[Talk-GB] Postcode centroids

Lester Caine lester at lsces.co.uk
Fri Jan 21 12:50:44 GMT 2011

Andy Robinson (blackadder-lists) wrote:
> Lester Caine [mailto:lester at lsces.co.uk]wrote:
>> Sent: 21 January 2011 11:41 AM
>> To: 'talk-gb OSM List'
>> Subject: Re: [Talk-GB] Postcode centroids
>> Andy Robinson (blackadder-lists) wrote:
>>> One thing that is absolutely clear to me is that you can't add
>>> postcodes unless you have been around and assigned the right houses to
>>> the right streets. On older  traditional streets where this is clear
>>> from imagery it's not so difficult but in new housing estates it's
>>> impossible unless you have walked the patch first. After that it all
>>> drops into place really rather easily.
>> In the final analysis, a building should have it's post code as part of the
>> address. Ideally that would be picked up from the 'road' that the building
> is
>> attached to. So the address would consist of a 'house name/number' on a tag
>> for the building, and a link somehow to the road which provides the other
>> data for the full address. Tagging ALL that information for every building
> is
>> something which should be avoided.
> Why to be avoided? Just because there is one way of achieving the same thing
> doesn't mean one way should be avoided.
I know that storage is cheap, but there seems little point having the full 
address attached as tags to every house. Just as other information that is 
available at 'higher level' does not need to be duplicated every time. If one 
looks up 'road' one should see a list of attached houses. How one finds 'road', 
be it name or postcode, does not matter. Having all that 'road' information on 
every building is just wrong ... just as having 'is_in' for every higher level 
search term would be. But then no one has ever agreed with my suggestions on 
hierarchy :(

>> The problem with the OS pointcode data is that it does NOT include the road
>> name since that is the bit that Royal Mail still demand payment for. The
>> file of cause has ALL of the buildings along with their coordinates, but
> the
>> licence prevents that being used, so we have to physically recreate it from
> the
>> ground up. Moving forward, where postcodes are already available as part of
>> postal information then no problem, but it would be useful if the missing
>> postcodes were added even if they still require linking to the relevant
> road.
>> There does seem to be a disagreement between authorities over how
>> postcodes are defined, but the Royal Mail rule is that a single road has a
> single
>> postcode for a 'walk'
>> group, so longer roads will be broken down ( and if one side of a road is
> on a
>> different 'walk' then it will have a different postcode ). Where a group of
>> roads in a small enough area, then the 'road' will be the main route that
> they
>> all link to, and the 'sub-road' is secondary information ... but THAT is an
> area
>> where council LLPG officers may quote different postcodes to the one listed
>> in PAF.
> Do we care about this? I say no. Just go out and put some house numbers on
> buildings and you will see how easy it is to add the majority of postcodes
> using the Copdepoint data. Job done, mostly end of story. We don't need
> anyone/anything else.
Correct ... and as my own customers manually add the fine detail of properties 
with coordinates from their GPS in place of the 'generic' location from the 
postcode things will get better ... but having the 'generic' one at least gets 
you to the right area to start with! Although I am now using my own postcode 
lookup/coordinates and using that to simply provide me with a location for osm 
so do I bother updating that information IN osm? Probably not until osm does 
handle things an a more logical manor. And I CAN manage hierarchy in a manor 
that works well for the search engine. :)

>> One thing that has been established is that a google lookup of a postcode
> may
>> give a number of properties on the related road and so provide the missing
>> information to link the postcode to a physical road.
> Don't go there
Why not? Look up a postcode, and find a link to the business you are working 
with, then confirm that postcode and address are correct. It's amazing how many 
businesses are actually using the wrong post code! And I have to confirm which 
is right via Royal mail - but then I'm probably not allowed to actually use the 
results :(

Lester Caine - G8HFL
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