Vision‐based road slope estimation methods using road lines or local features from instant images

LiDAR-Based Multi-Task Road Perception Network for Autonomous Vehicles

“…The first step of the procedure is to create a grid in the x-y plane of the LiDAR and to assign each element of the point cloud to one of its cells. The grid covers a region which is 30 meters wide, y ∈ [− 15,15], and 46 meters long, x ∈[0, 46]; its cells are squares of size 0.10 × 0.10 meters. Some basic statistics are then computed for each grid cell: number of points; mean reflectivity; minimum, mean, and maximum height of points in the cell.…”

“…The number of points N i is transformed to density feature by (14). The height values are normalized to [−1,1] by (15), thus the predicted height value in test phase should multiplied by 5 to obtain the real height value. In the training phase, the training data is augmented with random flipping left to right technique, which extends the training samples and reduces overfitting of the network.…”

“…On the other hand, the 3D information of the road is an important factor to control a vehicle. Some researchers [15], [16] pay attention to the lateral and longitudinal road slopes. Others [17], [18] are interested in reconstructing the road surface by various models.…”

Machine Vision-Based Method for Estimating Lateral Slope of Structured Roads

“…Hyun [30] proposed a method combining Bayesian tracking and Kalman filtering to jointly estimate the road lateral-slope angle by measuring the vehicle lateral acceleration as well as the vehicle lateral-tilt angle, which can not only accurately solve the series of problems mentioned above, but also has high estimation accuracy in the case of large slope angles; however, the algorithm is complex and has high hardware requirements. The advent of machine vision has provided a new idea for road-slope estimation, and Ustunel [31] proposed a monocular camera-based method for road lateralslope estimation with high accuracy; however, it has only been studied for curved roads with large radius of curvature. Nevertheless, ultra-high (i.e., lateral slope) is often designed to mitigate the effect of centrifugal forces on vehicle stability [14], so the estimation of lateral slope for small-curvature-radius roads is more practical in realistic situations.…”