Experimental Assessment of Multi-GNSS Baseline Processing under Various Observational Environments

This paper systematically analyzed the precision of multi-GNSS baseline processing under various urban environments by conducting simultaneous observations at five sites with differing levels of satellite visibility. The data were processed as very short and short baselines using eight constellation combinations and three commercial software packages. The results show that multi-GNSS integration generally improves precision compared with GPS-only, particularly in the vertical component, thereby confirming interoperability among constellations under favorable conditions. In harsh urban environments, however, degraded precision and the absence of ambiguity-fixed solutions are observed, likely due to insufficient satellite availability and unstable ISB (Inter-System Bias) estimation, with outcomes varying across software packages. Notably, the combination of four GNSS demonstrates potential for public and cadastral control surveys even under extremely obstructed conditions. Overall, the findings indicate that multi-GNSS baseline processing is effective for enhancing precision in challenging environments, though its performance depends on constellation availability, bias correction, and processing strategies, highlighting the need for careful software selection and further validation.