基于MODTRAN的双查找表法反演高光谱数据的水汽含量

基于MODTRAN辐射传输模型,假设近红外波段地物反射率随波长线性变化,考虑程辐射的影响,发展了一种通过双查找表反演高光谱遥感数据水汽含量的方法。建立查找表过程中,使用三次样条插值方法对查找表水汽含量值加密以减少MODTRAN运行时间。使用两个查找表,通过逐步搜索法对高光谱遥感数据进行水汽反演,得到水汽含量分布图。结果显示,使用三次样条插值方法得到的辐亮度值与MODTRAN计算结果只有0.1%的误差。对两景机载可见光/红外成像光谱仪(AVIRIS)高光谱数据进行水汽反演,得到水汽含量分布图,并用其对辐亮度数据进行大气校正,得到反射率数据。水汽含量分布图变化平缓,无亮/暗点出现,反射率数据在水汽吸收波段的光谱曲线没有过/欠校正现象,这表明水汽反演方法有效。

A MODTRAN-Based Double-Lookup-Tables Retrieval Algorithm for Water Vapor Amount of Hyperspectral Data

Assuming that surface reflectance changes linearly with wavelength in the near-infrared band and the impact of path radiance is considered. An algorithm based on radiative transfer model MODTRAN, which gets the column water vapor amount using two lookup-tables (LUTs) is developed. Cubic interpolation method is used to reduce the water vapor amount step in LUTs. Using the LUTs through a stepwise-search method, water vapor amount distribution image can be gained from hyperspectral data. It shows that the radiance gotten by cubic spline interpolation only has 0.1% error compared with MODTRAN simulated radiance. Water retrieval is performed to two scenes of airborne visible/infrared imaging spectrometer (AVIRIS) data, and two water vapor amount distribution images are obtained. Reflectance data are obtained using the images through atmosphere correction. Water vapor amount distribution images change smoothly without bright or dark spots in them, and there is no peaks or valleys in the water vapor absorption band of reflectance spectra. It is proved that the algorithm is valid.