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. ndrw6 On 4 October 2019 13:47:03 BST, Dave F via Talk-GB <[email protected]> wrote: >On 04/10/2019 01:52, [email protected] wrote: >> On 04/10/2019 00:26, Dave F via Talk-GB wrote: >>> I think you're missing the point. Most contributors believe >postcodes >>> 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 >database. > >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 >manually. >> However, this is not a process that can be automated (lack of >> buildings, single OSM buildings having more than one >address/postcode). > >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 >imports, >but I'm sure there are other examples. > >DaveF > >_______________________________________________ >Talk-GB mailing list >[email protected] >https://lists.openstreetmap.org/listinfo/talk-gb
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