-# Customization of the Database
-
-This section explains in detail how to configure a Nominatim import and
-the various means to use external data.
-
-## External postcode data
-
-Nominatim creates a table of known postcode centroids during import. This table
-is used for searches of postcodes and for adding postcodes to places where the
-OSM data does not provide one. These postcode centroids are mainly computed
-from the OSM data itself. In addition, Nominatim supports reading postcode
-information from an external CSV file, to supplement the postcodes that are
-missing in OSM.
-
-To enable external postcode support, simply put one CSV file per country into
-your project directory and name it `<CC>_postcodes.csv`. `<CC>` must be the
-two-letter country code for which to apply the file. The file may also be
-gzipped. Then it must be called `<CC>_postcodes.csv.gz`.
-
-The CSV file must use commas as a delimiter and have a header line. Nominatim
-expects three columns to be present: `postcode`, `lat` and `lon`. All other
-columns are ignored. `lon` and `lat` must describe the x and y coordinates of the
-postcode centroids in WGS84.
-
-The postcode files are loaded only when there is data for the given country
-in your database. For example, if there is a `us_postcodes.csv` file in your
-project directory but you import only an excerpt of Italy, then the US postcodes
-will simply be ignored.
-
-As a rule, the external postcode data should be put into the project directory
-**before** starting the initial import. Still, you can add, remove and update the
-external postcode data at any time. Simply
-run:
-
-```
-nominatim refresh --postcodes
-```
-
-to make the changes visible in your database. Be aware, however, that the changes
-only have an immediate effect on searches for postcodes. Postcodes that were
-added to places are only updated, when they are reindexed. That usually happens
-only during replication updates.
-
-## Installing Tiger housenumber data for the US
-
-Nominatim is able to use the official [TIGER](https://www.census.gov/geographies/mapping-files/time-series/geo/tiger-line-file.html)
-address set to complement the OSM house number data in the US. You can add
-TIGER data to your own Nominatim instance by following these steps. The
-entire US adds about 10GB to your database.
-
- 1. Get preprocessed TIGER 2021 data:
-
- cd $PROJECT_DIR
- wget https://nominatim.org/data/tiger2021-nominatim-preprocessed.csv.tar.gz
-
- 2. Import the data into your Nominatim database:
-
- nominatim add-data --tiger-data tiger2021-nominatim-preprocessed.csv.tar.gz
-
- 3. Enable use of the Tiger data in your `.env` by adding:
-
- echo NOMINATIM_USE_US_TIGER_DATA=yes >> .env
-
- 4. Apply the new settings:
-
- nominatim refresh --functions
-
-
-See the [developer's guide](../develop/data-sources.md#us-census-tiger) for more
-information on how the data got preprocessed.
-
-## Special phrases import
-
-As described in the [Importation chapter](Import.md), it is possible to
-import special phrases from the wiki with the following command:
-
-```sh
-nominatim special-phrases --import-from-wiki
-```
-
-But, it is also possible to import some phrases from a csv file.
-To do so, you have access to the following command:
-
-```sh
-nominatim special-phrases --import-from-csv <csv file>
-```
-
-Note that the two previous import commands will update the phrases from your database.
-This means that if you import some phrases from a csv file, only the phrases
-present in the csv file will be kept into the database. All other phrases will
-be removed.
-
-If you want to only add new phrases and not update the other ones you can add
-the argument `--no-replace` to the import command. For example:
-
-```sh
-nominatim special-phrases --import-from-csv <csv file> --no-replace
-```
-
-This will add the phrases present in the csv file into the database without
-removing the other ones.