What is the difference between GDA and WGS84?
In January 1994, GDA94 and the International Terrestrial Reference Frame (ITRF) coincided. At around the same time, the WGS84 reference frame was also aligned with ITRF. In January 1997 WGS84 was re-aligned with the then current version of ITRF, within a few centimetres. For most practical applications where an accuracy of only a metre or greater is required, GDA94 coordinates can be considered the same as WGS84. However, for applications where an accuracy of better than a metre is required, the difference must be taken into account. Standard 7-parameter transformations from ITRF to GDA94 are regularly computed from the known GDA94 and continually updated ITRF positions of the Australian Regional GPS Network (ARGN). These parameters can be used to transform between ITRF and GDA94 positions, remembering that ITRF positions may be used as accurate WGS84 positions.
