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

[Shaun McDonald]

On 27 May 2007, at 16:51, Mike Collinson wrote:

> 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.

Post codes can cover anything from a single house to a whole street  
or business park. However it is more common to have longer streets  
have many post codes. Where I used to stay had 105 as the max house  
number on the odd side and 72 on the even side of the street. The  
street had 4 different post codes.

>
> 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.

The main parts of post codes are often bounded by main roads, thus  
making them easy, if you know the boundaries.
[...]
Shaun