GB Postcode data for Nominatim

The Nominatim server import instructions allow optionally download gb_postcode_data.sql.gz. This document explains how the file gets created. Data is updated several times per year.

GB vs UK

GB (Great Britain) is more correct as the Ordnance Survey dataset doesn't contain postcodes from Northern Ireland.

Importing separately after the initial import

If you forgot to download the file, or have a new version, you can import it separately:

1. Import the downloaded gb_postcode_data.sql.gz file.

2. Run the SQL query SELECT count(getorcreate_postcode_id(postcode)) FROM gb_postcode;. This will update the search index.

3. Run utils/setup.php --calculate-postcodes from the build directory. This will copy data form the gb_postcode table to the location_postcodes table.

Converting Code-Point Open data

1. Download from Code-Point® Open data (select 'CSV').

2. Extract the downloaded file.

    unzip codepo_gb.zip
   

   You'll see a directory of CSV files.

    $ more codepo_gb/Data/CSV/n.csv
    "N1 0AA",10,530626,183961,"E92000001","E19000003","E18000007","","E09000019","E05000368"
    "N1 0AB",10,530559,183978,"E92000001","E19000003","E18000007","","E09000019","E05000368"
   

   The coordinates are "Northings" and "Eastings" in OSGB 1936 projection. They can be projected to WGS84 like this

    SELECT ST_AsText(ST_Transform(ST_SetSRID('POINT(530626 183961)'::geometry,27700), 4326));
    POINT(-0.117872733220225 51.5394424719303)
   

   Position on OpenStreetMap

3. Create a working directory and place the downloaded files in there

    mkdir workdir
    cp codepo_gb/Data/CSV/*.csv workdir
    cp codepo_gb/Doc/licence.txt workdir
   

4. Convert CSV files into a .sql database dump file

   That includes creating a database, table, import the files, add geometry column, dump the file, delete the database.

   Option A:

   • Install Postgresql and other required packages, e.g. on Ubuntu

       apt-get install -y postgresql-12-postgis-3 php unzip dos2unix
     

   • Edit the convert.sh script with your database user name and paths and run the script

   Option B:

   • Use Docker

       docker build --tag gb-postcode-data-convert .
     
       docker run --detach \
                  --name gb-postcode-data-converter \
                  --env POSTGRES_PASSWORD=sEKr3tT \
                  --volume $PWD/workdir:/data \
                  gb-postcode-data-convert
     
       docker exec -t gb-postcode-data-converter /app/convert.sh
     

5. Now you have new files gb_postcode_data.sql.gz and gb_postcodes.sql.gz in your working directory.

6. Cleanup

        docker container rm --force gb-postcode-data-converter
        rm -r workdir
   

License

The source code is available under a GPLv2 license.