The development of an Australian PPP-RTK processing platform is an important component of a multi-GNSS (global navigation satellite system) enabled national positioning infrastructure. The PPP-RTK concept extends the precise point positioning (PPP) concept by providing single-receiver users with information enabling integer ambiguity resolution, thereby reducing convergence times as compared to that of PPP. In this contribution we present and discuss the underlying principles of the PPP-RTK platform for both network and user. We demonstrate its GPS-based performance and provide an outlook for when multi-GNSS constellations, such as BDS, Galileo and QZSS, become fully operational.

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Knowledge of inter-system biases (ISBs) is essential to combine observations of multiple global and regional navigation satellite systems (GNSS/RNSS) in an optimal way. Earlier studies based on GPS, Galileo, BDS and QZSS have demonstrated that the performance of multi-GNSS real-time kinematic positioning is improved when the differential ISBs (DISBs) corresponding to signals of different constellations but transmitted at identical frequencies can be calibrated, such that only one common pivot satellite is sufficient for inter-system ambiguity resolution at that particular frequency. Recently, many new GNSS satellites have been launched. At the beginning of 2016, there were 12 Galileo IOV/FOC satellites and 12 GPS Block IIF satellites in orbit, while the Indian Regional Navigation Satellite System (IRNSS) had five satellites launched of which four are operational. More launches are scheduled for the coming years. As a continuation of the earlier studies, we analyze the magnitude and stability of the DISBs corresponding to these new satellites. For IRNSS this article presents for the first time DISBs with respect to the L5/E5a signals of GPS, Galileo and QZSS for a mixed-receiver baseline. It is furthermore demonstrated that single-frequency (L5/E5a) ambiguity resolution is tremendously improved when the multi-GNSS observations are all differenced with respect to a common pivot satellite, compared to classical differencing for which a pivot satellite is selected for each constellation.

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In this contribution we will focus on instantaneous (single-epoch) single-baseline Real- Time Kinematic (RTK) combining four CDMA satellite systems. We will combine the Chinese BeiDou, the European Galileo, the American GPS and the Japanese QZSS system. To further strengthen the underlying model and maximize the redundancy, attention will be given to overlapping frequencies between the systems. With calibrated Inter System Biases (ISBs), it enables one to use a common pivot satellite between the respective systems when parameterizing the double-differenced ambiguities. We make use of the LAMBDA method for ambiguity resolution, and the performance is evaluated by ambiguity success-rates and by comparing the estimated positions to very precise benchmark coordinates. This will be based on various elevation cut-off angles so as to mimic conditions with obstructed satellite visibility (such as in urban canyons). It will be shown by how much the increased strength of the combined models allow for improved ambiguity resolution performance and positioning robustness over the single-systems.@en