Precise Point Positioning – The evolution of an alternative GNSS positioning solution
Precise Point Positioning (PPP) employs readily available Global Navigation Satellite System (GNSS) orbit and clock correction products to perform point positioning using a single GNSS receiver. Over the last 20 years, the New South Wales (NSW) state government has invested in Continuously Operating Reference Station (CORS) infrastructure, currently comprising a 200-station network providing cm-level positioning using differential Network Real-Time Kinematic (NRTK) GNSS techniques to a growing market of commercial users who rely on this service. However, in remote western NSW, it is not economically feasible to maintain the same station density to enable NRTK services. In the last 10 years, developments in PPP, including Real-Time PPP (RT-PPP) and Ambiguity-Resolved PPP (AR-PPP), have allowed PPP to potentially offer a viable alternative to NRTK positioning without the need for such a high station density. This thesis investigates the development of PPP over the last 10 years from a practical perspective and highlights the advantages and disadvantages of this positioning technique. Existing static PPP services are found to be adequate for shortened observation periods. The various methodologies and advances in RT-PPP and AR-PPP services are presented. Three separate case studies using large real-time data-sets found potential for these techniques in remote areas lacking dense CORS network coverage. Multi-constellation GNSS and multi-frequency GNSS showed promise for improving initialisation times for real-time ambiguity resolution techniques, even for single-frequency PPP, which will be important for mass market users in the future. Satellite-based delivery of correction services over NSW was tested using the Japanese QZSS service in an Australian first static and kinematic PPP case study. Despite of all these advances in PPP methodology, this thesis has found that PPP, in the near future, will not be able to replace conventional NRTK, but can offer national or regional positioning solutions at specified accuracies, or as a ‘fill-in’ service for practical use in sparser local/regional CORS networks.
Real time, Precise Point Positioning (PPP), Ambiguity resolution, CORSnet-NSW, Global Navigation Satellite System (GNSS)
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