Continental observations provide accurate data

27 August 2012

The geomagnetic station in Antarctica
includes a building for recording
continuous magnetic field changes (left)
and another for scientists to make periodic
absolute measurements of the field (right).
Image, the Australian Antarctic Division

Travellers using the traditional magnetic compass could find they are a little off-course if they are relying on information found on old maps according to continuing research into Earth’s magnetic field.

Analysis by Geoscience Australia of observations from geomagnetic stations on the Australian mainland and Antarctica show Australia’s magnetic field is weakening and the relationship between magnetic north and true north is continuing to vary.

However, the observations reveal that the rate of change in the magnetic north direction differs significantly between northern Australia where it has decreased by one quarter of a degree over 10 years and at Mawson in Antarctica where it has decreased by one-and-a-half degrees in the same period.

Geoscience Australia scientist, Dr Adrian Hitchman, said that since the beginning of measurements at Mawson in 1955, the magnetic field direction there has changed by almost nine degrees.

“These variations can be particularly significant for people using magnetic directions on old maps for navigation,” Dr Hitchman said.

“By applying an old compass direction found on the map, people moving through the terrain could find themselves several kilometres off course over a journey of a few tens of kilometres,” he said.

“Because Earth’s magnetic field is constantly changing it is important to use the latest geomagnetic data to confirm its direction for navigation,” Dr Hitchman said.

As well as fundamental navigation, geomagnetic data is used extensively in mineral and petroleum exploration and recovery and for the analysis of space weather, particularly activity resulting from solar flares.

Geoscience Australia uses a network of 11 geomagnetic observatories in Australia, the sub-Antarctic and the Australian Antarctic Territory to monitor the changing magnetic field in the region. The data are retrieved in near real-time and distributed to Australian and international clients, including the International Real-time Magnetic Observatory Network (INTERMAGNET) to become part of the data set representing the magnetic activity of the entire planet.

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