OS Open Built Up Areas Technical Specification

This technical specification provides detailed technical information about OS Open Built Up Areas. It is targeted at technical users and software developers.

OS Open Built Up Areas is a dataset representing the built-up areas of Great Britain. It was designed primarily to underpin the statistical analysis that contributes to policy enablement across the public sector.

The Office for National Statistics (ONS) and Scottish Government made significant contributions in the design of the dataset to ensure it is fit for purpose and focussed on the needs of the wider public sector.

OS Open Built Up Areas is released and maintained as an OS OpenData product with Open Government Licensing (OGL), which means that anyone can use this data for a wide range of purposes.

Representative map showing OS Open Built Up Areas around London

Feature types

OS Open Built Up Areas was co-designed with ONS and Scottish Government and is based on their requirements. This collaboration enabled OS to create a customer-focussed product that underpins statistical analysis and supports policy development.

OS Open Built Up Areas is classified into three feature types:

• Built Up Areas is the aggregation of Built Up Extents and Non Built Up Extents.

  • This is a multipart area feature with a single Government Statistical Service (GSS) code and name or names.

• Built Up Extents is the representation of built-up areas only within the extent of Built Up Areas. This is the area that remains after Non Built Up Extents have been removed from Built Up Areas.

  • This is a multipart area feature with the same GSS code as the related Built Up Areas with the same name or names.

• Non Built Up Extents is the representation of non-built-up areas within the extent of Built Up Areas.

  • This is a multipart area feature with the same GSS code as the related Built Up Areas with the same name or names.

Each feature type has associated attribution that is detailed in this document.

Representation of a Built Up Areas Feature Type showing an area around Glasgow.

Represenation of a Built Up Extents Feature Type showing an area around Glasgow

Identifiers

The persistent managed identifier in OS Open Built Up Areas is the GSS code provided by ONS and Scottish Government. The GSS code is consistent across the three feature types and is prefixed with:

• E63 for England.

• S45 for Scotland.

• W45 for Wales.

• K08 for Built Up Areas that cross the Wales-England border.

Data sources

OS Open Built Up Areas is created from the following Ordnance Survey data content stores:

• Topographic Buildings, Roads, Residential Gardens and Made Surfaces.

• Land Use Sites.

• Settlement Named Areas.

Methodology

The OS Open Built Up Areas dataset is created by following the methodology detailed below:

1. Identify built-up cells: 25m by 25m cells are flagged as built up based on the proportion of the cell that is classified as Building, Road, Residential Garden, Made Surface, or built-up types of Land Use Site.

2. Assign names: Each cell is assigned a name from the Settlement Named Area dataset.

3. Create initial built-up area polygons:

   • Adjacent, identically-named 25m x 25m cells are merged together.

   • Adjacent built-up areas that are not Cities or Towns are merged together.

   • Smaller built-up areas are merged into nearby larger built-up areas.

4. Filter to create final geometry:

   • Built-up areas >=200 000m2 are retained and become Built Up Extents.

   • Built Up Areas and Non Built Up Extents are then generated from the Built Up Extents.

5. Refine names: The name or names of the most significant constituent settlements are applied to Built Up Areas that are not Cities or Towns.

   • If two or more Built Up Areas have the same name, the name of the lowest-tier local authority in which the Built Up Area is located is appended in brackets.

   • If two or more Built Up Areas have the same name within a single local authority, the name of the parish in which the Built Up Areas is located is appended in brackets.

   • If two or more Built Up Areas have the same name within a single parish, the name of the nearest Built Up Area is appended in brackets.

6. Assign GSS codes: GSS codes, supplied by ONS (for England and Wales) and Scottish Government, are applied to the three feature types.

Available formats

OS Open Built Up Areas is supplied in the following formats:

• CSV (comma-separated values).

• GeoPackage.

See Supply formats overview here for more information.

Currency

The first release of OS Open Built Up Areas was in December 2022. After this, the product is scheduled to be released every two years.

Index

• Feature types

• Structured data types

• Code list

• Supply formats