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GDA

Australia has a new datum for horizontal coordinates or position - the Geocentric Datum of Australia (GDA).

All State and Commonwealth surveying and mapping agencies have introduced the new datum. Other public and private organisations in NSW that deal with spatial data in any form will need to assess the impact of the new datum and implement their own changes over time.

Detailed information and the GDA 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 - The new datum is proclaimed and coordinates of GDA94 origin sites (Australian Fiducial Network) 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.

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

2000, March - Surveyor General's Directions is 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 Information System (SCIMS) is released on-line.

2001, September - 'NTv2' National Transformation Grid is released.

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

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

Coordinate Systems in NSW

All users of spatial data must have a basic understanding of datums and coordinate systems during this transition period. The previous datum in NSW was the Australian Geodetic Datum 1966 (AGD66). Coordinates were expressed in terms of latitude/longitude, the Australian Map Grid (AMG) or the Integrated Survey Grid (ISG).

The official projection system for GDA is the Map Grid of Australia (MGA), with the significant difference being an apparent shift of the coordinates by approximately 200 metres. The Surveyor General of NSW has also endorsed the use of a 'GDA Lambert' projection for state-wide GIS and mapping applications. See the Policy for NSW Lambert Conformal Conic Projection (PDF 3.64 MB) for more information.

Details of the parameters for all projections and ellipsoids relevant to NSW are listed in our map projections page.

For those with an interest in height above sea level, i.e. the Australian Height Datum (AHD), adoption of GDA has no effect whatsoever. This is because GDA is the datum for horizontal coordinate systems only.

SCIMS

The Survey Control Information Management System (SCIMS) contains coordinates for the state survey control network in both GDA94 and AGD66. SCIMS online allows registered users to search the SCIMS database and retrieve coordinates and other related information.

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