将 GPS 经纬度坐标与 XY 坐标相互转换的 python 程序 - II，函数

1.import 和 常数

放在文件最开始：

import math
import numpy as np
CONSTANTS_RADIUS_OF_EARTH = 6371000.     # meters (m)

2.GPS经纬度转XY坐标

输入目标经纬度坐标和参考经纬度坐标，得到相对XY坐标。
代码如下：

def GPStoXY(self, lat, lon, ref_lat, ref_lon):
        # input GPS and Reference GPS in degrees
        # output XY in meters (m) X:North Y:East
        lat_rad = math.radians(lat)
        lon_rad = math.radians(lon)
        ref_lat_rad = math.radians(ref_lat)
        ref_lon_rad = math.radians(ref_lon)

        sin_lat = math.sin(lat_rad)
        cos_lat = math.cos(lat_rad)
        ref_sin_lat = math.sin(ref_lat_rad)
        ref_cos_lat = math.cos(ref_lat_rad)

        cos_d_lon = math.cos(lon_rad - ref_lon_rad)

        arg = np.clip(ref_sin_lat * sin_lat + ref_cos_lat * cos_lat * cos_d_lon, -1.0, 1.0)
        c = math.acos(arg)

        k = 1.0
        if abs(c) > 0:
            k = (c / math.sin(c))

        x = float(k * (ref_cos_lat * sin_lat - ref_sin_lat * cos_lat * cos_d_lon) * self.CONSTANTS_RADIUS_OF_EARTH)
        y = float(k * cos_lat * math.sin(lon_rad - ref_lon_rad) * self.CONSTANTS_RADIUS_OF_EARTH)

        return x, y

3.XY坐标转GPS经纬度

输入相对XY坐标和参考经纬度坐标，得到目标经纬度坐标。
代码如下：

def XYtoGPS(self,x, y, ref_lat, ref_lon):
        x_rad = float(x) / self.CONSTANTS_RADIUS_OF_EARTH
        y_rad = float(y) / self.CONSTANTS_RADIUS_OF_EARTH
        c = math.sqrt(x_rad * x_rad + y_rad * y_rad)

        ref_lat_rad = math.radians(ref_lat)
        ref_lon_rad = math.radians(ref_lon)

        ref_sin_lat = math.sin(ref_lat_rad)
        ref_cos_lat = math.cos(ref_lat_rad)

        if abs(c) > 0:
            sin_c = math.sin(c)
            cos_c = math.cos(c)

            lat_rad = math.asin(cos_c * ref_sin_lat + (x_rad * sin_c * ref_cos_lat) / c)
            lon_rad = (ref_lon_rad + math.atan2(y_rad * sin_c, c * ref_cos_lat * cos_c - x_rad * ref_sin_lat * sin_c))

            lat = math.degrees(lat_rad)
            lon = math.degrees(lon_rad)

        else:
            lat = math.degrees(ref_lat)
            lon = math.degrees(ref_lon)

        return lat, lon

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