| --- |
| license: other |
| license_name: open-government-licence-v3 |
| license_link: https://www.nationalarchives.gov.uk/doc/open-government-licence/version/3/ |
| tags: |
| - geospatial |
| - postcodes |
| - gb |
| - pmtiles |
| - vector-tiles |
| - inspire |
| - land-registry |
| pretty_name: Inspired Postcodes — GB Postcode Boundaries (PMTiles) |
| --- |
| |
| # Inspired Postcodes |
|
|
| GB postcode boundary polygons derived from open Land Registry and ONS data, published as [PMTiles](https://protomaps.com/docs/pmtiles) vector tile files. |
|
|
| Interactive map: [markmclaren.github.io/inspired-postcodes](https://markmclaren.github.io/inspired-postcodes/) |
|
|
| The approach was inspired by Mark Longair's blog post: |
| [Open Data GB Postcode Unit Boundaries](https://longair.net/blog/2021/08/23/open-data-gb-postcode-unit-boundaries/) |
|
|
| Mark's Voronoi-processed postcode data, derived from Mapit, is also available as PMTiles: |
| [github.com/markmclaren/mapit-postcode-pmtiles](https://github.com/markmclaren/mapit-postcode-pmtiles) — [live viewer](https://markmclaren.github.io/mapit-postcode-pmtiles/) |
|
|
| --- |
|
|
| ## Files |
|
|
| | File | Layer name | Description | |
| |---|---|---| |
| | `inspire_original.pmtiles` | `inspire` | All INSPIRE property boundary polygons. Where a parcel spans multiple postcodes, it is split into segments using Voronoi cells seeded from UPRN coordinates. No-postcode parcels are retained. | |
| | `inspire_single_pcds.pmtiles` | `inspire` | Property parcels that map cleanly to exactly one postcode. Parcels with multiple or unresolved postcodes are excluded. | |
| | `inspire_dissolved_pcds.pmtiles` | `pcds_dissolved` | Postcode unit boundaries (e.g. `AB10 1AB`), formed by dissolving all single-postcode parcel geometries by postcode. | |
| | `inspire_sector_dissolved_pcds.pmtiles` | `pcds_sector_dissolved` | Postcode sector boundaries (e.g. `AB10 1`), formed by dissolving the unit boundaries. | |
| | `inspire_district_dissolved_pcds.pmtiles` | `pcds_district_dissolved` | Postcode district boundaries (e.g. `AB10`), formed by dissolving the sector boundaries. | |
| | `inspire_area_dissolved_pcds.pmtiles` | `pcds_area_dissolved` | Top-level postcode area boundaries (e.g. `AB`), formed by dissolving the district boundaries. | |
|
|
| All parcel-level layers (`inspire_original`, `inspire_single_pcds`) include the following properties: |
|
|
| | Property | Description | |
| |---|---| |
| | `pcds_single` | The single postcode assigned to the parcel (e.g. `AB10 1AB`). | |
| | `uprn_count` | Number of UPRNs within the parcel. | |
| | `pcds_count` | Number of distinct postcodes within the parcel. | |
| | `colour_index` | Integer (0–5) for neighbour-contrast polygon colouring. | |
|
|
| Dissolved layers include the postcode key for their level (`pcds`, `pcds_sector`, `pcds_district`, or `pcds_area`) plus `source_unit_count` and `source_polygon_count`. |
|
|
| --- |
|
|
| ## How the Data Was Produced |
|
|
| The pipeline was run on the [Isambard 3](https://docs.isambard.ac.uk/) HPC system using a set of Python/DuckDB scripts and Slurm job definitions. |
|
|
| 1. **Download** INSPIRE GML zip files (one per local authority, ~318 councils for England and Wales) from the [HM Land Registry INSPIRE download service](https://use-land-property-data.service.gov.uk/datasets/inspire/download). |
| 2. **Load** each GML into DuckDB via GDAL/`ST_Read`, with offline GML sanitisation to avoid remote schema fetches on HPC compute nodes. |
| 3. **Enrich** polygons with postcode data by spatially joining NSUL UPRN points (converted from EPSG:27700 to WGS 84) onto each parcel. |
| 4. **Split** multi-postcode parcels by constructing Voronoi cells from the UPRN point coordinates within each parcel and intersecting them with the original polygon. |
| 5. **Export** to newline-delimited GeoJSON per council. |
| 6. **Tile** each GeoJSON to MBTiles with [Tippecanoe](https://github.com/felt/tippecanoe) (zoom 0–16, geometry simplification, no tile size limit to prevent feature dropping at low zoom). |
| 7. **Merge** all per-council MBTiles with `tile-join`, then convert to PMTiles with the `pmtiles convert` CLI. |
| 8. **Dissolve** the single-postcode merged layer progressively by postcode unit, sector, district, and area (with a 2 m buffer to close small gaps between adjacent parcels before union), producing four dissolved PMTiles outputs. |
|
|
| --- |
|
|
| ## Data Sources |
|
|
| - **INSPIRE Index Polygons** — HM Land Registry Cadastral Parcel data for England and Wales. |
| [use-land-property-data.service.gov.uk/datasets/inspire](https://use-land-property-data.service.gov.uk/datasets/inspire/download) |
|
|
| - **National Statistics UPRN Lookup (NSUL)** — ONS dataset mapping Unique Property Reference Numbers (UPRNs) to postcodes and British National Grid coordinates (December 2025, Epoch 123). |
| [geoportal.statistics.gov.uk/datasets/4e0b4b3fbc2540caae27e7be532e61be](https://geoportal.statistics.gov.uk/datasets/4e0b4b3fbc2540caae27e7be532e61be/about) |
|
|
| --- |
|
|
| ## Licence |
|
|
| Contains HM Land Registry data © Crown copyright and database right 2025. |
| Contains National Statistics data © Crown copyright and database right 2025. |
| Licensed under the [Open Government Licence v3.0](https://www.nationalarchives.gov.uk/doc/open-government-licence/version/3/). |
|
|
