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Ask Fuzzy: Finding the middle ground

Question: Where is the centre of Australia?

According to Geoscience Australia, there is no centre of Australia. This is because there are many complex but equally valid methods that can determine possible centres of a large, irregularly shaped area – especially one that is curved by the Earth's surface. Let's compare these methods and their results.

The centre of gravity method is based on weight. Imagine you have a perfect cut-out of Australia with thousands of tiny weights distributed along the coast. Thecentre is the place where thecut-out is balanced on a pin. The result with this method is:

23° 07' 00" south, 132° 08' 00" east.

The Royal Geographical Society of Australasia's method is similar to the centre of gravity method, but is calculated using thousands of points located on the high water mark of Australia's coastline. This point, known as the Lambert Gravitational Centre, was named after DrBruce Lambert, a former director of the Division of National Mapping, and is:

25° 36' 36.4" south, 134° 21' 17.3" east.

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The furthest point from the coastline method involves placinga circle over the map of Australia that is large enough to touch the coastline at three points. The centre of that circle isconsidered the centre of Australia. The result here is:

23° 02' 00" south, 132° 10' 00" east.

As its name implies, the median point method is calculated as the midpoint between the extremes of latitude and longitude of the continent, resulting in:   25°56' 49.3" south, 133° 12' 34.7" east.

Finally, Johnston Geodetic Station was once the central reference point for all Australian surveys. This trigonometric survey landmark, situated about one kilometre north of Mt Cavenagh homestead, was built by officers of the Division of National Mapping in 1965. Its location is:

25° 56' 49.3" south, 133° 12 34.7" east.

Regardless of which method is used, the results all fall within an area that includes the town of Alice Springs and the MacDonnell Ranges, two icons of central Australia.

To learn about  Geoscience Australia and how it impacts your everyday life, go along to its open day on Sunday, August 21, 10am to 3pm, corner of Hindmarsh Drive and Jerrabomberra Avenue, Symonston.

Response by: Geoscience Australia

Brought to you by the Fuzzy Logic science show, 11am Sundays on 2XX 98.3FM. Send your questions to askfuzzy@zoho.com