在没有15英里半径的情况下定位最近的lng / lat位置的方法？

Question

Project: I have a MySQL database of alumni home address locations stored as lng/lat. I want to be able to identify groups of 15 members or more of alumni that live within a 15 mile radius of each other.

Given a lng/lat, how do I select the other lng/lat locations that are within a 15 mile radius? I've installed on Linux the PHP geonames package from PEAR. It isn't clear to me if I can use this package for aid in this function. It contains radius routines, but they appear to be for returning information such as postal codes within a lng/lat radius. Thanks!

Answer 1

You'll need to look into using the Haversine Formula. You'll find plenty of online examples showing you how to implement the formula in both PHP and SQL.

Google has a nice example for MySQL:

SELECT id, ( 3959 * acos( cos( radians(37) ) * cos( radians( lat ) ) * cos( radians( lng ) - radians(-122) ) + sin( radians(37) ) * sin( radians( lat ) ) ) ) AS distance 
FROM markers HAVING distance < 25 ORDER BY distance LIMIT 0 , 20;