Locating and Characterizing Unexploded Ordnance Using Time Domain Electromagnetic Induction
Abstract
An assumption is made that the Time Domain Electromagnetic (TEM) response of a buried axisymmetric metallic object can be modeled as the sum of two dipoles centered at the midpoint of the body. The strength of the dipoles depends upon the relative orientation between the object of the source field and also upon the shape and physical properties of the body. Upon termination of the source field, each dipole is assumed to decay as Kappa(t+alpha)(sup -Beta)e(exp -1/gamma). The parameters Kappa, Alpha, Beta, and Gamma depend upon the conductivity, permeability, size, and shape of the object, and these can be extracted from the measurements by using a nonlinear parametric inversion algorithm. Investigations carried out using an analytic solution for a sphere and laboratory measurements of steel and aluminum rectangular prisms suggest the following two-step methodology: (1) The value of % is first used as a diagnostic to assess whether the metallic object is nonmagnetic or magnetic, (2) the ratios of Kappa 1/Kappa 2 and Beta 1/Beta 2 are then diagnostic indicators as to whether the geometry is plate-like (uninteresting) or rod-like (a high candidate for being an unexploded ordnance (UXO)). Results from the application of this algorithm to a TEM field data set acquired at the U.S. Army Engineer Research and Development Center (ERDC) UXO Test Site have successfully identified a UXO to be magnetic and rod-like.
Document Details
- Document Type
- Technical Report
- Publication Date
- Aug 01, 2001
- Accession Number
- ADA394435
Entities
People
- Douglas W. Oldenburg
- Leonard R. Pasion
Organizations
- University of British Columbia