GNSS Collaborative Positioning and Performance Analysis

As the rapid development of global navigation satellite systems (GNSS) and their related applications in recent years, there will be many scenarios that multiple users work in certain region in the near future. However, facing occlusions and other issues in challenging environments such as urban canyons and forests, up to now there is no good positioning solutions. The ability for most conventional standalone GNSS receivers to independently estimate their locations using GNSS may be degraded in these environments. With the popularity of the applications of GNSS and wireless networks, the GNSS collaborative positioning is becoming possible. In collaborative positioning, each user shares its processed data with the user group, measures the relative distances with its neighbouring users and conducts joint data processing to improve the positioning performance such as availability, stability and accuracy. Compared with standalone positioning, the measurements utilized in collaborative positioning are obtained by the user group, which can help to solve the issues such as lack of visible satellites in challenging environments. In this paper, the collaborative data model and weighted least square (WLS) positioning algorithm are presented first. Then, the theoretical performance analysis and simulation tests are proposed by using the collaborative dilution of precision (CDOP) model, which focuses on the impacts of the number and distribution of collaborative users and the accuracy of relative distance measurements that are not considered in standalone positioning. Finally, the collaborative positioning algorithm is tested in some real scenarios such as building roof, balcony, windowsill by using several real-time GNSS receivers. Theoretical analysis and experimental results both verify the impacts of various factors on the positioning performance, and prove that the positioning availability and accuracy can be improved by collaboration.