Australian urban centre
The six-digit ASGS code for an Australian Urban Centre or Locality, including state and population-class identifiers.
An Urban Centre or Locality is a statistical urban footprint defined using population density and urban development criteria, with a population of 200 or more. It is not an administrative unit and does not line up with a council area or a gazetted suburb.
Six digits, and hierarchical rather than flat. The first digit is the state or territory. The second is the Section of State: 0 Major Urban, 1 Other Urban, 2 Bounded Locality, 3 Rural Balance. The third completes the Section of State Range, a population band within that section. The last three are the center itself. Adelaide is 401001: South Australia, Major Urban, the one-million-and-over band, center 001.
Two of the six digits encode population classes, so reclassification can change a center's code even when the place remains. The final three-digit identifier is unique only with the preceding state, Section of State, and Section of State Range identifiers; those prefixes are already included in the full six-digit code. Codes must be read with their ASGS edition.