GNSS-Based Cooperative Instantaneous Precise Positioning Aided by Multi-Epoch and Multi-Agent Associations

Multi-agent cooperative positioning (CP) is widely applied in many applications of unmanned ground vehicles and unmanned aerial vehicles. Global Navigation Satellite System (GNSS) is an effective tool to conduct CP on a large scale. However, the performance of traditional GNSS-based CP algorithms is limited by the accuracy of single-agent self-positioning. In this paper, we propose a robust GNSS-based cooperative algorithm to achieve instantaneous precise positioning of multiple agents. In the proposed algorithm, precise point positioning-real-time kinematic (PPP-RTK) is utilized to conduct single-agent self-positioning, which is capable of achieving centimeter-level positioning rapidly with precise atmospheric corrections. Moreover, inter-agent associations derived from double-differenced carrier-phase observations and inter-epoch associations obtained via time-differenced carrier-phase observations are integrated with single-agent self-positioning by a factor graph-based optimizer. To evaluate the proposed scheme, real-world experiments with four agents in different scenarios were carried out. Based on the 30-minute field experimental results, the proposed scheme showed superior positioning performance with minimum and maximum three-dimension root mean square errors (3D-RMSEs) of 5.9 cm and 10.3 cm, respectively. It turned out that benefiting from PPP-RTK's characteristic of achieving precise positioning, the proposed method can converge to centimeter-level accuracy instantaneously.