Abstract

The problem of calculating the normalized vegetation index (NDVI) from satellite data is considered. The index values calculated from the MODIS/Aqua radiometer data by the SeaDAS software package algorithm are compared with the values obtained at the La Crau research site (France) for 7 years. The site is located near the Mediterranean coast and is a flat field where grass grows. The measurements are carried out by the ROSAS automatic photometric station. Calculations show the proximity of satellite and field measurements: bias of 0.005 and standard deviation of 0.03. The algorithm used does not take into account the effect of aerosol on the NDVI value. However, the errors due to the lack of accounting for aerosol lie within the limits of the total calculation error. There is a slight dependence of the error on the zenith angle of the sun, which varied in the range from 20° to 70°. The bidirectional reflectance distribution function of the surface on the site is uniform, except for the directions close to the sunbeam. The measurements were far from the sunbeam zone. However, the accuracy of the calculation depends on the difference between the azimuth angle of the site survey and the azimuth to the sun. NDVI mismatches due to differences in the central wave numbers of different satellites also turned out to be significant. The comparison was made for the following radiometers: MODIS/Aqua, Landsat-8/OLI-1, Landsat-9/OLI-2, and Kanopus-V/MSS.

中文翻译：

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观测条件对地球遥感数据NDVI植被指数计算精度的影响

摘要

考虑从卫星数据计算归一化植被指数（NDVI）的问题。将通过 SeaDAS 软件包算法根据MODIS/ Aqua辐射计数据计算出的指数值与 La Crau 研究地点（法国）7 年获得的值进行比较。该场地位于地中海沿岸附近，是一片长满青草的平坦田野。测量由 ROSAS 自动光度站进行。计算显示卫星和现场测量的接近度：偏差为 0.005，标准偏差为 0.03。使用的算法没有考虑气溶胶对NDVI值的影响。然而，由于未考虑气溶胶而产生的误差在总计算误差的范围内。误差对太阳天顶角有轻微的依赖性，太阳天顶角的变化范围为 20° 到 70°。除靠近太阳光的方向外，场地表面的双向反射率分布函数是均匀的。测量结果远离阳光区。然而，计算的准确性取决于现场测量的方位角与太阳方位角之间的差异。由于不同卫星的中心波数差异导致的 NDVI 不匹配也很显着。对以下辐射计进行了比较：MODIS/ Aqua、Landsat-8 /OLI-1、Landsat-9 /OLI-2 和Kanopus-V /MSS。