How will continental drift affect GDA?
The Australian plate is known to be moving in a north easterly direction at a rate of about 6 cm per year, but there is little known distortion within the plate. This means that continental drift will have no real effect on relative GDA positions, but over time the absolute position of all points will change by a similar amount. Those seeking accurate positions from GPS generally work with differential positions and will not detect any change in absolute position. With a single hand-held GPS receiver the best absolute position that can be obtained by routine means is about 10 metres. This means that it would take about 150 years before the change could be detected. With more sophisticated GPS equipment (dual frequency surveying recievers) and long observing periods (at least several hours) it is possible to obtain positions with an accuracy of few centimetres. With this accuracy, the shift due to “continental drift” since GDA94 was introduced (1994) can be measured. However, GeoScience
