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OS MasterMap Topography Layer (Sites) support

Sites are now part of the Topography Layer.

What are the main components of Sites?

Sites consist of three features: the functional site extent, access points and routing points. These features reference each other and other layers of OS MasterMap, as well as other Ordnance Survey products such as AddressBase. Detailed attribution is also provided for all the features within the product.

I can’t find a particular site. Will this be captured in future releases of the product?

Ordnance Survey has taken the decision to develop Sites using an iterative development process; thus dividing the capture of the product into two phases. During the initial capture, a decision was taken to focus capture on certain themes. More information about the sites that have been provided can be found in the user guide. Sites that are part of the initial release themes will be updated using our existing integrated capture process to ensure completeness in line with our published quality levels.

What other themes may be captured in the future?

Ordnance Survey has been in consultation with various customers and partners regarding the features that they would like to see in future product enhancements, and we are interested in hearing more from our customers regarding the features that you would like captured.

If you would like to share your views regarding this, please contact us at customerservices@os.uk

Can I use Sites with other Ordnance Survey datasets?

Yes, Sites can be used with any other Ordnance Survey data.

I require the definitive or legal extent of a site; will this product provide this?

Currently, Sites does not indicate legal extent; rather, it provides the extent of usage or function, and is created using intelligence sourced from OS MasterMap Topography Layer.

How often is Sites updated?

Sites is created using intelligence sourced from OS MasterMap Topography Layer. OS MasterMap datasets are created from a single master dataset, which is refreshed regularly. Currently, the refresh period for OS MasterMap Topography Layer supply is every six weeks.

The Sites Layer creation process involves taking a view/snapshot of the current OS MasterMap Topography Layer and OS MasterMap Imagery Layer as a base for the definition and capture of the extents and access points. Initially, Sites updates will be supplied twice a year, with a roadmap to increase to a either quarterly or six-weekly refresh in the future.

What are the advantages of the TOID® as a referencing system?

Each and every feature within Sites has the TOID as a unique reference. This makes it possible to identify any single feature within the dataset without any ambiguity. Current referencing systems, such as coordinates and addresses, are subject to interpretation between users.

This creates fuzzy matching issues between organisations wanting to exchange data; for example, will the building ‘St James School’ be picked up in another system where it is spelt ‘St James' School’?

The TOIDs will stay the same throughout the life cycle of each feature. In other words, if a feature changes, the TOID will stay the same as long as it is deemed to be the same feature; for example, a hospital having an extension built is still the same hospital and fulfils the same purpose. This provides a continuity of reference even though a feature may undergo changes.

This makes the TOID a robust referencing system that customers can use alongside, or instead of, their own referencing systems and can link to their own information about the feature.

Having unique references is essential to making the most out of storing data within a relational database management system, as these rely on unique referencing to be able to store, sort, manage, query and retrieve data efficiently.

What scale is OS MasterMap Sites Layer data?

The source data for Sites is captured and designed for display at 1:1250, 1:2500 and 1:10 000 scales in urban, rural and mountain/moorland areas respectively. In a geographical information system (GIS) or a web map, Sites can be viewed over a considerable range of scales.

The most scale-sensitive feature types are access and routing points; they are fixed in size and rapidly become less clear at smaller display scales (that is, when zoomed out). OS MasterMap Sites Layer is also suitable for use in non–cartographic applications where the concept of scale is less applicable.

In which format is Sites delivered?

Sites is currently supplied in GML 3.2.1, which is INSPIRE compliant.

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