G-NAF links official to ‘in-use’ addresses
Addresses are a cultural artefact, created from language rather than rules and legislation
It may surprise you to know that governments do not control the creation of all addresses.
In fact, addresses are simply an idea: an artefact of human communication; a shared syntax for referring to location; an agreement between our institutions regarding names, numbers, and invisible administrative boundaries.
Given its human origins, we must understand that an address is transient and subjective – and may or may not be accepted by all in the community all of the time. Social and cultural preferences come into play and people may ‘interpret’ their address if they don’t know or like the official reference. The consistent use of an unofficial address will see it appear in multiple government and business databases. This address then becomes a data type that lacks the mathematical consistency required for rigorous matching and analysis.
Every week in Australia, thousands of new addresses are captured by multiple organisations and stored in a variety of formats; generating a multitude of raw address datasets that vary widely in content, quality and accuracy.
Because of these reasons, one of the most valuable features of G-NAF is the linkages created between ‘official’ and ‘in-use’ addresses. Over the years, we have developed increasingly sophisticated processes to identify different labels that a site is known as, increasing the usability of G-NAF and reinforcing its position as the authoritative geocoded address file.
The following graphs show the number of alias relationships we have created in G-NAF in the last few years alone. We create aliases at three levels:
- address e.g. for ranged addresses we make 5 Beresford Road alias to 5-7 Beresford Road
- street e.g. long streets where the street name changes from one locality to the next
- locality e.g. names areas are known for are linked to the actual suburb name such as Manuka and Kingston in Canberra
The fourth graph shown below relates to secondary aliases. Complex sites, such as an apartment building, have a primary address and secondary addresses. The primary address is usually the street address, for example, PSMA’s is 113 Canberra Avenue. Additionally, our office is located in the second floor and the building manager refers to our office as Unit 6. Therefore the secondary address is Unit 6 Level 2 113 Canberra Avenue.
In addition to creating linkages between addresses, we also look to pinpoint the location of every address.
Every address in G-NAF is allocated at least one a geocode (latitude and longitude values). Geocodes are allocated at three levels:
- property – pinpoint the location of the property parcel
- street – pinpoint midway of the length of the street
- locality – pinpoint the centre of the locality polygon
The graph below shows the spread of each type of geocode across the jurisdictions. We are progressively moving towards having a property level geocode for each G-NAF address.
This final graph shows confidence level of G-NAF addresses. There are three types of contributors to G-NAF, when one contributor supplies an address, it is allocated a confidence level of 0. When two contributors supply an address, it is allocated a confidence of 1, and when all contributor types supply an address, it is allocated a confidence of 2. Our aim to is to keep driving up the number of confidence 2 addresses as this provides G-NAF users with certainty around the validity of the address.