ABSTRACT
In this chapter, the authors review some theoretical and experimental research in 3D building tomography using microwave remote sensing. They outline the basic concepts of the geometric optics (GO) approach, including ray initiation by a transmitter, ray propagation and scattering, and ray detection by a receiver. The authors discuss the uniform asymptotic theory of diffraction, showing how precomputed microscopic scattering data may be used to enhance pure GO to describe the splitting of a single incoming ray into a large number of outgoing rays. They consider reflection and transmission from perfect, flat walls, but with an arbitrary layered structure. The authors summarize the most important considerations in the efficient numerical implementation of the features in a ray tracer, including ray initiation, efficient hierarchical storage of multiply splitting rays, and ray termination at a receiver. They provide examples of forward calculations, and then show tomographic inversion results.
