C++大地计算，由两点经纬度计算距离方位

使用C++可以通过以下公式计算两点之间的距离和方位：

1. 将经度和纬度转换为弧度：

double deg2rad(double deg) {
    return (deg * PI / 180);
}

double lat1_rad = deg2rad(lat1);
double lon1_rad = deg2rad(lon1);
double lat2_rad = deg2rad(lat2);
double lon2_rad = deg2rad(lon2);

其中，PI为圆周率，需要定义。

2. 计算两点之间的距离：

double dlon = lon2_rad - lon1_rad;
double dlat = lat2_rad - lat1_rad;
double a = pow(sin(dlat / 2), 2) + cos(lat1_rad) * cos(lat2_rad) * pow(sin(dlon / 2), 2);
double c = 2 * atan2(sqrt(a), sqrt(1 - a));
double distance = R * c;

其中，R为地球半径，需要定义。

3. 计算两点之间的方位：

double y = sin(dlon) * cos(lat2_rad);
double x = cos(lat1_rad) * sin(lat2_rad) - sin(lat1_rad) * cos(lat2_rad) * cos(dlon);
double angle = atan2(y, x);
double bearing = fmod((angle * 180 / PI + 360), 360);

其中，bearing为方位角，需要定义。

完整代码如下：

#include <iostream>
#include <cmath>

#define PI 3.14159265358979323846
#define R 6371 // 地球半径，单位为千米

double deg2rad(double deg) {
    return (deg * PI / 180);
}

int main() {
    double lat1, lon1, lat2, lon2;
    std::cout << "请输入第一个点的纬度和经度（以度为单位，用逗号隔开）：" << std::endl;
    std::cin >> lat1 >> lon1;
    std::cout << "请输入第二个点的纬度和经度（以度为单位，用逗号隔开）：" << std::endl;
    std::cin >> lat2 >> lon2;

    double lat1_rad = deg2rad(lat1);
    double lon1_rad = deg2rad(lon1);
    double lat2_rad = deg2rad(lat2);
    double lon2_rad = deg2rad(lon2);

    double dlon = lon2_rad - lon1_rad;
    double dlat = lat2_rad - lat1_rad;

    double a = pow(sin(dlat / 2), 2) + cos(lat1_rad) * cos(lat2_rad) * pow(sin(dlon / 2), 2);
    double c = 2 * atan2(sqrt(a), sqrt(1 - a));
    double distance = R * c;

    double y = sin(dlon) * cos(lat2_rad);
    double x = cos(lat1_rad) * sin(lat2_rad) - sin(lat1_rad) * cos(lat2_rad) * cos(dlon);
    double angle = atan2(y, x);
    double bearing = fmod((angle * 180 / PI + 360), 360);

    std::cout << "两点之间的距离为：" << distance << "千米" << std::endl;
    std::cout << "两点之间的方位为：" << bearing << "度" << std::endl;

    return 0;
}