'Returns a tuple of the ellipsoid parameters:
(semimajor axis, semiminor axis, and inverse flattening).'

@property
def ellipsoid(self):

    if gdal.HAS_GDAL:
        return self.srs.ellipsoid
    else:
        m = self.spheroid_regex.match(self.wkt)
        if m:
            return (float(m.group('major')), float(m.group('flattening')))
        else:
            return None
