Question

I am creating a mobile app using Phonegap and JQuery.

The app collects the longitude and latitude of users and stores them in a database (using a PHP script – web service), and with some algorithm it detects whether there is traffic or not. What I need is to grab all the longitude and latitude values from the database which are close to each other, say in the same street/200m range.

Lets say you have a list in the database with 5 lon/lat which are near each other (in the same street A), 3 lon/lat which are near each other in some Street B, and some other representing users randomly in other streets. Can anyone tell me how I can detect the lon/lat values that are near each other? The values I am storing them as separate values in the MySQL database, ie one field for longitude and another for latitude.

Once I obtain the lon/lat which are near each other, then I would need to find the center point between the users in street A, and users in street B to mark as a traffic congestion (based on some other detections).

Answer 1

You should look into the Haversine formula. Please see below:

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;

This will return all records that are within 25 miles of the input long / lat pair.