黄河源区遥感数据的大气校正及其效果分析

利用6S模型结合暗目标法确定TM过境时的最优气象能见度,分别使用MODIS气溶胶产品(MOD04)、最优气象能见度作为TM的气溶胶光学厚度,对黄河源区的Landsat TM数据进行大气校正。以同步野外实测地面数据为标准,比较了两种气溶胶参数输入方法的校正结果,并从光谱曲线、植被指数、草地生物量的估算三方面探讨了大气校正的效果,两种气溶胶参数输入方法均可以对遥感图像进行有效的大气校正,消除因散射增加的辐射能量,同时补偿因吸收而损失的辐射能量。经过大气校正后的TM光谱更接近真实地表光谱,更有助于地物真实光谱信息的提取,同时对与该地区相似气候条件下影像的大气校正有借鉴意义。

Atmospheric Correction of Remote Sensing Images in the Source Region of the Yellow River and Analysis of Its Effect

This paper deals with a suitable atmospheric correction method based on Landsat TM image in the source region of the Yellow River,a method based on 6S radiation transfer code and dark object was used to determine the optimal meteorological visibility on sensing time,and the MODIS aerosol product(MOD04) and the optimal meteorological visibility were used to extract Aerosol Optical Thickness(AOT) values at 550 nm respectively in the atmosphere correction.Validation analysis was conducted by comparing the reflectance data corrected and uncorrected atmospherically,significant differences occurred between them.The values of the corrected reflectance of TM visible bands decreased obviously,whereas those of TM near-infrared band increased.The retrieved surface reflectance and vegetation index after atmospheric correction were evaluated against the ground-based reflectance measured by ASD Field Spec Handheld during Landsat TM satellite overpass,and it is shown that the curves of the figures are similar.Furthermore,the vegetation index after atmospheric correction used for estimating grassland biomass can achieve better results.That is to say both methods used in this paper to extract AOT values could carry out the radiation correction to radiation-induced distortion caused by atmospheric effects,which can eliminate the radiative energy increased by scattering and simultaneously compensate the radiative energy lost by absorption,the atmospheric corrected TM spectrum is closer to measured objects spectrum,so it is more conducive to extracting ground object spectrum information,This method also can be applied in the regions with similar climate conditions for references.