遥感影像邻坡反射辐射计算与分析探讨

Calculating and Analyzing Radiance Reflected from Neighboring Slopes on Remote Sensing Image

通过对邻坡反射辐射机理的剖析,考虑邻坡反射路径中气柱程辐射、透过率等影响因素,建立了邻坡反射辐射物理模型,实现了对像元接收到的邻坡反射辐射照度及其比例的定量化计算。影像实验结果表明,像元接收到的邻坡反射辐射照度取决于周边下垫面反射率、地形、太阳入射光谱等因素的共同影响,高反射率的周边下垫面推升邻坡反射辐射照度;像元的邻坡反射辐射比例取决于它接收到的直接辐射、散射辐射与邻坡反射辐射的综合计算,低照度像元的邻坡反射辐射比例较高,阴影像元在弱散射波段的邻坡反射辐射比例一般高于强散射波段。

A physically-based model for calculating radiance reflected from neighboring slopes is devel-oped. The path radiance and atmospheric transmittance of reflected terrain radiance between two adja-cent slopes are considered. The model computes terrain irradiance illumination and its ratio to total ir- radiance as quantitatively supported by DEM data and atmospheric parameters. According to an exper- iment with spot images and the principle of terrain irradiance, terrain irradiance illumination depends on the surface reflectance of the adjacent objects, terrain, the total irradiance reaching the adjacent slopes and other factors. The radiance reflected from neighboring slopes usually is small, but it has to be accounted in high surface reflectance areas. The ratio of terrain irradiance to total irradiance de- pends on direct irradiance, diffused irradiance, and terrain irradiance, which are received by a target pixel. The ratio of terrain irradiance to total irradiance of low illumination pixels is larger than that of its surrounding pixels. For a shadow pixel, the ratio of terrain irradiance to total irradiance of the weak scattering bands is larger than that of the strong scattering bands.