Continental drift calls for rethink of Australia's geographic coordinates

Since 1994, the Australian continent has shifted about 1.5 m (4.9 ft). Smartphones and other GPS-reliant technology already adjust for the discrepancy, but that's not a long-term solution.

The Land Down Under is slowly becoming less down under, drifting north at a rate of 7 cm (2.8 in) per year. While that might not sound like much, over time it's significantly thrown off Australia's latitude and longitude coordinates, causing accuracy issues for GPS technologies.

An Australian government organization is now working to correct the discrepancy, by updating the country's coordinate system for the first time in over 20 years.

The Geodetic Datum of Australia was developed in 1966 and last updated in 1994 (GDA94). It relies on relative distance between points in Australia to produce latitude and longitude coordinates, so as the plate containing the entirety of Australia shifts north, the relative distance moves along with it.

The problem is that this plate-centric data clashes with coordinates from more accurate space-based systems, with discrepancies emerging because of the rapid northbound shift of the continent.

Since 1994, the continent has shifted about 1.5 m (4.9 ft). Smartphones and other GPS-reliant technology already adjust for that discrepancy, but that's not a long-term solution. Instead, Geoscience Australia is modernizing the country's coordinate system with the GDA2020, changing the basis of those measurements rather than forcing every piece of technology to make those additional calculations.

"The lines of latitude move with the continent," Geoscience Australia's Dan Jaksa tells New Atlas. "So when it's moving so fast like Australia does, eventually they're so far different to the positions given by global satellite navigation systems, like GPS, that we have to move it. And that's what's happening."

The GDA2020 will move the longitude and latitude coordinates by 1.8 m (5.9 ft), which, as its name suggests, will be based on the continent's projected location for 2020. This will go part of the way towards catering for the advances in GPS technology on the horizon.

"There are technologies which are coming, in the next few years, called space-based augmentation systems, which enhance the positioning capability of everybody that has a smartphone down to sub-3 cm (1.2 in)," says Jaksa. Preparing for this and the increasing use of other GPS-based technologies, like drones and autonomous vehicles, is the main goal of the GDA2020.

But of course, the problem will just crop up again down the track. In the long term, coordinates will be subjected to a time-dependent reference frame that automatically adjusts for the movement. Under this system, the lines of latitude and longitude will remain fixed to the Earth, not to the Australian plate. Doing so simplifies some things, Jaksa says, but creates a whole host of further complications that need to be worked through, as a fourth dimension is added to location tracking.

"The future is, things will be measured by XYZ-time," he says. "We don't particularly want to do a GDA2040. By that time we're hoping that systems will be so connected that you won't even notice any datum changes."

The GDA2020 will be put into effect on January 1, 2017.

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