Improved Navigation Application Precise Point Positioning Method in Railways [铁路导航精密单点定位方法改进及性能验证]

Traditional navigation and positioning applications in railways adopt DGNSS, a differential reference station network has to be established along tracks in order to meet the requirements of positioning accuracy, which requires high construction and subsequent operation and maintenance costs. Precise Point Positioning (PPP) is one of GNSS positioning techniques, which resolves position, velocity based on code and carrier-phase measurements combined with globally distributed GNSS reference station networks. PPP is capable of obtaining centimeter-level accuracy in static mode and decimeter-level one in kinematic mode. In addition, its performance won't degrade with the increase of distance and no additional reference stations are required. This paper introduced PPP fundamentals based on CSRS-PPP software platform coming from Natural Resources Canada (NRC). The authors analyzed PPP's capacity of real-time, availability and safety issues in typical railway navigation application environments. Then a modified integrated positioning method of PPP/INS-based extended Kalman filter was proposed. The results show that integrated solution could solve the availability issue caused by transitory observation unavailability without degrading the accuracy of positioning.