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巴丹吉林沙漠地区地物类型单一,地形起伏,形成了天然的二向反射数据集;因此,本研究利用巴丹吉林沙漠地区的ASTERGDEM产品提供的地面高程数据,计算出每个坡元所对应的太阳-观测几何信息(包括太阳天顶角与方位角和观测天顶角与方位角),假设沙丘上每个坡元的表面结构不随其坡度和坡向变化,加上Landsat-TM/ETM+对地观测的信息,就形成了对同一地物的多角度观测数据集,从而可以提取该地区的BRDF特征。为了检验该方法,利用该方法获取的BRDF特征信息模拟了25景Landsat-TM/ETM+数据,并与实际的Landsat-TM/ETM+图像进行对比分析。结果表明,Landsat-TM/ETM+前4个波段的模拟图像与真实图像地表平均反射率相比,平均误差分别为2.80%、1.92%、2.68%和2.32%,高于一般辐射定标中5%—7%的误差要求,因此本研究方法可为高分辨率数据的交叉辐射定标等应用提供参考。
In Badain Jaran Desert, the landform type is single and the topography is undulating, forming a natural bi-directional reflection dataset. Therefore, based on the surface elevation data provided by the ASTERGDEM product in the Badain Jaran Desert region, this study calculates the value of each slope element (Including the solar zenith angle and azimuth and observed zenith angle and azimuth), assuming that the surface structure of each element in the dune does not change with its slope and aspect, and Landsat-TM / ETM + Earth observation information, the formation of a multi-angle observation of the same feature dataset, which can be extracted from the region BRDF features. In order to test this method, the Landsat-TM / ETM + data from 25 Landsat-TM / ETM + images were simulated using the BRDF feature information obtained from this method and compared with the actual Landsat-TM / ETM + images. The results show that the average errors of the simulated images of the first four bands of Landsat-TM / ETM + are 2.80%, 1.92%, 2.68% and 2.32%, respectively, which are higher than the average reflectance of 5% -7% of the error requirements, the method of this study for cross-radiation calibration and other applications of high-resolution data provide a reference.