OpenStreetMap data for Great Britain were downloaded from Geofabrik on 22 Jan. 2011, uploaded to a PostGIS database using osm2pgsql. Nodes and Ways tagged with amenity=pub were assigned to centroids of 5 km square grid based on the Ordnance Survey National Grid and the number of pubs in each square counted.
The grid was generated, pubs counted, and output generated using Quantum GIS.
Pub density is obviously population dependant, but on OSM it is also a likely indication of ground survey (named pubs even more so). It is unlikely that many 5km squares in England actually lack pubs, so gaps in the background probably indicate poorly surveyed areas. More on this anon.
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A short postscript. There were around 56,000 pubs in Great Britain in 2008 (source). The dataset I used had over 27,000.
ReplyDeleteAnother link of interest density maps based on Beer in the Evening pub records. It doesn't say how the data were obtained, but interesting the dataset is of similar size to the OSM one. BITE now claim 42,000 pubs, but like OSM some will be marked as closed.
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