GDA94 – The Map Room https://www.maproomblog.com Blogging about maps since 2003 Sat, 06 Aug 2016 01:10:03 +0000 en-US hourly 1 https://www.maproomblog.com/xq/wp-content/uploads/2017/04/cropped-logo-2017-04-32x32.jpg GDA94 – The Map Room https://www.maproomblog.com 32 32 116787204 Australia to Correct Tectonically Induced GPS Discrepancy https://www.maproomblog.com/2016/08/australia-to-correct-tectonically-induced-gps-discrepancy/ Sat, 06 Aug 2016 01:10:03 +0000 http://www.maproomblog.com/?p=2546 More]]> Decades of continental drift mean that GPS coordinates in Australia are off by approximately 1.5 metres (5 feet), which has implications for self-driving cars and other applications that require very precise positioning. See coverage from Atlas Obscura, BBC News, Popular Mechanics and the Washington Post.

Basically, the discrepancy comes from the fact that GPS is based on the Earth’s core rather than any point on the surface, whereas local coordinates are based on a geodetic datum—in Australia’s case, GDA94 (North America uses NAD83)—that is based on a fixed point on the surface. But with plate tectonics, points are not fixed: Australia moves northward at seven centimetres a year.

On 1 January 2017 Australia will shift its coordinates north by 1.8 metres, overshooting things a bit so that the continent and GPS will be in sync by 2020, with plans to keep the datum continually updated after that.

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