Changes from the previous edition of the ASGS

Overall, the Main Structure and Greater Capital City Statistical Areas (GCCSAs) provides high stability and good statistical comparability to ASGS 2016. Changes to Mesh Blocks, Statistical Areas Level 1 (SA1s) and Statistical Areas Level 2 (SA2s) mainly reflect population growth, largely on the edge of urban areas. In this edition there are no major changes to Statistical Areas Level 3 (SA3s), Statistical Areas Level 4 (SA4s), or GCCSAs.

All boundaries have been aligned with updated state and territory borders. Figure 2 shows an example of this type of change. There may also be other alignment changes to align with source data. These are very minor differences in cartographic representations to the ASGS boundaries and are not considered significant.

Alignment shifts for state and territory borders will be evident in area correspondences between ASGS Edition 3 and previous ASGS editions. However, most population based correspondences will not be affected as alignment has not affected any dwellings.

When analysing population data, ASGS Edition 3 can be successfully compared to previous editions of the ASGS for time series. There may be some cases, for example when using environmental data, where alignment changes will need to be considered.

Alterations to Mesh Blocks, SA1s and SA2s are made, primarily through splitting areas, to mirror changes occurring on the ground, such as new housing developments or altered transport infrastructure. These changes reflect recent population growth, and allow users to access meaningful statistics on communities of interest. The resulting net increase in numbers of Mesh Blocks, SA1s and SA2s is shown below.

The number of both Mesh Blocks and SA1s has increased, by 2.8% and 7.5% respectively. A relatively small number have changed; 1% of Mesh Blocks and 4% of SA1s changed since ASGS Edition 2 (2016), as shown in Figure 3. This very small amount of change is mainly due to splitting large areas in growth areas into two or more smaller areas.

Changes to SA2s are similar, with an increase of 7% for ASGS Edition 3. Only 8% of 2016 SA2s changed as shown in Figure 2. These changes were made to improve data accessibility and reflect high growth, particularly in some inner city SA2s which were previously close to the 25,000 person threshold.

The only changes to the boundaries for SA3s, SA4s and GCCSAs are minor alignment changes. A net increase of 1 for SA3s, SA4s and GCCSAs is due to the creation of a new Outside Australia special purpose code.

The boundaries for a region have not changed unless they no longer met the design criteria.

The following principles apply to Main Structure and GCCSA design:

• Where possible, changes are accommodated by simple splits of existing regions.
• Where a simple split is not possible, they are based on merges and redistribution of whole regions from the next level down in the hierarchy.
• Regions are designed with a view to them remaining stable.
• Minor boundary alignment changes are made to maintain alignment to the underlying State and Territory boundaries, and source data for physical infrastructure and physical geography.

In accordance with these principles most of the change in ASGS Edition 3 is the result of simple splits. Figures 4a and 4b show an example of one large Mesh Block that was split into 176 smaller Mesh Blocks. This kind of design is typical for growth areas on the edge of large cities. Figures 5a and 5b show a similar design process where two large SA2s have been split into 6 smaller SA2s.

Merges were minimised in ASGS Edition 3. Where necessary, boundaries were merged to avoid cutting through existing infrastructure or a new growth area. Figures 6a and 6b show an example of two Mesh Blocks that have been merged together to ensure two halves of a showground can be address coded more accurately.

In some circumstances, simple splits and merges are not enough to account for growth and change on the ground. Where 2016 boundaries had to be both merged and split, areas are considered ‘redesigned’. This typically occurs in high growth areas where old features on the ground have been replaced by new development.

Figures 7a and 7b show an example of SA1 redesign on the edge of Caloundra on the Sunshine Coast. The 2016 SA1 boundary followed an old suburb boundary which has since been revised to accommodate new housing developments. The original areas were merged and then split into new SA1s. Redesigning boundaries in this way has minimal effect on the comparability of data over time as in previous editions of the ASGS, growth areas generally contained little or no population.

Alignment refers to small area changes that do not affect population. This type of change will be evident in area based correspondences between ASGS Edition 3 and other ASGS editions, but will not affect population based correspondences. Unlike other boundary changes, alignment does not trigger a code change.

In this edition the most significant alignment occurred along state and territory borders. All Mesh Blocks next to state borders were aligned to the official state land borders released by Geoscience Australia in 2020. These official state land borders are endorsed by the Surveyors General of each state and territory, the Spatial Information Council (ANZLIC) and the Intergovernmental Committee on Surveying and Mapping (ICSM). These changes will help ensure geospatial comparability to other State and Federal Government datasets. Future updates to state borders and the coastline, as agreed by the Surveyors General, ANZLIC and ICSM, will be adopted where applicable in future editions of the ASGS.

The codes and names associated with statistical areas change when an area is split, merged, or redesigned.

Changes in higher level statistical areas also result in code changes to the lower level regions contained within, except for Mesh Blocks as these are the building blocks. The smaller area may also be split, merged, redesigned, or may remain unchanged. This is due to the hierarchical coding system.

Alignment changes do not result in code or name changes at any level.

For more information on the ASGS code changes please refer to the tables below in the list of changes section. 

The ABS provides several resources to help users understand changes to boundaries and codes, and to help them manage the transformation of data across different ASGS editions and other geographies. These resources include ABS Maps, various correspondences and the list of changes section. 

In ASGS Edition 3, change flags have been included on all Main Structure and Greater Capital City Statistical boundaries as an attribute. This attribute informs users whether an area has changed since ASGS 2016 and what the nature of that change is.