # Alias is for backwards-compatibility purposes.
- add_postgis_srs = add_srs_entry
|
