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OS MasterMap Sites Layer Technical Specification
This technical specification provides detailed technical information about OS MasterMap Sites Layer . It is targeted at technical users and software developers.
Last updated
This technical specification provides detailed technical information about OS MasterMap Sites Layer . It is targeted at technical users and software developers.
Last updated
OS MasterMap Sites Layer provides a nationally consistent polygonised representation of areas or extents of particular function or activity, and which are attributed to best reflect that function. It also contains access points and routing points to navigate in and out of the captured sites. These access points reference the OS MasterMap Highways Network product for easy interoperability between the two products.
All the source data used in the creation of OS MasterMap Topography Layer contains insight about a site’s function or purpose, and the Sites Layer is intended to not only make this information available, but to enhance its analytical capabilities. OS MasterMap Sites Layer features are a representation of the boundary of real-world facilities, such as a school, where the site consists of more than an addressable main building.
The features are derived from Ordnance Survey’s highly detailed core data, and therefore the classification and grouping of features is dependent upon the source data capture specification. The product contains three feature types:
Functional site polygons (FunctionalSite)
Functional site access points (AccessPoint)
Functional site routing points (RoutingPoint)
These three types are defined in this document in INSPIRE-compatible terms, with reference to the INSPIRE data specifications for facilities. The attribute naming convention also takes into consideration consistency with attribute names in other OS MasterMap layers and products.
It is important to note that the attribute naming has been carried over from the former OS MasterMap Integrated Transport Network (ITN) Layer. This has been done to minimise the impact of the implementation of OS MasterMap Highways Network.
The components that make up these features, and their relationships are shown in the product’s logical model diagram below.
A main premise of the OS MasterMap product family is that layers of the differing products can be integrated with each other.
Layers are integrated by the sharing of common coordinate systems and contextual identifiers. Except for the Imagery Layer, the TOID feature identification attribute provides a unique feature-level reference that can be used to identify and track a feature between related OS MasterMap layers. For example, in OS MasterMap Sites Layer, there is an explicit link between the access point feature and the OS MasterMap Highways Network Layer road node that is closest to it.
The 'accessMechanism', 'accessDirection', 'accessUseRestriction', 'dateTimeQualifier', 'heightQualifier', 'widthQualifier', 'weightQualifier', 'lengthQualifier' and 'natureOfAccess' attribute values are currently not populated in OS MasterMap Sites Layer.
The OS MasterMap Sites Layer product is supplied in three different formats:
Geography Markup Language (GML) version 3.2.1
GeoPackage
Vector tiles (MBTiles)
The OS MasterMap Sites Layer technical specification contains the following sections:
The Geography Markup Language (GML) and GeoPackage formats use the British National Grid (BNG) spatial reference system. BNG uses the OSGB36 geodetic datum and a single Transverse Mercator projection for the whole of Great Britain. Positions on this projection are described using easting and northing coordinates in units of metres.
Vector tile format is supplied in Web Mercator projection (EPSG:3857). Web Mercator projection uses WGS84 geodetic datum to render the vector tiles.
A Guide to Coordinate Systems in Great Britain provides a comprehensive tutorial on the topic.
A general introductory guide to BNG is provided at:
