Landsat-5 TM影像增益偏置值对地面反射率计算影响分析

The Analysis of Impaction on Calculating Surface Reflectance of Landsat-5 TM Caused by Gain and Bias Values

增益和偏置是对TM影像计算反射率的两个基本参数,如果这两个参数存在偏差,辐射定标、辐射校正及大气校正的结果都会出现错误。由于Landsat-5卫星的老化,辐射精度有一定程度的下降,USGS多次公布了不同的辐射校正参数。根据USGS公布的结果以及影像头文件中的增益和偏置值,对1998年获取的Landsat-5 TM影像进行了实验;求解了地面反射率并对2种地物(茂密植被和清洁水体)的地面反射率与标准值进行了对比分析。实验结果表明,利用影像头文件中的增益和偏置值对影像进行处理能获得最好的结果;如果影像不包含头文件,则建议使用USGS公布的相同时期的参数。

Gain and Bias are two basic parameters for the reflectance calculation of TM images.The deviations of the two parameters will lead to the erroneous results of radiometric calibration,radiometric correction and atmospheric correction.Because of the ageing of Landsat-5 TM and the decrease of the radiation accuracy to some extent,the USGS has published different parameters of radiation correction in the past few years.Based on the Gain and Bias values acquired from the USGS and the image head file,the authors calculated the surface reflectance of water and vegetation and compared the calculation result with the standard reflectance.The results show that the Gain and Bias acquired from the head file is the best way.If the image has no head file,the Gain and Bias offered by the USGS could be used.