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