Landsat7的双向扫描模式、姿态波动和增强型专题制图仪ETM (Enhanced Thematic Mapper )传感器本身的特点等必然导致遥感图象的几何畸变,同时复杂的成像几何模型也增加了几何校正的难度.为此,在研究了其成像几何模型,分析了影响畸变的因素后,给出了完整的系统级几何校正算法,包括视线产生和投影、姿态合成和重采样等,并对重采样中的间隙插值和延迟进行了深入分析,采用了简化方法.实验结果表明,校正后图象的定位精度、变形度和行间相关度达到了系统级几何校正的要求,验证了算法在保证速度的前提下,具有较高的正确性.

The bi-directional cross track scanning, attitude fluctuation and the ETM sensor itself of Landsat7 result in the geometrical distortions including underscan, overscan and misalignment, which make geometric calibration more difficult than other kinds of model. The complicated imaging model increase the difficulty of geometric calibration as well. After the geometric model of imaging is studied, and the factors influencing imaging are analyzed, the systematically geometric calibration algorithms are derived, including generation and projection of line of sight, combination of attitude, generation of correction grid, finding corresponding input grid cell for a given output space, resampling, and so on. The model of line of sight are built in detail. Especially, the gap interpolation and detector delay are considered, and simplified methods are introduced to settle them. Finally, three parameters are introduced to evaluate the result of geometric calibration, including location precision, distortion and correlation between two lines. Experimental results show that the algorithms lead to good location precision, small distortion and good correlation between lines which all reach the requirement of the systematically geometric calibration, so validate the algorithms.