地形起伏对陆地卫星的NDVI影响研究

Study on the Effect of Topographic Relief on NDVI of Landsat

NDVI是表征植被叶面积密度的重要遥感指数,是估测植被盖度、林分郁闭度、生物量及碳储量、植被生长状况和作物产量的重要参数。相关研究表明地形起伏对光谱数据有较大的影响,但其对NDVI的影响特征值得进一步研究。针对以上问题,选用C校正模型对Landsat数据进行地形校正,消除了地形起伏对光谱数据的影响,并对比和分析了地形校正及未经地形校正提取的NDVI。结果表明:地形校正前后图像总体的NDVI有显著性差异,其中较小坡度植被区域无显著性差异,较大坡度植被区域存在显著性差异;阴坡整体的NDVI有变大趋势、阳坡略微减少,半阴半阳坡无明显变化;农地在不同坡向下无显著差异且整体变化不明显,针叶林、阔叶林在阴坡和阳坡上的NDVI变化幅度大于半阴半阳坡。地形校正对NDVI估测值存在着一定影响,从而进一步影响着基于NDVI参量的各种遥感估算结果,故消除地形起伏对光谱的影响,可以提高定量遥感估测精度。

NDVI is an important remote sensing index of characterization of vegetation leaf area density and an important parameter in the estimation of vegetation coverage,forest canopy density,biomass and carbon storage and vegetation growth status and crop yield.Correlation study have indicated that the to-pography fluctuation has a great influence on the spectral data,but its effect on NDVI is worth further studying.In view of the above problems,the C calibration model was used to correct the topographic cor-rection of Landsat data,eliminating the influence of topographic relief on spectral data,and comparing and analyzing the NDVI.The results show that the terrain correction and overall image of NDVI have significant difference,of which smaller slope vegetation areas have no significant difference,the larger slope vegetation region has significant difference;shady slope overall NDVI tends to be bigger,sunny slope slightly reduced,semi shaded slope has no obvious change;farmland at different slopes has no significant difference and overall change is not obvious,for coniferous forest and broad-leaved forest at shady slope and sunny slope,change of NDVI amplitude is greater than that of half shade and semi sunny slopes.Topo-graphic correction of NDVI estimated value has some influence,thus further influences based on NDVI parameters of various remote sensing estimation results,so eliminating the influence of relief on the spectra can improve the accuracy of quantitative estimation by remote sensing.