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针对大角度倾斜成像航空相机拍摄距离远,激光测距设备作用距离有限的问题,提出了一种不依赖距离测量设备的直接对地目标定位算法。依据载机POS测量的载机位置、姿态信息以及航空相机中位置编码器测量的框架角位置信息,利用齐次坐标变换的方法求解目标在大地坐标系下的指向,再利用地球椭球模型和数字高程模型确定目标点的经纬度信息。采用蒙特卡洛法仿真分析载机位置姿态测量误差及相机框架角位置误差对视轴指向精度的影响,相比于仅采用地球椭球模型的目标定位算法,该算法有效降低了地形起伏对目标定位影响,在目标区域地形起伏标准差大于10m时,大角度倾斜成像的定位精度明显提高。采用飞行试验数据验证了该目标定位算法的有效性,在飞行高度18 000m拍摄框架横滚角小于63°时,目标定位圆概率误差小于70m,可满足工程实际需要。
Aiming at the problem of shooting distance of large-angle tilt imaging aerial camera and limited distance of laser ranging device, a direct-to-ground target localization algorithm without distance measurement equipment is proposed. According to the position and attitude information of the carrier and the frame angular position information measured by the position encoder in the aerial camera, the homogeneous coordinate transformation method is used to solve the target’s orientation in the geodetic coordinate system. The ellipsoid model and The digital elevation model determines the longitude and latitude information of the target point. The Monte Carlo method is used to simulate the effect of the error of position and attitude measurement of the aircraft and the error of the angular position of the camera frame on the pointing accuracy of the optic axis. Compared with the target localization algorithm using only the geo-ellipsoid model, the algorithm effectively reduces the influence of the topography on the target When the standard deviation of relief in the target area is more than 10m, the positioning accuracy of large-angle tilt imaging is obviously improved. The flight test data are used to verify the effectiveness of the target localization algorithm. When the shooting frame roll angle is less than 63 ° at a flight altitude of 18 000m, the error of the target locating circle is less than 70m, which can meet the actual engineering needs.