50 lines
2.0 KiB
Python
50 lines
2.0 KiB
Python
def add_postgis_srs(srs, auth_name='EPSG', auth_srid=None, ref_sys_name=None):
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"""
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This function takes a GDAL SpatialReference system and adds its
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information to the PostGIS `spatial_ref_sys` table -- enabling
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spatial transformations with PostGIS. This is handy for adding
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spatial reference systems not included by default with PostGIS.
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For example, the following adds the so-called "Google Maps Mercator
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Projection" (available in GDAL 1.5):
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>>> add_postgis_srs(SpatialReference(900913))
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Keyword Arguments:
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auth_name: This keyword may be customized with the value of the
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`auth_name` field. Defaults to 'EPSG'.
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auth_srid: This keyword may be customized with the value of the
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`auth_srid` field. Defaults to the SRID determined
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by GDAL.
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ref_sys_name: For SpatiaLite users only, sets the value of the
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the `ref_sys_name` field. Defaults to the name
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determined by GDAL.
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"""
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from django.contrib.gis.db.backend import SpatialBackend
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from django.contrib.gis.models import SpatialRefSys
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from django.contrib.gis.gdal import SpatialReference
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if SpatialBackend.oracle or SpatialBackend.mysql:
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raise Exception('This utility not supported on Oracle or MySQL spatial backends.')
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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 compatible with PostGIS.')
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# Initializing the keyword arguments dictionary for both PostGIS 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 keyword settings.
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if SpatialBackend.postgis: kwargs['srtext'] = srs.wkt
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if SpatialBackend.spatialite: kwargs['ref_sys_name'] = ref_sys_name or srs.name
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# Creating the spatial_ref_sys model.
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sr, created = SpatialRefSys.objects.get_or_create(**kwargs)
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