Discrimination of buried targets via the singularity expansion

A problem of recent interest is the identification of buried unexploded ordnance (including mines). This paper reviews recent progress in the use of the singularity expansion method for electromagnetic and acoustic/elastodynamic scattering for discriminating the various types (specific models with prescribed shapes and materials). Each type having an aspect-independent set of natural frequencies, these can be used as a set of target signatures in a library. Three different types of such natural frequencies (and associated pole residues) are discussed.