-- Deprecated in v0.70. Use distance(other, ellipse = 'sphere') instead --

        Returns great circle distance between two lat/lon coordinates on a sphere
        using the Haversine formula. The default radius corresponds to the FAI sphere
        with units in km.

def distance_sphere(self, other, radius = 6371.0):
        '''
        -- Deprecated in v0.70. Use distance(other, ellipse = 'sphere') instead --

        Returns great circle distance between two lat/lon coordinates on a sphere
        using the Haversine formula. The default radius corresponds to the FAI sphere
        with units in km.
        '''
        warnings.warn("Deprecated in v0.70. Use distance(other, ellipse = 'sphere') instead",
                      DeprecationWarning)
        lat1, lon1 = self.lat.decimal_degree, self.lon.decimal_degree
        lat2, lon2 = other.lat.decimal_degree, other.lon.decimal_degree
        pi = math.pi/180.
        # phi is 90 - latitude
        phi1 = (90. - lat1)*pi
        phi2 = (90. - lat2)*pi
        # theta is longitude
        theta1 = lon1*pi
        theta2 = lon2 *pi
        cos = (math.sin(phi1)*math.sin(phi2)*math.cos(theta1 - theta2) +
               math.cos(phi1)*math.cos(phi2))
        arc = math.acos(cos)
        return arc*radius