Researches On GNSS Vulnerability Reliable Detection And Its Substitution

Global Navigation Satellite System(GNSS)has provided indispensable Positioning,Navigation and timing(PNT)services for many fields in these years.Nonetheless,its vulnerability has gradually been exposed.The service offered by GNSS is threatened by factors such as electromagnetic interference,atmospheric interference and building shielding.These vulnerability factors may affect the service performance of GNSS in the potential process which may bring huge risks to users.The study of vulnerability aims to guarantee the security and reliability of GNSS services,and is of great significance to the continuity of PNT services.The research on GNSS vulnerability can be roughly divided into three parts: vulnerability assessment,traceability and substitution.Assessment is a quantitative study on the current vulnerability of GNSS;traceability is the research on detection,traceability and mitigation of vulnerability factors;substitution is about the compensation and substitution when GNSS is too vulnerable.The focus of this paper is GNSS vulnerability assessment technology and alternative technology to GNSS focusing on visual/inertial positioning,aiming at providing users with safe and reliable positioning services in complex environment.This paper first discusses the necessity and current status of GNSS vulnerability research and supplements the vulnerability research system.Then the position where the research work in this paper belongs to in vulnerability research is explained.A new vulnerability model was defined according to the user’s positioning requirements and a real-time vulnerability assessment method driven by a large amount of data is proposed.The superiority of the method is verified by a semi-physical simulation system.Under the premise that GNSS is highly vulnerable,the advantages and disadvantages of visual-inertial navigation system are analyzed,and a complete state estimation modeling is given for the fusion of the two.A real-time positioning system is designed in which visual fiducial is used to assist visual-inertial odometry.The experiment using simulation data as observation data proves that the method proposed in this paper can effectively reduce the positioning error in visual-inertial odometry.