Flexible SRID/SRS GeometryField

gistfile1.py

from django.contrib.gis.db import models

class FlexibleSRSGeometryField(models.GeometryField):
    """
    GeoDjango field that allows storing of geometries with different SRIDs.
    """

    def __init__(self, *args, **kwargs):
        kwargs['srid'] = -1
        super(FlexibleSRSGeometryField, self).__init__(*args, **kwargs)

    def get_placeholder(self, value, compiler, connection):
        """
        Returns the placeholder for the geometry column for the
        given value.
        """
        if value is None or self.srid == -1:
            return '%s'
        else:
            return connection.ops.get_geom_placeholder(self, value, compiler)

    def get_srid(self, geom):
        "Gets the SRID for the geometry, returns None if no SRID is set."
        if self.srid == -1:
            return geom.srid
        else:
            return super(FlexibleSRSGeometryField, self).get_srid(geom)