Modelling and inversion techniques for radar applied to archaeological investigations

As test sites for ground penetrating radar (GPR), archaeological sites offer a set of demanding (high-resolution) application contexts in a situation where repeated studies may be made over a range of non-trivial targets (i.e. not always clearly defined or predictable, hence requiring diagnosis and evaluation, rather than mere detection). When the points above are further taken into account, they offer excellent opportunities for the test, evaluation and development of equipment, modelling approaches, and interpretational/processing tools. The modelling approach discussed is the transmission line matrix method (TLM). This method represents the volume of interest as a mesh of two-wire transmission lines and provides a formalism where Maxwell´s equations governing propagation of an electromagnetic wave through a variable media can be described in a discrete circuit theory form. A discrete-time approach is taken where scattering takes place at the nodes of the mesh due to discontinuities in the line impedances: the propagation of the waves can then be established over time, with one time-step being defined by the node-node travel time. The approach can be successfully applied to the use of GPR systems in a wide variety of contexts and can cope with complex subsurface structures