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Wang Z.,Nanjing Normal University | Zhang Y.,Nanjing Normal University | Liu X.,Nanjing Normal University | Liu X.,Key Laboratory of Police Geographic Information Technology Ministry of Public Security | And 2 more authors.
Guofang Keji Daxue Xuebao/Journal of National University of Defense Technology | Year: 2015

Camera coverage is an important basis of camera network initial configuration, optimal deployment and so on. Its precision and efficiency are the critical influences on the results of coverage analysis, which are very important to the application of large area camera coverage analysis, but many methods do not consider them. A new method to efficiently estimate camera coverage was proposed. Firstly, the geographic space was dispersed into grids. Secondly, the statuses of the four corners of each grid were computed. If the corner was covered by the camera, the status was denoted by using 1 or 0. So the status of the gird can be presented by the code which is either 0 or 1. Consequently there are 16 statuses to represent the status of a grid. Finally, if the code of the grid was not (0000) or (1111), the gird would be divided into four isometrical sub-girds until the sub-girds were small enough or their codes were (0000) or (1111). According to the levels and statues of all grids, the whole camera coverage was estimated. Experimental results show that the proposed method can obtain more precise camera and can give consideration to both efficiency and accuracy. ©, 2015, National University of Defense Technology. All right reserved.


Liu D.,Nanjing Normal University | Liu X.,Nanjing Normal University | Liu X.,Key Laboratory of Police Geographic Information Technology Ministry of Public Security | Wang M.,Nanjing Normal University | Wang M.,Key Laboratory of Police Geographic Information Technology Ministry of Public Security
Guofang Keji Daxue Xuebao/Journal of National University of Defense Technology | Year: 2015

The camera calibration from vanishing points is easily distracted by noise in the image, leading to inaccurate results which are often inadmissible for camera calibration. To overcome the limitation, an iterative optimization approach, which makes full use of geometric constraints of vanishing points and ellipse in the image, was presented for self-calibration from single image. According to the pole-polar relationship and the orthogonality represented by it, a set of orthogonal conjugate vanishing point pairs were calculated through using the ellipse curve and the coplanar vanishing line. A nonlinear model of the principle distance and principle point was established on the basis of these vanishing point pairs. Choosing the minimum variance of principle distances as optimization criterion and setting multiple points as the initial values of the principle point, the principle distance and principle point were iteratively optimized and their optimal results were obtained. Simulated results and real data show that the approach can effectively realize camera self-calibration from a single image. Compared with the camera calibration method using vanishing points, the approach achieves more satisfactory calibration results. ©, 2015, National University of Defense Technology. All right reserved.

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