Relative Azimuthal-Angle Matching (RAM): A Screening Method for GEO-LEO Reflectance Comparison in Middle Latitude Forests
Relative Azimuthal-Angle Matching (RAM): A Screening Method for GEO-LEO Reflectance Comparison in Middle Latitude Forests
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DOI：
10.3390/rs11091095
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发表时间：
2019-05
期刊：
影响因子：
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通讯作者：
Y. Adachi;R. Kikuchi;K. Obata;H. Yoshioka
中科院分区：
文献类型：
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作者：
Y. Adachi;R. Kikuchi;K. Obata;H. Yoshioka
介绍了一种数据筛选方法，用于比较地球静止轨道（GEO）卫星和低轨（LEO）卫星在中纬度森林地区收集的反射率。该方法试图减小GEO和LEO观测的相对方位角之间的差异。该方法被称为相对方位角匹配（RAM），利用GEO卫星的高时间分辨率，这使得能够在一天内收集大范围的相对方位角。RAM方法的性能进行了评估，使用的Himawari-8/高级Himawari成像仪（AHI）和Terra/中分辨率成像光谱仪（MODIS）收集的可见光和近红外波段的数据。比较了用RAM方法选取的MODIS和AHI反射率对与两个传感器同时获取的反射率对的一致性。在进行大气校正和云筛选之后，对数据进行了逐像素匹配。结果表明，RAM提高了约10%的反射率的平均相对于同时观测的红色和近红外波段。观察到两个波段的显著改善（20%），特别是在秋季和冬季收集的数据中。RAM的性能在很大程度上取决于季节。特别是在夏季，RAM选择的反射率对表现出比太阳天顶角匹配（SZM）更少的一致性。结果还表明，光谱响应函数对两种传感器的绿色和红色波段有较大的影响。
This study introduced a data screening method for comparing the reflectances in middle latitude forest regions collected by a Geostationary Earth Observing (GEO) satellite and a Low Earth Orbit (LEO) satellite. This method attempts to reduce the differences between the relative azimuth angles of the GEO and LEO observations. The method, called relative azimuthal-angle matching (RAM), takes advantage of the high temporal resolution of the GEO satellites, which enables collection of a wide range of relative azimuth angles within a day. The performance of the RAM method was evaluated using data in the visible and near-infrared bands collected by the Himawari-8/Advanced Himawari Imager (AHI) and the Terra/Moderate Resolution Imaging Spectroradiometer (MODIS). The consistency of the reflectance pairs of MODIS and AHI selected by the RAM method was compared with the consistency of the reflectance pairs acquired simultaneously by the two sensors. The data were matched pixel-by-pixel after applying atmospheric corrections and cloud screening. The results show that RAM improved the reflectance ratio by approximately 10% for the red and NIR bands on average relative to the simultaneous observations. Significant improvements in the two bands were observed (20%), especially among data collected in the fall and winter. Performance of RAM depends largely on season. Especially in summer, the reflectance pair chosen by RAM showed less consistency than solar zenith-angle matching (SZM). The results also indicated the relatively large influence of the spectral response functions on the green and red bands of the two sensors.