Abstract
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.
Highlights
In 2018, the four global navigation systems showed prosperity
We found that all dual-system combinations have a Geometrical Dilution of Precision (GDOP) value of no more than 5, enabling seamless positioning on a global scale
More detailed statistical results of GDOP for dual-system are shown in Figure 17 and Table 3.By analyzing the statistical results, it can be found that almost all GDOP values are in the 1-2 interval when the dual system is combined, which means that the dual system combination provides almost the same geometric observation conditions
Summary
In 2018, the four global navigation systems showed prosperity. GPS launched the first new generation of GPS satellites during 2018, marking the beginning of a new era in the modernization process [1]–[3]. In the afternoon of December 27, 2018, China announced through an official announcement that BDS services have expanded from the region to global, marking the entry of the BDS system into the global era [6], [7]. Galileo system had completed its current deployment and planned to lay out the second generation system in 2018 [8], [9]. As at January 11, 2019, the number of satellites available for the four major global navigation systems had reached 115, comprising 32 GPS satellites, 25 GLONASS satellites, 34 BDS satellites and 24 Galileo satellites (as shown in Figure 1 and Table 1 at the end of this section).
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