US Patent 7477988 Dual road geometry representation for position and curvature-heading

A way to represent roads as data is disclosed. Vehicle systems that provide driver assistance features relating to road curvature, such as curve warning systems or lane departure systems, use data that indicates road shape and data that indicate road position. To support these vehicle systems, a dual data representation of road geometry is provided. One road geometry data representation indicates the road position, e.g., road centerline or lane centerline, and the other road geometry data representation indicates the road shape, e.g., curvature and/or heading. Several different dual shape representations may be provided and can co-exist with existing and future database representations.