Urban Traffic Monitoring from LIDAR Data with a Two-Level Marked Point Process Model

In this report we present a new object based hierarchical model for joint probabilistic extraction of vehicles and coherent vehicle groups - called traffic segments - in airborne and terrestrial LIDAR point clouds collected from crowded urban areas. Firstly, the 3D point set is segmented into terrain, vehicle, roof, vegetation and clutter classes. Then the points with the corresponding class labels and intensity values are projected to the ground plane. In the obtained 2D class and intensity maps we approximate the top view projections of vehicles by rectangles. Since our tasks are simultaneously the extraction of the rectangle population which describes the position, size and orientation of the vehicles and grouping the vehicles into the traffic segments, we propose a hierarchical, Two-Level Marked Point Process (L2MPP) model for the problem. The output vehicle and traffic segment configurations are extracted by an iterative stochastic optimization algorithm. We have tested the proposed method with real aerial and terrestrial LiDAR measurements. Our aerial data set contains 471 vehicles, and we provide quantitative object and pixel level comparions results versus two state-of-the-art solutions

Urban Traffic Monitoring from Aerial LIDAR Data with a Two-Level Marked Point Process Model

In this paper we present a new model for joint extrac- tion of vehicles and coherent vehicle groups in airborne LIDAR point clouds collected from crowded urban areas. Firstly, the 3D point set is segmented into terrain, vehicle, roof, vegetation and clutter classes. Then the points with the corresponding class labels and intensity values are projected to the ground plane, where the optimal vehicle and traffic segment configuration is described by a Two-Level Marked Point Process (L2MPP) model of 2D rectangles. Finally, a stochastic algorithm is utilized to find the optimal configuration

A Marked Point Process Model for Vehicle Detection in Aerial LIDAR Point Clouds

http://www.isprs2012.org/abstract/82.as

Extraction of Vehicle Groups in Airborne Lidar Point Clouds with Two-Level Point Processes

In this paper we present a new object based hierarchical model for joint probabilistic extraction of vehicles and groups of corresponding vehicles - called traffic segments - in airborne Lidar point clouds collected from dense urban areas. Firstly, the 3-D point set is classified into terrain, vehicle, roof, vegetation and clutter classes. Then the points with the corresponding class labels and echo strength (i.e. intensity) values are projected to the ground. In the obtained 2-D class and intensity maps we approximate the top view projections of vehicles by rectangles. Since our tasks are simultaneously the extraction of the rectangle population which describes the position, size and orientation of the vehicles and grouping the vehicles into the traffic segments, we propose a hierarchical, Two-Level Marked Point Process (L2MPP) model for the problem. The output vehicle and traffic segment configurations are extracted by an iterative stochastic optimization algorithm. We have tested the proposed method with real data of a discrete return Lidar sensor providing up to four range measurements for each laser pulse. Using manually annotated Ground Truth information on a data set containing 1009 vehicles, we provide quantitative evaluation results showing that the L2MPP model surpasses two earlier grid-based approaches, a 3-D point-cloud-based process and a single layer MPP solution. The accuracy of the proposed method measured in F-rate is 97% at object level, 83% at pixel level and 95% at group level

Instant Object Detection in Lidar Point Clouds

In this paper we present a new approach for object classification in continuously streamed Lidar point clouds collected from urban areas. The input of our framework is raw 3-D point cloud sequences captured by a Velodyne HDL-64 Lidar, and we aim to extract all vehicles and pedestrians in the neighborhood of the moving sensor. We propose a complete pipeline developed especially for distinguishing outdoor 3-D urban objects. Firstly, we segment the point cloud into regions of ground, short objects (i.e. low foreground) and tall objects (high foreground). Then using our novel two-layer grid structure, we perform efficient connected component analysis on the foreground regions, for producing distinct groups of points which represent different urban objects. Next, we create depth-images from the object candidates, and apply an appearance based preliminary classification by a Convolutional Neural Network (CNN). Finally we refine the classification with contextual features considering the possible expected scene topologies. We tested our algorithm in real Lidar measurements, containing 1159 objects captured from different urban scenarios

Fast 3-D Urban Object Detection on Streaming Point Clouds

Efficient and fast object detection from continuously streamed 3-D point clouds has a major impact in many related research tasks, such as autonomous driving, self localization and mapping and understanding large scale environment. This paper presents a LIDAR-based framework, which provides fast detection of 3-D urban objects from point cloud sequences of a Velodyne HDL-64E terrestrial LIDAR scanner installed on a moving platform. The pipeline of our framework receives raw streams of 3-D data, and produces distinct groups of points which belong to different urban objects. In the proposed framework we present a simple, yet efficient hierarchical grid data structure and corresponding algorithms that significantly improve the processing speed of the object detection task. Furthermore, we show that this approach confidently handles streaming data, and provides a speedup of two orders of magnitude, with increased detection accuracy compared to a baseline connected component analysis algorithm

Towards 4D Virtual City Reconstruction From Lidar Point Cloud Sequences

In this paper we propose a joint approach on virtual city reconstruction and dynamic scene analysis based on point cloud sequences of a single car-mounted Rotating Multi-Beam (RMB) Lidar sensor. The aim of the addressed work is to create 4D spatio-temporal models of large dynamic urban scenes containing various moving and static objects. Standalone RMB Lidar devices have been frequently applied in robot navigation tasks and proved to be efficient in moving object detection and recognition. However, they have not been widely exploited yet for geometric approximation of ground surfaces and building facades due to the sparseness and inhomogeneous density of the individual point cloud scans. In our approach we propose an automatic registration method of the consecutive scans without any additional sensor information such as IMU, and introduce a process for simultaneously extracting reconstructed surfaces, motion information and objects from the registered dense point cloud completed with point time stamp information

Viewpoint-free Video Synthesis with an Integrated 4D System

In this paper, we introduce a complex approach on 4D reconstruction of dynamic scenarios containing multiple walking pedestrians. The input of the process is a point cloud sequence recorded by a rotating multi-beam Lidar sensor, which monitors the scene from a fixed position. The output is a geometrically reconstructed and textured scene containing moving 4D people models, which can follow in real time the trajectories of the walking pedestrians observed on the Lidar data flow. Our implemented system consists of four main steps. First, we separate foreground and background regions in each point cloud frame of the sequence by a robust probabilistic approach. Second, we perform moving pedestrian detection and tracking, so that among the point cloud regions classified as foreground, we separate the different objects, and assign the corresponding people positions to each other over the consecutive frames of the Lidar measurement sequence. Third, we geometrically reconstruct the ground, walls and further objects of the background scene, and texture the obtained models with photos taken from the scene. Fourth we insert into the scene textured 4D models of moving pedestrians which were preliminary created in a special 4D reconstruction studio. Finally, we integrate the system elements in a joint dynamic scene model and visualize the 4D scenario