TM图像大气校正及其对地物光谱响应特征的影响分析

基于辐射传输理论的大气校正模型,具有明确的物理意义,易于操作,应用广泛.虽然这类模型通常会提供几种标准大气模式供用户选择,但是有限的几种模式难以合理描述具体研究区的大气状况,因此,在缺乏实测资料时,有必要对大气参数进行合理选择或估计,参数的选择直接影响大气校正的结果.因此,首先对Landsat-5 TM图像大气校正参数的确定进行了详尽分析,然后从光谱响应曲线、归一化植被指数(NDVI)、能见度等方面,探讨了大气校正对TM图像地物光谱响应特征的影响.研究表明:(1)TM图像经大气校正后,地物在可见光波段反射率明显减小,而在近红外和短波红外反射率增大;(2)大气校正后的NDVI增幅明显;(3)能见度对水体和植被在可见光波段的地表反射率影响均较大;在近红外波段对水体的影响比对植被的更为强烈;随着能见度的增大,地物地表反射率增大.采用的参数确定方法可为类似研究提供参考与借鉴.

Atmospheric Correction on TM Image and Its Influence Analysis on Spectral Response Characteristics

Based on the radiative transfer model,atmospheric correction model has specific physics meaning,and it can be applied widely and operated easily.Though there are several kinds of standard atmospheric modes in the model,it is difficult to reasonably describe the atmospheric condition of a certain study field by using these limited modes.So it is necessary to choose and estimate atmospheric parameters reasonably when there is lack of measured data of the study field because parameter choosing can influence the result of atmospheric correction.Firstly,the parameter determination of 6S code on Landsat-5 TM image was analyzed carefully in this study.Then,influence of atmospheric correction on typical object spectral response characteristics of TM image was discussed on the spectral response curves,The normalized difference vegetation index(NDVI) and visibility respectively.The results show:(1) Surface reflectance of typical objects decreases evidently after atmospheric correction in visible band,but in near-infrared band and shortwave-infrared band,surface reflectance increases.(2) NDVI of typical objects increases after atmospheric correction.(3) Visibility has a significant influence on surface reflectance of water body and vegetation in both visible band and near-infrared band.The farther the visibility becomes,the higher the surface reflectance is.Finally,methods of the parameter determination here can be used for reference in similar studies.