Study On The Spectral Model Of Rocks And Minerals Based On Fractal

Along with the ceaseless enlargement and deepening of the application of hyperspectral and multi-angle remote sensing technology, new requirements of remote sensing quantification model have been put forward. In the optic remote sensing, the bidirectional reflectance spectral model of rocks and minerals also plays important roles in the research of geological and planetary remote sensing. In this thesis, the precise BRDF models of rocks and minerals were established by synthetically using different nonlinear tools of fractal, radiative transfer, rough surfaces scattering theory and so on. Summarily, the main studies and achievements of thesis are listed as following:Firstly, three radiative transfer models of rocks and minerals powder have been compared to each other:the Hapke model, the improved Hapke model and the DISORT model. Reflectance spectroscopy of several minerals have been calculated using mineral radiative transfer model and compared with measured spectroscopy in USGS spectral database.The comparison indicates that Mie/Hapke model can simulate reflectance spectral features of minerals powder.Secondly, considering the Mie/Hapke model, the computational methods of model parameters were deseribed and the sensitivity of model parameters were anslyzed. Based on the Mie theory,the numerical calculation of the asymmetry factor of mineral mono-particle was carried out,and relationship between the asymmetry factor,size factor and optical constant was analyzed. Moveover, by utilizing Gaussian fitting algorithm, a quantitative expression is given to reveal the relationship between the asymmetry factor in the Henyey-Greenstein phase function with the size factor and optical constant of mineral particle.Thirdly, to establish the spectral model of rough surfaces of rocks and minerals, the simulation of rough surfaces of rocks and minerals was studied in this thesis. The simulation rationality of fractal rough surfaces was demonstrated by comparing the shadowing effect from the fractal surface with the shadowing effect from the Gaussian surface and Hapke model. Moveover, an experiential expression is given to reveal the shadowing effect from the fractal surface.To consider the effect of surface shape for the light scattering, a new BRDF model of rocks and minerals powder was proposed. The main steps have two parts:firstly, fBm model was presented for describing the rough surface of rocks and minerals and the BRDF of surface scattering was calculated according to the Kirchhoff Approximation. Secondly, the BRDF of volume scattering was calculated according to radiative transfer theory. Then, the total BRDF was calculated from the sum of two parts. The model was verified by simulation experiment.To the aspect of spectral model of massive rocks and minerals, the Weierstrass Mandelbrot fractal function was presented for describing the rough surface of rocks and minerals, the BRDF of surface scattering was calculated according to the Kirchhoff Approximation. The model was verified by simulation experiment and introducing the particle swarm optimization algorithm into spectral model inversion. In order to inverse the BRDF model of rocks and minerals powder,a multistage inverse strategy was introduced according to parameters sensitivity analysis,and good results were obtained with small inverse errors.