Contributions of multi-gnss constellations to Precise Point Positioning (PPP) with raw measurements model Fu Zheng, Yidong Lou, Shengfeng Gu Charles Wang, Hailin Guo, Yanming Feng GNSS Centre, Wuhan University Queensland University of Technology
Outline Background Multi-GNSS PPP observation model Function model of multi-gnss PPP Biases in multi-gnss PPP models Experimental results and performance analyses Experiments with different system combinations Experiments with different frequency numbers Conclusions
Background Precise Point Positioning(PPP) Long convergence time: it may take 30-60min to get the position accuracy better than 10 cm (Bisnath and Gao, 2008) Traditional PPP limitation: not applicable for single frequency model Multi-GNSS challenges: more satellites, more signals and more biases. Aim of this study Explore the general model with capacity of processing multi-gnss, multi-frequency PPP and the benefit of multi- GNSS
Multi-GNSS PPP observation models Observation model Traditional PPP model (IF-PPP) Zero-combined PPP (ZC-PPP) ZC-PPP is more flexible for multi-gnss and multi-frequency data processing
Multi-GNSS PPP observation models Comparison of IF-PPP and ZC-PPP model Item IF-PPP ZC-PPP Ionosphere Ionosphere Ionosphere-free delay Estimated (Shi et al., σions combination r 2012; Gu et al.,2014) Uncalibrated code delay ucd Uncalibrated phase delay upd Not considered for CDMA Estimated or corrected Estimated as float solution; The process strategy is different in PPP-AR
Multi-GNSS PPP observation models
GPS GLONGSS BDS GPS+GLONASS GPS+BDS Multi-GNSS
104 MGEX stations, one month (July, 2014) 3 visible BDS/Galileo satellites at minimum are required in multi-gnss PPP. Convergence analysis Dual-frequency: the time when the horizontal and vertical positioning error is better than 0.2m(95%)and 0.1m(68%) Single-frequency: the time when the horizontal and vertical positioning error is better than 0.5m(95%)and 0.3m(68%) Accuracy analysis Accuracy analysis after convergence(four hours later)
Experiment design 1. Comparison of ZC-PPP and IF-PPP 2. GLONASS PPP performance analysis 3. Role of different BDS satellite types in Multi-GNSS PPP performance 4. Benefit of multi-gnss in PPP
Experiment 1: comparison of IF-PPP and ZC-PPP
Single-frequency PPP: convergence time and PPP accuracy Single constellation case Positioning accuracy (unit:m)
Experiment 2: GLONASS PPP performance analysis GLONASS dual-frequency case R: Global R1: low latitude region R2: mid latitude region R3: high latitude region GPS/GLONASS dual-frequency case
Experiment 3: role of different BDS satellite type GC1: GPS + BDS (with GEO) using global network GC2: GPS + BDS (without GEO) using global network GC3: GPS+BDS(without GEO) using pacific region network single-frequency case dual-frequency case
Experiment 4: benefit of multi-gnss: convergence time Single-frequency case Dual-frequency case
Experiment 4:benefit of multi-gnss: accuracy improvement Station:MRO1 Single-frequency case Dual-frequency case
Experiment 4: benefit of multi-gnss: accuracy improvement Accuracy after convergence: Single-frequency case Dual-frequency case
Conclusion The ZC-PPP model achieves shorter overall convergence time and better positioning accuracy than IF-PPP model GLONASS PPP performance depends on latitude and it is caused by constellation design In multi-gnss PPP,the advantages of BDS can be taken only if GEOs are disabled or down-weighted. Combining four GNSS systems can improve convergence time by more than 60% in both the single- and dualfrequency cases with regarding to the GPS-only case
Thank you!