CPF变化对Landsat TM/ETM+辐射校正结果的影响

Influence of Calibration Parameter File(CPF)to Radiometric Correction on Landsat TM/ETM +

随着时间的推移,卫星传感器的老化会使得原有的辐射定标参数文件(CPF)失效。最典型的当属Landsat-5卫星,该卫星自1984年发射以来,已经进行了多次CPF修正;而Landsat-7卫星的CPF也经过了数次修改,以保证辐射校正结果的准确性。以Landsat TM/ETM+遥感影像为例,分别以2003、2009年的CPF对它们进行辐射校正,并对结果进行对比。结果表明,除ETM+的绿光波段外,TM、ETM+影像基于2009年CPF计算的各波段均值都要小于2003年。而这一变化也使得由此计算的指数产生差异:归一化植被指数(NDVI)间的差异可达0.48%,建筑用地指数(IBI)间的差异可达5.94%。

As time goes by,the aged satellite sensors have made the original Calibration Parameter File （CPF）of the sensors become invalid.Typically the CPF of the Landsat 5 Thematic Mapper （TM） was modified several times since its launch in 1984,and so did the CPF of Landsat 7 Enhanced Thematic Mapper Plus （ETM＋）.Otherwise the accuracy of the image radiometric correction is not ensured.In this study,two scenes of Landsat TM and ETM＋ images have been corrected using their CPFs issued in 2003 and 2009,respectively.These radiometrically-corrected images were then compared to see whether there was any difference between the correction results.The band-by-band comparison reveals that,except the green band of ETM＋,the mean value of TM and ETM＋ bands calculated with the 2009 CPF is less than that calculated with the 2003 CPF.This also has influenced on the Normalized Difference Vegetation Index （NDVI）and build-up index （IBI）computation.The difference in the mean value between the NDVIs calculated using the 2003 and 2009 CPFs amounts to 0.48%,while this figure between the IBIs can reach to 5.94%.