How to implement proximity search with postcode?

Question

Hi, I have to use proximity search with postcode for Australia. Going through some links like http://www.randommouse.com/rms/about/product/FNDRY/docs/tutorial/08/how-to-add-google-maps-to-your-review-site-intro.html

I found that I have to manage the the post codes with latitude and longitude if I am not mistaken. But i could not find how to implement this. Can anyone suggest me how to do this with php or give some links so that i could see more on this.

Thanks in advance.

Edited:

I have edited my question:

Can I use google api for this i.e. to get the post codes within given range. I have found a link that is for the drupal. So can I use google api just to get postcodes. The link have followed is http://svendecabooter.be/blog/implementing-location-proximity-search-for-belgium-with-drupal-and-google-maps

Answer 1

You'll need to find a database that has the longitude and latitude of each postal code. Once you have the longitude and latitude you'll use the havesine formula (http://www.codecodex.com/wiki/Calculate_Distance_Between_Two_Points_on_a_Globe) to calculate the distance between points. To do a proximity search you'll have to calculate the distance from your starting point to all the points in your dataset. You may also consider using a bounding box and then searching for points inside that bounding box. A geo spatial database like PostGIS has built in functions that can help with all this.

Answer 2

You might also want to look at GeoHash as a way to speed up searching for a long/lat within an area (proximity). There are 'plugins' in various languages eg. GeoHash in Ruby is very easy to use.