OpenStreetMap
Recently I have been experimenting with extracting UK addresses from OSM data. Where a postcode has not been tagged, I have assigned the nearest one using the OS Opendata Codepoint centroids. The nearest postcode will quite often not be the correct one, but this is sufficiently accurate for my intended use of identifying the correct city and suburb.
Having done this, I thought it would be interesting to look at which postcode areas contain the most mapped addresses, so I made a list, which I have put on the following page in case anybody else is interested: http://wiki.openstreetmap.org/wiki/User:Will_P/UK_Addresses
The Birmingham (B) postcode contains the most addresses with 80,996 tagged, followed by Colchester (CO) with 52,257 and Nottingham (NG) with 41,313. At the other end, Llandrindod Wells (LD) and, somewhat surprisingly, Sunderland (SR) only contain 9 tagged addresses.
I have also made lists for the postcode districts and sectors within postcode areas with the most mapped addresses. It should be noted that the number of addresses within these areas varies greatly, so those areas at the top of the lists are not necessarily more complete than those further down.
Having added a lot of addresses myself, its interesting to identify other places where extensive address mapping has taken place, and to look at the different styles of mapping and tagging used.
Here are the postcode districts and sectors with the most mapped addresses -
WA7 5 - Runcorn (5384 addresses)
NG9 2 - Beeston (part) and Lenton Abbey, Nottingham (5100 addresses)
BA13 3 - Westbury, Wiltshire (4987 addresses)
CV3 5 - Coventry (Cheylesmore) (4919 addresses)
NG9 3 - Bramcote and Trowell, Nottingham (4866 addresses)
B27 7 - Acocks Green, Birmingham (4857 addresses)
B11 3 - Sparkhill, Birmingham (4549 addresses)
B76 1 - Walmley, Sutton Coldfield (4441 addresses)
CO12 4 - Harwich, Essex (4315 addresses)
CB1 3 - Cambridge (south east) (4184 addresses)
CO15 4 - Clacton-on-Sea (4078 addresses)
Discussion
Comment from Tom Chance on 25 June 2013 at 09:24
Thanks. A few things I noticed:
Comment from chillly on 25 June 2013 at 19:04
Your results are interesting. I mapped HU14, ensuring that all of the addresses were added, including postcodes. So I estimate that HU14 is 100% complete, regardless of how many actual addresses there are, but I don’t see a good way to measure this.
I maintain a postcode overlay; more info here http://onspd.raggedred.net/
Comment from RobJN on 25 June 2013 at 20:31
There is also Milliams postcode tool. One part of it attempts to match the Land Registry open data to objects in OSM. For example see CV3 5 below (it’s a little slow and I recommend not searching for anything below CV3+, where “+” is needed for the space character):
http://milliams.dev.openstreetmap.org/postcodefinder/landregistry/search/?postcode=cv3+5
If you look now you will see some in the “Wrong Postcode” section. These are those addresses tagged only as CV3. Every few months I look on this tool and add the full postcodes to OSM (Land Registry data is updated once a month).
Comment from will_p on 25 June 2013 at 22:17
Tom: Looking at the Westbury addresses, they all appear to have been added in 2009, so I suspect the mapper didn’t have access to good enough aerial imagery to add buildings. And StreetView wasn’t available then either.
Regarding postcode ‘stubs’, I have never bothered with them, but I suppose they might be of some use, particularly on the borders of postcode districts, where trying to determine the postcode from centroids or other inexact sources is going to be unreliable.
A quick query on the address data I’ve extracted indicates there are 20,934 addresses with just a postcode stub, and of these, 11,980 are in Birmingham and 3,951 in Coventry. So it’s obviously favoured by West Midlands mappers.
chillly: My lists certainly aren’t a good indicator of completeness. I did unsuccessfully search for data about the total number of addresses in each postcode district, so I could show the level of completeness, but possibly this isn’t available without access to the PAF database.
I suppose I could just use the total number of postcodes in each area as a rough indicator of the number of addresses. But it would require filtering out the inactive postcodes usually located at sorting offices first, and then, I’m not sure it would be accurate enough to be worthwhile.
I make regular use of your postcode overlay. It’s much appreciated.
RobJN: I’m aware of the Postcode Finder tool. It is very useful, although it’s a shame it doesn’t support the ‘street’ relations that I have used a lot. I mostly use it to easily look at the Land Registry data.
Regarding the “Wrong Postcode” lists, it is necessary to be careful that it is matching the correct street, because most of the mismatches it’s highlighted in my area have turned out to be a different street with the same name, sometimes several miles away. I appreciate that matching the correct street is quite difficult to do. Perhaps it could use the postcode centroids to pin down the location.