根据经纬度获取地理位置

  public function  car_source_location($lng,$lat,$log){

        $sql = "select a.*,  ROUND(6378.138*2*ASIN(SQRT(
                 POW(SIN(({$lat}*PI()/180-lat*PI()/180)/2),2)
                 +COS({$lat}*PI()/180)
                 *COS(lat*PI()/180)
                 *POW(SIN(({$lng}*PI()/180-lng*PI()/180)/2),2)
             ))*1000) AS distance
         FROM `tp_group` a

         HAVING distance <= {$log}";

//        Log::record("car_source_location: ".$sql)." -- ".time();
        $group= M("group");
        $location = $group->query($sql);

        return $location;
    }