THE PROPOSED MAIN STRUCTURE
The proposed Main Structure will be a nested hierarchy of four geographical units between mesh block and state. Each level consists of one or more units from the level immediately below it. The levels of the classification are referred to as SA 1 to 4. All levels of the classification cover the whole of Australia without gaps or overlaps and nest within state boundaries.
CONCEPTUAL BASIS OF THE MAIN STRUCTURE
Pivotal to the Main Structure is the idea of the functional zone of a centre. This is the area from which people come to a centre for employment, to buy goods, access services and socialise. In regional areas the centre will be a town or city. In urban areas the centre will be an urban hub - generally a major shopping area with a nearby transport hub and its surrounding commercial area and possibly government offices. This idea is reflected in all the levels of this structure. The functional zone concept cannot be strictly applied to all areas. It is impossible to create a simple nested hierarchy of areas using the concept of functional zones. Furthermore, natural or man made barriers and corridors create distinct regions which the structure should also reflect, as this is the way people perceive themselves and the basis on which government and commercial goods and services are delivered.
The proposal also attempts to maximise the amount of data available at each level of the classification while applying the functional zone concept. For example the minimum population of the SA2 level of the classification will be set at 3,000 people as this is the minimum population for which ERP can be reliably generated.
Defining the functional zones will involve the analysis of Place of Work data, the transport network and any data that may be available on where people access goods and services. In practice it will involve considerable feedback from state and local stakeholders.
LEVELS OF THE PROPOSED MAIN STRUCTURE
Note that the accompanying maps are for illustrative purposes only. The final boundaries may be quite different as their definition will involve intensive data analysis and consultation with stakeholders.
SA1: CENSUS DISSEMINATION UNIT
The SA1 will replace the current CD as an output unit for the dissemination of Census data. The ABS will research the optimum population size for the SA1 for the release of Census data and they will be built around this. The optimum is likely to be around 400 people.
SA1s will be as nearly circular as possible to facilitate approximating larger regions. They will be internally linked by road, to avoid arbitrarily combining unrelated populations.
Small rural and indigenous communities will be bounded by SA1s where practical. Gazetted rural localities will be a consideration in their design and will be reflected as closely as possible in the SA1s.
Where appropriate zero population mesh blocks may be amalgamated into zero population SA1s.
SA2: SUBURBS, REGIONAL TOWNS AND LOCAL REGIONS
The SA2 is the level of the structure for which ERP and other ABS data will become generally available. They have a lower population limit of 3,000 as this is the smallest population for which reasonably accurate ERP data can be derived. Over the whole of Australia they will have an average population of 10,000 and a maximum of 25,000.
In regional areas they will represent the functional zones of a towns with a population between 3,000 and 19,999. They will have a maximum population of around 20,000 and the average will be about 7,000. Where practical they will be made up of whole gazetted rural localities.
In urban areas SA2s will be built around suburbs, combinations of small suburbs or parts of very large suburbs. They will probably have a greater population than regional SA2s.
Where functional areas cannot be reasonably identified (likely in remote or very remote areas) they will represent an identifiable local region.
Where appropriate, zero population SA1s will be aggregated into zero population SA2s. The likely circumstances include large industrial or commercial areas in urban areas, such as airports, and large areas of unsettled land in regional and remote areas such as National Parks.
Illustrative SA2 Boundaries for Central Brisbane
Illustrative SA2 Boundaries in North Central Victoria
SA3: FUNCTIONAL ZONES OF MAJOR URBAN HUBS, REGIONAL CITIES AND MEDIUM SIZED REGIONS
The SA3 level aims to represent moderately large sized regions. In regional areas those dominated by the largest regional centres with a population between 20,000 and 99,999 people. In urban areas those dominated by large urban retail service and employment hubs. In areas where such functional zones cannot be reasonably identified they will represent medium sized regions.
Consideration will be given into incorporating state planning regions in this level.
The population of SA3s will range from about 30,000 to 130,000.
Illustrative SA3 Boundaries in Regional South Australia
Illustrative SA3 Boundaries in Canberra
SA4: FUNCTIONAL ZONES OF THE LARGEST URBAN HUBS, MAJOR CITIES AND LARGE REGIONS
The SA4 level is intended to identify the largest regions within each State and Territory. In regional areas they will represent either large identifiable regions or the functional zones of regional cities with a population in excess of 100,000.
In Urban Areas they will represent the functional zones of the largest urban hubs within Sydney, Melbourne, Brisbane, Adelaide and Perth.
SA4s are intended to be suitable for the publication of survey data, including Labour Force. Labour markets will be a consideration in their design. Their population will range from about 250,000 to 500,000.
Illustrative SA4 Boundaries in Sydney
Illustrative SA4 Boundaries in South-west WA