[Talk-GB] Import UK postcode data?

Andrzej ndrw6 at redhazel.co.uk
Fri Oct 4 13:29:24 UTC 2019

Hi Dave,

CPO centroids are in fact _not_ centroids at all. The are delivery points nearest to the centroid. I've been using them a lot and they are indeed very accurate in identifying buildings or entrances. 

To be fair, some postcodes are given approximate coordinates (this usually happens on construction sites before a survey is conducted) but there are very few of them and they are clearly marked as such.

A point with an addr:postcode is no different from a point with addr:housenumber. Both are valid and commonly used address points.

As for merging them, I am responsible for about 1/4 of all unique UK postcodes in the OSM database (~3% of all unique UK postcodes). I have recently stopped adding them because of all the negativity surrounding this topic but I can tell you having points in the database would have made my work a lot more efficient. 


On 4 October 2019 13:47:03 BST, Dave F via Talk-GB <talk-gb at openstreetmap.org> wrote:
>On 04/10/2019 01:52, ndrw6 at redhazel.co.uk wrote:
>> On 04/10/2019 00:26, Dave F via Talk-GB wrote:
>>> I think you're missing the point. Most contributors believe
>>> on buildings or property nodes, add quality to the OSM's database, 
>>> but object to the import of codepoint as it's just not accurate 
>>> enough as stated in this, & numerous other threads.
>> This is incorrect. CPO/ONSPD postcodes _are_ accurate, up to date and
>> include all postcodes in the UK except NI. 
>Please note: "not accurate *enough*"
>> They are not complete (contain one and only one delivery point per 
>> postcode), 
>No. The centre point is not associated with *any* delivery point. It is
>an arbitrary mean, calculated mathematically. it could, in theory, be 
>located in the middle of a park.
>Even postcodes unique to one property/business aren't accurate as their
>positions are misaligned by the effect of adjacent areas.
>> which is pity, but that's not a reason not to use the ones that are 
>> available, which is still _far_ more that what we have in the
>Quantity does not equate to quality.
>> This may not be a perfect solution but the information CPO/ONSPD 
>> contains is still extremely useful for geocoding. Search for a 
>> postcode and you are _guaranteed_ to get an address in a close 
>> vicinity to a place you are looking for. 
>No. With an import of the centroids points you're only guaranteed to be
>given the location of the node with the postcode.
>> How about not needing to start Google Maps when searching for a 
>> location on the go?
>>> There's no point in importing to stand alone nodes as deliveries are
>>> destined for buildings. Adding to streets is also pointless for the 
>>> same reason plus they can have multiple postcodes.
>> Addresses on nodes are commonly used in the UK OSM. Many mappers 
>> prefer them over placing addresses on buildings. There are also many 
>> cases (POIs) where nodes are objectively better than buildings. So, 
>> no, there right and wrong solution here.
>Allow me to clarify. I should have maybe said 'properties' which can be
>represented by nodes instead of 'buildings'.
>My objection, which I thought was clear, was to "standalone nodes" with
>just a postcode tag.
>> Besides, the main reason for importing these data is that we can get 
>> _all_ postcodes in the database.
>Again quantity /= quality. If you can't manipulate data then it's 
>useless. These standalone postcode nodes will relate to nothing.
>> This gives users confidence that when they search for a postcode they
>> will reliably get a result they are looking for. This is not possible
>> when merging postcodes with buildings simply because we still have 
>> only a small fraction of buildings in the database.
>> By the way, I'm not against merging addr:postcode with buildings, 
>> that's exactly what I was doing myself when adding postcodes
>> However, this is not a process that can be automated (lack of 
>> buildings, single OSM buildings having more than one
>Then add buildings.
>> Based on my experience with mapping postcodes with CPO, I would 
>> recommend starting with an import and merge postcodes and buildings 
>> later.
>Experience has shown that doesn't happen. I'm thinking US TIGER
>but I'm sure there are other examples.
>Talk-GB mailing list
>Talk-GB at openstreetmap.org
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