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38 lines
1.7 KiB
Markdown
38 lines
1.7 KiB
Markdown
# External postcode data
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Nominatim creates a table of known postcode centroids during import. This table
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is used for searches of postcodes and for adding postcodes to places where the
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OSM data does not provide one. These postcode centroids are mainly computed
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from the OSM data itself. In addition, Nominatim supports reading postcode
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information from an external CSV file, to supplement the postcodes that are
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missing in OSM.
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To enable external postcode support, simply put one CSV file per country into
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your project directory and name it `<CC>_postcodes.csv`. `<CC>` must be the
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two-letter country code for which to apply the file. The file may also be
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gzipped. Then it must be called `<CC>_postcodes.csv.gz`.
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The CSV file must use commas as a delimiter and have a header line. Nominatim
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expects three columns to be present: `postcode`, `lat` and `lon`. All other
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columns are ignored. `lon` and `lat` must describe the x and y coordinates of the
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postcode centroids in WGS84.
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The postcode files are loaded only when there is data for the given country
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in your database. For example, if there is a `us_postcodes.csv` file in your
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project directory but you import only an excerpt of Italy, then the US postcodes
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will simply be ignored.
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As a rule, the external postcode data should be put into the project directory
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**before** starting the initial import. Still, you can add, remove and update the
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external postcode data at any time. Simply
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run:
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```
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nominatim refresh --postcodes
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```
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to make the changes visible in your database. Be aware, however, that the changes
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only have an immediate effect on searches for postcodes. Postcodes that were
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added to places are only updated, when they are reindexed. That usually happens
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only during replication updates.
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