Converting Data to the ASGS
 

CONVERTING DATA TO THE AUSTRALIAN STATISTICAL GEOGRAPHY STANDARD (ASGS)

Converting data to the Australian Statistical Geography Standard

Address Coding

Correspondences

Allocation tables


Converting data to the Australian Statistical Geography Standard

This page provides users with basic advice on how to associate data with a geospatial attribute such as an address, part address or other geographic identifier, to geographic regions in the Australian Statistical Geography Standard (ASGS).

There are two main options for converting data to geographic regions in the ASGS: address coding and geographic correspondences.

Address Geocoding

Address geocoding is the process of associating an address with a location on the Earth’s surface. In a statistical agency it is common for address geocoding to be used to allow statistics to be aggregated to both statistical areas (e.g. Urban Centres) and administrative areas (e.g. Local Government Areas).

The ABS uses address geocoding, in combination with the Australian Statistical Geography Standard (ASGS), to collect, process and disseminate statistics for a range of different statistical and administrative areas.

In Australia, a physical address is a textual description of an addressable object (e.g. dwelling, mail delivery point, etc). The hierarchical nature of an address enables a location to be derived from different components of an address. Usefully, when used together the combination of Locality, State and Postcode can effectively code data to Statistical Area level 2 and above in the ASGS. The ABS provides a number of Coding Indexes that support this process which are available through data.gov.au.

If the complete street address is available, it is possible to code these addresses to smaller areas within the ASGS, using commercially available address matching and coding software. This software associates a latitude and longitude coordinate with each address using the Geocoded National Address File (G-NAF). The coordinate can be used to locate the address with sufficient accuracy and precision to associate the address with any statistical area defined by the ASGS.

For more information on address coding and coding indexes please refer to the ABS publication: Information Paper: Converting Data to the Australian Statistical Geography Standard, 2012 (cat. no. 1216.0.55.004).

Addressing Standards

The current addressing standard for Australia and New Zealand is Geographic Information - Rural and Urban Addressing (AS/NZS 4819:2011). Guidance on the collection and storage of address information specified by AS/NZ 4819 is provided by Australian Standard Interchange of client information (AS 4590.1:2017).

These addressing standards provide requirements and guidelines that authorities can use in assigning addresses, naming roads and localities, and recording and mapping the related information. They outline the various elements of an address and provide guidelines for their storage and use.

Correspondences

Correspondences can be used where data is associated with a geographic area, rather than more detailed address information.

Correspondences mathematically reassign data from one geographic region to another. As most ABS data relates to population, standard correspondences have a weighting calculated based on the location of the population, and uses population data modelled to residential address locations. Correspondences based on land area or other variables are available on request.

Correspondences are less reliable than address coding and the results can be misleading in some circumstances. This is because they are based on the assumption that the data to be converted is distributed across the original regions in the same way as the correspondence's weighting. This assumption may or may not be reasonable depending on the circumstance. Correspondences, therefore, need to be used with a great deal of care.

Correspondences are more accurate where the regions on which the data was originally aggregated are smaller than the new regions. For example, corresponding data from Census Local Government Areas (LGAs) to SA4s is generally accurate because most LGAs are smaller than SA4s and most LGAs are completely or largely contained within a single SA4.

A Quality Indicator is provided on each correspondence generated by the ABS. This indicator provides the user with a basic indication of the resulting data accuracy as a result of converting the data between regions. This is based on the geographic overlap between the geographic regions and the underlying population. It is recommended that this indicator is considered before working with every correspondence.

For more information about correspondences, please refer to the ABS publication: Information Paper: Converting Data to the Australian Statistical Geography Standard, 2012 (cat. no. 1216.0.55.004).

Standard correspondences, coding indexes and allocation tables are available through the following resources:

    • For a full collection of correspondences and coding indexes on both ASGC and ASGS geographic regions see data.gov.au. Search for; ‘ABS’, the year, and ‘correspondences or coding indexes’
    • For correspondences and allocation tables relating to specific ASGS boundaries see the downloads tab of the relevant ASGS Publications
    • For a selection of correspondences developed to assist users in converting data from the ASGC to the 2011 ASGS see the ASGS Correspondences Publication
    • For a selection of correspondences relating to the ASGC see the ASGC Correspondences Publication
    • For custom correspondence requests please contact us

Allocation tables

Allocation tables, or hierarchy tables, are often included in the term correspondence. These reflect the situation where one set of regions is precisely nested within a second. For example, by definition, one or more whole Statistical Areas Level 1 (SA1) make up a Statistical Area Level 2 (SA2). Allocations only contain 1 to 1 or many to 1 relationships and are straightforward to use as they are simple aggregations.

Allocation tables are available as .csv files under the ‘Downloads’ tab of each ASGS Publication.