How to validate geographic locations (like on careers.stackoverflow.com)?

Question

On http://careers.stackoverflow.com, the edit page under

• http://careers.stackoverflow.com/cv/edit

– section Where do you want to work? – has the neat property, that it validates geographic locations and gives them some canonical name. E.g. I enter

Subotica

and it will complete to

Zubotica, Severna Bachka, Serbia

Does it use any public API? Are there any open source implementations of such a geocompleter available for further studies? Are the sanitizations provided by http://www.geonames.org/?

Answer 1

http://webarto.com/googlemaps

http://webarto.com/34/php-geo-ip-locator

Something like this?