Although Global Navigation Satellite Systems (GNSS) have been widely used in aviation, vehicle and marine navigation, and have also found non-safety railway applications, they still cannot be used in a standalone mode for safety critical railway applications. This is because GNSS suffers from the line-of-sight problem, namely, GNSS might be unavailable when trains run through the areas with low satellite visibility. A potential solution is to integrate satellite navigation measurements with other sensors such as a track database, INS or an augmentation system. This book is concerned with...