Multi-GNSS Relative Positioning with Fixed Inter-System Ambiguity

Hua Chen,Jiancheng Li,Weiping Jiang

doi:10.3390/rs11040454

Abstract

In multi-GNSS cases, two types of Double Difference (DD) ambiguity could be formed including an intra-system ambiguity and an inter-system ambiguity, which are identified as the DD ambiguity between satellites from the same and from different GNSS systems, respectively. We studied the relative positioning methods using intra-system DD observations and using Un-Difference (UD) observations, and developed a frequency-free approach for fixing inter-system ambiguity based on UD observations for multi-GNSS positioning, where the inter-system phase bias is calculated with the help of a fixed Single-Difference (SD) ambiguity. The consistency between the receiver-end uncalibrated phase delays (RUPD) and the SD ambiguity were investigated and the positioning performance of this new approach was assessed. The results show that RUPD could be modeled as a constant if the receiver were tracking satellites continuously. Furthermore, compared to the method using DD observations with only an intra-system DD ambiguity fixed, the new ambiguity fixing approach has a better performance, especially in hard environments with a large cut-off angle or serve signal obstructions.

Highlights

Global Navigation Satellite Systems (GNSSs) have been applied in many fields ranging from scientific research to engineering surveying due to their high precision and accuracy
In order to validate this method, the data of the baselines KIR8-KIRU(4.5 km), AGGO-LPGS (19.3 km) and NNOR-PERT (88.5 km) from days 063–076, 2017, were adopted. These data are processed with two strategies: (a) the traditional Double Difference (DD) method where only intra-system DD observations are formed and only intra-system ambiguities are fixed; (b) the method proposed in this research, where UD observations are used and both intra-system and inter-system ambiguities are fixed
We studied the relative positioning methods using intra-system DD observations and using UD observations

Summary

Introduction

Global Navigation Satellite Systems (GNSSs) have been applied in many fields ranging from scientific research to engineering surveying due to their high precision and accuracy. Relative and absolute positioning are the two typical GNSS positioning modes. The broadcast ephemeris is reported to be precise enough for relative positioning to achieve the accuracy of the mm level with only a few hours of observations in short baseline cases [2,3]. Relative positioning is widely applied to engineering control network establishments and deformation monitoring. More and more GNSS systems, such as Beidou [4] and Galileo [5], are becoming available; together, there will probably be more than 100 satellites in operation soon. Integrating the data of all available GNSS satellites could improve the positioning accuracy and reliability [6,7,8]

Methods

Results

Conclusion