卫星遥感影像数据的地形影响校正

地形影响校正是遥感影像辐射校正的主要内容，是获得地表真实反射率的必不可少的一步。本文提出的方法中，将6S大气校正模型与数字高程模型（DEM）结合起来，计算出水平地面上接收到的直接辐射与漫射辐射，并采用一个简单公式将其转化到地形坡面上，从而实现了对地面的辐射能量校正，同时，6S模型对卫片还进行了大气改正，可输出卫片在大气层底部的辐射亮度与反射率；然后将基于坡面的反射率换算到其在水平面上的对应值，即实现了对反射率的地形影响校正。在我们所实施的“滇金丝猴保护项目”的植被研究中，应用本方法对梅里雪山区域的ETM＋影像进行了校正，大大减小了地形对遥感数据的附加影响。

Correcting Satellite Imagery for Topographic Effects

Topographic correction is one of the major tasks for remote sensing imagery correction, and it is also a necessary step to get the real reflectance from surface.. In this article, the 6S atmospheric model with a digital elevation model(DEM) is used to calculate direct and diffuse illumination on horizontal surface, and the illumination is then transformed to sloping surface, meanwhile, 6S model can perform atmospheric correction over the imagery and output the radiance and reflectance at the bottom of atmosphere; Then the sloping surface reflectances are transformed to their horizontal surface equivalents, that is the result of topographic correction. This method is used in our "Yunnan Golden Monkey Conservation Project" to process ETM imagery for vegetation mapping in moirigkawagarbo area, the effect over satellite imagery induced by topography is reduced greatly.