A Parametric Hot Spot Model for Optical Remote Sensing Applications

This article presents a new formula for the joint transmission in homogeneous leaf canopies which relies on the existing definition of the conditional probability for events that there exist gaps in the incidence and emergence lines. Rather than applying a hot spot correction term to the independent events, the mean probability between the independent and the dependent events is estimated. The problem is solved graphically by analogy with the physical processes of light extinction by finite objects. Then a parametric hot spot model is derived which performs rather well when compared with airborne hot spot measurements over a conifer forest target and shows that the hot spot phenomenon is only a feature of the observed directional signature in the backscattering region. The findings suggest the requirement of an hot spot kernel in a host bidirectional reflectance model. Bearing in mind its simplicity, the hot spot model of this study is clearly not designed for inversion but will serve to improve albedo calculation from multiangular measurements from the new generation of remote sensing sensor systems.