航空长焦距斜视影像二分法像方投影坐标计算

Image Projection Coordinate Calculation for Aerial Long Focal Oblique Camera Based on Bisection Method

根据像方二维坐标计算其对应的物方三维坐标即像方投影坐标计算,是航空长焦距斜视影像处理的重要内容。针对长焦距斜视相机大倾角成像的特点,提出一种利用二分法进行像方投影坐标计算的算法。首先利用传统迭代方法进行计算,在迭代次数超过一定阈值时进入二分法计算流程;根据传统迭代计算的高程最大最小值构建二分窗口,利用二分窗口的高程中值,分别与高程最大值和最小值进行比较判断,构建新的二分窗口;继续进行二分窗口的迭代更新直至窗口的大小小于一定阈值。通过包含不同地形特征的数据在长焦距斜视成像条件下的仿真实验结果表明,该方法坐标投影计算的像方精度优于0.008像素,能够适用于大倾角成像方式的像方投影坐标计算。

Calculating the corresponding object three-dimensional coordinates according to the image point coordinates is an important part of the aerial long focal oblique image processing.On the basis of analyzing the existing method,an algorithm of image projection coordinates calculation using bisection method is proposed in consideration of the characteristics of the long focal oblique camera.Firstly,the calculation is made by the conventional iteration method.When the number of iterations exceeds a certain threshold,bisection calculation flow is conducted.Then,a bisected window is constructed according to the maximum and minimum elevation of the routine iteration calculation.By using the median value of the bisected window,a new window is compared and judged.Iteratively updating the bisected window is continued until the size of the window is less than a certain threshold.The simulation results of the long focal oblique imaging data with different topographic features show that the image-side accuracy of the coordinate projection calculation is better than 0.008 pixels and thus the method can be applied to the image-side projection coordinate calculation of large-angle imaging.