An investigation, usually into the size and nature of a population, but occasionally into other things, such as traffic. A census tract, known in the UK as an enumeration district, is a small unit of area used in collecting, recording, and reporting census data. Census geography is the spatial organization of conducting a census and the geographical analysis and thematic mapping of census data (N. Castree, R. Kitchin, and A. Rogers 2013). In the UK, Census Output Areas are geographical areas consisting of about 125 households, with a population of about 300.
Census geography design is the delineation of appropriate geographical base units from which to create and use geography; see Vickers and Rees (2007) JR Statist. Soc. A 170, 2 and Rees and Martin in P. Rees et al., eds (2002). The UK Office of National Statistics (ONS) offers a range of 2011 Census geography products for England and Wales.
https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/137664/Census_geography.pdf For more detail on census output areas.