Australian maps and GPS will align by 2020

The Earth moved for all of us but spatial wonks got out of bed and did something about it

Geo-boffins are getting ready to nudge Australia to the north, so its national map data agrees with the new world of GPS.

The country's maps are currently based on a standard called the Geocentric Datum of Australia 1994 (GAD94), which is more than 20 years old and ties map references to locations fixed on the Australian continent.

Since GDA94 was created, however, the country has moved about 1.5 metres, because its fast-moving tectonic plate moves 7 cm a year (we're colliding with the Pacific Plate, which is heading west 11 cm a year).

That's a problem for a world in which accurate location is becoming part of everyday life and carried in the hand, and civilian GPS is expected to be accurate to around four metres.

As the Australian Broadcasting Corporation reports, the country's geodata agency Geosciences Australia (GA) plans to start using a new datum, GDA2020, from 2017.

GA has based GDA2020 on where it expects Australia to be in 2020, so in 2017, the datum will have a 20 cm error that will converge on the “correct” position over time.

That phase of GDA2020 will, however, still be fixed to the continent, so GA is planning a second phase: the Australian Terrestrial Reference Frame (ATRF), which will be rolled out out between 2020 and 2023. The ATRF is designed to stay in synch with global navigation satellite systems (GNSS), making local spatial information directly interoperable with sat-nav.

The update is being overseen by the ANZLIC Intergovernmental Committee on Surveying and Mapping (ICSM).

A recent ICSM survey (PDF) found a surprisingly large number of spatial data users aren't completely across the detail of GDA2020, with 25 per cent of respondents to the survey unaware that GNSS and GDA94 aren't directly interoperable.

However, 80 per cent of respondents said they deal with datasets of 0.1 metre or better accuracy. ®


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