Topology-Consistent Trajectory Event Matching for GNSS-Denied Vehicle Initial Localization

Vehicle initial localization under global navigation satellite system (GNSS)-denied conditions remains challenging because an odometry trajectory provides relative motion but no absolute road-network reference. Inspired by the coordinated use of self-motion information, recognizable route cues, and route continuity in biological navigation, this paper proposes a topology-consistent trajectory-event matching method. The method organizes odometry into ordered trajectory structure pairs formed by adjacent normal turning events and their intervening corridors, while a standard road-network map is automatically enhanced with internal direction-change points to construct corresponding map-side structures. Local candidates are retrieved according to direction, length, turning, and corridor-morphology consistency, and successive candidates are jointly confirmed under topological continuity. The confirmed discrete correspondence is then refined by local trajectory-image matching to estimate the continuous starting position. Experiments on KITTI-360 sequences 00, 08, and 09 with 135 starting positions yield an overall initialization success rate of 88.9%; successful trials achieve a mean error of 2.46 m and a median error of 2.29 m. The results show consistent performance across the evaluated road scenarios while indicating that sparse turning events and locally ambiguous road structures remain important limiting conditions.