一种改进的遥感影像地形校正物理模型

An Improved Physical Model to Correct Topographic Effects in Remotely Sensed Imagery

遥感影像地形校正是提高光谱反射率反演精度的一个重要的预处理步骤。目前已经出现了多种遥感影像地形校正模型,这些模型各有优缺点。针对现有地形校正模型存在的问题和不足,在Shepherd地形校正模型的基础上,利用更高精度的天空散射辐射计算方法对其加以改进。将改进的地形校正模型和6S大气辐射传输模型相结合以2006年7月12日北京北部山区的Landsat 5 TM影像为数据源进行了地表光谱反射率反演试验。从三个方面对遥感影像地形校正效果进行了检验,结果表明该改进模型能够取得较好的地形校正效果,校正效果优于Shepherd和C校正模型。该改进模型是一种物理模型,可以应用于各种光学遥感影像。

Topographic correction for remotely sensed imagery is an important preprocessing step in order to improve the retrieval accuracy of land surface spectral reflectance in mountainous area. Various kinds of topographic correction models have been proposed in the literature. Each model has its advantages and limitations. In consideration of the limitations of the topographic correction models in the literature, an improved Shepherd topographic correction model is proposed in this paper. Diffuse irradiance is an essential factor in the physically based topographic correction model. While in the Shepherd model （originally proposed by Shepherd et al. in 2003）, accuracy of the method to compute the diffuse irradianee is relatively low; therefore, the accuracy of the land surface spectral reflectance retrieved with the Shepherd model is impacted. In order to improve the accuracy of diffuse irradiance, hence the accuracy of land surface spectral reflectance, a different method （named the Perez model）, is used to obtain the diffuse irradiance with higher accuracy in the improved Shepherd model. Landsat 5 Thematic Mapper （TM） imagery acquired on July 12th 2006, over the mountainous areas in the north of Beijing city, was employed to retrieve land surface spectral reflectance with the improved Shepherd topographic correction model and 6S （Second Simulation of the Satellite Signal in the Solar Spectrum） atmospheric radiative transfer model. Correction results were tested with three different methods. Testing result shows that the improved Shepherd topographic correction model can achieve a good correction result and is better than Shepherd and C topographic correction model. What is more, this improved model is physically based and can be applied to all kinds of optical satellite imagery.