Characteristics Of Granite Bidirectional Reflectance Spectroscopy

The bidirectional reflectance model is the basis of quantitative remote sensing.Because of the traditional geometry is very difficult to describe the special shape ofthe rock surface, there are few papers focused on the bidirectional reflectance modelof rock. The lithology recognition by using spectrum is still far from achieving theaccuracy requirements for practical application. Multifractal has been introduced todescribe the structure of the rocks in this paper. We expect to use some value of themultifractal spectrum to describe the characteristics of the rock surface and find howthe characteristics of the rock surface influent it’s bidirectional reflectance distributionfunction.The texture of rock is an important feature for rock. This paper focused on thepossibility of using multifractal spectrum as a mathematical model to describe thegranite surface. Multifractal spectrums for astronautic images, aerial DEM image,hand specimens image and microscope photos have been used to prove the validitythat multifractal spectrum can describe the texture and structure characteristics ofimage in different scale. By comparing the multifractal spectrums of images withdifferent texture in the same scale, the relationship between multifractal spectrumsand texture in different frequency has been revealed. The peak of the multifractalspectrum indicate different crystallization degree of rock and the shape can be used todistinguish the texture of rock. Furthermore, the physical significance of themultifractal spectrum in different interval values has been discussed in this paper.Multifractal spectrum is proved be able to describe the structure information of therock quantitatively and it can be used in bidirectional reflectance model study forrock.In order to study the bidirectional reflectance characteristics of the rock, wedevelop an precise spectral measurement system and design experiments to measurethe spectrums of9rock samples with different structure, then we got11405validspectrums. To highlight the influence of surface texture on spectrums, we compare thenatural surface spectrums and section spectrums of the of the same rock sample and got in same incidence and observation conditions. Data analysis indicate:(1)Bidirectional reflectance characteristics of rock section has low correlation withwavelength and it’s weakened with incident zenith angle increase;(2) Surfacefluctuation caused by mineral crystals will affect the morphology of reflectancespectrum, smaller mineral particles influence on the longer wavelength, the largerparticles influence on the visible light, while fluctuations exceed crystal scale do notaffect the morphology of the spectrum;(3)By analyzing the bidirectional reflectancecharacteristics in4bands of6granite samples, the BDRF of granite section has beenimproved;(4)the natural surface of fine-grained granite cause strong backscattering,smooth coarse grain granite surface generate strong forward scattering and change theforward angle;(5) the crystal scale fluctuation on the flat coarse grain granite surfacehas no influence on bidirectional reflectance. However, while there is large scalefluctuation, granite surface has similar bidirectional reflectance characteristic withdiffuse reflection.In this paper, we explore the new way of research on BRDF of rock, introducemultifractal spectrum to describe the rock texture and provide a feasible way to studyon physical model for the BRDF of rock.