30-Mar-2005 -- There is no official centre of Australia, although the Lambert Gravitational Centre comes very close and is the one shown in the first picture. Over time several centres have been calculated using different methods, they are each quite legitimate, all close together and it would be interesting to have them all visited and photographed.

I am indebted to the very useful National Mapping Centre of Australia website for much of the explanation below of how the various centres of Australia are calculated. You can find out almost anything geographical about Australia at their excellent website at www.ga.gov.au

The search for the centre of Australia started very early after settlement. Numerous attempts where made to reach the centre of Australia by various explorers in a series of epic and highly dangerous expeditions. In November 1845 the explorer Charles Sturt said:

"Let any man lay the map of Australia before him, and regard the blank upon its surface, and then let me ask him if it would not be an honourable achievement to be the first to place foot at its centre?

Then, at the age of forty-nine and partially blind from his previous expeditions Sturt left his beloved wife Charlotte and started on a third and final expedition aimed straight at the heart of the continent. There, he believed he would find 'a large body of inland waters', so he equipped the expedition with a boat for sailing on this mythical sea. Instead, he discovered a sea of seemingly endless sand dunes, the Simpson Desert, and temperatures so extreme they shrivelled his supplies, prostrated his horses and burst his thermometer.

"I looked upon Central Australia as a legitimate field, to explore which no man had a greater claim than myself…" he said.

Although drought and extreme heat thwarted Sturt's attempts one of his party, John McDowall Stuart, for whom the Stuart Highway is named, achieved the Centre sixteen years later, writing in his journal:

"Sunday, 22 April 1860, Small Gum Creek, under Mount Stuart, Centre of Australia - today I find from my observations of the sun, 111° 00' 30", that I am now camped in the centre of Australia. I have marked a tree and planted the British flag there."

(The above is paraphrased from T. Flannery (ed.), The Explorers, The Text Publishing Company, Melbourne,1998, a must read for explorers of Australia.)

But the problem was not just reaching the centre but working out how to define it. There are several valid methods to determine the centre of a large, irregularly-shaped area curved by the earth's surface and they have probably all been used to find the centre of mainland Australia, here are five.

The Australia Map shows where they are in Australia and the Alice Map shows how you might get to them. Here’s how they were calculated:

Lambert Gravitational Centre This is the main one, the only one calculated inside of 10m, and is the one shown in the photograph; although there is no official Centre of Australia, this one is as good as. There is a track into it and it’s a day trip from Alice Springs but you will need a 4WD. The monument is a miniature of the flag pole atop the Commonwealth Parliament House, Canberra.

In 1988 the Royal Geographical Society of Australasia determined this to be the geographical centre of Australia as a Bicentennial of Federation project.

The monument is named for Dr. Bruce P Lambert, a former Director of the Division of National Mapping, for his achievements in the national survey, levelling and mapping of the continent. The calculation used 24,500 points at the mainland high water mark; the maths used isn’t clear but the obvious method would have been Calculus.

In the 1930s when Dr C.T. Madigan travelled through Central Australia he used a centre of gravity method with a metal cut-out of Australia and a plumb bob. Dangle the cut-out vertically from a point on the coast, mark the line of the plumb bob string through this point and across the face, do this lots of times and the centre is where the string marks intersect. It’s a sort of mechanical Calculus, crude but it worked because it came out under eleven kilometres west of the Lambert Centre.

There is also a geocache here called Geocentrical. The computed result of the 1988 Lambert project is:

S25° 36.607’, E134° 21.288’

Centre of Gravity Method Here’s another centre of gravity method. Imagine a perfect cut-out of Australia with thousands of tiny weights distributed around the perimeter; the centre would be the place where the cut-out would balance horizontally on a pin. It was done mathematically ‘though using over 50,000 digitised points along the coastline of mainland Australia each assigned a unit weight and their moments calculated assuming equal units of latitude and longitude varied by the cosine of latitude. The results for this method only claim a precision of one minute and came out at:

S23° 07.000’, E132° 08.000’

Furthest Point from the Coastline This is the centre of the largest circle that can fit inside Australia. It was found by overlaying a series of concentric circles drawn on transparent film on a 1:5 million scale map of Australia until one circle touched the inside of the coastline at three points; the centre of the circle was then marked and the coordinates scaled off the map. This method resulted in a surprisingly good agreement with the previous Centre Of Gravity Method and is due to Australia's shape rather than correlation between the two methods.

S23° 02.000’ E132° 10.000’

Median Point The median point was calculated as the midpoint between the extremes of latitude and longitude of the continent. A rectangle enclosing Australia and touching the extremities north, east, south, and west was drawn; the point of intersection of the diagonals gave the coordinates below. Although it looks dodgy both this method and the Furthest Point from the Coastline method produce points that fall close to the centre of gravity methods. That means that despite the irregular coastline, Australia's distinctive shape actually has a relatively high degree of symmetry.

Median Point is at: S24° 15.000’, E133° 25.000’

Exocentre As you can see there is quite a lot of scope for flexibility in determining where the centre of Australia really is and none of the centres are much of a scenic experience when you get there. With this in mind I have added another centre, which only needs a tsunami to carve a sliver off Cape Leeuwin for it to be the really truly mathematical centre. I also believe it is close to being the exocentre of Australia, which is the centre of a circle that encloses the continent. I have shown it by the red ring in the attached diagram but I haven’t been able to find any calculation for this. It is on top of the McDonnell Ranges in Alice Springs, has magnificent 360° desert views and you can visit it on foot. There is a geocache at the point called Top Red Centre. If you go it is strongly advised that you visit www.geocaching.com for instructions on how to get there and back safely.

Top Red Centre (GCJ703) is at S23° 43.643’, E133° 52.705’

The centres are summarised in the Centres Table. All the locations are effectively WGS84 so use that in your GPS. Technically, they are projected using the Australian datum GDA94. The difference between GDA94 and WGS84 varies across Australia from 10 to 72millimetres, in other words less than the length of your GPS or the width of your foot but you could try switching between the two to convince yourself it makes no difference at all.

.

I don’t know if anyone has ever tried to visit all of the centres. They could all be done from Alice Springs. If anyone does do it perhaps we could get the definitive photographic record of them in here. If you fly Adelaide to Darwin you will get an aerial tour of the lot.