Functional site extent overview

A functional site is a geolocated polygon representing the extent encompassing features with a collective type of function or activity. The functional site is thematically attributed and accompanied by access points. All the source data used in the creation of the OS MasterMap Topography Layer contains information about a feature’s function or purpose. Much of this data has been exposed in the Functional Sites Layer as a means of enhancing its analytical functionality. Functional sites are a representation of an assembly of cartographic features that share a common function (such as a school). It could also be a contiguous collection of features; for example, ‘General Hospital’.

Functional sites are created using the base form and function attributes of topographic areas. Information, such as ownership is not included within those attributes and cannot be used to ascertain extent. Because of this, functional site extents should not be confused with, or applied as legal extents.

A functional site can have multiple functions, or they can share some topographical features with another functional site. Shared topographic features, such as a sports field shared by two schools, will have the field captured to both school functional sites. Should there be a sports club on the grounds, such as a football club, then the field will be captured to this as well.

Rules have been developed for defining the differing types of functional site based on their function and the Topographic features that are visible from aerial photography. These rules specify what area features will be included within a functional site and how the boundary extent of the site can be delineated.

For example, the figure below demonstrates the extent of a simple functional site using OS MasterMap Topography Layer area features to identify and capture its extent. This is done by assessing a group of features that appear within a recognisable obstructing boundary and assigning them to the same functional site. This is also ratified using stereo aerial imagery and investigation through Change Intelligence. In the example shown below, this methodology has been used to assign all the features within the fence to a common function, in this case, a gas hub.

Topographic representation of a site prior to functional site capture

Equivalent topographic representation with the functional site extent captured

Each functional site has its own unique TOID and will be maintained throughout its lifecycle including versioning, changes and updates to its component features and alterations to its extent should they be warranted (for instance if the site increases in size due to land purchase). In addition, private roads that are wholly contained within a functional site and support the function are included in the extent.

It is important to note that obscured and underground features are not captured. This is because the OS MasterMap Topography Layer is captured at ground level from what is visible by aerial photography. However, all above ground features will be captured as normal.

While typically a functional site will usually be a connecting collection of polygons from OS MasterMap Topography layer, it is also possible for the functional site to consist of one or more disparate extents. Some sites, such as university campuses, will be a collection of several functional site extents belonging to a single stakeholder. These will be captured as one or more functional sites depending on the distance between the captured extents.

The stakeholder name will be captured if it is clear and unambiguous and is obtained through investigation where possible. The primary use of the stakeholder attribute is to define extensive and widely dispersed sites that come under the control of a single stakeholder; for example, universities.

In instances where multiple stakeholders exist for a given site, they will be listed in alphabetical order in the Stakeholder 1 attribute. Each new stakeholder will be separated with ‘+’. The Stakeholder 1 attribute will continue to hold only one role. The Stakeholder 2 attribute and role should not be populated.

The attributes currently not populated have been greyed out in the attribute definitions table in the following section.