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41 lines
1.2 KiB
Markdown
41 lines
1.2 KiB
Markdown
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# Postcodes in Nominatim
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The blog post [Nominatim and Postcodes](https://www.openstreetmap.org/user/lonvia/diary/43143)
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describes the new handling in Nominatim 3.1.
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Postcode centroids (aka 'calculated postcodes') are generated by looking at all postcodes of
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a country, grouping them and calculating the geometric centroid. There is currently no logic
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to deal with extreme outliers (typos or other mistakes in OSM data). There is also no check
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if a postcodes adhere's to a countries format, e.g. if Swiss postcodes are 4 digits.
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## Regular updating calculated postcodes
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The script to rerun the calculation is `build/utils/update.php --calculate-postcodes` and
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runs once per night on nominatim.openstreetmap.org.
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## Finding places that share a specific postcode
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In the Nominatim database run
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```sql
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SELECT osm_type, osm_id, class, type, st_x(centroid) as lon, st_y(centroid) at lat
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FROM placex
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WHERE country_code='fr'
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AND upper(trim (both ' ' from address->'postcode')) = '33210';
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```
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Alternatively on [Overpass](https://overpass-turbo.eu/) run the following query
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```
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[out:json][timeout:250];
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area["name"="France"]->.boundaryarea;
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(
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nwr(area.boundaryarea)["addr:postcode"="33210"];
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);
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out body;
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>;
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out skel qt;
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```
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