Rigorous modeling of ultrawideband VHF scattering from tree trunks over flat and sloped terrain

Three electromagnetic models are employed for the investigation of ultrawid eband VHF scattering from tree trunks situated over flat and sloped terrain . Two of the models are numerical, each employing a frequency-domain integr al-equation formulation solved via the method of moments (MoM). A body-of-r evolution (BoR) MoM formulation is applied for a tree trunk on a flat terra in, implying that the BoR axis is perpendicular to the layers of an arbitra ry layered-earth model. For the case of sloped terrain, the BoR model is in applicable, and therefore the MoM solution is performed via general triangu lar-patch basis functions. Both MoM models are very accurate but are comput ationally expensive. Consequently, we also consider a third model, employin g approximations based on the closed-form solution for scattering from an i nfinite dielectric cylinder in free space. The third model is highly effici ent computationally and, despite the significant approximations, often yiel ds accurate results relative to data computed via the reference MoM solutio ns. Data from the three models are considered, and several examples of appl ication to remote sensing are addressed.