iOS通过经纬度计算两个地点之间的距离

+(double)distanceBetweenOrderBy:(double)lat1 :(double)lat2 :(double)lng1 :(double)lng2{

    double dd = M_PI/180;

    double x1=lat1*dd,x2=lat2*dd;

    double y1=lng1*dd,y2=lng2*dd;

    double R = 6371004;

    double distance = (2*R*asin(sqrt(2-2*cos(x1)*cos(x2)*cos(y1-y2) - 2*sin(x1)*sin(x     2))/2));

    //km  返回

    //return  distance*1000;

    //返回 m

    return   distance;

}