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Datums

The Geocentric Datum of Australia (GDA2020) is the current gazetted national datum of Australia (October 2017). Currently, GDA94 is the legislated datum in NSW.

These high-accuracy coordinates are a fundamental requirement for a seamless positioning network and the provision of network solutions.

GDA2020

GDA2020 refers to the Geocentric Datum of Australia 2020.

GDA94(2010)

GDA94(2010) refers to a new realisation of the Geocentric Datum of Australia 1994. Coordinates in GDA94(2010) are derived through direct connection to the Australian Fiducial Network (AFN) - see Regulation 13 Certification.

GDA94 coordinates from CORSnet-NSW are provided with respect to this realisation of GDA94 to provide uniform solutions across the network and to be compatible with other CORS networks around Australia.

GDA94(1997)

The NSW State Control Survey is based on GDA94(1997), an earlier realisation which was adjusted in 1997.

Coordinates in GDA94(1997), including those for CORS, are available through SCIMS Online and are sometimes referred to as local coordinates.

Although GDA94(1997) coordinates also stem from the AFN, most of them are only linked indirectly through many layers of measurements and adjustments.

Measurement inaccuracies and errors propagate through these layers resulting in distortions of up to 0.3 m in the horizontal component and up to ±0.3 m vertically.

To connect to GDA94(1997), and AHD71 for elevation, using CORSnet-NSW, it is necessary to perform a site localisation (also known as site transformation or site calibration).

More information

Refer to our GDA page for some general information. Our GNSS Publications contain several publications related to datums, transformations and projections. Additional information is available in the GDA2020 Technical Manual, on ICSM’s GDA2020 page and on Geoscience Australia’s Geodetic Transformations and Conversions page.


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