WGS84 and the Geocentric Datum of Australia 1994

Jim Steed and Geoff Luton

Abstract:	The Geocentric Datum of Australia 1994 (GDA94) is based on the International Terrestrial Reference Frame 1992 (ITRF92) positions at 1st January 1994, computed for the eight Australian Fiducial Network (AFN) sites. GDA94 replaces the former Australian Geodetic Datum (AGD) and was developed to be directly compatible with the Global Positioning System (GPS). However, the relationship between GDA94 and WGS84 is subject to ongoing assessment. In 1993 the National Imagery and Mapping Agency (NIMA) used their GASP software (Malys et al, 1993) to compute WGS84 positions for nineteen Australian sites, five of which are part of the AFN. In 1999 a similar exercise was repeated using data from the eight AFN sites that now form part of the Australian Regional GPS Network (ARGN). These WGS84 positions have been compared with the equivalent GDA94 positions and recently computed ITRF positions and have been used to compute transformation parameters between theses reference frames. The results indicate that GDA94 is compatible with WGS84 for most practical applications, but tectonic plate movement and the future availability of accurate positions, independent of nearby coordinated positions (absolute positions) will put increasing pressure on the static GDA94 coordinate system.
Published in:	Proceedings of the 13th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2000) September 19 - 22, 2000 Salt Palace Convention Center Salt Lake City, UT
Pages:	432 - 437
Cite this article:	Steed, Jim, Luton, Geoff, "WGS84 and the Geocentric Datum of Australia 1994," Proceedings of the 13th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2000), Salt Lake City, UT, September 2000, pp. 432-437.
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