Centre points of Australia

23 degrees 7 minutes south latitude, 132 degrees 8 minutes east longitude (23°07′S 132°08′E); position on SF53-13 Hermannsburg 1:250 000 and 5351 Glen Helen 1:100 000 scale maps.[5]

23 degrees 2 minutes south latitude, 132 degrees 10 minutes east longitude (23°02′S 132°10′E); position on SF53-13 Hermannsburg 1:250 000 and 5351 Glen Helen 1:100 000 scale maps.[1] There are a few other contenders for this centre, including the tidal centre, which judges the centre from the furthest from the tidal penetration up rivers and streams.

There are two ways to judge the median centre point of Australia. The linear centre, which is the halfway points of Australia's extreme points (Cape York, Cape Byron, South Point and Steep Point). The second is the geodetic median point, which is a more accurate method used by surveyors. It uses a box to shape Australia's extreme points and diagonal lines from the corners of the box which cross at the geodetic median centre.

Plaque at the Lambert Centre (note that Lambert died in 1990, not 1992 as written in the plaque)

In 1988, the Royal Geographical Society of Australasia determined the geographical centre of Australia as a Bicentennial project. A monument was erected to mark the location and named in honour of Dr. Bruce Philip Lambert, a former Director of the Division of National Mapping, for his achievements in the national survey, levelling and mapping of the continent.[6] The plaque contains an error, as Lambert died in 1990, not 1992. Similar to the centre-of-gravity method, the location was calculated from 24,500 points at the high-water mark of Australia's coastline.[7][8] The computed result of the 1988 project was 25 degrees 36 minutes 36.4 seconds south latitude, 134 degrees 21 minutes 17.3 seconds east longitude (25°36′36.4″S 134°21′17.3″E); position on SG53-06 Finke 1:250 000 and 5746 Beddome 1:100 000 scale maps.[1][9]

Dr Cecil Madigan studied Central Australian geology in the 1930s. He calculated the centre of gravity by using a metal cut-out of Australia with a plumb bob and string, and selected a point less than 11 kilometres due west of the present position.[10][11]

This trigonometric survey cairn, situated about 1 kilometre (0.62 mi) north of Mount Cavanagh Homestead, was built by officers of the Division of National Mapping in 1965, and was once the central reference point for all Australian surveys. It was named after Fredrick Marshall Johnston, former Commonwealth Surveyor General and the first Director of National Mapping. Today, surveys are based on the Geocentric Datum of Australia (GDA), a new and more accurate Australian coordinate system which has replaced the Australian Geodetic Datum (AGD) of which the Johnston station is a major part. Further information on datum types and their applications is available from the geodesy pages, or from the Inter-governmental Committee on Surveying & Mapping (ICSM).

This point is at 25 degrees 56 minutes 49.3 seconds south latitude, 133 degrees 12 minutes 34.7 seconds east longitude (25°56′49.3″S 133°12′34.7″E) position on SG53-05 Kulgera 1:250 000 and 5546 Kulgera 1:100 000 scale maps.