[Talk-GB] Postcodes map

[Robert (Jamie) Munro]

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Dave wrote:
> Hi All,
> 
> I've made a slippy map showing postcode areas:
> http://beerwarmer.randomjunk.co.uk/osm/postcodes/

> The data comes from the current list at NPE maps ( http://www.npemap.org/ ).
> I've got it overlaying the mapnik layer from OSM at the moment.
> 
> It's currently rendered down to level 11, and level 12 in places.
> The black lines are the boundaries of the first letters (eg: SW). The
> blue lines are for the first part of the post code (eg: SW15). And the
> thin green lines are the first number of the second part (eg: SW15 2)
> 
> If anyone is interested, it's a python script that generates shapefiles,
> which are then rendered using mapnik and the generate_tiles.py script
> that OSM uses.
> The script works by:
>  - feeding in the post code points into a voronoi diagram generator
>  - extracting edges from the diagram where post code boundaries meet
>  - forming polylines from these edges, and writing them to a shapefile

Excellent work. I wonder if we can extend it to do work with other POIs.
I.e. make a map to show me my nearest pub :-)

> There's a couple of bugs at the moment:
>  - post codes on the coast may have missing edges
>  - the post code boundaries need clipping to the coastline
>  - I think there are some degenerate cases, or incomplete post codes
> which cause things to go a little wrong.

Would that cover this:
http://beerwarmer.randomjunk.co.uk/osm/slippy/moretiles/postcode/11/1016/678.png

There's two black areas called OX inside a bigger OX. Also there is an
OX2 inside a bigger OX2. Perhaps these are caused by trailing spaces in
the NPEMaps database or something - they seem to be common across the
whole thing.

Robert (Jamie) Munro
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