public static double GetDistance(double lat1, double lng1, double lat2,            double lng2) {　　//latitude纬度     longitude 经度        double a, b, R;        R = 6378137; // 地球半径        lat1 = lat1 * Math.PI / 180.0;        lat2 = lat2 * Math.PI / 180.0;        a = lat1 - lat2;        b = (lng1 - lng2) * Math.PI / 180.0;        double d;        double sa2, sb2;        sa2 = Math.sin(a / 2.0);        sb2 = Math.sin(b / 2.0);        d = 2                * R                * Math.asin(Math.sqrt(sa2 * sa2 + Math.cos(lat1)                        * Math.cos(lat2) * sb2 * sb2));        return d;    }