'Returns the coordinate transformation object.'

def coord_transform(self):

    SpatialRefSys = self.spatial_backend.spatial_ref_sys()
    try:
        target_srs = SpatialRefSys.objects.using(self.using).get(srid=self.geo_field.srid).srs
        return CoordTransform(self.source_srs, target_srs)
    except Exception as msg:
        new_msg = ('Could    not    translate    between    the    data    source    and    model    geometry:    %s' % msg)
        six.reraise(LayerMapError, LayerMapError(new_msg), sys.exc_info()[2])
