docs: 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