关键词: 未标定视频, 消失点, 消失线, 交比, 身高测量

Abstract: Considering that measurements of the pedestrian’s height from video usually depend on the knowledge of 3D scene information, or the camera’s internal calibration, a visual metrology algorithm is proposed to measure the height of a pedestrian in the uncalibrated video. Firstly, the foreground pedestrian is extracted in each frame image by simple frame difference algorithm. Then the major axis of the foreground is estimated to determine the pedestrian’s top（head） and bottom（foot） points, and two parallel virtual planes are constructed by the top/bottom points to determine the horizontal vanishing line, while the vertical vanishing point is obtained by the intersection of the major axes. Finally, the pedestrian’s height is estimated by the cross ratio theorem. This method is based on the reasonable hypothesis that a pedestrian’s height has very small difference during the normal walking process, and uses motion information sufficiently. Experimental results show that the average relative error is less than 2. 2%, so the precision can achieve the requirement.

Key words: uncalibrated video, vanishing point, vanishing line, cross ratio, height measurement