一种基于物方几何约束的线阵推扫式影像坐标反投影计算的快速算法

A Fast Algorithm for Back Project Calculation of Linear Array Pushbroom Imageries Based on Object-space Geometric Constraints

根据物点坐标计算其对应的像点坐标即坐标反投影计算,是线阵推扫式影像处理的基础。由于线阵推扫式影像多中心成像的特点,必须通过迭代计算物点在成像时刻对应的扫描行,然后再精确计算物点对应的像点坐标,因此,坐标反投影计算的效率直接影响线阵推扫式影像的处理效率。本文提出一种基于物方几何约束的线阵推扫式影像坐标反投影计算的快速算法。该算法采用了一种高效的基于物方投影几何约束的最佳扫描线搜索策略,基于线阵推扫式影像特有的摄影几何约束,将传统的基于CCD探元焦平面坐标约束的像方迭代搜索过程,转化为基于各扫描行中心投影面约束关系的物方简单几何计算的搜索过程,从而有效地避免了传统像方搜索策略中基于严密传感器数学模型的繁琐计算,有效减少了最佳扫描线搜索的计算量。通过对机载和星载推扫式影像数据的实验,验证了该算法的可行性、精确性和高效性。

Linear array pushbroom sensors have been widely researched and applied in the aerospace area and ex plore new approaches for photogrammetric and remote sensing applications, with broad utilization foreground as well as great challenge. Calculating the image-space coordinates of the ground points, which can be also called hack project calculation, is the basis for the processing and applications of linear array pushbroom image ries, such as the stereoscopic mapping, incorrect image geometric rectification and so on. As a result of the multiple central perspectives imaging principle, each scanline captured by the CCD linear array sensor owns six exterior orientation parameters at its corresponding exposure time, that is to say, the image point coordinates will not be accurately calculated out until the best scanline is determined by iterative search process. Obvious ly, the best scanline search is the foremost problem for the back project calculation, the efficiency of which now becomes the bottleneck of processing efficiency of linear pushbroom images. After a brief review of the various existing image-space oriented search strategies and the pushbroom principle of line sensors, this paper proposes a fast algorithm for back project calculation of linear pushbroom images, which adopts an effective best scanline search strategy based on the novel Central Perspective Plane of Scanline （CPPS） constraints. According to the CPPS constraints, the best scanline search process can be simply carried out by analytical geo- metric calculations, thus greatly releasing the burden on object to image back project calculations during image data processing. Experiments tested on airborne and spaceborne linear pushbroom images demonstrate the al gorithm＇s feasibility, accuracy, robustness and high efficiency.