Highway Lane Line Edge Extraction by Incorporating Improved α-Shape and Cubic B-Spline Curve Fitting Algorithms

With the rapid development of autonomous driving technology and high-accuracy maps, accurate detection of lane line edges has become critical. Traditional methods, especially those relying on visual sensors, are often limited by light variations and environmental factors. Mobile laser scanning (MLS) systems is capable of generating high-accuracy 3D point cloud, but it still faces challenges such as incomplete information extraction and lack of precision in the process of extracting lane line edges. To solve these problems, this study proposes a highway lane line edge extraction method that combines an improved α-shape with a cubic B-spline curve fitting algorithm. Firstly, statistical filtering and radius filtering algorithms are used to remove isolated points from the point cloud and obtain pure highway laser point cloud. Based on the geometric properties and spatial proximity of the point cloud, adaptive voxel filtering is used for downsampling, and a region-growing algorithm is used to accurately extract the road point cloud. Secondly, based on the reflection intensity information of the point cloud, the optimal threshold is automatically determined with the help of the OTSU (Maximum Between-Class Variance Method) algorithm to separate the lane line point cloud from the road surface point cloud; and the shape parameters are adjusted based on the improved α-shape algorithm to control the completeness of the lane edge extraction, and to accurately extract the edge contour of the lane line. Finally, the improved cubic B-spline curve fitting method is used to approximate the generated lane edge fitting curves, and the vectorized extraction of the curves is achieved by introducing specific constraints. In this paper, point cloud experiments are conducted on both straight and curved sections of the highway to verify the reliability of the algorithm. Experimental results show that the root mean square error of lane line edge extraction and fitting is 7.8 mm in the curved section and 19 mm in the straight section, demonstrating that the proposed method is able to accurately extract the complete lane line edges of highways.