Study On Spectral BRDF Characteristics Of Typical Vegetation And Anisotropic Sea Surface

The bidirectional reflectance distribution function(BRDF)of the material and the target surface can reflect its spatial reflection characteristics,providing a theoretical basis for studying the radiation characteristics in a complex surface environment.This article introduced several typical vegetation BRDF models and analyzed the advantages and disadvantages of each model.According to the digital elevation model(DEM)in the Kwamenling area,three different undulating terrains were randomly created using 3DS MAX.Based on the nuclear-driven vegetation BRDF model and overlaid on different undulating terrain,the seasonal variations,topographic relief,and incidence were analyzed.Zenith angle and variation of the incident spectrum on vegetation BRDF.The MODIS vegetation remote sensing data were used to analyze the influence of different seasons and different incident spectra on vegetation BRDF in the Kumen area.The results show that the vegetation canopy structure affects the shadowing effect between the foliage and the surface of the vegetation and thus directly affects the vegetation BRDF.value.The vegetation canopy of the Kwamenling area in different seasons will have obvious differences.In spring,the canopy structure is sparse,the leaves are small,and the mutual shielding between the branches and leaves is small,so the front and back scattering characteristics are relatively strong;summer and autumn When the canopy structure is dense and the shielding between the blades is enhanced,only the backscattering characteristics are strong;when the leaves fall in winter,the shielding effect is reduced again,and therefore the value of the BRDF is overall larger.Based on the Cok-Munk sea surface reflectivity model,the slope probability density distribution function for anisotropy is deduced by generalizing the one-dimensional sea surface to two-dimension,and the function is degenerated to a one-dimensional case.The calculation results are in agreement with the Cok-Munk model.The good agreement shows the correctness of the function.The isotropic and anisotropic sea-surface obscuration function is proposed by assuming the visibility probability function.The anisotropic sea surface reflectance model is obtained,and the changes of the sea surface reflectance after different wind speeds,wind directions,and shadowing effects are analyzed.characteristic.Based on the relationship between reflectance and BRDF,an anisotropic sea surface BRDF model was derived,and the characteristics of the sea surface BRDF at different incident zenith angles,wind speeds,and wind directions were analyzed.Based on the relationship between dielectric constant and refractive index of seawater,the effects of seawater temperature,salt concentration and spectrum on the BRDF were analyzed.The results show that the higher the temperature,the longer the wavelength and the smaller the salt concentration,the smaller the BRDF value of the sea surface.Based on the sea surface temperature obtained by MODIS,the characteristics of BRDF variation in typical Taiwan Strait during different seasons are discussed.Finally,using the P-N sea spectrum model,the sea level fluctuations at different wind speeds and wind directions were calculated.