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GDA

Australia has a new national datum for horizontal coordinates or position – the Geocentric Datum of Australia 2020 (GDA2020).

Detailed information and the GDA2020 Technical Manual are available from the Intergovernmental Committee on Surveying and Mapping (ICSM). See also Geoscience Australia for more information.

History

1988, July - ICSM resolution recommending the adoption of an appropriate geocentric datum on 1 January 2000.

1994, November - The Geocentric Datum of Australia 1994 (GDA94) is adopted by ICSM.

1995, September – GDA94 is proclaimed and coordinates of GDA94 origin sites (Australian Fiducial Network, AFN) are listed in the Commonwealth Gazette.

1995, October - Coordinates of Australian National Network (ANN) sites are gazetted in NSW.

1997, March - National GDA94 readjustment is complete.

1999, July - The NSW Legislative Council passes the Survey (Geocentric Datum of Australia) Act 1999.

2000, March - Survey (Geocentric Datum of Australia) Act 1999 is gazetted at the NSW Legislation website.

2000, March - Surveyor General’s Directions are amended to require MGA coordinates to be used for cadastral surveys.

2000, March - Amendments to Mining Regulations are gazetted.

2000, March - The ‘GDA compliant’ Survey Control Information Management System (SCIMS) is released online.

2001, September – AGD66-GDA94 ‘NTv2’ National Transformation Grid is released.

2002, October - Surveying Act 2002 is assented at the NSW Legislation website.

2003, June - Amendments are made to the Surveying Regulations 2001. Refer to the NSW Legislation website.

2010, April – GDA94(2010) released through CORSnet-NSW.

2015, May – ICSM indorsement for the “two-frame” datum modernisation strategy (static and time-dependent).

2017, July – GDA2020 Technical Manual is released.

2017, October – GDA2020 is gazetted as Australia’s new national datum, with adoption planned for 1 January 2020.

2017, December – GDA94-GDA2020 ‘NTv2’ transformation grids are published.

2019, February – CORSnet-NSW provides services in both GDA94 and GDA2020.

2019, July – SCIMS delivers coordinates and metadata in both GDA94 and GDA2020.

Datums and coordinate systems in NSW

All users of spatial data must have a basic understanding of datums and coordinate systems. Previous datums in NSW were the Australian Geodetic Datum 1966 (AGD66) and the Geocentric Datum of Australia1994 (GDA94). Coordinates were expressed in terms of latitude/longitude, the Map Grid of Australia (MGA), the Australian Map Grid (AMG) or the Integrated Survey Grid (ISG).

The official projection for GDA is the Map Grid of Australia (MGA), i.e. MGA94 when referered to GDA94 and MGA2020 when referred to GDA2020. The Surveyor-General of NSW has also endorsed the use of a ‘GDA Lambert’ projection for state-wide GIS and mapping applications. Refer to the Policy for NSW Lambert Conformal Conic Projection (PDF 3.6 MB) for more information.

Details of the parameters for all projections and ellipsoids relevant to NSW are listed on our Map Projections page.

Heights above mean sea level continue to refer to the Australian Height Datum (AHD). However, when connecting to AHD via GNSS observations, it is important to remember that AUSGeoid2020 can only be used in conjunction with GDA2020 ellipsoidal heights, while AUSGeoid09 must be used to convert GDA94 ellipsoidal heights to AHD. These quasigeoid models and datums cannot be mixed and matched.

SCIMS

The Survey Control Information Management System (SCIMS) contains coordinates and metadata for the state survey control network in both GDA94 and GDA2020. SCIMS Online allows registered users to search the SCIMS database and retrieve coordinates and other related information.


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