The Historic County Borders Project - Project Description

Project Aims

The Historic County Borders Project digitised the borders of the historic counties of the United Kingdom and made them available for public and commerical use.

The 92 historic counties of the UK form the most natural geographical framework in many contexts, particulary in the fields of history, geography and education. For example:

The historic counties remain important cultural and geographical entities. Hence, the geography provided by the historic counties can also be made use of in many contemporary contexts:

However, the geography of the historic counties has been underused in all of these fields. A major reason for this has been the lack of a digitised dataset of the historic county borders, essential in the era of computerised mapping and GIS. The Historic County Borders Project put right this deficiency.


Project Methodology

The Historic County Borders Project is based on the Historic Counties Standard, which provides a comprehensive definition of the names, areas and borders of the historic counties of the UK. Users of the data from the Project are advised to become familiar with the Standard.

The historic county borders were digitised, where possible, based on the primary source data as defined within the Historic Counties Standard:

"The primary source data for the borders of the historic counties of Great Britain shall be that obtained by the Ordnance Survey during its first national survey of Great Britain and presented on the resultant First Edition 1:2500 and 1:10560 maps; the primary source data for the borders of the historic counties of Northern Ireland shall be that obtained by the Ordnance Survey during its survey of Ireland commenced in 1824, and presented on the resultant 1:10560 maps. "

Where this was not possible, reference was made to one or more of the secondary sources of data as defined within the Historic Counties Standard.

Land borders. In general these have been transcribed from the primary source data onto modern, georeferenced mapping and then digitised. Even at the time of the compilation of the primary source data many land-based borders were 'defaced' (i.e. could no longer be identified by features on the ground). Many further stretches of border have become defaced since the compilation of the primary source data. Nonetheless, it is usually possible to transcribe defaced stretches of border to high accuracy onto modern mapping.

Non-Esuarine Watercourse borders. According to the Standard: " where a non-estuarine watercourse forms the border between two historic counties, the border between the two historic counties shall be considered to lie at the centre of the watercourse (normal winter flow levels) for the time being. Hence, for natural and gradual changes to the watercourse, the border shall be considered to change with the course of the watercourse. Changes to the watercourse due to man-made activities or flooding shall not be considered to alter the border: the old watercourse shall remain the border."

From a comparison between the primary source data and modern mapping, it is usually clear whether the course of a watercourse has been altered by man-made actvities or flooding. If so, then the border from the primary source data has been retained as the border. This fact is noted in the Notes field of the Historic County Borders Database. If the course of the watercourse has not been altered by man-made activities or flooding, then the border has been digitised from the centre of the watercourse on modern mapping (this may be slightly different to that on the primary source data due to natural, gradual changes in the course of the watercourse).

Estuarine watercourse borders. According to the Standard: "where an estuarine watercourse forms the border between two historic counties (i.e. below the normal tidal limit of a watercourse, Point C), the border between the two historic counties shall be considered to be the centre channel at low water. "

This convention has been followed, based on the centre channel at low water from modern mapping.

Coastal borders. According to the Standard:
"there shall be no formal definition of the coastal extent of an historic county. However, for practical purposes, the historic counties may be considered to extend to either the Mean High Water (MHW) line or the Mean Low Water (MLW) line, as appropriate in a given context. Similarly, where an estuarine watercourse forms the border between two historic counties, that border may be considered to extend to the line where the level of the watercourse meets the level of the sea at low water (Point B). "

At present the digitised borders follow the MHW line. It is intended to provide alternative borders out to the MLW line as a future development of the project. The MHW line has, of course, changed significantly since the primary source data was compiled and, indeed, is continually changing. That presented in the dataset was obtained from modern mapping in comparison with primary source data. This comparison was essential in establishing the points at which the historic county borders meet the present day MHW line. No problems result where land has been lost to the sea. Where land has been accreted from the sea, then the Standard's guidance (Section 4.9) on accreted land is followed. In a few cases this has required the definition of a short section of historic county border across accreted land.

In using the MHW line as the basis for defining the seaward extents of the borders in this dataset, a degree of pragmatism has been employed. In some areas the MHW does not provide a single unbroken line along a section of coast, for example in marshy areas which the MHW line traces many, small, closely spaced islands. In such areas, only the outermost line of the coast is traced by the digitised border (i.e. not every such small 'island' is separated digitised as a polygon). The guiding principle here is that no piece of land above the MHW line should be excluded from the digitised dataset.

As noted above, where an estuary meets the sea, then the historic county border is denoted as at the centre of the channel at low water above 'Point B'. The border at Point B has been joined to the digitised MHW line for the surrounding coast by extending the border from Point B along a line perpendicualr to the flow of the river until it meets the MHW line. There are only a few places in the UK where the Point B convention is inpractical.

Offshore Islands. These are digitised as separate polygons but associated with the digitised polygon for the main body of the historic county to which they belong.

Detached Parts. According to the Standard: "Following historical precedent, detached parts of historic counties shall be considered to be associated with both their parent historic county and the historic county in which they locally lie (their 'host' county). "

This means that two sets of areas are defined by the Standard:
Historic Counties Definition A: detached parts are not separately identified, but are considered to lie within their host historic county.
Historic Counties Definition B: all detached parts are separately identifed and associated with their parent historic county.

Data for both definitions have been created and released.