Broadband Electromagnetic Detection and Discrimination of Underwater UXO
Abstract
The two aspects of this research consisted of computer modeling and analysis, and experiments in shallow seawater. The methodology for the computer modeling was to develop analytic algorithms for special cases that would provide insight as to the fundamental physics related to the EMI response of a metal object when immersed in a conductive host medium as well as quantify the effects of seawater that would allow prediction of the spectral distortion of the GEM-3 response to UXO in seawater. The special cases included finitely conductive and permeable spheres in a conductive background, spheres encased in a shell (2-layered sphere) with different conductivity and/or permeability immersed in a conductive background, and infinitely conductive (or insulating) spheroids immersed in a finitely conductive background. The experimentation provided confirmation of the modeling as well as measurements for UXOlike objects that could not be modeled. We also encountered noise unique to the marine environment that can be anticipated to be an issue in operational surveys, and we have a better understanding of these noise sources and the impact on data. We performed a series of controlled experiments in which broadband GEM-3 EMI data were collected for a number of targets at various distances and orientations. The first two sets of experiments were aimed at demonstrating the salient effects of the seawater on the spectral EMI response of these targets and provide a firm understanding of the physics involved. We also wanted to learn the appropriate adjustments that are needed to the sensor parameters (i.e. frequencies used, sensor-target geometry restrictions for target classification) when working in seawater. The setup for the first experiment was simple, but with marginal control on target position and orientation (Figure 1); the second setup employed an indexed linear platform that improved the control (Figure 2).
Document Details
- Document Type
- Technical Report
- Publication Date
- Aug 31, 2005
- Accession Number
- ADA476338
Entities
People
- Bill San Filipo
- I. J. Won