bounds.py 文件源码

def buffer(self, buffer_m):
        """
        Takes a buffer distance in meters and extends the bounds by that
        distance. Uses the average latitude of the current bounds to calculate
        new latitude bounds. Over extremely large latitude bounds, the results
        will lose accuracy.
        """
        calculator = vincenty(meters=buffer_m)

        ave_lng = (self.w_lng + self.e_lng) / 2
        ave_lat = (self.n_lat + self.s_lat) / 2

        self.n_lat = calculator.destination((self.n_lat, ave_lng), 0).latitude
        self.s_lat = calculator.destination((self.s_lat, ave_lng), 180).latitude
        self.e_lng = calculator.destination((ave_lat, self.e_lng), 90).longitude
        self.w_lng = calculator.destination((ave_lat, self.w_lng), 270).longitude

        return self