Performance of precise point positioning using current triple-frequency GPS measurements in Australia

GNSS Network Real-Time-Kinematic (NRTK) has become a common service for many precise positioning applications over the last two decades. However, NRTK cannot service or support user applications if they are outside the Continuously Operating Reference Stations (CORS) network coverage area, such as in the case of offshore surveying. In addition, NRTK requires a fairly dense network of CORS (typically station separation <80 km) to generate reliable corrections for centimetre-level positioning, and ground communication channels to disseminate the corrections to users. Precise Point Positioning (PPP) is a viable alternative for some GNSS applications as it does not have the onerous requirement of a dense network of CORS infrastructure. However the current major limitation of the PPP technique is the slow solution convergence time (tens of minutes for the solutions to converge to decimetre-level accuracy). This is not adequate to support many real-time positioning and navigation applications requiring high accuracy positioning. This paper describes the prospects, effectiveness as well as challenges in using triple-frequency GPS measurements in a PPP model. In particular, the paper describes research into assessing the performance of triple-frequency PPP. One week of triple-frequency GPS observations from eight CORS stations in Australia were processed in static mode. The estimated positions were then compared with the known coordinates. The results indicate that the use of triple-frequency GPS measurements improves the 3D positioning accuracies as well as shortens solution convergence times compared to dual-frequency PPP.