Development of factor graph and its application technology in positioning and navigation

Factor graphs are widely used in the fields of coding, statistics, signal processing, and artificial intelligence as a modeling tool that represents factorization. The application of factor graphs in the navigation field is also gradually developed. The combination of multiple sensor information provides a more accurate and robust navigation state estimate than the information from a single sensor. However, various sensors have different error characteristics and these sensors usually operate at different frequencies. Considering that some sensors cannot supply the linear measurement information, and it brings the challenges to the design of the integrated navigation system. The navigation algorithm based on the factor graph model enables the system to have plug-and-play characteristics and achieve better results under nonlinear measurement conditions. The state estimation and information fusion problems in the navigation system can be represented by the factor graph model. Sum-product algorithm based on factor graph is the main method in navigation and positioning system.This paper summarizes the factor graph theory and its application in the navigation system, including: 1) Mathematical theoretical basis of factor graph and its related application fields 2) Development and application of factor graphs in the field of positioning and navigation.