[Talk-GB] UK cities

[Ed Loach]

I was watching the quiz show "Holding out for a Hero" last night on
TV and one of the questions was how many cities are in the UK. The
correct answer out of 26, 46 and 66 was 66. Sorry for the spoiler if
anyone had recorded it to watch later and couldn't have guessed.

However I idly wondered at the time how accurately UK cities are
mapped. This morning, with the help of a Geofabrik British Isles
extract and a .poly file I created moments before finding the
existing UK one on the Cloudmade website, I can confirm that we have
69. After finding an official list on a UK Gov website[1] and
comparing:

We are missing: Chichester, Lichfield, Ripon, Salford, St David's,
Stoke-on-Trent, and Westminster
We have extra: Bournemouth, Chelmsford, Colchester, Ipswich,
Jedburgh, Middlesborough, Milton Keynes, Northampton, Reading, and
Swindon

I have a feeling that some of the extra ones have been tagged as
cities for the renderer as rendering of cities doesn't take into
account area (of a node?) or population as far as I know.

Having said that, the Key:place wiki page[2] seems to suggest that
the convention varies by countries with suggested tagging based on
population for those countries that haven't established a
convention. In other word it fudges the issue because mappers
disagree. Map Features[3] suggests "Urban settlement of national
importance as defined by national/state/provincial government. May
be state capital, provincial capital or center of a metropolitan
statistical area. Often over 100,000 people", which leans towards
using official city definitions in countries where those exist.

So currently, if someone wants a list of UK cities from OSM, they
can't get it by using osmosis to extract place=city nodes. Or they
can, but they would find our data to be wrong.

So, should we correct the tagging of cities in the UK so people can
extract correct information? Discuss...

Ed

[1] http://is.gd/1dUxfR
[2] http://wiki.openstreetmap.org/wiki/Key:place
[3] http://wiki.openstreetmap.org/wiki/Map_Features#Places