1 def add_postgis_srs(srs, auth_name='EPSG', auth_srid=None, ref_sys_name=None):

     2     """

     3     This function takes a GDAL SpatialReference system and adds its

     4     information to the PostGIS `spatial_ref_sys` table -- enabling

     5     spatial transformations with PostGIS.  This is handy for adding

     6     spatial reference systems not included by default with PostGIS.

     7     For example, the following adds the so-called "Google Maps Mercator

     8     Projection" (available in GDAL 1.5):

     9 

    10     >>> add_postgis_srs(SpatialReference(900913))

    11 

    12     Keyword Arguments:

    13      auth_name: This keyword may be customized with the value of the

    14                 `auth_name` field.  Defaults to 'EPSG'.

    15 

    16      auth_srid: This keyword may be customized with the value of the

    17                 `auth_srid` field.  Defaults to the SRID determined

    18                 by GDAL.

    19 

    20      ref_sys_name: For SpatiaLite users only, sets the value of the

    21                    the `ref_sys_name` field.  Defaults to the name

    22                    determined by GDAL.

    23     """

    24     from django.contrib.gis.db.backend import SpatialBackend

    25     from django.contrib.gis.models import SpatialRefSys

    26     from django.contrib.gis.gdal import SpatialReference

    27 

    28     if SpatialBackend.oracle or SpatialBackend.mysql:

    29         raise Exception('This utility not supported on Oracle or MySQL spatial backends.')

    30 

    31     if not isinstance(srs, SpatialReference):

    32         srs = SpatialReference(srs)

    33 

    34     if srs.srid is None:

    35         raise Exception('Spatial reference requires an SRID to be compatible with PostGIS.')

    36 

    37     # Initializing the keyword arguments dictionary for both PostGIS and SpatiaLite.

    38     kwargs = {'srid' : srs.srid,

    39               'auth_name' : auth_name,

    40               'auth_srid' : auth_srid or srs.srid,

    41               'proj4text' : srs.proj4,

    42               }

    43 

    44     # Backend-specific keyword settings.

    45     if SpatialBackend.postgis: kwargs['srtext'] = srs.wkt

    46     if SpatialBackend.spatialite: kwargs['ref_sys_name'] = ref_sys_name or srs.name

    47 

    48     # Creating the spatial_ref_sys model.

    49     sr, created = SpatialRefSys.objects.get_or_create(**kwargs)