Simon Willison’s Weblog

Freeing the postcode

UK postcodes have some interesting characteristics: a full six character post code identifies an average of around 14 house holds, and postcodes are mainly hierarchical—W1W will always be contained within W1 for example. They’re useful for a huge range of interesting things.

The problem is that the postcode database (of nearly 1.8 million postcodes) is owned by the Royal Mail and licensed at a not inconsiderable fee of between £150 and £9,000 per year.

Free the postcode was set up a while ago to try to remedy this situation, by asking people to enter their postcode along with the latitude/longitude coordinates collected from a GPS. Having people enter coordinates from online mapping services is no good as EU database law may see that as a derivative work. It’s had some success, but the GPS requirement has seriously stunted its growth.

Then a few weeks ago, npemap.org.uk launched. It’s an interface for browsing scans of out-of-copyright maps from the 1950s (credits at the bottom of the FAQ). The site asks people to enter post codes based on that old mapping data, which can then be placed in the public domain.

If you haven’t already done so, you should go and add any postcodes that you know about now. It takes no time at all, and is especially important if you live in one of the 230 districts for which no data has yet been collected.

You can grab the data they’ve already collected from here. There’s a really cool interactive visualisation of their data here, based on previous work by Chris Lightfoot using the commercially licensed postcode database.