从数据库读取某经纬度附近1km的地点

$slat = $banner_content['jd'];
$slng = $banner_content['wd'];

$sql = "select *, acos(
sin(($slng*3.1415)/180) * sin((wd*3.1415)/180) + 
cos(($slng*3.1415)/180) * cos((wd*3.1415)/180) * cos(($slat*3.1415)/180 - (jd*3.1415)/180)
)*6370.996 AS juli  FROM {$this->model->pre}post where status=1 and cid=29 HAVING juli <= 1";

$list = $this->model->query($sql);


数据库字段  jd 经度   wd 纬度

某点的坐标
$slat 经度  
$slng 纬度