# File lib/geo_ruby/simple_features/envelope.rb, line 26
      def extend(envelope)
        e = Envelope.from_points([Point.from_x_y(lower_corner.x,lower_corner.y),
                          Point.from_x_y(upper_corner.x,upper_corner.y)],srid,with_z)
        e.extend!(envelope)
        e
      end