Research In GNSS Based Train Positioning Integrity

Real time train positioning is important in Communication Based Train Control System. With GNSS train locator, the operator can reduce wayside equipment, cut down the system cost, meanwhile obtaining high precise location. More and more advantages make GNSS locator the trend in train positioning application.Considering current GNSS quality in accuracy, integrity, continuity, availability and the safety integrity requirement from safety-critical rail application, the thesis asserts the necessity to utilize GNSS augmentation to approach and guarantee RAMS in rail as well as the corresponding GNSS augmentation solution.According to rail safety requirement, the thesis presents a deep analysis to integrity of GNSS train locator, integrity parameters to train positioning, integrity risk evaluation and control methods. Based on the multi-sensor locator comprises of GNSS receiver, INS, odometer, a train autonomous integrity monitoring algorithm is presented; according to the feature of rail application, the dedicated local augmentation and wide area augmentation system for railway are proposed.Train autonomous integrity monitoring is based on integrity analysis, aims to monitor train safety in run time. The mechanics is to establish a safety buffer interval via a real time error estimation method. Safety buffer interval is used to execute safety protection and running control. When interval exceeds the alert limit, train operation mode will degrade. The thesis describes the integrity procedure, analyses and verifies this performance of proposed algorithm with data adopted in related projects. Finally, several suggestions are given.