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Agriculture, forestry and woodland account for 90% of Wales’s land use, generating a wealth of insightful statistical information. The Senedd Cymru / Welsh Parliament uses this data to inform policy, assist decision-making and help deliver a wide range of services to rural communities.
NHS North West was established under government policy to strengthen primary care trusts (PCTs) and give GPs greater ability to commission or purchase health services directly for their patients. The organisation replaced the three former strategic health authorities in Cumbria and Lancashire, Cheshire and Merseyside, and Greater Manchester. The Association of Greater Manchester PCTs is taking forward a data analysis and reporting tool called the TIS Analyser, which was developed by Greater Manchester health organisations as part of the Tactical Information Service (TIS).
This document contains additional theoretical information related to Boundary-Line. All users will find the Product Information document useful and informative.
Boundary-Line has three feature classes:
Administrative units with attributes
Polygon features with attributes
Polyline features with attributes
Each feature has the following component:
Feature attribute data
Each geometric feature has an additional component:
Feature position
The geometry of map features is defined in terms of coordinates. All coordinates used in Boundary-Line are based on the Ordnance Survey National Grid (NG) coordinate referencing system and are quoted to a 0.1 m resolution. Despite this, Boundary-Line data can be no more accurate than its source, primarily the generalised 1:10 000 scale mapping.
There will be positional differences between the boundaries in Boundary-Line and Ordnance Survey large-scale topographic products. This is due to the large-scale products being surveyed to a higher degree of accuracy and associated to ground surface features, at scales such as 1:1 250 and 1:2 500.
Boundary-Line has been created as a more generalised set of administrative and electoral boundaries for the whole of Great Britain. It has been digitised against Ordnance Survey (generalised) 1:10 000 scale OS VectorMap Local mapping. The process of generalising for 1:10 000 scale mapping may have caused certain features to be moved from their true ground position for the purposes of map clarity. The result being that Boundary-Line and large-scale boundaries will not always be coincident.
An attribute is the descriptive characteristic of a feature, that is, a non-spatial element. In Ordnance Survey map data terms, an attribute can be a feature type (these are character codes), or a distinctive name, number or code, for example, Bassett Ward or 145.232 hectares.
Each administrative unit is classified by means of an area code (AC). These area codes are allocated when each feature is initially interpreted and captured from source. This means that a county is distinguished from a ward by the area code allocated to it. The polygon features can be classified by tracing their relationships to administrative units. Consequently, links can be classified by tracing their relationships to polygons.
It is possible, with appropriate software, for you to add other names or values of your own choice as attributes of features.
There are two identifiers in Boundary-Line that help you identify features, and which are provided to create consistent references between successive releases of Boundary-Line data. They are unique within each feature type throughout the whole dataset and maintained through successive annual updates. These identifiers are never modified – only created or deleted. If a feature is deleted from the Boundary-Line database, then the identifier ceases to exist.
The two attributes are LINK_ID and POLYGON_ID.
There is no direct cartographic text in Boundary-Line. Names, area values and GSS codes are held as attributes.
INSPIRE compliant metadata in conjunction with UK Location Programme is available to access as either:
The Boundary-Line product supplies the administrative area relationships.
A district is a division of a county; a civil parish is a division of a district. A county is divided for voting purposes into electoral divisions (EDs) and a district is divided for voting purposes into district wards.
With the introduction of unitary authorities, there are now two- and three-tier local government hierarchies. The three-tier system remains unchanged. The two-tier system has unitary authorities replacing the county and district levels of administration.
Unitary authorities may be divided into civil parishes or communities (except in Scotland), and unitary authority wards or unitary authority EDs for voting purposes. In Wales, the voting area is the unitary authority ED; in Scotland it is the unitary authority ward and in England it is the unitary authority ward or unitary authority ED.
England also has metropolitan districts; these have no county administration. These districts are divided for voting purposes into metropolitan district wards.
With the introduction of the regional government for London, in this document called the Greater London Authority, the proportional representation voting area for this new administration is the Greater London Authority Assembly constituency. The existing London borough structure also has a relationship with the new Greater London Authority and each London borough is divided for voting purposes into London borough wards.
Scotland is divided into parliamentary constituencies for voting purposes to elect Members of the Scottish Parliament (MSPs). The Scottish Parliament electoral region is a grouping of Scottish Parliament constituencies.
Wales is divided into parliamentary constituencies for voting purposes to elect parliamentary members (MS) to the Welsh Parliament. The Welsh Parliament electoral region is a grouping of Welsh Parliament constituencies.
The exit of the United Kingdom from the European Union on 01 January 2021 resulted in the repeal of the European Regions as active electoral areas. For the purposes of Boundary Review, the original European Regions in England have been retained as nine English Regions in the Boundary-Line product. A frozen layer of European Region features, preserved as of 01 April 2021, is available as a supplementary historical dataset.
England, Scotland and Wales are divided into parliamentary constituencies for voting purposes to elect members (MPs) to the Westminster Parliament. Parliamentary constituencies are made up of combinations of wards (or electoral divisions in Wales).
The closeness of the results of observations, computations or estimates to the true values or the values accepted as being true. Accuracy relates to the exactness of the result and is the exactness of the operation by which the result is obtained.
A blanket term used by Ordnance Survey to refer to all public administrative areas, specifically local government management and electoral areas.
A single administrative area.
A spatial extent is defined by circumscribing lines that form a closed perimeter that does not intersect itself.
An attribute is a property of an entity, usually used to refer to a non-spatial qualification of a spatially referenced entity. For example, a name or descriptive code indicating what an entity represents or how it should be portrayed.
Boundaries define the areas of the various national, local government and some European authorities.
An alphanumeric attribute code used in digital map data to describe each feature in terms either of the object surveyed or its representation on the map (or both).
Allocation of a feature code to a feature being created from constituent construction data: points and/or segments; with optional linking to an existing feature of the same feature code.
Pairs of numbers expressing horizontal distances along original axes. Alternatively, triplets of numbers measuring horizontal and vertical distances. Row and column numbers of pixels from raw imagery are not considered coordinates for the purpose of the standard.
An expression of the up-to-dateness of data.
The defined logical arrangement of data as used by a system for data management; a representation of a data model in computer form.
A text feature consisting of a text string(s) which form(s) a proper name.
Something about which data is stored in a databank or database, for example, boundary and name. The data may consist of relationships, attributes, positional and shape information and so on. Often synonymous with feature.
Data that is directly represented in digital form. For example, the relationship between two objects is explicit if recorded by such means as pointers and does not have to be deduced by further analysis of the data.
An item of detail within a map that can be a point and/or symbol, text or line.
A system for capturing, storing, checking, integrating, analysing and displaying data that is spatially referenced to the Earth. This is normally considered to involve a spatially referenced computer database and appropriate application software.
A subset of digital map data selected on a basis other than position. For example, one layer might consist of all features relating to counties and another to wards. Also known as a level.
A level corresponds to a single type of administrative unit (for example, a ward or a district) and is conceptual in form. See also layer.
A series of connected coordinated points forming a simple feature with homogeneous attribution.
The spatial abstraction of an object in one dimension. Lines may intersect with other lines. They are defined as a series of two or more coordinate pairs and may be curved or straight. Curved lines consist of a series of very short straight-line segments. As an object abstraction, a line has no width.
Links are the representation of line features. They are made up of one or more consecutive
non-intersecting link segments with common attributes between two terminating nodes. Links have no connection with other links except at the start or end, via common (shared) terminating nodes (points). All links contain their terminating coordinates. Links may form the boundaries of polygons and may be shared between polygons.
The proper name or label of an object (real world) or feature (object abstraction). The descriptive name might consist of one or more text strings or be an attribute of the object or object abstraction.
A unique referencing system that can be applied to all Ordnance Survey maps of Great Britain (GB) at all scales. It is used by Ordnance Survey on all post-war mapping to provide an unambiguous spatial reference in Great Britain for any place or entity whatever the map scale. The National Grid is defined by the OSGB36 spheroid.
A collection of entities which form a higher-level entity within a specific data model.
A recognisable discrete part of the real world.
The date the order was made; not necessarily the day it becomes ‘live and in use’.
The zero point in a system of rectangular coordinates.
Polygons are a representation of areas. A polygon is defined as a closed line or perimeter completely enclosing a contiguous space and is made up of one or more links. At least one node occurs on the perimeter of a polygon where the bounding link completes the enclosure of the area. There may be many nodes connecting the bounding links of a polygon. Links may be shared between polygons. Polygons may wholly contain other polygons; or be contained within other polygons.
The degree to which the coordinates define a point’s true position in the world, directly related to the spheroid and/or projection on which the coordinate system is based.
A set of related data fields grouped for processing.
Also known as X-Y coordinates and as eastings and northings. These are two-dimensional coordinates that measure the position of any point relative to an arbitrary origin on a plane surface, for example, a map projection.
The measure of the internal consistency of the positional measurements in a dataset. For many local area purposes (for example, records of utility plant), relative accuracy is more important than absolute accuracy. In this case, accurate measurement of offsets from fixed points is required rather than knowledge of the true position in space.
A measure of the ability to detect quantities. High resolution implies a high degree of discrimination but has no implication as to accuracy. For example, in a collection of data in which the coordinates are rounded to the nearest metre, resolution is 1 metre, but the accuracy may be ± 5 metres or worse.
A chord defined by two consecutive coordinates in a line string.
An order made by a Minister under delegated power from Parliament. Contains changes to boundary information, the alignment, type or relationship to a named area (amalgamation) or a change of name to an area are made by order.
The format used to transfer data between computer systems. In general usage, this can refer not only to the organisation of data, but also to the associated information, such as attribute codes, which are required in order to successfully complete the transfer.
A straight line joining two data points.
This section explains the representation of features in Boundary-Line and describes various definitions and exceptions.
This term is used by Ordnance Survey to refer to all public administrative areas. For the Boundary-Line dataset, the following are included under this term:
County
Unitary authority
Metropolitan district
District
Civil parish (Note: Depicted if appropriate notification has been received. Not all parishes have councils.)
English region
Parliamentary (Westminster) constituency
Electoral division (of county or unitary authority)
Ward (of district, metropolitan district, London borough, unitary authority)
London borough (including the county of the City of London)
Greater London Authority
Greater London Authority Assembly constituency
Unitary authority
Community (Note: Depicted if appropriate notification has been received.)
Parliamentary (Westminster) constituency
Electoral division (of unitary authority)
Welsh Parliament constituency
Welsh Parliament electoral region
Unitary authority
Parliamentary (Westminster) constituency
Ward (of unitary authority)
Scottish Parliament constituency
Scottish Parliament electoral region
Area values exist for every polygon in Boundary-Line; area values are quoted to the current Department for Communities and Local Government (DCLG) specification of 0.001 hectare. The value is subject to the inherited accuracies of the generalised 1:10 000 scale published mapping used as the source for Boundary-Line.
A boundary is the limit of a pre-set and established area whose limit is determined by one or more lines. For example, in Boundary-Line, an administrative unit boundary is represented by a county area boundary.
A ceremonial county is an area that has an appointed Lord Lieutenant and High Sheriff. Ceremonial counties are not explicitly represented in Boundary-Line.
Complex polygons are polygons that wholly enclose other polygons. They only occur when an administrative unit wholly encloses one or more others at the same level, for example, a rural district surrounding an urban district.
The description ‘Detached (Det)’, only applies to portions of local government or parliamentary constituency areas which are separated from the main area, being completely surrounded by other local government or parliamentary constituency areas and not connected by direct access on the ground.
The description will not be applied to islands or parts of islands in the sea. Detached parts have the same GSS code (where applicable) as the main area.
Part of a boundary separated from another, originally on the same alignment. Divorcements are created by the revision of one boundary and not the other.
The figure above shows a boundary divorcement. The unitary boundary between Vale of Glamorgan and Cardiff has been realigned, whilst the parliamentary (Westminster) constituency boundary has remained in its original position. It is likely that the parliamentary (Westminster) constituency boundary will also be realigned at some time in the future.
These are the dates on which an Act, Order or Statutory Instruments are ‘effective’. They may or may not be the same as the operative date or the appointed day or days. The term is particularly applied to parliamentary (Westminster) constituency changes that are effective at the date of the next general election after the operation of the order making change. This is the ‘effective’ date, that is, the date of the proclamation dissolving an existing Parliament and calling a new Parliament.
The following are specific exceptions to the normal rules:
Greater London and the metropolitan counties:
Greater London covers the area of the 32 London boroughs plus the City and county of the City of London.
Greater London is no longer a county. The Greater London Authority, which has no authority over the autonomous London boroughs, is held as one named file with all the sub-levels of boundary within it.
The London boroughs and the City and county of the City of London have been classified as London boroughs.
The metropolitan districts within the former metropolitan counties (disbanded in 1985) are classified as metropolitan districts:
Greater Manchester
Merseyside
South Yorkshire
West Yorkshire
Tyne and Wear
West Midlands
Government Office Regions (GORs) in England are not represented as specific boundary features in Boundary-Line; however, the boundaries that are used to define the GORs are represented as English Regions. A full list of the counties and unitary authorities that represent each English Region which the GORs are based on can be found in the Boundary-Line release note.
The Government Office Network closed on 31 March 2011.
Honorary titles granted to local government areas such as city and town are not included in Boundary-Line.
Boroughs in England have been identified, as from the October 2006 release, with (B) in the file name and
(B) in the Name attribute, for example:
The borough (B) will only be depicted on unitary authorities, district and metropolitan districts. This addition is to purely denote which boundaries have borough status in England without creating polygons or altering the specification in any way.
The boundaries between England and Wales and England and Scotland are represented by the boundaries between countries in the supplementary Country layer. These are maintained boundary extents based off local authority boundaries.
Government Statistical Service (GSS) codes are a unique system of referencing for administrative units.
All types of units are coded in Boundary-Line except for Greater London Authority, county electoral divisions and non-civil-parish areas. The County ED code for Greater London Authority is set at 999999999. The code is blank when the administrative unit does not have a code, for example, non-civil- parish areas.
The codes are allocated by the Office for National Statistics (ONS) for England and Wales and by the General Register Office for Scotland (GROS) for Scottish areas.
This is a calendar date, given in an Order, Act or Statutory Instrument, on which the specified boundary changes will come into operation. Dates given may be up to four years after the publication of the Order, Act or Statutory Instrument and may apply to any type of boundary other than parliamentary or European regions.
The Westminster (parliamentary) constituency boundaries have an Effective date, rather than an Operative Date ‘The Effective Date will be the date of a general election, meaning any changes to these boundaries will apply as and from the date of the next election.’
The represented boundaries and administrative unit names are defined and modified by Orders, Acts and Statutory Instruments (SIs). A document signed by the relevant Secretary of State or a local authority letter describing and giving legal authority for boundary changes.
Orders, Acts and SIs, in exceptional circumstances due to processing or constitutional constraints, may be excluded until the next suitable release.
This is the last date on which a boundary was current. Where an effective date applies, the superseded date will be the day before the next dissolution of Parliament.
Boundaries are no longer shown in Boundary-Line if they have been superseded at the time of the annual snapshot of boundaries that each release of Boundary-Line represents.
When changes occur to tidelines, rivers or streams caused by natural and gradual forces, any boundaries that are linked to these altered features will move with them. When the movement of a boundary, MHW or EOR alignment in Boundary-Line reflects such changes, this will be noted in the update notes that accompany each release of Boundary-Line.
This is an area within the realm that is not included in all the relevant administrative units. The area will remain unannexed until further legislation changes its situation and the polygon represents a hole in that level of administration.
Unitary authorities and counties effectively create a contiguous layer of administrative units throughout the whole of Great Britain. They represent single-tier administrations with responsibility for all areas of local government.
Boundary-Line data is output in a layered structure. This is a simplified file structure whereby the boundaries are supplied as individual files; for example, the county file contains only counties.
Ceremonial and Historical counties are provided in separate directories called Supplementary_Ceremonial and Supplementary_Historical, respectively. Historic European Regions are provided in a separate Supplementary_Historic_European_Region directory and Country outlines are provided in a separate Supplementary_Country directory.
The ‘places’ known as ‘The Inner and Middle Temples’ are within the City of London only for some purposes. They are not shown in Boundary-Line, but their areas have been wholly included within the city and its wards for this dataset. There are two distinct areas with other areas held jointly, and the boundaries are so intermixed that they have never been published by Ordnance Survey separately. A record of these boundaries is, however, held in the Boundary Record Library for reference purposes.
Divisions of parishes (England) and communities (Wales) not included in Boundary-Line.
These are areas where the limits of the parishes concerned have not been determined and the area itself is common to (or belongs to) two or more parishes. In Boundary-Line, they are classified as separate parishes with the name LANDS COMMON TO THE PARISHES OF… applied (sometimes abbreviated to LCPs…).
The boundary between Wirral metropolitan district in the former county of Merseyside and Cheshire West and Chester unitary authority in the former county of Cheshire and the Flintshire unitary authority area has not been determined, and the line adopted in Boundary-Line is for the purposes of Ordnance Survey only, so that polygons can be created.
Certain sections of the boundary between the former county of Merseyside (containing the metropolitan districts of Liverpool and Wirral), and in the former county of Cheshire, now Cheshire West and Chester, and Halton have never been determined.
For the purposes of Boundary-Line and by agreement with DCLG:
The district boundaries of those parts of Cheshire West and Chester that abut the Mersey estuary have been made coincident with the limits of the relevant district’s wards at the centre of the channel at high water (CCHW).
The undetermined part of the southern boundary of Liverpool district, in the Mersey estuary, has been made coincident with the limits of that district’s wards at the CCHW.
The undetermined part of the county boundary between the former county of Merseyside and the former county of Cheshire in that part of the estuary between the new Cheshire West and Chester and Liverpool has been made coincident with the limits of the wards at the CCHW.
The northern limit of the parliamentary constituency of Ellesmere Port and Neston is the mean high-water mark on the south side of the Mersey estuary.
These ‘wards’, which include the personal apartments of the Sovereign have no relevance to the election of councillors to electoral areas and are wholly included within the district of Windsor and Maidenhead and its wards.
The external bounding line of the Boundary-Line dataset is the extent of the realm (EOR). This means the boundary extent is digitised on the alignment of the mean low water (springs) (MLWS) for the seaward extent. Boundary-Line does not contain a separate mean low water (springs) (MLWS), only CODE 0071 representing the mean high water (MHW).
To display the EOR, both MHW and another type of boundary (for example, European electoral region or Westminster constituency) need to be displayed together.
The Territorial Waters Jurisdiction Act 1878 and the Territorial Waters Order in Council 1964 confirm that the EOR of Great Britain as used by Ordnance Survey is properly shown to the limit of mean low water for the time being, except where extended by Parliament.
This means that the EOR will be:
The mean low water mark (mean low water springs in Scotland) except when landward of a seaward extension or as shown in Figure 5a and indicated as Point B.
The mean high water mark (mean high water springs in Scotland), where coincident with mean low water or mean low water springs, but not when landward of a seaward extension or Point B.
Point B
Seaward extensions
In the figure below, the EOR follows mean low water (springs), crossing the estuaries at LWL.
The figure below shows how these features are represented in Boundary-Line.
The foreshore is taken to be the area of land between mean high water (springs) mark and the EOR which will include:
Tidal water within a seaward extension.
Tidal water above Point B, to the normal tidal limit (NTL), together with the area between mean high water (springs) mark and the edge of the channel at mean low water (springs).
Mean high water (springs) mark is represented in Boundary-Line by a polyline feature with CODE 0071. Mean low water (springs) mark is not shown, although it is generally coincident with the EOR.
The area of non-inland is referenced within each administrative unit using the NA attribute.
The following rules govern the representation in Boundary-Line of offshore islands and rocks in the sea:
Offshore rocks and islands will be shown if 0.4 hectares or more in area at high tide.
Offshore islands with buildings will always be shown, irrespective of size.
Offshore islands or rocks will not be shown if they are:
Beyond the defined EOR, irrespective of size.
Covered at high tide.
If an offshore island or rock is shown, it will be contained within all the relevant administrative unit collections.
The mean high water (springs) mark is shown to NTL.
Areas of salt marsh, mudflats and so on often have very complicated tide lines. For ease of digitising and to reduce data volumes, mean high water may be generalised in these areas (not Scotland).
Mean high water (springs) mark is represented in Boundary-Line by a polyline feature with CODE 0071.
Mean high water (springs) mark is subject to continuous change but the captured alignment of a tide line is a snapshot on one day. It is not practical to revise tide lines very frequently.
Mean low water (springs) mark is shown as the EOR, except when contained within a seaward extension, when it is then omitted.
Banks of sand, mud, shingle or rock separated from the main line of mean low water (springs), and covered at high tide, are not shown. When there are large areas of these banks separated from the main foreshore by narrow channels, the channels are ignored and the whole bounded by mean low water (springs).
The extension of the line of mean low water (springs) into a channel above Point B becomes edge of channel and is not shown.
Mean low water (springs) mark, and hence EOR is subject to continuous change but the captured alignment of a tide line is a snapshot on one day. It is not practical to revise tide lines very frequently.
The normal tidal limit (NTL) is the point at which the level of a river or stream ceases to be affected by the tidal flow. This point is often an artificial barrier such as a lock or weir.
A pier under which water flows is not normally considered to be within the realm. There are some cases, however, where a structure has specifically been included within the realm by act or order, in which case mean high water (springs) mark and EOR are shown around the limits of the structure.
This is the intangible line across a channel where the level of the river meets the level of the sea at low water.
Within large channels or estuaries, Point B is defined on the source documents for Boundary-Line and is therefore shown as the EOR.
In small channels, Point B is not shown on the source documents, so is assumed to be along the general line of low water and is shown as the EOR.
These are artificial extensions to the realm that have been made by an Act of Parliament. They extend the local government and parliamentary areas seaward of mean low water (springs) mark.
Breakwaters are structures of wood, stone, metal or other material built to break the force of waves. They can be separate from or joined to the mainland. If joined, they are generally included in the local government and parliamentary areas. If separate, they are not part of the local government and parliamentary area unless they are placed therein by legislation of some kind; for example, Plymouth breakwater is included in the local government area, whilst the centre portion of the Portland Harbour breakwater is not.
Permanent or solid structures in the sea, such as the forts in the Solent off Portsmouth Harbour and Brighton Marina, are usually included in local government and parliamentary areas.
Additional GOR information can be found at and This will identify the GORs defined by the Office for National Statistics (ONS), which only covers England.
