Preliminary Availability Assessment of Multi-GNSS: A Global Scale Analysis

The aim of this paper is to assess the impact of multi-GNSS constellation on positioning calculation in terms of number of available satellites and geometrical distribution in the sky. In the paper, the Geometrical Dilution of Precision (GDOP) was used as criteria to make a preliminary assessment of the global availability of the four GNSS in 2019, including a single navigation system and a combination of multiple navigation systems. The benefits of their combinations are investigated: The combination of dual-system and three-system can reduce the average value of GDOP to 1.0–1.5, which can make the user positioning have better performance. Particularly, GPS+GLONASS+BDS+Galileo supplies higher performances compared to the other combination, and the GDOP value in more than 80% areas is less than 1. Therefore, in the case of a 4 system combination, the effect of the GDOP value is not to “dilute” the positioning accuracy, but to “improve” the positioning accuracy, this phenomenon only occurs when the 4 system combination (approximate rate). The research results of multi-system global available in this paper can offers a reference for the selection of satellite number participating in solution of multi-system combined navigation.