gmplot.py 文件源码

def get_cycle(self, lat, lng, rad):
        # unit of radius: meter
        cycle = []
        d = (rad / 1000.0) / 6378.8
        lat1 = (math.pi / 180.0) * lat
        lng1 = (math.pi / 180.0) * lng

        r = [x * 10 for x in range(36)]
        for a in r:
            tc = (math.pi / 180.0) * a
            y = math.asin(
                math.sin(lat1) * math.cos(d) + math.cos(lat1) * math.sin(d) * math.cos(tc))
            dlng = math.atan2(math.sin(
                tc) * math.sin(d) * math.cos(lat1), math.cos(d) - math.sin(lat1) * math.sin(y))
            x = ((lng1 - dlng + math.pi) % (2.0 * math.pi)) - math.pi
            cycle.append(
                (float(y * (180.0 / math.pi)), float(x * (180.0 / math.pi))))
        return cycle