Akademik Veri Yönetim Sistemi
MEASUREMENT SCIENCE AND TECHNOLOGY, cilt.32, sa.1, 2021 (SCI-Expanded)
Ultra-rapid products, which do not require any external connection unlike real-time services, are an important alternative for real-time global navigation satellite system (GNSS) applications. Especially, the inclusion of newly-emerged satellite systems in ultra-rapid products opens up considerable opportunities to improve the positioning performance. In this regard, this study concentrates on the employment of the most recent ultra-rapid products besides traditional ones for real-time single-frequency multi-GNSS positioning using code and carrier phase measurements. In the study, experimental tests were conducted for the ionosphere-free code-carrier combination to evaluate the performance of single-receiver single-frequency positioning. The results reveal that single-frequency positioning is able to provide sub-meter level positioning accuracy with ultra-rapid products despite its performance alters depending on the applied product. Also, the performance of single-frequency positioning which based on code-carrier combination is not influenced significantly from the possible decline in the precision of ultra-rapid products over time due to the convergence of phase ambiguities. On the other hand, the results demonstrate that the accuracy of pseudorange positioning can significantly be improved with the integration of multi-constellation and the improvement ratio can reach 30% compared with the GPS-only solutions. Furthermore, the convergence time of GPS-only solution can be decreased by a ratio of 37% on average with multi-GNSS combinations. Finally, the results show that for the multi-constellation analyses, the solutions which utilize the ultra-rapid product of Wuhan University provide the best performance in terms of positioning accuracy and convergence time.