THE FIVE CENTRE POINTS OF AUSTRALIA
CENTRE OF GRAVITY METHOD
Determined using 50,000 equally-weighted points around the mainland Australian border, then calculating the point at which that hypothetical cutout would balance perfectly.
Otherwise known as the gravitational centre of Australia. It uses similar methodology to the centre of gravity method, but based on the high-tide mark of 24,500 points around the mainland.
FARTHEST POINT FROM THE COASTLINE
The centre of the largest circle that can be drawn in Australia.
The intersection of the midpoint of the longitude and latitude extremes of the country.
JOHNSTON GEODETIC STATION
Defined in 1965 and set up in 1966, the trigonometric survey location was set up by the Division of National Mapping as the central reference point. Modern technology, including GPS mapping, has seen modern surveys shift to the more accurate Geocentric Datum of Australia, a moving target that accounts for small movements in tectonic plates.
Five thousand kilometres gives you plenty of time to think, especially when every second headline has something to do with Donald Trump, global warming or rising sea levels – or a combination of the three.
This got us thinking about the methods used to calculate the centre of the country.
Even a small rise in sea levels could have a large impact on what is considered the centre of Australia. Larger tides in the north, for example, combined with shallow tidal flats, like those seen at Broome, could easily change the defined point of where the coastline starts by many metres, in turn requiring a recalculation of exactly where the centre is. All of which is for another day.