How do high-definition maps enable precise localization for autonomous vehicles?

HD maps contain centimeter-accurate data about roads: Lane geometry, road boundaries, traffic signs, traffic lights, road markings, and static features. Localization process: Vehicle sensors detect features (lane markings, signs, poles), matching algorithm correlates observed features with map features, position is refined to centimeter accuracy. Methods include point cloud matching for lidar, semantic feature matching for cameras, and particle filter or graph-based optimization. HD maps enable: Planning with accurate lane information, anticipating road geometry beyond sensor range, and functioning when markings are obscured. Challenges include map creation cost, keeping maps current, and handling unmapped areas.