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From Census Settlements to Built Up Areas

CSO statistical publication, , 11am
Census Results 2022 Branding

 

Introduction

A review of the geographical boundaries is undertaken by the Central Statistics Office (CSO) after each Census, i.e. every five years. As part of the most recent review which took place after Census 2016, it was decided to broaden the examination of urban boundaries to include key stakeholders and a working group was formed in 2019 between the CSO, the Department of Housing, Local Government and Heritage (DHLGH), and Ordnance Survey Ireland (OSi, now Tailte √Čireann). The three organisations agreed to examine urban boundaries in Ireland, and a formal methodology was developed and agreed.

The outcome of this working group was the creation of a new urban geography called Built Up Areas (BUAs) which has been used to produce Census 2022 data for urban areas. The BUAs were developed from clusters of urban development and their boundaries reflect land use for urban purposes. In order to remove the risk of statistical disclosure, the BUAs are comprised in their entirety of whole Statistical Small Areas, which were subject to a separate review following the last census. The identification of BUAs and the extent of their boundaries were generated using an objective algorithm run across the State based on building clustering and urban land use.

As BUAs have been defined differently to the Settlements used in Census 2016, it is not possible to compare them directly. BUAs and Census 2016 Settlements differ primarily in that BUAs are based upon a land-use definition whereas Settlements were based more on population concentration. This entails that there was more green space in Settlement footprints than is the case for BUAs. The BUAs will be the primary urban geography for the Census 2022 dissemination programme and will be used in the thematic publications and other statistical products. Total population from Census 2022 for the 2016 Settlements is available as part of Profile 1, but this is provided for comparison purposes only. No attribute data will be published for the Settlements as this would create disclosure risk.

Background

Across the history of censuses in Ireland, towns have been defined in different ways. For the censuses of 1926 to 1951, a census town was defined simply as a cluster of 20 or more houses and the boundaries of towns were left to the discretion of the individual enumerator concerned. As part of the general review of towns for the 1956 census, the boundaries for the census towns were drawn up in consultation with the various Local Authorities applying uniform principles in all areas of the country. Following this, the definition of a census town was changed at the 1956 census, from 20 houses to 20 occupied houses; this definition was also applied at the 1961 and 1966 censuses.

From 1971 to 2006, Census towns were defined as a cluster of 50 or more occupied dwellings where, within a radius of 800 metres, there was a nucleus of 30 occupied dwellings (on both sides of a road, or 20 on one side of a road), along with a clearly defined urban centre (e.g. a shop, a school, a place of worship or a community centre). Census town boundaries were extended over time where there was an occupied dwelling within 200 metres of the existing boundary.

To avoid the agglomeration of adjacent towns caused by the inclusion of low-density one-off dwellings on the approach routes to towns, the 2011 criteria were tightened, in line with UN criteria.

In Census 2016, a new Census town or Settlement was defined as a minimum of 50 occupied dwellings, with a maximum distance between any dwelling and the building closest to it of 100 metres, accompanied by evidence of an urban centre (shop, school etc). The proximity criteria for extending existing 2006 census town boundaries was also amended to include all occupied dwellings within 100 metres of an existing building. Other information based on OSi mapping and orthogonal photography was also taken into account when extending boundaries. Boundary extensions were generally made to include the land parcel on which a dwelling was built or using other physical features such as roads, paths etc.

The CSO also previously published census data for legal town boundaries. The 80 legal towns were abolished as part of the Local Government Reform Act 2014.

Development of BUAs for Census 2022

The development of the BUAs is an example of best practice across civil institutions, maximising collaboration and, in so doing, providing a better outcome for both the citizens, departments and agencies using CSO data for decision making. For Census 2022, using the BUAs, urban areas are defined objectively, using GIS technology and a methodology agreed by an inter-governmental group. 

More information on BUAs, including the rationale and the methodology for developing them can be found in this section.

For further details, please refer to the Census 2022 Urban Settlement Boundaries and Built Up Areas FAQ.

A Technical Briefing video presentation is also available.

A Technical Paper of detailed methodology is available, courtesy of Tailte √Čireann.


The Shapefiles are available on the Ordnance Survey Ireland (now part of Tailte √Čireann) website.

  • Introduction
  • Frequently Asked Questions
  • Presentation
  • Technical Paper