<html><head></head><body>Hi Dave,<br><br>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. <br><br>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.<br><br>A point with an addr:postcode is no different from a point with addr:housenumber. Both are valid and commonly used address points.<br><br>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. <br><br>ndrw6<br><br><br><div class="gmail_quote">On 4 October 2019 13:47:03 BST, Dave F via Talk-GB <talk-gb@openstreetmap.org> wrote:<blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">
<pre class="k9mail">On 04/10/2019 01:52, ndrw6@redhazel.co.uk wrote:<br><blockquote class="gmail_quote" style="margin: 0pt 0pt 1ex 0.8ex; border-left: 1px solid #729fcf; padding-left: 1ex;">On 04/10/2019 00:26, Dave F via Talk-GB wrote:<br><blockquote class="gmail_quote" style="margin: 0pt 0pt 1ex 0.8ex; border-left: 1px solid #ad7fa8; padding-left: 1ex;">I think you're missing the point. Most contributors believe postcodes <br>on buildings or property nodes, add quality to the OSM's database, <br>but object to the import of codepoint as it's just not accurate <br>enough as stated in this, & numerous other threads.<br></blockquote>This is incorrect. CPO/ONSPD postcodes _are_ accurate, up to date and <br>include all postcodes in the UK except NI. <br></blockquote><br>Please note: "not accurate *enough*"<br><br><blockquote class="gmail_quote" style="margin: 0pt 0pt 1ex 0.8ex; border-left: 1px solid #729fcf; padding-left: 1ex;">They are not complete (contain one and only one delivery point per <br>postcode), <br></blockquote><br>No. The centre point is not associated with *any* delivery point. It is <br>an arbitrary mean, calculated mathematically. it could, in theory, be <br>located in the middle of a park.<br>Even postcodes unique to one property/business aren't accurate as their <br>positions are misaligned by the effect of adjacent areas.<br><br><blockquote class="gmail_quote" style="margin: 0pt 0pt 1ex 0.8ex; border-left: 1px solid #729fcf; padding-left: 1ex;">which is pity, but that's not a reason not to use the ones that are <br>available, which is still _far_ more that what we have in the database.<br></blockquote><br>Quantity does not equate to quality.<br><br>><br><blockquote class="gmail_quote" style="margin: 0pt 0pt 1ex 0.8ex; border-left: 1px solid #729fcf; padding-left: 1ex;">This may not be a perfect solution but the information CPO/ONSPD <br>contains is still extremely useful for geocoding. Search for a <br>postcode and you are _guaranteed_ to get an address in a close <br>vicinity to a place you are looking for. <br></blockquote><br>No. With an import of the centroids points you're only guaranteed to be <br>given the location of the node with the postcode.<br><br><br><blockquote class="gmail_quote" style="margin: 0pt 0pt 1ex 0.8ex; border-left: 1px solid #729fcf; padding-left: 1ex;"> How about not needing to start Google Maps when searching for a <br> location on the go?<br><br><blockquote class="gmail_quote" style="margin: 0pt 0pt 1ex 0.8ex; border-left: 1px solid #ad7fa8; padding-left: 1ex;">There's no point in importing to stand alone nodes as deliveries are <br>destined for buildings. Adding to streets is also pointless for the <br>same reason plus they can have multiple postcodes.<br></blockquote>Addresses on nodes are commonly used in the UK OSM. Many mappers <br>prefer them over placing addresses on buildings. There are also many <br>cases (POIs) where nodes are objectively better than buildings. So, <br>no, there right and wrong solution here.<br></blockquote><br>Allow me to clarify. I should have maybe said 'properties' which can be <br>represented by nodes instead of 'buildings'.<br>My objection, which I thought was clear, was to "standalone nodes" with <br>just a postcode tag.<br><br>><br><blockquote class="gmail_quote" style="margin: 0pt 0pt 1ex 0.8ex; border-left: 1px solid #729fcf; padding-left: 1ex;"><br> Besides, the main reason for importing these data is that we can get <br> _all_ postcodes in the database.<br></blockquote><br>Again quantity /= quality. If you can't manipulate data then it's <br>useless. These standalone postcode nodes will relate to nothing.<br><br><blockquote class="gmail_quote" style="margin: 0pt 0pt 1ex 0.8ex; border-left: 1px solid #729fcf; padding-left: 1ex;"> This gives users confidence that when they search for a postcode they <br> will reliably get a result they are looking for. This is not possible <br> when merging postcodes with buildings simply because we still have <br> only a small fraction of buildings in the database.<br><br> By the way, I'm not against merging addr:postcode with buildings, <br> that's exactly what I was doing myself when adding postcodes manually. <br> However, this is not a process that can be automated (lack of <br> buildings, single OSM buildings having more than one address/postcode).<br></blockquote><br>Then add buildings.<br><br><blockquote class="gmail_quote" style="margin: 0pt 0pt 1ex 0.8ex; border-left: 1px solid #729fcf; padding-left: 1ex;">Based on my experience with mapping postcodes with CPO, I would <br>recommend starting with an import and merge postcodes and buildings <br>later.<br></blockquote><br>Experience has shown that doesn't happen. I'm thinking US TIGER imports, <br>but I'm sure there are other examples.<br><br>DaveF<hr>Talk-GB mailing list<br>Talk-GB@openstreetmap.org<br><a href="https://lists.openstreetmap.org/listinfo/talk-gb">https://lists.openstreetmap.org/listinfo/talk-gb</a><br></pre></blockquote></div></body></html>