Multi-GNSS Induced Performance Enhancements in Constrained Environments

Nowadays, three global navigation satellite systems (GNSS), namely GPS, GLONASS and China's BeiDou System (BDS), are fully-operational in the Asia-Pacific region. Furthermore, the European Galileo system and the Japanese Quasi Zenith Satellite System (QZSS), which is a regional navigation satellite system (RNSS), jointly provide 4 to 8 additional visible satellites in the region. Thus, it is expected that a combination of the above five systems will improve positioning performance as a result of enhanced satellite availability provided by multi-GNSS. In this research, we develop a method to combine GPS, GLONASS, BDS, Galileo, and QZSS pseudorange and carrier phase observations, and investigate positioning performance improvements brought by multi-GNSS. Experimental data were collected in Southern Taiwan to perform pseudorange-based, meter-level absolute (point) positioning as well as carrier phase-based, centimeter-level relative positioning. Test results indicate that (1) using multi-GNSS can effectively improve the accuracy of absolute (single point) and relative positioning, particularly in highly-masked, constrained environments, such as urban areas; (2) combining the five constellations can significantly shorten the Time-To-First-Fix (TTFF) for rapid ambiguity resolution required by Real-Time Kinematic (RTK) applications in constrained environments.