This outlines Ordnance Survey's policy for updating its large-scale products. The product most directly affected by the revision policy is OS MasterMap Topography Layer.

Background

As the national mapping agency of Great Britain, Ordnance Survey maintains around 234 000 km² of topographic information, ranging from dense urban conurbations to mountain and moorland areas. In order that our customers benefit from the most up-to-date mapping, it is essential that we regularly update our data.

We constantly strive to improve the quality, accuracy and content of our products even further. We value the feedback that we receive from formal market research, customer seminars and directly through our account managers. We welcome input and comment on revision policy and any other aspect of our activities.

Details of the policy

Revision activity is split into two processes: continuous revision and cyclic revision.

Continuous revision is undertaken for those features of most importance to the majority of customers – mainly built development. We aim to capture these features within six months of construction being completed on the ground.

Cyclic revision is undertaken periodically mainly for changes to the natural environment, which tend to be slower and less evident than additions to the built environment. This information is of use to many customers, with certain areas surveyed purely in the national interest. Capture can be most economically achieved using systematic revision at fixed intervals, typically through aerial photography.

Under the current revision policy, our priorities when capturing new detail are based on the following categories.

Currency of categories of change

This section defines the timescales for capture of real-world change. The classification of real-world change is described in Definition of categories of change.

Prestige sites

All designated prestige sites are captured before they are open to the public or the official unveiling. All directly-associated change, such as access roads, paths, landscaping and so on, is captured at the same time whenever it is possible to do so.

Category A change

All category A change and directly-associated detail not within the scope of prestige sites will be captured within six months of completion.

Category B change

Category B change is captured when directly associated with either a prestige site or category A change. All other category B change is captured through a programme that is integrated with capture of OS MasterMap Imagery Layer. The current revision cycle varies between two and ten years.

Category C change

Category C change is captured when directly associated with either a prestige site, category A or category B change. In urban areas, all other category C change is captured through a programme that is integrated with capture of OS MasterMap Imagery layer. The current revision cycle varies between two and four years.

In rural areas, category C change is not currently captured.

Tidal data

Tidal data is an exception to the classifications employed for other change; the update of this is defined as follows:

• Alterations to tidal data associated with real-world change that falls into other categories is updated at the same time as that change.
• Significant changes to tidal data are captured within 12 months of us becoming aware of it.
• Imagery newly captured for OS MasterMap Imagery Layer will be reviewed to identify areas of significant change for capture within 12 months. Minor changes to tidal data are not routinely captured.

Archaeological and antiquity information

New archaeological and antiquity information, and revision to information already existing, is supplied to Ordnance Survey by the national heritage bodies. The relevant heritage bodies are:

• England – English Heritage.
• Scotland – Royal Commission on the Ancient and Historic Monuments of Scotland.
• Wales – Royal Commission on the Ancient and Historic Monuments of Wales.

Updates from the heritage bodies will be added within six months of receipt.

Definition of categories of change

Definition of a site

A site is defined as a self-contained location for an identifiable purpose, for example, a retail outlet, a flat, a local authority office, a group of agricultural buildings, an industrial unit, a pumping station and so on. Sites may consist of a single feature, for example a communications mast, or more commonly, two or more area features. Sites may lie spatially within other sites, for example, an electricity substation within the grounds of a hospital.

Background

Prestige sites

Prestige sites are new sites that meet the following criteria:

• developments or structures that may reasonably be expected to attain a high profile in the national media. These can occur in any locality and are captured irrespective of the type of area they fall in or their size; or
• new publicly-accessible community sites of the following type:
  • bus/coach stations;
  • conference, exhibition and concert venues;
  • further and higher education sites;
  • health centres/surgeries/clinics;
  • hospitals;
  • law courts;
  • public libraries;
  • local authority offices – town halls, civic centres and so on;
  • railway stations including, light railway and underground railway stations;
  • schools funded by the local education authority or central Government; or
• new publicly-accessible retail developments (including complete redevelopments) that exceed 1 hectare in extent, for example new superstores, shopping centres or retail parks; or
• important new transport routes of the following type:
  • motorways and motorway junctions;
  • additional entry or exit slip roads to existing motorway junctions;
  • A and B roads creating a new route (not alterations to existing routes or new junctions unless part of a motorway); and
  • railway routes, including light rail networks.

Sites for the London 2012 Olympic Games may be subject to special treatment.

Category A change

Category A change is that which meets the definitions below.

Built development – except residential, agricultural or forestry

• A new site of any size represented by topographic area features.
• A new site represented by a point feature that is described with a real-world term of wind turbine, telecommunications mast, or is a structure associated with utilities.
• A new site not represented by topographic area or topographic point features that has a postal address. For example, a business underneath a railway arch.
• Within an existing site, a new building greater than 0.10 hectares (1 000 m²) in size.
• An extension greater than 0.10 hectares (1 000 m²) in size to an existing building.
• Extension or contraction of an existing site that involves a change of topographic area ‘Form' attribution where the total area changed is greater than 0.25 hectares. For example a factory site extends into a ‘greenfield' area.
• Change within an existing site that involves a change of topographic area ‘Form' attribution where the total area changed is greater than 0.25 hectares. For example the creation of all weather pitches within the limits of a school playing field.
• New or changed proper names for any site (except postal names or numbers of existing individual sites) where such names are represented as cartographic text.

Built development – residential dwellings

New residential dwellings, including:

• houses;
• purpose-built flats;
• mobile or park homes;
• conversions of buildings to permanent residential use, (where such change is represented in the data, for example, new boundary features, access roads, distinctive names and so on associated with agricultural or industrial buildings converted to dwellings);
• a new site not represented by a topographic area feature that has a postal address, for example a houseboat;
• major systematic refurbishment programmes of community housing greater than 0.25 hectares in area, for example, changes to property extents, road layouts, pedestrian accesses and communal areas; and
• new or changed proper names for any site (except postal names or numbers of existing individual sites) where such names are represented as cartographic text.

Built development – agriculture or forestry

NOTE: this covers the built infrastructure associated with the activity. For example barns, slurry tanks, timber harvesting plant storage and so on.

• Areas of land under crop or with growing trees are considered as vegetation, landform and land surfaces.
• A new site greater than 0.25 hectares in extent;
• a new site not represented by topographic area or topographic point features that has a postal address;
• extension or contraction of an existing site involving a change in topographic area ‘Form' attribution greater than 0.25 hectares in extent, for example, a farm where hardstanding exceeding 0.25 hectares in area has been built over an area that was previously a field;
• changes within an existing site involving a change in topographic area ‘Form' attribution greater than 0.25 hectares in extent, for example, a farm where barns, silos and similar structures are built or demolished over an area exceeding 0.25 hectares; and
• new or changed proper names of any site.

Built linear features

Roads

• All new public roads;
• all new sealed private roads;
• any change that affects road network lines on existing Department for Transport (DfT) classified roads, other public roads, junctions and sealed private roads;
• any change that extends for more than 250 m on existing DfT classified roads, including alterations that do not affect road network lines;
• routing information that restricts the passage of vehicles;
• DfT road numbering – new and changed; and
• new or changed proper names of roads.

Railways

• New railway routes;
• changes to the curtilage of existing railway routes; and
• new railway lines (not sidings, points, crossovers and so on) within the curtilage of existing railways.

Other built linear features

• New or reopened canals;
• new or significantly-changed airport runways and taxiways; and
• electricity transmission lines carried on double poles or pylons.

For supporting sites, such as bus stations, service areas, electricity and so on, see Built development – except residential, agricultural or forestry .

Flood and coastal defences

Sea and non-coastal defences designed to reduce the risk of flooding that extend continuously for more than 100 m.

Coastal zone

• Natural erosion and deposition in the coastal zone resulting in a change of alignment of more than 10 m over a length of more than 100 m for the following coastal features when well defined;
• top and bottom of cliffs; and
• coastal slope limits.

Vegetation, landform and land surfaces including bounding features

Major landscape changes greater than 25 hectares, for example, landfill, quarries, forestry, reservoirs and coastal changes.

Category B change

Category B change is that which meets the definitions below.

In general, all change not defined as category A or C is considered to be category B.

The following are typical examples:

Built development – not residential, agricultural or forestry

• Sites that are structures represented by a single point feature not explicitly listed as category A, for example, a telephone call box or letter box;
• within an existing site, new or extended buildings, where the new building or extension is less than 0.10 hectares in size;
• extension or contraction of an existing site that involves a change of topographic area ‘Form' attribution where the total area changed is less than 0.25 hectares;
• change within an existing site that involves a change of topographic area ‘Form' attribution where the total area changed is less than 0.25 hectares;
• change of status from active to inactive of an existing site not otherwise specified; and
• Changes to bounding features not otherwise captured.

Built development – residential dwellings

• Garages outside private residential gardens built after the initial development;
• changes to the postal names and numbers of existing individual dwellings; and
• changes to bounding features not otherwise captured.

Built development – agriculture or forestry

• A new site less than 0.25 hectares in area;
• extension or contraction of an existing site by less than 0.25 hectares;
• changes within an existing site where the change is less than 0.25 hectares; and
• changes to bounding features not otherwise captured.

Built linear features

Roads, tracks and paths

• Unadopted and not publicly-accessible, unsealed roads – typically for forestry or agricultural purposes;
• changes to features that define road carriageway limits not identified as category A;
• traffic-calming measures represented by topographic area features;
• routing information that provides information but does not restrict the passage of vehicles;
• private driveways within private gardens;
• tracks; and
• paths.

Railways

Changes to railway track alignments not identified as category A.

Other built linear features

• Changes to existing canals not identified as category A;
• electricity transmission lines carried on single poles;
• pipelines and other linear utility infrastructure;
• fences, hedges, walls and other bounding features for built linear items; and
• Changes to bounding features not otherwise captured.

For supporting sites, such as bus stations, service areas, electricity and so on, see Built development – except residential, agricultural or forestry .

Flood and coastal defences

Sea and non-coastal defences designed to reduce the risk of flooding that extend for less than 100 m.

Coastal zone

Change within in the coastal zone not considered to be category A.

Vegetation, landform and land surfaces including bounding features

• Vegetation and surface cover ‘Form' attribution;
• watercourses – rivers, streams, lakes (where change is less than 25 hectares);
• landscape changes less than 25 hectares, for example landfill, forestry, quarries, coastal changes and reservoirs;
• forestry changes less than 25 hectares in extent;
• changes to bounding features not otherwise captured; and
• natural and gradual change to tidelines not meeting the requirements outlined in Tidal data .

Category C change

Category C change is that which meets the definitions below.

Built development – not residential, agricultural or forestry

• No change under this heading.

Built development – residential dwellings

• Permanent buildings within private residential gardens built after initial development; and
• extensions to existing residential buildings.

Built development – agriculture or forestry

• No change under this heading.

Built linear features

• Street furniture such as guide posts, mile stones, water taps.

Flood and coastal defences

• No change under this heading.

Coastal zone

• No change under this heading.

Vegetation, landform and land surfaces including bounding features

• No change under this heading.

Further information on categorisation of change

This section provides further guidance and clarification on the categorisation of change.

Completion

As a general principle, a feature is considered complete once it is ready for its intended use.

For details on specific examples, see the relevant sections below.

Residential housing and associated features

Complete – when the roof, windows and doors are in place and the housing is ready to be lived in. This applies whether they are single houses, flats, small sites or phases of a developing estate. Associated features such as garages, fences and house numbers do not have to be finished for the change to be regarded as complete.

Property boundary fences – any changes to or the addition of a boundary fence after the completion and capture of the initial development are category B. Exceptionally, such changes will be counted as category A when they form part of a major refurbishment programme as described below.

Major refurbishment programmes – these are systematic improvements to residential areas, for example, a clear pattern of building improvements, road alignment alterations and changes to access routes. Such changes would normally involve realigned paths, roads, property boundaries and so on. The erection of fences or walls along existing feature alignments alone are not considered to be category A.

Mobile homes (caravans, chalets and so on). Permanent buildings and roadways within mobile home and caravan parks are category A.

Non-residential sites

Complete – when all major external structural work is complete and developments are ready for occupation. Associated features, such as kerb lines and external fences do not have to be finished for the change to be regarded as complete.

Associated features – elements such as car parking areas, access areas, gardens, fences and so on. The overall area of change assessed for the decision on whether a change is category A includes these associated features.

Extensions to buildings – the combined area of the new portion of extended buildings should be used to determine whether change is category A or category B; for example, an extension consisting of a combination of three new buildings greater than 0.10 hectares in total area is category A.

Utility structures – structures associated with utility supply, such as gas, water, electricity, telecommunications and so on are category A.

Divisions – the addition and removal of divisions within existing buildings is not considered to be category A change.

Linear features

Complete – for roads, this is defined as all kerb alignments being in place and the road being driveable; the road may or may not be open. Complete for other changes is defined as when all change has within a project or recognisable phase of a project has occurred.

Alterations to carriageways limits – the length criteria for change to be regarded as category A applies to the total length of changed carriageway, not to the length of the road. Small sections of change, the result of a single scheme, should be added together to ascertain the overall length, excluding unchanged portions.

Demolitions

Demolitions of an existing site where the area is left ready for redevelopment are revised to the same timescale as the construction of a similar feature would be, for example, the demolition of a house and creation of a vacant plot is category A. When a demolition precedes the completion of any new build by more than the update requirement, it is regarded as a separate task, for example, changes consisting of demolitions classified as category A should be captured within six months of the demolition being completed.

Significant agricultural and horticultural buildings

Size criteria for buildings – the combined area of the all new buildings should be used to determine whether change is category A or category B, for example, three new buildings greater than 0.25 hectares in total area is category A.

Names

All new, altered or deleted proper names, with the exception of house names or numbers, are category A. All descriptive names and house names or numbers that are associated with detail captured as part of an initial development are category A. Changes to names or numbers of existing individual houses are category B. An alteration to, or the addition or deletion of a descriptive name after the completion of the initial development stage is regarded as either category B or C change, depending upon the feature to which they are associated.