Comparison of satellite- and ground-based NDVI above different land-use types
Comparison of satellite- and ground-based NDVI above different land-use types
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DOI：
10.1007/s00704-009-0103-3
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发表时间：
2009-01
影响因子：
3.4
通讯作者：
A. Tittebrand;U. Spank;C. Bernhofer
中科院分区：
文献类型：
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作者：
A. Tittebrand;U. Spank;C. Bernhofer
为了评估使用卫星（中分辨率成像光谱仪：MODIS）和地面测量（高光谱光谱仪和宽带微气象传感器）归一化差异植被指数（NDVI），本研究比较了NDVI来自五个实验（FLUXNET）现场网站（草地，冬小麦，玉米，云杉，山毛榉）在德国在2006年6月和2007年4月至9月。此外，在一个特定的土地利用类（草和冬小麦）内测量的地面辐射的空间变异性进行了调查，以分析FLUXNET塔值的准确性。此外，光谱仪值对视角的角度依赖性被确定，以提高光谱仪测量的空间代表性，特别是在树木上方，在最低点测量时受土壤部分和塔结构的影响。卫星和地面测量的NDVI之间的最佳协议被发现为冬小麦（2006年）的值从0.79-0.88其次是草（2006年），显示NDVI值在0.71和0.86之间。同一土地利用类型内的空间变异性小于不同测定方法引起的差异。在更开阔的树冠（玉米，山毛榉），光谱仪测量与60°视角的太阳平面方向被认为是更好地对应于卫星派生的归一化植被指数。我们的地面结果与宽带归一化差异植被指数一起，可以补充卫星得出的归一化差异植被指数。
In order to evaluate the use of satellite (moderate resolution imaging spectroradiometer: MODIS) and ground-measured (hyperspectral spectrometer and broadband micrometeorological sensors) normalized difference vegetation index (NDVI), this study compares NDVI derived from five experimental (FLUXNET) field sites (grassland, winter wheat, corn, spruce, and beech) in Germany in June 2006 and April-September 2007. In addition, the spatial variability of ground radiation measured within one specific land-use class (for grass and winter wheat) was investigated to analyze the accuracy of the FLUXNET tower values. Furthermore, the angular dependence of spectrometer values on viewing angles was determined in order to enhance the spatial representativeness of spectrometer measurements which, especially above trees, are affected by soil parts and the tower structure when measured in nadir. The best agreement between the satellite- and ground-measured NDVI was found for winter wheat (2006) with values from 0.79–0.88 followed by grass (2006), showing NDVI values between 0.71 and 0.86. The spatial variability of NDVI within one land-use type was lower than the differences caused by the different NDVI determination methods. Above more open canopies (corn, beech), spectrometer measurements with 60° viewing angle in solar plane direction were found to better correspond to satellite-derived NDVI. Together with broadband NDVI, our ground-based results can complement satellite-derived NDVI.