Session B3: Precise GNSS Positioning Applications

An Architecture for Seamless Handover of PPP-RTK Corrections across Redundant Networks
Cheolmin Lee, Sulgee Park, Sanghyun Park, Maritime PNT Research Office
Location: Beacon B

PPP-RTK service operators generally utilize a redundant reference station network to ensure operational resilience. These redundant networks share identical geometry but use distinct receivers and antennas. Although atmospheric and satellite delays, such as time and phase biases, should theoretically be identical, practical discrepancies arise due to hardware biases and ambiguities between the receivers in the two networks. This leads to differences in the estimable parameters for common satellite delay components. Therefore, this paper presents a seamless handover algorithm for PPP-RTK corrections across redundant networks. In this study, IGS Ultra-rapid precise orbits were utilized, and the Kalman filter was applied in conjunction with the least-squares ambiguity decorrelation adjustment (LAMBDA) method. Additionally, the common-view technique was employed using the Global Positioning System (GPS) single constellation dual-frequency code and carrier phase observations. The proposed architecture continuously levels the redundant networks by imposing common satellite delay components and tropospheric delays from the primary network as additional constraints on the secondary network. However, when the pivot stations of the redundant networks differ, their original PPP-RTK estimable parameters cannot be utilized in the leveling process. For the leveling process, we defined new estimable parameters for the secondary network with a different pivot station, which are estimated using the weighted least squares method following the processing of each redundant network's Kalman filter. Subsequently, the full state vector of the secondary network is updated once again using a conditional adjustment method to finalize the leveling process. The proposed architecture facilitates the resilient provision of PPP-RTK corrections even during handovers across redundant networks, thereby eliminating the need for users to re-estimate ambiguities and ensuring seamless positioning performance. To evaluate the performance of the architecture, two resilient PPP-RTK networks were configured using continuously observed reference stations (CORS) throughout South Korea. Finally, the feasibility of the leveling process and its positioning performance were evaluated using long-term CORS observational data.