Satellite positioning technology has improved so much in the last decade that absolute positioning accuracy anywhere on Earth at cm level accuracy is now readily available to users. Government and commercial wide area augmentation systems such as WAAS, Omnistar and Starfire promise decimeter accuracy to users in near real-time. Other web-based services such as AUSPOS, the Canadian NRCan service and OPUS provide an absolute coordinate in a few minutes to an accuracy of a few centimetres using the International GNSS Service (IGS) ground station network. Continuously Operating Reference Station (CORS) networks also provide a range of positioning services to users, predominantly in GDA. However the heritage of our national coordinate system, the Australia Geodetic Datum (AGD), was built on older techniques. The incredible precision of new satellite based positioning has revealed many distortions, even in the modern GDA datum. So how do we quantify the accuracy of coordinates?

The Intergovernmental Committee on Surveying and Mapping (ICSM) have introduced a new term called Positional Uncertainty (PU) which refers to connection to datum (GDA94). Class will remain as a relevant measure and another new term Local Uncertainty (LU) will replace Order. According to the ICSM Special Publication for Control Surveys (SP1), this change will occur in 2005. So how many States have implemented PU to their geodetic networks and made these numbers freely available to users?

This paper will present an overview of PU and call for a national approach to implementing this important piece of meta- data across Australia.