Customize WP-Query for radius search

Hello,

I need some help to convert this Radius Search SQL query into a WordPress Query.

When I use this with a mySQL table it works but how do I use this with the wordpress query?

$lat_set - entered by customer
$lng_set - entered by customer
$lat_post - custom field in Post
$lng_post - custom field in Post
$markers - CPT
$search_distance - the wished search radius

SELECT id, ( 6371 * acos( cos( radians( $lat_set ) ) * cos( radians( $lat_post ) ) * cos( radians( $lng_post ) - radians( $lng_set ) ) + sin( radians( $lat_set ) ) * sin( radians( $lat_post ) ) ) ) AS distance FROM $markers HAVING distance < $search_distance ORDER BY distance LIMIT 0 , 20;

Any suggestions?

Thanks,
Denis