Radius of 40 kilometers using latitude and longitude [duplicate]

Answer 1

I use this query to get all points within a $radius around $lat/$lng:

SELECT
    *,
    ( 6371 * acos( cos( radians({$lat}) ) * cos( radians( `lat` ) ) * cos( radians( `lng` ) - radians({$lng}) ) + sin( radians({$lat}) ) * sin( radians( `lat` ) ) ) ) AS distance
FROM `positions`
HAVING distance <= {$radius}
ORDER BY distance ASC

6371 is the earth radius im km. And I have not invented it: http://code.google.com/intl/en/apis/maps/articles/phpsqlsearch.html https://developers.google.com/maps/articles/phpsqlsearch_v3#findnearsql (edit: URL changed)