根据经纬度计算两点距离的方法

#include <iostream>
#include <cmath>
using namespace std;
#define pi 3.1415926535897932384626433832795
#define EARTH_RADIUS 6378.137 //地球半径 KM
double rad(double d)
{
  return d * pi / 180.0;
}
double RealDistance(double lat1, double lng1, double lat2, double lng2)//lat1第一个点纬度,lng1第一个点经度,lat2第二个点纬度,lng2第二个点经度
{
  double a;
  double b;
  double radLat1 = rad(lat1);
  double radLat2 = rad(lat2);
  a = radLat1 - radLat2;
  b = rad(lng1) - rad(lng2);
  double s = 2 * asin(sqrt(pow(sin(a / 2), 2) + cos(radLat1)*cos(radLat2)*pow(sin(b / 2), 2)));
  s = s * EARTH_RADIUS;
  s = s * 1000;
  return s;
}
int main()
{
  cout << RealDistance(20.194970489552652, 110.564224161560745, 20.195110378886003, 110.564232333140893) << std::endl;
  getchar();
  return 0;
}

RealDistance(lat1, lng1, lat2, lng2) * 180 / pi;