OS MasterMap revision policy

This is our policy for updating large-scale data. The product most directly affected is OS MasterMap Topography Layer.

OS MasterMap Topography Layer

OS MasterMap background

As the national mapping service of Great Britain, Ordnance Survey maintains around 234,000 km² of topographic information, ranging from dense urban conurbations to mountain and moorland areas. We want you to benefit from the most up-to-date mapping, therefore it's essential we regularly update our data.

We constantly strive to improve the quality, accuracy and content of our products. We value the feedback 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.

  1. Continuous revision
    Undertaken for those features of most importance to the majority of customers – mainly built development such as new houses and roads. We aim to capture these features within six months of construction being completed on the ground.

  2. Cyclic revision
    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.

How we prioritise revision activity

Under the current revision policy, when capturing new detail our priorities 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 below.

All designated prestige sites are captured before they are open to the public or the official unveiling.

All category A and associated change after the initial development on prestige sites is captured as soon as economically possible and not exceeding three months from completion.

Category B change is captured when directly associated with either a prestige site or category A change.

Category C change is captured when directly associated with either a prestige site, or with category A or category B change.

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

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

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.

NOTE: This covers the general definition of a site within OSMasterMap not the features within OSMasterMap Topography Layer-Sites product.

Criteria of categories of change

Read the background and criteria of categories of change.

Prestige sites are new sites which meet the following criteria:

Category A change criteria is defined as follows:

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

The following are typical examples:

Category C change criteria is defined as follows:

Further details of categories of change

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

Residential housing and associated features fall into three categories:

Non-residential categories are defined as follows:

Linear features are defined as follows:

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.

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.

All new, altered or deleted proper names, with the exception of house names or numbers, are category A.

Related links

  • OS MasterMap Topography Layer support

    Support for OS MasterMap Topography Layer including specifications, user guides, release notes, and other useful documents.

  • OS MasterMap updates

    Get the latest refresh dates for OS MasterMap Topography Layer data. Find past publication dates with their accompanying release note.

  • Open Identifiers policy

    We encourage the widest possible use and sharing of UPRNs, through our Open Identifiers policy.