Vehicle speed measurement based on gray constraint optical flow algorithm |
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Authors: | Jinhui Lan Jian Li Guangda Hu Bin Ran Ling Wang |
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Institution: | 1. Department of Instrument Science and Technology, School of Automation and Electrical Engineering, University of Science and Technology Beijing, Beijing 100083, China;2. Department of Civil and Environmental Engineering, School of Engineering, University of Wisconsin-Madison, Madison, WI 53706, USA |
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Abstract: | Vehicle speed measurement (VSM) based on video images represents the development direction of speed measurement in the intelligent transportation systems (ITS). This paper presents a novel vehicle speed measurement method, which contains the improved three-frame difference algorithm and the proposed gray constraint optical flow algorithm. By the improved three-frame difference algorithm, the contour of moving vehicles can be detected exactly. Through the proposed gray constraint optical flow algorithm, the vehicle contour's optical flow value, which is the speed (pixels/s) of the vehicle in the image, can be computed accurately. Then, the velocity (km/h) of the vehicles is calculated by the optical flow value of the vehicle's contour and the corresponding ratio of the image pixels to the width of the road. The method can yield a better optical flow field by reducing the influence of changing lighting and shadow. Besides, it can reduce computation obviously, since it only calculates the moving target contour's optical flow value. Experimental comparisons between the method and other VSM methods show that the proposed approach has a satisfactory estimate of vehicle speed. |
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Keywords: | Vehicle speed measurement Gray constraint optical flow algorithm Improved three-frame difference algorithm Moving detection |
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