大气校正对九连山植被覆盖度。感估算的影响

    Effects of atmospheric correction on remote sensing estimation of vegetation coverage in Jiulianshan

    • 摘要: 以江西九连山保护区为例,利用基于归一化差异植被指数(NDVI)的像元二分法模型分别在TM 影像的原始DN 值、表观反射率以及经过基于MORTRAN 辐射传输模型和经过简单传输模型的黑暗像元法校正后的地面反射率的基础上对研究区的植被覆盖度进行提取,将所得4 类植被覆盖度的估算值与实测值进行比较,分析大气校正对植被覆盖度。感估算的影响。结果表明,FLAASH 和DOS 两种大气校正方法虽校正原理不同,但通过对样地实测值的拟合度来看,均能有效消除大气影响,有效提高植被覆盖度。感估算的精度;而辐射定标后的表观反射率却与原始影像DN 值估算的植被覆盖度差异不明显,说明植被覆盖度估算精度的提高来源于大气校正作用,辐射定标影响甚小。因此,在植被覆盖度较高的亚热带区域,有必要进行大气校正,以改善估算精度。

       

      Abstract: The pixel dichotomy model based on normalized difference vegetation index (NDVI) was adopted to extract the vegetation coverage from original DN values of TM image, top of atmospheric, surface reflectance with MORTRAN radioactive transfer model and dark-object method of simple transmission model, which were compared with observed values of vegetation coverage, in order to analyze the effects of atmospheric correction on remote sensing estimation of vegetation coverage. The target area was Jiulianshan reserve located in southern Jiangxi province, an eastern province of China. Result showed that although the correction principle of two atmospheric correction approaches, including FLAASH and DOS, was different, but they performed significant for eliminating atmospheric effects, and the accuracy of remote sensing estimation on vegetation coverage was effectively improved, based on the degree of fitting to observed values in the sample plots. The vegetation coverage estimated by top of atmospheric after radiation calibration and original image DN values were not significantly different, illustrating that the improvement of vegetation coverage estimation accuracy was derived from the atmospheric correction, and the effect of radiation calibration on vegetation coverage estimation was very small. Therefore, atmospheric correction is meaningful for improving estimation accuracy in subtropical areas with high vegetation coverage.