+(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(x2))/2));      //km  返回      //     return  distance*1000;              //返回 m      return   distance;      }