Vision-based Detection, Tracking and Classification of Vehicles using Stable Features with Automatic Camera Calibration

A method is presented for segmenting and tracking vehicles on highways using a camera that is relatively low to the ground. At such low angles, 3D perspective effects cause significant appearance changes over time, as well as severe occlusions by vehicles in neighboring lanes. Traditional approaches to occlusion reasoning assume that the vehicles initially appear well-separated in the image, but in our sequences it is not uncommon for vehicles to enter the scene partially occluded and remain so throughout. By utilizing a 3D perspective mapping from the scene to the image, along with a plumb line projection, a subset of features is identified whose 3D coordinates can be accurately estimated. These features are then grouped to yield the number and locations of the vehicles, and standard feature tracking is used to maintain the locations of the vehicles over time. Additional features are then assigned to these groups and used to classify vehicles as cars or trucks. The technique uses a single grayscale camera beside the road, processes image frames incrementally, works in real time, and produces vehicle counts with over 90% accuracy on challenging sequences. Adverse weather conditions are handled by augmenting feature tracking with a boosted cascade vehicle detector (BCVD). To overcome the need of manual camera calibration, an algorithm is presented which uses BCVD to calibrate the camera automatically without relying on any scene-specific image features such as road lane markings

Vision based real time traffic monitoring

A system and method for detecting and tracking one or more vehicles using a system for obtaining two-dimensional visual data depicting traffic flow on a road is disclosed. In one exemplary embodiment, the system and method identifies groups of features for determining traffic data. The features are classified as stable features or unstable features based on whether each feature is on the frontal face of a vehicle close to the road plane. In another exemplary embodiment, the system and method identifies vehicle base fronts as a basis for determining traffic data. In yet another exemplary embodiment, the system and method includes an automatic calibration procedure based on identifying two vanishing points

Vehicle segmentation and tracking from a low-angle off-axis camera

We present a novel method for visually monitoring a highway when the camera is relatively low to the ground and on the side of the road. In such a case, occlusion and the perspective effects due to the heights of the vehicles cannot be ignored. Features are detected and tracked throughout the image sequence, and then grouped together using a multilevel homography, which is an extension of the standard homography to the low-angle situation. We derive a concept called the relative height constraint that makes it possible to estimate the 3D height of feature points on the vehicles from a single camera, a key part of the technique. Experimental results on several different highways demonstrate the system’s ability to successfully segment and track vehicles at low angles, even in the presence of severe occlusion and significant perspective changes.

Vehicle Segmentation and Tracking in the Presence of Occlusions

A novel method is presented for automatically visually monitoring a highway when the camera is relatively low to the ground and on the side of the road. In such a case, occlusion and the perspective effects due to the heights of the vehicles cannot be ignored. Using a single camera, the system automatically detects and tracks feature points throughout the image sequence, estimates the 3D world coordinates of the points on the vehicles, and groups those points together in order to segment and track the individual vehicles. Experimental results on different highways demonstrate the ability of the system to segment and track vehicles even in the presence of severe occlusion and significant perspective changes. By handling perspective effects, the approach overcomes a limitation of commercially available machine vision-based traffic monitoring systems that are used in many intelligent transportation systems (ITS) applications. The researchers are targeting this system as a step toward a next generation ITS sensor for automated traffic analysis