计算距离，返回米

double getDistanceByGps(double lat1,double lng1,double lat2,double lng2){
    double PI = 3.1415926;
    double EarthRadius = 6378137;
    double Rad = PI / 180.0;

    double radlat1 = lat1 * Rad;
    double radlat2 = lat2 * Rad;
    double a = radlat1 - radlat2;
    double b = (lng1 - lng2)*Rad;
    double s = 2*asin(sqrt(pow(sin(a/2),2)+cos(radlat1)*cos(radlat2)*pow(sin(b/2),2)));
    s = s*EarthRadius;
    s = round(s * 10000) / 10000;
    return s;
}

计算方位，返回0到360°

double getAngleByGps(double lat1,double lng1,double lat2,double lng2){
    double PI = 3.1415926;
    double x = sin(lng2 - lng1) * cos(lat2);
    double y = cos(lat1) * sin(lat2) - sin(lat1) * cos(lat2) * cos(lng2 - lng1);
    double angle = atan2(x,y) * 180 / PI;
    return angle>0?angle:angle+360;
}