OSNI Open Data: 50,000 Townland Boundaries for Ireland

Mid-scale vector polygon data showing approximately 50,000 townland boundaries, an ancient land measurement system unique to Ireland. The dataset was derived from the Ordnance Survey Northern Ireland (OSNI) Largescale database, topologically cleansed, and published for OpenData by the Government Digital Service. The temporal coverage and last update date are unknown.

Use Cases

• Mapping historical land divisions based on the townland polygon boundaries.
• Conducting genealogical research based on the ancient land measurement system described.
• Performing geospatial analysis on small-scale administrative areas based on the vector polygon data.
• Integrating historical boundary data into modern GIS applications based on the seamless, topologically cleansed dataset.

Strengths

• Approximately 50,000 boundaries provide a detailed view of land divisions.
• Data is topologically cleansed to create a seamless polygon dataset.
• Derived from the authoritative OSNI Largescale database.
• Available in multiple geospatial formats including GeoJSON and ESRI Shapefile.

Limitations

• Row count and dataset size are unknown, which may limit suitability assessment.
• Column-level documentation is absent; field semantics must be inferred after download.
• Last update date is unknown; freshness unverified.

Provenance

Source

Ordnance Survey Northern Ireland (OSNI) Largescale database.

Collection Method

Derived, topologically cleansed, and attributed from source database.

Time Range

unknown

Freshness

unknown

Geography

Ireland (Northern Ireland and likely the Republic of Ireland, given the mention of townlands as an Irish system).