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为解决基于单张图像的传统无人机对地定位方法的精度不能满足精确打击作战需求的问题,本文提出一种新的无人机对地定位方法。该方法通过线性化共线条件方程建立摄像机姿态角和焦距迭代计算模型,根据非共线位置拍摄的多帧图像及至少3个可识别同名像点坐标迭代计算摄像机姿态角和焦距的精确值,然后利用多摄站前方交会法求取地面目标的三维坐标。该方法不依赖于数字高程模型(DEM)及像片内外方位元素的测量值,消除了传统无人机对地定位方法三个定位误差源中的两个,因此具有较高的定位精度。仿真与真实图像实验计算表明:摄站本身坐标误差的大小是决定对地定位精度的主要因素,当采用DGPS定位摄站时,可以获得很高的目标定位精度。
In order to solve the problem that the accuracy of the traditional method of locating the ground based on a single image can not meet the demand of precision strike operation, a new method of locating the ground to UAV is proposed in this paper. In this method, the camera pose angle and the focal length iterative calculation model are established by linearizing the collinear condition equation. Based on the multi-frame images taken at non-collinear positions and at least three recognizable coordinates of the same name point, the exact values of attitude and focal length of the camera are iteratively calculated. Then use the multi-camera intersection method to get the three-dimensional coordinates of the ground target. This method does not depend on the digital elevation model (DEM) and the measured values of the azimuth and azimuthal elements inside the image, eliminating two of the three positioning error sources of the traditional UAV-to-ground positioning method, and therefore has higher positioning accuracy. Experimental results of simulation and real images show that the size of the coordinate error of the station itself is the main factor that determines the accuracy of the location. When the DGPS is used to locate the station, a high target location accuracy can be obtained.