Locating And Determining Dimensionality Of Uxos Using Time Domain Electromagnetic Induction

In this paper we assume that the Time Domain Electromagnetic (TEM) response of a buried<br>axisymmetric metallic object can be modelled as the sum of two dipoles centered at the midpoint of<br>the body. The strength of the dipoles depends upon the relative orientation between the object and<br>the source field, and also upon the shape and physical properties of the body. Upon termination of<br>the source field, each dipole is assumed to decay as k (t + a)-’ e-‘/y. The parameters k, LY, p and y<br>depend upon the conductivity, permeability, size and shape of the object, and these can be extracted<br>from field or laboratory measurements by using a nonlinear parametric inversion algorithm. Our<br>preliminary work, carried out using an analytic solution for a sphere and laboratory measurements<br>of steel plates, suggest the following methodology. The value of p might be used as a diagnostic<br>to assess whether the metallic object is non-magnetic or magnetic. If the object is thought to be<br>magnetic, then the ratios of ICI/k2 and pi//3 2 are diagnostic indicators as to whether the geometry<br>is plate-like (uninteresting) or rod-like (a high candidate for being a UXO).