The Geocentric Datum of Australia (GDA2020) is the current gazetted national datum of Australia (October 2017) and is the prescribed datum for Surveying and Spatial Information in NSW (commencing 01 January 2020). GDA2020 supersedes GDA94.
High-accuracy coordinates in a defined national datum are a fundamental requirement for CORSnet-NSW to deliver seamless positioning and the provision of network solutions.
GDA2020 refers to the Geocentric Datum of Australia 2020. Coordinates in GDA2020 are derived through direct connection to the Australian Fiducial Network (AFN) - see Regulation 13 Certification.
GDA94(2010) refers to a specific realisation of the Geocentric Datum of Australia 1994 defined in 2010 for CORSnet-NSW.
GDA94 coordinates derived for CORSnet-NSW are provided with respect to GDA94(2010) to provide uniform solutions across the network and to be compatible with other CORS networks around Australia.
GDA94(1997) refers to an earlier realisation of GDA94 which was adjusted in 1997.
SCIMS Online provides GDA94 coordinates in GDA94(1997), including for CORSnet-NSW. These 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).
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.