Combination of Direct and Double-Bounce Ground Responses in the Homogeneous Oriented Volume Over Ground Model

Complex interferometric coherence expressions for the homogeneous (random or oriented) volume-over-ground model are originally derived in a simplified way by neglecting one of the two possible contributions of the ground response: direct return from the ground surface or double-bounce interaction with stems or trunks. The influence of these depends on both system and scene parameters, and in many cases, none of them should be ignored a priori. Therefore, a more general formulation accounting for the simultaneous presence of both ground contributions should be developed. This letter derives this formulation and analyzes the combined effect of both ground returns on the complex coherences. In addition, the implications for a subsequent inversion procedure based on this model are also discussed.