据说是Google Maps中计算的逻辑(C#)：
private const double EARTH_RADIUS = 6378.137;
private static double rad(double d) { return d * Math.PI / 180.0; }
public static double GetDistance(double lat1, double lng1, double lat2, double lng2) {
double radLat1 = rad(lat1);
double radLat2 = rad(lat2);
double a = radLat1 - radLat2;
double b = rad(lng1) - rad(lng2);
double s = 2 * Math.Asin(Math.Sqrt(Math.Pow(Math.Sin(a / 2), 2) + Math.Cos(radLat1) * Math.Cos(radLat2) * Math.Pow(Math.Sin(b / 2), 2))); // 原文链接http://www.hijtr.com/csharp-gps2dis/
s = s * EARTH_RADIUS;
s = Math.Round(s * 10000) / 10000*1000;
return s;
}
还原其中计算公式：
formula
deduct
