There is a good paper on MySQL geolocation performance here.

*EDIT* Pretty sure this is using fixed radius. Also I am not 100% certain the algorithm for calculating distance is the most advanced (i.e. it’ll “drill” through Earth).

What’s significant is that the algorithm is cheap to give you a ball park limit on the number of rows to do proper distance search.

The algorithm pre-filters by taking candidates in a square around the source point, then calculating the distance in **miles**.

Pre-calculate this, or use a stored procedure as the source suggests:

```
# Pseudo code
# user_lon and user_lat are the source longitude and latitude
# radius is the radius where you want to search
lon_distance = radius / abs(cos(radians(user_lat))*69);
min_lon = user_lon - lon_distance;
max_lon = user_lon + lon_distance;
min_lat = user_lat - (radius / 69);
max_lat = user_lat + (radius / 69);
```

```
SELECT dest.*,
3956 * 2 * ASIN(
SQRT(
POWER(
SIN(
(user_lat - dest.lat) * pi() / 180 / 2
), 2
) + COS(
user_lat * pi() / 180
) * COS(
dest.lat * pi() / 180
) * POWER(
SIN(
(user_lon - dest.lon) * pi() / 180 / 2
), 2
)
)
) as distance
FROM dest
WHERE
dest.lon between min_lon and max_lon AND
dest.lat between min_lat and max_lat
HAVING distance < radius
ORDER BY distance
LIMIT 10
```