Abstract

I. INTRODUCTIONThis work is motivated by the problem of video motion class detection in order to understand object behaviors. The underlying issue is the content-based exploitation of video footage which is of continuously increasing interest in numerous applications, e.g., for retrieving video sequences in large TV archives [12] [42], creating automatic video summarization of sport TV programs [32], or detecting specific actions or activities in video-surveillance [6] [26]. It implies to shorten the well-known semantic gap between computed low-level features and high-level concepts. Considering 2D trajectories is attractive since they form computable image features which capture elaborated spatiotemporal information on the viewed actions. Methods for tracking moving objects in an image sequence are now available to get reliable enough 2D trajectories in various situations. These trajectories are given as a set of consecutive positions in the image plane (x, y) over time. If they are embedded in an appropriate modeling framework, highlevel information on the dynamic scene can then be reachable.

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ABSTRACT:Scene analysis, in urban environments, deals with street modeling and understanding. A street mainly consists of roadways, pavements (i.e., walking areas), facades, still and moving obstacles. In this paper, we investigate the surface modeling of roadways and pavements using LIDAR data acquired by a mobile laser scanning (MLS) system. First, road border detection is considered. A system recognizing curbs and curb ramps while reconstructing the missing information in case of occlusion is presented. A user interface scheme is also described, providing an effective tool for semi-automatic processing of large amount of data. Then, based upon road edge information, a process that reconstructs surfaces of roads and pavements has been developed, providing a centimetric precision while reconstructing missing information. This system hence provides an important knowledge of the street, that may open perspectives in various domains such as path planning or road maintenance.