OS NGD Structures
Introduction to the theme
The OS National Geographic Database (NGD) Structures Theme contains structure features which are of manmade construction but are not buildings, such as clock towers, bridges, arches, and bandstands. Embedded height attribution is available for chimneys, roofed tanks and glasshouses, enabling users to create simple height models of these structures. Both manmade and vegetated field boundaries are regarded as Structures.
OS NGD structures data has been enriched with additional attribution, including the following:
Geometry change metadata
A Description attribute to provide a one-word or simple phrase description of a feature
Detailed land use classification
Detailed land cover classification
Capture specification to give details about the geography of the area a feature resides in (that is, urban, rural, or moorland)
Height and width values for Field Boundary features
Data structure
The OS NGD Structures Theme is made up of the Structure Features Collection, which in turn is comprised of five feature types: Compound Structure, Field Boundary, Structure, Structure Line and Structure Point.
Unique identifiers
With the exception of Compound Structure and Field Boundary features, two unique identifiers are provided with each feature within the OS NGD Structures Theme:
OSID (Ordnance Survey Identifier): The primary identifier and unique key for this theme.
TOID (Topographic Identifier): An additional secondary identifier which can aid further data linking. TOIDs are an optional attribute and therefore will not always be provided with every feature.
Compound Structure features do not have a TOID allocated to them; however, they do have an OSID allocated to them.
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