Postal codes in the United Kingdom
Most addresses in the UK can be identified by house number and postcode, but the postcode database is not fully available for free.
The postcode project most closely involved with OSM is the Postbox locator on dracos.co.uk. This uses a list of all post boxes (with the postcode area they serve) supplied by the Royal Mail and tries to map them onto OSM data. You can help by adding the 'ref' when you add a post box. See Tag:amenity=post_box for details.
Prior to the release of postcode centroids there were a number of projects which aimed to collect postcode data by user contribution. These were:
- Free the Postcode which asked you to enter your postcode and GPS coordinates.
- npemap which let you find your postcode on a scanned out-of-copyright map.
Some data from these two collections was imported into OSM using the
uk_postcode_centroid=* tag (stats) on a node that is roughly the centre of a postcode prefix area (for example