大气校正前后山地流域NDVI变化特征对比

Comparison of change characteristics of NDVI in mountain basin before and after atmospheric correction

大气校正是遥感影像处理的重要环节,探究大气校正前后归一化植被指数(normalized difference vegetation index,NDVI)特征及其地形梯度特征具有一定理论意义。以贵州省境内包溪河流域为例,基于Landsat8遥感影像和FLAASH大气校正,探究NDVI分等级和分地形计算误差。得出以下结论:①未进行大气校正所得NDVI在空间上总体被低估;②未经大气校正所得NDVI不能反映各阶段趋势和比例关系,存在严重偏差,NDVI> 0. 6时绝对误差超过20%;③大气校正与否影响各海拔NDVI变化趋势和数值高低,海拔在1 000 m以下时绝对误差上升,其后波动下降;④大气校正与否对各坡度NDVI趋势和数值均有影响,随坡度上升,绝对误差先上升后下降,坡度在[45°,50°)时绝对误差最大;⑤大气校正与否对各坡向NDVI趋势均有影响,西坡绝对误差最大,东坡最小。

Atmospheric correction is an important part of remote sensing image processing.It is of theoretical significance to explore the characteristics of normalized difference vegetation index(NDVI)and its terrain gradient before and after atmospheric correction.This paper draws the following conclusions:①The NDVI obtained without atmospheric correction is generally underestimated in space.②The NDVI obtained without atmospheric correction cannot reflect the trend and proportional relationship of each stage.The NDVI without atmospheric correction has serious deviation,and the NDVI is more than 0.6.The absolute error is over 20%.③Whether the atmospheric correction is made or not affects the NDVI change trend and the numerical value of each altitude;the absolute error increases below 1000 m,and the absolute error fluctuation decreases thereafter.④Whether the atmospheric correction is made or not has an effect on the slope NDVI trend and value;as the slope increases,the absolute error first rises and then falls,and the slope(45°,50°)absolute error is the largest.⑤Whether the atmospheric correction is made or not has an effect on the NDVI trend of each slope;the absolute error of west slope is the largest,and the east slope is the smallest.