The functional urban area (FUA) classification identifies small urban areas and rural areas that are integrated with larger urban areas to create FUAs.Workplace address and usual residence address data from the 2018 Census of Population and Dwellings were used to identify satellite urban areas (1,000–4,999 residents), and rural statistical area 1s (SA1s) from which at least 40 percent of workers commuted to urban areas with more than 5,000 residents.An FUA includes Urban rural (UR) 2018 urban areas, rural settlements and rural SA1s where there is: an urban core, one or more secondary urban cores, one or more satellite urban areas, and rural hinterland (rural settlements or rural SA1s).The FUA indicator (IFUA) classifies UR2018 urban areas and rural SA1s according to their character within their FUA, e.g. urban core, satellite urban area.The 53 FUAs are classified by population size. The urban core’s population rather than the entire FUA’s population is used to maintain consistency between the descriptions of UR2018 urban area and FUA type (TFUA).FUAs that have more than 100,000 residents living in their urban core are known as metropolitan areas, while smaller FUAs are divided into large (core population 30,000–99,999), medium (core population 10,000–29,999), and small regional centres (core population 5,000–9,999).The Greymouth urban area population is less than 10,000 but is classified as a medium regional centre, consistent with its treatment as a medium urban area in the Urban accessibility (UA) 2018 classification.
The FUA classification is applied at the statistical area 1 (SA1) geographic level. The geography also uses the UR2018 and IUR2018 classifications to define urban areas within FUAs. Rural settlements are not separately identified by those which are included in an FUA along with other rural SA1s are classified as hinterland.