A unified model of bidirectional reflectance distribution function for the vegetation canopy

作者：Xu XiRu; Fan WenJie^*; Li JuCai; Zhao Peng; Chen GaoXing

来源：Science China Earth Sciences, 2017, 60(3): 463-477.

DOI：10.1007/s11430-016-5082-6

• Vegetation BRDF
• Unified model
• Clumping Index
• Proportion of direct solar radiation and diffuse sky radiation
• Recollision probability

An accurate and operational bidirectional reflectance distribution BDRF) canopy model is the basis of quantitative vegetation remote sensing. The canopy reflectance should be approximated as the sum of the single scattering reflectance arising from the sun, rho (1), and the multiple scattering reflectance arising from the canopy, rho (m) , as their directional characteristics are dramatically different. Based on the existing BRDF model, we obtain a new analytical expression of rho (1) and rho (m) in this paper, which is suitable for different illumination conditions and different vegetation canopies. According to the geometrical optic model at the leaf scale, the anisotropy of rho (1) can be ascribed to the geometry of the object, sun and the sensor, multiple scale clumping, and the fraction of direct solar radiation and diffuse sky radiation. Then, we parameterize the area ratios of four components: the sunlit foliage, sunlit ground, shadow foliage and shadow ground based on a Poisson distribution, and develop a new approximate analytical single scattering reflectance model. Assuming G=0.5, a recollision probability theory based scattering model is developed which considers the effects of diffuse sky radiation, scattering inside the canopy and rebounds between the canopy and soil. Validation using ground measurements of maize and black spruce forest proves the reliability of the model.

• 出版日期2017-3
• 单位北京大学