【摘要】 地形效应是影响遥感定量分析的主要障碍之一。尤其对于航空高光谱遥感而言,其地形效应更为显著,地形高程、角度带来的影响都不可忽略。基于青海雪鞍山地区的CASI高光谱影像和LiDAR地形数据,开展地形高程变化对航空高光谱遥感的影响研究。在假定每一个高程点为水平朗伯体的前提下,首先,基于MODTRAN软件模拟计算不同高程对应的大气上行辐射、地物至传感器之间的大气透过率、大气半球反照率和下行总辐射,进行地形高程变化对4个参量的影响分析;然后,设计实现了加入高程因子的大气辐射校正,完成了测区航空高光谱影像的反射率反演计算;最后,与FLAASH大气校正的反射率结果进行比较,发现同类地物的反射率曲线在谱形方面接近,但反射率数值存在差异,尤其是FLAASH大气校正结果中短波波段甚至出现负值,无疑是错误的。实验表明,高程因子的变化对山地航空高光谱影像成像过程的影响不可忽略,要实现精确的航空高光谱影像大气辐射校正必须消除其影响。更多还原

【Abstract】 Topographic effect is one of the main obstacles in quantitative analysis of remote sensing. For the airborne hyperspectral remote sensing,both of the impact of terrain height and angle can’t be ignored,and this causes more severe topographic effects. By taking the CASI image and Li DAR data of Qinghai Province as experimental data,the impact of elevation factor was analyzed in this paper. Firstly,on the premise that each elevation point is a horizontal Lambert body,four different elevation values were taken as reference to calculate the corresponding atmospheric radiation correction parameters by performing MODTRAN,which contain path radiance,atmospheric transmittance between the object and the sensor,atmospheric hemisphere albedo,and total downward radiance. Then an atmospheric radiation correction method with elevation factor was designed and applied to the atmospheric correction of CASI image. Finally, the CASI hyperspectral image was also processed by using FLAASH,which could only take one elevation value as reference. A comparison of two results shows that the reflectance spectrum shapes of the same ground objects are roughly the same,but the reflectance values are different. Especially, the short-wavelength reflectance values of FLAASH results are negative, and it is undoubtedly wrong. The experiment shows that the impact of elevation factors can’t be neglected. Atmospheric correction by adding elevation factors can get better results. For achieving accurate topographic correction of airborne hyperspectral image,both elevation and topographic angle factors should be considered simultaneously.更多还原