[Talk-GB] Postcode centroids

Richard Bullock rb357 at cantab.net
Thu Jan 20 23:09:33 GMT 2011

> Please do not just add the centroid to the map. I don't see the value of
> that. I am interested in the experience people gain from using this
> data, for example to add postcodes to an address such as addr:postcode.
I've added a few addr:postcode to my existing addr:* house numbering. In the 
vast majority of cases, I've found that the centroid itself isn't actually a 
centroid in the geometric sense - but more sort of a "median" house.

e.g. even on a curved road, the "centroid" lies at the position of one of 
the houses that the postcode applies to, not at the geometric centroid - 
which would be some distance away and make it very tricky to assign 
post-codes to addresses.

The following seem quite common in my area;

*    Short roads often have just one post code covering every address on the 
*    Slightly longer roads will often have one post code for one side of the 
road, and one for the other.
*    Some roads will be split into segments where each address on both sides 
of the road have one postcode - then further up the road, each will have a 
different one etc.
*    Then there are ones with one for each side of the road - and split into 

The roads mostly seem to split into segments if there is a convenient 
junction splitting up the housing - but sometimes not - and this requires a 
bit of educated guesswork sometimes.

What I've done in the past is created a .osm file with my particular 
post-code of interest - and then added the file as a new layer in JOSM - so 
I can overlay it. I would certainly be interested to use this new site - 
when my postcode areas of interest have been loaded.

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