data-sources/gb-postcodes/README.md

   1 # GB Postcodes
   2
   3
   4 The server [importing instructions](https://www.nominatim.org/release-docs/latest/admin/Import-and-Update/) allow optionally download [`gb_postcode_data.sql.gz`](https://www.nominatim.org/data/gb_postcode_data.sql.gz). This document explains how the file got created.
   5
   6 ## GB vs UK
   7
   8 GB (Great Britain) is more correct as the Ordnance Survey dataset doesn't contain postcodes from Northern Ireland.
   9
  10 ## Importing separately after the initial import
  11
  12 If you forgot to download the file, or have a new version, you can import it separately:
  13
  14 1. Import the downloaded `gb_postcode_data.sql.gz` file.
  15
  16 2. Run the SQL query `SELECT count(getorcreate_postcode_id(postcode)) FROM gb_postcode;`. This will update the search index.
  17
  18 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.
  19
  20
  21
  22 ## Converting Code-Point Open data
  23
  24 1. Download from [Code-Point® Open](https://www.ordnancesurvey.co.uk/business-and-government/products/code-point-open.html). It requires an email address where a download link will be send to.
  25
  26 2. `unzip codepo_gb.zip`
  27
  28    Unpacked you'll see a directory of CSV files.
  29
  30    ```
  31    $ more codepo_gb/Data/CSV/n.csv
  32    "N1 0AA",10,530626,183961,"E92000001","E19000003","E18000007","","E09000019","E05000368"
  33    "N1 0AB",10,530559,183978,"E92000001","E19000003","E18000007","","E09000019","E05000368"
  34    ```
  35
  36    The coordinates are "Northings" and "Eastings" in [OSGB 1936](http://epsg.io/1314) projection. They can be projected to WGS84 like this
  37
  38    ```
  39    SELECT ST_AsText(ST_Transform(ST_SetSRID('POINT(530626 183961)'::geometry,27700), 4326));
  40    POINT(-0.117872733220225 51.5394424719303)
  41    ```
  42    [-0.117872733220225 51.5394424719303 on OSM map](https://www.openstreetmap.org/?mlon=-0.117872733220225&mlat=51.5394424719303&zoom=16)
  43
  44
  45
  46 3. Create database, import CSV files, add geometry column, dump into file
  47
  48    ```
  49    DBNAME=create_gb_postcode_file
  50
  51    createdb $DBNAME
  52    echo 'CREATE EXTENSION postgis' | psql $DBNAME
  53
  54    cat data/gb_postcode_table.sql | psql $DBNAME
  55
  56    cat codepo_gb/Data/CSV/*.csv | ./data-sources/gb-postcodes/convert_codepoint.php | psql $DBNAME
  57
  58    cat codepo_gb/Doc/licence.txt | iconv -f iso-8859-1 -t utf-8 | dos2unix | sed 's/^/-- /g' > gb_postcode_data.sql
  59    pg_dump -a -t gb_postcode $DBNAME | grep -v '^--' >> gb_postcode_data.sql
  60
  61    gzip -9 -f gb_postcode_data.sql
  62    ls -lah gb_postcode_data.*
  63
  64    # dropdb $DBNAME
  65    ```