[Talk-GB] UK Geocoder algorithm - workable? legal?

[Mike Collinson]

At 01:44 PM 26/05/2007, David Earl wrote:
>I have been wondering about postcodes. We have a postal_code tag which can
>be applied to streets and it would be nice to collect these. However it is
>not something like name plates that you find in the street by observation.
>There are about 2 million postcodes in the UK, so gathering them manually
>via the freethepostcode project is hard. But using data from most other
>places is subject to copyright. 

Answering David's posting very obliquely, how close are we in the current search engine(s) to being able to geodecode at the postal district level?  (i.e the LS21 part of LS21 3LW; 3,094 districts [http://en.wikipedia.org/wiki/UK_post_codes]).  This would be a more modest and achievable interim goal and useful for searching features in a roughly 5-10km radius.  Good enough at least for now??

Also, as a full post code is a postman's route, it is very possible that many streets straddle more than one full post code so it may not make sense to tag it as such - I've no proof of that so far.

In my short UK experience so far, postal districts are much easier to determine than full post codes as (all?) villages and at least smaller towns lie within one such area, so you just need to find out  one representative address for an area. The freethepostcode project may also already have at least one known point per district.  West Yorkshire councils also kindly put them on street signs, so better boundaries can be determined over time if folks would add a postal_code= tag to a random set of streets in each area they map in.

As an experiment, I'm systematically entering the following data where I can find it out with reasonable certainty from sources without copyright issues: a postal_code= tag for suburbs, towns, villages; a postal_code=  and/or is_in=<suburb/city, town or village> for at least some streets in an area.   This should allow search engine authors various options for mining raw OSM data, for example if a street is_in Otley, its postal code district can be determined by searching for the nearby place tag.

Mike