What is the positional difference between WGS84, AGD84 and GDA94?
The difference in position between GDA94 and WGS84 can be ignored for normal GPS use. GDA94 is the ‘official’ horizontal datum for precise surveying in Australia but for general use, WGS84 is compatible with GDA94. However, when plotting positions using a WGS84 (or GDA94) coordinate from a GPS onto a map based on the older datum of AGD84, your position could be out by up to 200 m in a north-east/south-west direction. The size of this shift varies from place to place. On even older maps and charts, there may be a reference to AGD66 datum. This was the ‘official’ survey datum adopted by Australia in 1966 and there is about a one to two metre difference between AGD66 and AGD84 datum.
