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NGD Structures Theme describes vegetated field boundaries and manmade construction features in Great Britain which are not buildings. It comprises the OS NGD Structure Features Collection, which in turn has five feature types:

- Compound Structure: polygon features representing manmade constructions built for a specific purpose (e.g. bridges, dams, aqueducts, tunnels). Also includes descriptions for networks passing over or under bridges where identified and provides embedded height attribution enabling users to create simple height models.

- Structure: polygon features representing manmade constructions that are not buildings (e.g. telecoms masts, chimneys, cranes), including absolute and relative height information and whether the feature is considered ‘historic’ (before AD1714 unless deemed of national importance). Also provides a cross-reference table of OS land cover classification to EUNIS and BAP Broad Habitats (EUNIS; European Nature Information System and BAP; UK Biodiversity Action Plan (BAP) mapping

- Structure Line: line features representing linear, freestanding, manmade constructions that are not buildings and not wide enough to capture as a structure (e.g. gate, barrier, pipeline, sea wall), including features of historic and/or national importance.

- Structure Point: point features representing freestanding manmade constructions that are not buildings and which are less than 4 metres square, but of sufficient interest (e.g. statues, telephone call boxes, post boxes) and features of historic and/or national importance.

  - Field Boundary: line features located in rural and moorland areas (predominately) representing a field boundary adjacent to, or contained within, areas of agricultural land, trees, rough grassland, or heath. Also includes features adjacent to land in the Rural Payment Agency's Rural Land Register situated within urban areas in England. Field Boundary features replicate all, or part of, the underlying OS NGD Structure (Built Obstruction) Line and are classified as Tree Canopy, Wooded Strip, Hedge, Wall, Other, or Unknown (in hierarchy order).

NGD Structures Theme provides unique identifiers, including Ordnance Survey ID (OSID) and Topographic identifier (TOID) for data linking and analysis.