Vehicle speed measurement using an imaging method

The feasibility of a simple imaging technique for measuring vehicle speed was studied. The camera axis was perpendicular to the road and a single interlaced frame was captured by a frame store. The basis of the speed measurement method is the comparison of just two consecutive half frames, using a matching technique to determine the displacement of the vehicle between consecutive half frames. Using a conventional video camera, these images were significantly blurred, although this did not hinder the procedure for determining the pixel displacement. From the displacement, the vehicle speed was determined from known vehicle dimensions. Reasonable agreement was obtained between speed observed on the speedometer and speed calculated from the speed and scale data. Since the image pair is created by separating the interlaced picture into half frames, the separated images must be aligned by one scan line to achieve a proper correlation. For both half frames, each empty line was filled by repeating the previous active scan line to make a full 512×512 image