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.

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.

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

Non Built Up Extents Notional polygons representing non-built up areas (for example, wooded strips, waterbodies, and roadside land) within the extent of a Built Up Area polygon, derived from a 25 m x 25 m grid of topographic data, and based on the classification of OS topographic area and land use features.

Non Built Up Extents attributes

geometry

Polygon geometry for the feature with area in square metres. Type: MultiSurfaceWithAreaType Multiplicity: [1]

relatedtogsscode

A reference to the GSS code for Built Up Areas provided by ONS and Scottish Government. Type: CharacterString Multiplicity: [1]

name

The name, including any language alternatives, of the highest classification of settlement that relates to a Built Up Area polygon or, if there are multiple settlements for the same classification, the names of the most significant settlements. Type: NameType Multiplicity: [1..2]

areahectares

The area of each Non Built Up Extent polygon in hectares. Type: Measure Multiplicity: [1]

Notional polygons representing built-up areas, derived from a 25 m x 25 m grid of topographic data, and based on the classification of OS topographic area and land use features.

Built Up Areas attributes

geometry

Polygon geometry for the feature with area in square metres.

• Type: MultiSurfaceWithAreaType

• Multiplicity: [1]

gsscode

A GSS identifier for Built Up Areas provided by ONS and Scottish Government.

• Type: CharacterString

• Multiplicity: [1]

name

The name (including any language alternatives) of the highest classification of settlement that relates to a Built Up Area polygon or, if there are multiple settlements for the same classification, the name of the most significant settlement.

• Type: NameType

• Multiplicity: [1..2]

areahectares

The area of each Built Up Area polygon in hectares.

• Type: Measure

• Multiplicity: [1]

This section describes the structured data types which make up OS Open Built Up Areas. The attributes associated with these data types are listed below along with a brief description of their data properties.

A spatial area object describing the geometry, extent and area of the feature.

MultiSurfaceWithAreaType attributes

geometry

Definition: Geometry for the feature.

• Type: GM_MultiSurface

• Multiplicity: [1]

area

Definition: The measured area of the geometry in square metres.

• Type: Measure

• Multiplicity: [1]

Notional polygons representing built-up areas, excluding non-built up areas (for example, wooded strips, waterbodies, and roadside land), within the extent of a Built Up Area polygon, derived from a 25 m x 25 m grid of topographic data, and based on the classification of OS topographic area and land use features.

Built Up Extents attributes

geometry

Polygon geometry for the feature with area in square metres.

• Type: MultiSurfaceWithAreaType

• Multiplicity: [1]

relatedtogsscode

A reference to the GSS code for Built Up Areas provided by ONS and Scottish Government.

• Type: CharacterString

• Multiplicity: [1]

name

The name (including any language alternatives) of the highest classification of settlement that relates to a Built Up Area polygon or, if there are multiple settlements for the same classification, the name of the most significant settlement.

• Type: NameType

• Multiplicity: [1..2]

areahectares

The area of each Built Up Extent polygon in hectares.

• Type: Measure

• Multiplicity: [1]

GeoPackage

OS Open Built Up Areas is supplied as a single GeoPackage for Great Britain. GeoPackage (*.gpkg) is an open, non-proprietary, platform-independent, standards-based data format for geographic information systems (GIS), as defined by the Open Geospatial Consortium (OGC). It is designed to be a lightweight format that can contain large amounts of varied and complex data in a single, easy-to-distribute and ready- to-use file. GeoPackage is natively supported by numerous software applications.

GeoPackage offers users the following benefits:

• The single file is easy to transfer and offers the end user a rich experience.

• Attribute names are not limited in length, making the format user friendly.

• The file size limit is large at 140 TB.

• It supports raster, vector and database formats, making it a highly versatile solution.

• It is an OGC standard.

• In most cases, it is a plug-and-play format.

CSV

A comma-separated values (CSV) file is a common interchange format for spreadsheets and databases that facilitates the simplistic use of data. Each field is either textual or numeric. Within the CSV, each field is separated from the next by a comma. CSV file format is universally supported for easy ingestion into all major database products.

The CSV supply has the following features:

• Geometry is provided as Well-Known Text (WKT).

• Header rows are included in each file.

• There is one record per line in each file.

• Fields are separated by commas.

• Where string fields contain commas, they are delimited by double quotes.

• Double quotes inside strings are escaped by doubling.

• Records are terminated by carriage returns and line feeds.

• Files use UTF-8 character encoding.

Attribute naming format comparison

The names of attributes in CSV and GeoPackage format are very similar. The following table maps CSV attribute names to GeoPackage attribute names:

OS Open Built Up Areas is classified into three feature types: Built Up Areas, Built Up Extents, and Non Built Up Extents. The attributes associated with these feature types are listed below along with a brief description of their data properties.

Code list: LanguageValue

A code list or enumeration is a controlled set of values which can be used to populate a specific column.

OS Open Built Up Areas code list

• LanguageValue

An object that describes the proper nouns (and their language) that apply to the feature.

NameType attributes

text

Name assigned to identify the feature.

• Type: CharacterString

• Size: 254

• Multiplicity: [1]

language

The language type associated with the name. The valid values are defined in the LanguageValue code list.

• Type: CharacterString

• Size: 3

• Multiplicity: [0..1]