New features on MaPit

Written by Matthew Somerville on October 6th, 2010 in Developers, Launches, Technical

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We’ve added a variety of new features to our postcode and point administrative area database, MaPit, in the past month – new data (Super Output Areas and Crown dependency postcodes), new functionality (more geographic functions, council shortcuts, and JSONP callback), and most interestingly for most people, a way of browsing all the data on the site.

Firstly, we have some new geographic functions to join touches – overlaps, covered, covers, and coverlaps. These do as you would expect, enabling you to see the areas that overlap, cover, or are covered by a particular area, optionally restricted to particular types of area. ‘coverlaps’ returns the areas either overlapped or covered by a chosen area – this might be useful for questions such as “Tell me all the Parliamentary constituencies fully or partly within the boundary of Manchester City Council” (three of those are entirely covered by the council, and two overlap another council, Salford or Trafford).
As you can see from that link, nearly everything on MaPit now has an HTML representation – just stick “.html” on the end of a JSON URI to see it. This makes it very easy to explore the data contained within MaPit, linking areas together and letting you view any area on Google Maps (e.g. Rutland Council on a map). It also means every postcode has a page.
From a discussion on our mailing list started by Paul Waring, we discovered that the NSPD – already used by us for Northern Ireland postcodes – also contains Crown dependency postcodes (the Channel Islands and the Isle of Man) – no location information is included, but it does mean that given something that looks like a Crown dependency postcode, we can now at least tell you if it’s a valid postcode or not for those areas.
Next, we now have all Lower and Middle Super Output Areas in the system; thanks go to our volunteer Anna for getting the CD and writing the import script. These are provided by ONS for small area statistics after the 2001 census, and it’s great that you can now trivially look up the SOA for a postcode, or see what SOAs are within a particular ward. Two areas are in MaPit for each LSOA and MSOA – one has a less accurate boundary than the other for quicker plotting, and we thought we might as well just load it all in. The licences on the CD (Conditions of supply of SOA boundaries and Ordnance Survey Output Area Licence) talk about a click-use licence, and a not very sraightforward OS licence covering only those SOAs that might share part of a boundary with Boundary-Line (whichever ones those are), but ONS now use the Open Government Licence, Boundary-Line is included in OS OpenData, various councils have published their SOAs as open data (e.g. Warwickshire), and these areas should be publicly available under the same licences.
As the UK has a variety of different types of council, depending on where exactly you are, the postcode lookup now includes a shortcuts dictionary in its result, with two keys, “council” and “ward”. In one-tier areas, the values will simply by the IDs of that postcode’s council and ward (whether it’s a Metropolitan district, Unitary authority, London borough, or whatever); in two-tier areas, the values will again be dictionaries with keys “district” and “council”, pointing at the respective IDs. This should hopefully make lookups of councils easier.
Lastly, to enable use directly on other sites with JavaScript, MaPit now sends out an “Access-Control-Allow-Origin: *” header, and allows you to specify a JSON callback with a callback parameter (e.g. put “?callback=foo” at the end of your query to have the JSON results wrapped in a call to the foo() function). JSONP calls will always return a 200 response, to enable the JavaScript to access the contents – look for the “error” key to see if something went wrong.