The Inversion Of Surface Reflectance Of Landsat8 OLI Image In Mountain Area

The surface reflectance represents the reflectivity of ground objects to solar radiation of a certain band in a certain direction.As an important variable in the inversion of the surface parameters,it reflects the energy budget of the surface,which is of great significance for the quantitative remote sensing.The remote sensing information received by satellite sensors is affected by both the scattering and absorption of atmospheric molecules and aerosols and the influence of mountainous terrain.It results in the low accuracy of surface reflectivity inversion,which seriously limits the following study of the model of Radiation energy balance between ground gas,water and climate.The purpose of atmospheric correction is to remove the influence of the atmosphere so as to obtain the surface reflectivity that is consistent with the real information of the ground targets.The traditional 6S radiative transfer model adopts uniform atmospheric parameters and assumes that the surface has the same altitude.Therefore,the accuracy of retrieving the surface reflectance of remote sensing image in mountainous area with large changes in atmospheric composition and complex topography is often low.Through the sensitivity analysis of several important parameters of atmospheric correction,a high dimensional look-up table for atmospheric correction coefficient is established,which can quickly and accurately retrieve the surface reflectance of remote sensing images in mountain area,which is set up based on the Landsat8 OLI satellite remote sensing image.Moreover,the DEM of the study area is used as the input parameter of the 6S radiation transmission model.In order to evaluate the accuracy and applicability of the model,this paper selects research areas in Fuzhou Tianmenshan Mountain to analyze the atmospheric correction effect and the anti terrain performance.The main research contents are as follows:(1)The construction of fast atmospheric correction model for pixel by pixel based on look-up table.The sensitivity analysis of the main factors affecting the atmospheric correction is carried out,including The sun zenith angle,atmospheric vapor content,ozone concentration,aerosol optical thickness(AOT)and target height.Then a high dimension atmospheric correction look-up table is constructed.And the atmospheric vapor content,ozone concentration and aerosol optical thickness are derived from the Terra MODIS atmospheric parameters synchronized with the Landsat8 transit time.Fuzhou Tianmenshan Mountain is selected as the research area.The accuracy and versatility of the model are verified by visual analysis,spectral analysis,and cross validation with the surface reflectivity product released by USGS,Visual analysis shows that the surface reflectance image corrected by this model is more clear.The spectral analysis showed that the normalized vegetation index(NDVI)after the correction of this model was significantly greater than that before the correction.Cross validation shows that the surface reflectance of each band based on this model is highly correlated with the USGS surface reflectance products.(2)The influence analysis on topographic correction of vegetation index.GEMI,NDVI,RVI,PVI,NLI,RDVI,SAVI,MSR and other common vegetation indices are selected to compute the correlation with Cosi,combined with DEM data.According to Landsat8 OLI data of the Tianmenshan Mountain in Fuzhou made a correction,the vegetation indexes before correction,that based on the proposed model and that based on the C topographic correction are compared and analyzed in the respect of the shady and sunny slope and different slopes.The results show that in view of vegetation index generated by band ratio,the effect of the atmosphere and terrain can be eliminated by the correction of this model,and the effect of the correction is better than the C correction(3)Performance comparison of NDVI,RVI and TAVI based on this model.Taking the Tianmenshan Mountain in Fuzhou as the research area,the visual analysis,vegetation index and Cosi analysis,as well as the difference between shady slopes sunny slopes were compared and analyzed.The experimental results show that the effect of NDVI and RVI based on this model is equivalent to the effect of eliminating terrain.