HD map

A centimetre-accurate 3D map of lanes, kerbs, signs and signals that some self-driving systems use as prior knowledge.

• Survey vehicles record roads with lidar and cameras, and the data is processed into lane geometry, traffic rules and landmarks.
• Matching live sensor data to the map pins the car's position to within about 10 cm, far better than GPS.
• It lets the car 'see' beyond its sensors, knowing a lane ends past a hill or where a stop line lies under snow.
• Roads change constantly, so maps need continual updating; that cost is why many firms now lean more on real-time perception.