UK Constituencies

UK Parliamentary Constituencies

ONS Open Geography Portal — ArcGIS FeatureServer for Westminster parliamentary constituency boundaries (July 2024, 650 constituencies).

Data Model

• Constituency — A Westminster parliamentary constituency with boundary geometry and metadata.
• PCON24CD — ONS constituency code (e.g. "E14001063" for Aldershot). Prefix: E=England, W=Wales, S=Scotland, N=Northern Ireland.
• PCON24NM — Constituency name in English.
• PCON24NMW — Constituency name in Welsh (blank for non-Welsh constituencies).
• BNG_E / BNG_N — British National Grid easting/northing of the centroid.
• LONG / LAT — WGS84 longitude/latitude of the centroid.
• Shape__Area — Boundary area in square metres.
• Shape__Length — Boundary perimeter in metres.

Key Patterns

• ArcGIS FeatureServer query endpoint with where, outFields, f=json parameters.
• Name search uses SQL LIKE: PCON24NM LIKE '%Oxford%' (case-insensitive on server).
• Code lookup uses exact match: PCON24CD='E14001063'.
• returnGeometry=false omits polygon coordinates (much smaller response).
• resultRecordCount limits results (max 2000 per request).

Gotchas

• No pagination token: Use resultOffset for pagination.
• Geometry is large: Always set returnGeometry=false unless polygon data is specifically needed.
• Welsh names: PCON24NMW is blank (single space) for non-Welsh constituencies.
• July 2024 boundaries: These are the current boundaries after the 2023 boundary review.