My new site worldinpictures.org¹ is now up and running. The concept is fairly simple - you enter an address or location and in return get to see photos taken nearby.
Photos are obtained from flickr using the flickr API. Only "geotagged" photos can be used though. This is a convention whereby photos in flickr are tagged with the latitude and longitude at which they were taken. Such photos should have the following three tags:

• geotagged


• geo:lon=XXXX


• geo:lat=YYYY

where XXXX and YYYY are the decimal longitude and latitude values (see geotagging on wikipedia).
With this information I can build up a database of photos indexed by latitude and longitude. This can then be queried for photos within a certain distance of a specified coordinate.
Next step is to allow a user to enter a location, address or placename rather than a latitude or longitude. Google comes to the rescue here with their geocoder (which is part of the Google Maps API). I supply it with an address and get a latitude/longitude in return.