Data overview

Basic principles

Boundary-Line is the key dataset of administrative and voting boundaries in Great Britain. It is a representation in computer-readable form of a specialist large-scale map, including real-world objects, which may be tangible (such as the mean high water mark) or intangible (such as a district boundary).

GIS software provides the functionality to store, manage and manipulate this digital map data. The properties of the data make it suitable as a key base for users wishing to develop applications. Boundary-Line is also suitable for use within other digital mapping systems. It's coordinated on the National Grid, which allows for the easy superimposition of other datasets.

Polygons are continuous areas defined by sets of bounding closed lines. They are representational of areas, such as electoral wards, and have relationships to administration collection features in order to convey descriptive characteristics of the polygon. These are explicit within the data and can be viewed and manipulated with appropriate software.

Boundary-Line data source

Boundary-Line is currently updated by mapping against OS VectorMap Local (1:10 000 scale) and, in certain cases, large-scale sources.

Boundary-Line features

A list of the features within Boundary-Line includes:

• Area measurements

• Civil parish (England) and community (Wales)

• County

• Distinctive names

• District

• Electoral division (county and unitary)

• English region

• Extent of the realm (EOR): either mean low water mark (England and Wales), mean low water springs mark (Scotland) or seaward boundary extensions

• Greater London Authority

• Greater London Authority Assembly constituencies (the London proportional representation voting areas)

• GSS codes in England, Wales and Scotland for all units, with the exception of Greater London Authority, county electoral divisions and non-civil-parish areas

• London borough (including the county of the City of London)

• Mean high water mark (England and Wales) and / or mean high water springs mark (Scotland): both are abbreviated to MHW in product documentation

• Metropolitan district

• Scottish parliamentary constituency and electoral region

• Unitary authority

• Unique administrative unit, link and polygon identifiers

• Ward (district, unitary, metropolitan and London borough)

• Welsh Parliament constituency and electoral region

• Westminster (parliamentary) constituency

Supplementary layers in Boundary-Line

There are several supplementary layers included alongside the main Boundary-Line product. These supplementary layers sit separately to the main GB Boundary-Line folder and are included as separate directories in the shapefile and MapInfo TAB file formats.

Features included as supplementary in the supplementary directory are:

• Historical counties

• Ceremonial counties

• Historical European regions (frozen as of 1 April 2021)

• Country

Boundary-Line folder directory structure

Boundary-Line folder directory structure.