Talk:United Kingdom postcodes

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Dracos and the like

Is there any plan to import the data (refs and postcodes) from the dracos database? I think this is a good way of getting good coverage of postcodes for the whole county down to a fairly good detail. Or is there some licensing problem in the way? --Milliams 00:07, 13 April 2009 (UTC)

AFAIK, the dracos site is live OSM data - The refs show up in OSM straight away. --Rjmunro 14:32, 26 August 2009 (UTC)

Levels of postcode data

Currently there seem to be a lot of ways to encode postcodes, roughly in order of accuracy:

  • The Karlsruhe Schema which proposes the key addr:postcode on individual properties. (I think it would be better if each postcode was a relation of all the address / building nodes contained by it, so that a single postcode was a single DB object, but that's not too important). This method provides extreme accuracy - down to a few m.
  • The key postal_code on the way - presumably multiple postcodes separated by semicolons, and it might make sense to put it on the street relation, rather than the way, if a street was made of multiple ways that didn't match postcode boundaries. This gives a per-street accuracy.
  • Go and look at FreeThePostcode, which has a relatively small number of relatively accurate GPS-derived postcodes. They are accurate in the sense that the nearest building to the coordinates given will have the postcode given, but they don't accurately tell you where the borders of each postcode are. Sometimes a house might be nearer the next postcode's point as the crow flies than to it's own postcodes point which might be further down it's own road. They are probably good enough for routing in most cases.
  • Go and look at NPEMaps which has a much larger number of less accurate "click on an old map" derived postcodes. These are usually accurate to within a few streets, and are fine for roughly positioning the map, but not at the highest zoom levels. They are also usable in a "find my nearest branch of a shop" kind of system which only requires accuracy of a couple of miles.
  • uk_postcode_centroid nodes. These are derived from the above and only show the first half of postcodes. They are useful for find my nearest services, and rough map positioning.

Additionally, the namefinder search system (the main OSM search) searches for the postcode in Google, parses the context looking for an address, then does an address search. When this works, it works very well, down to the per-street level. When it fails, it tends to give a random result somewhere else in the country more often than failing with an error, so it can be dangerous.

--Rjmunro 14:57, 26 August 2009 (UTC)