[Talk-GB] Postcodes

SK53 sk53.osm at gmail.com
Mon Dec 5 21:07:43 UTC 2016

You may also not be aware of Geolytix set of postcode areas/districts &
sectors which is built from the ONS data and other OS OpenData sets:
https://www.geolytix.co.uk/ look in Geodata menu.

You also have to process the centroids to remove very noisy data (RM
Delivery centres, some local govt offices, some businesses) where many
postcodes share a centroid. Also be aware of oddities such as NG80 & NG90
(& formerly I think L99) for businesses with high mail volumes (Boots,
Experian & the Liverpool pools companies).

There are algorithms to assign postcodes to roads which work for roads with
only one postcode or two postcodes for evens/odds. This would have been a
lot easier if the Land Registry Prices Paid data did not turn out to be
tainted. 3 datasets which do help are Companies House, FHRS & National
Register of Social Housing, but I'd be surprised if this covered more than
30% of postcodes in E&W. Obviously many centroids can be assigned
provisionally to a road just by using st_shortestline, but quite a lot of
iteration is required to deal with the errors.

Once assigned to roads buffers can be used to approximate geometries, but
more work & iteration to then tessellate the country. Always the
fly-in-the-ointment is that a postcode is not a true polygon but a
collection of delivery points, so it's actually fairly meaningless to place
a road lacking any addresses with a given postcode.


On 5 December 2016 at 20:32, Chris Hill <osm at raggedred.net> wrote:

> On 05/12/16 20:19, Dave Barter wrote:
>> Excuse the noob question as I’ve not been on the list long.
>> I’m doing a bit of work trying to create an open version of the OS
>> Codepoint Polygons. To do this I need as much postcode data as possible.
>> I’ve been looking at extracting this from OSM and as far as I can tell I’m
>> looking for the following tags:-
>> -addr:postal_code
>> -addr:postcode
>> -postal_code
>> -postcode
>> Are there any others I’m missing? And I guess I am (sadly) right in
>> thinking there is not a huge amount of data in there, circa 40-50k records?
>> Thanks
>> Dave
> Have you looked at the OS Opendata Codepoint? They are centroids, not
> polygons. You can see an overlay on OSM on my map here:
> http://oscompare.raggedred.net/?zoom=15&lat=53.73731&lon=-0.
> 48844&layers=BFFTFF I have a simple overlay, that the map uses, too. More
> details here: http://codepoint.raggedred.net/
> There are Office of National Statistics postcode files too under Open Gov
> licence. They have the same active postcode centroids as Codepoint but with
> extra detail for each postcode and expired postcodes too.
> --
> Cheers, Chris (chillly)
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> Talk-GB at openstreetmap.org
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