【作者】 吴雨航；

【导师】 陈春；

【作者基本信息】 东北师范大学 ， 地图学与地理信息系统， 2006， 硕士

【摘要】 太阳辐射在大气传播过程中遇到大气中气体分子、气溶胶、冰晶等粒子的吸收、反射和散射等作用,使部分光线改变方向。使原来传播方向上的太阳辐射减弱,而增加其它方向的辐射,从而使传至地物表面的辐射能量,或由大气上界直接散射向外空间和地面辐射散射经大气衰减而传至遥感器的辐射能量,成分复杂且难于定量计算。而向上传播的大气程辐射被传感器接收,成为遥感图像中的噪声成分,影响图像质量,是遥感图像重要的辐射校正部分。本文根据辐射传输机理和遥感影像特征,研究了大气程辐射定量化计算方法。首先,研究大气程辐射对遥感影像的影响,以及程辐射各因子模型的确定。然后利用一系列辐射传输方程,研究大气参数,辐射传输参数等对大气程辐射的影响。研究表明,在太阳观测角较小,大气混浊度较大时,大气程辐射值的大小依赖于气溶胶粒子大小的尺度组合分布,而对于较干洁状态的大气,大气程辐射值随光学厚度的增加而线性增加。另外,光谱值的变化表明,随着波长的减小,大气程辐射值增加。最后,根据大气程辐射方程计算搭载在卫星Landsat-7上的多光谱成像仪ETM记录的辐射亮度光谱图像的大气程辐射值,并对ETM影像进行基于辐射传输理论的大气程辐射值修正。实验结果表明,在ETM 1波段,大气程辐射值校正精度基本上保证在17%以内,而2、3波段在10%以内,优于目前常用的简易算法。更多还原

【Abstract】 The radiance reaching the satellite sensor includes the photons coming from the sun,which do not reach the surface and are backsacttered towards space, namely path radiance.This is an inerference term that does not carry any information about the terrestrial objects. Asecond contribution is due to photons scattered by the atmosphere into the path from thesurface to the satellite. A third contribution represents the radiance reflected by the target thatis not absorbed or scattered on its way to the sensor, this signal carries information about theterrestrial surface.The interaction of solar radiation with the constituents of terrestrial atmosphere is animportant problem in atmospheric correction of the remote sensing images. The intensity ofscattered radiation and its angular distribution depend on the nature of the scatterer and itssize in relation to the wavelength of the interacting radiation. With the increasing use ofair-borne and space-borne techniques for remote sensing of the earth’s surface, quantitativestudy of the atmospheric effects on the upwellling solar radiation, reflected by terrestrialobjects, has become more important since these effects cause the radiance of a ground objectas measured by the remote sensor to differ from its actual value. Meanwhile, quantitativestudy of the effects of path radiance on remote sensing data aslo has become very important.Solar radiation, as it passes through the terrestrial atmosphere, undergoues extinction due toabsorption and scattering by both air molecules and aerosols. Though both these processescause attenuation of the direct radiation, scattering causes diffuseness due to the angularredistribution of the scattered radiation. Consequently, a scene on ground is illuminated notonly by the directly transmitted solar radiation but also by the scattered radiation from thesurrouding hemispher of the sky. The gound scene reflects a part of the incident radiationtowards the sensor, which forms the directly transmitted solar radiance. To this direct radiance,is added the path radiance(Lp) comprising of the radiances reflected by the target surroundingand subsequently scattered diffusively by the atmosphere. The total radiance reaching thesensor is the sum of solar radiance and path radiance.In this paper, using a set of simplified radiative transfer equations, the effects of thechanges in the physical properties(such as columnar size distribution, optical depth andrefractive index)of atmospheric aerosols on the upwelling atmospheric path radiance areinvestigated for a nadir viewing remote sensor at various solar illumination angles in thecontext of developing operational methods for correcting path radiances received by remotesensing satellites for atmospheric effects. It is seen that at low solar illumination angles andhigh haze conditions (aerosol optical depths>0.5) the path radiance depends strongly on thenature of the aerosol size distribution, whereas for low to moderate values of aerosol opticaldepths (<0.5), the path radiance increases nearly linearly with optical depths. Spectralvariations indicate a large increase in path radiance with decrease in wavelength.Simultaneous measurements of spectral optical thickness and path radiance are used totest the relationship between path radiance and aerosol optical thickness for a given geometryof illumination and observation. The selected geometry is representative of satellite remotesensing conditions. Finally, the quantitative study of the effects of path radiance on remotesensing images has been performed. This method has been tested to be feasible and havingmore precision than methods used before.更多还原