Landsat 7采用双向扫描的方式，由于扫描非线性及卫星姿态和轨道的波动，使得建立卫星视线的计算量增大。引入一种求视线的快速方法，将图像上的扭曲分解为标称扫描镜及卫星运动引起的和7个偏离标称运动的微扰量引起的两个部分，详细分析了各个微扰量造成的影响，建立了一个新的视线求解方程。最后用实际的数据验证了方法的速度和精度。

With the nonlinearity of bi-directional mirror scan, motion of spacecraft and attitude variability, the model of the line of sight and Projection for Landsat 7 are very complex, and it cost much time during systematically geometric correction. In order to solve this problem, a method to simplify the model and speed up the calculation process is introduced. Image distortion is decomposed into nominal distortions and perturbation caused by seven deviations from nominal motions including one mirror-scan component, three spacecraft-motion components and three attitude components. The nominal mirror scan is selected as an estimated linear model. The nominal spacecraft motions are selected as three forecast orbit components. Three nominal attitudes are all selected as zero. The nominal line of sight can be calculated in advance which cost a great amount of time, and real-time calculation will cost only a little part of time. The whole process is modeled in detail. A new method is introduced in this paper when only partial components can be described. At last, through the analysis in theory and the experiments with real data, the speed and precision of the model are discussed, and the model is validated.