There is a need to implement new electromagnetic induction (EMI) technologies capable of improved detection and discrimination of unexploded ordnance (UXO) in order to reduce the cost of site characterization and cleanup. The objective of this project was to provide the information required to understand, process, and evaluate the potential of time-domain induction technology on-time signals and to quantify the value that associated data parameters add to current advanced discrimination technology.
Recent advances in EMI sensor capabilities have incorporated sensing mechanisms to more fully exploit the spatial response of UXO targets. These next generation systems utilize multi-axis and multi-static transmitter and receiver configurations to increase the spatial sampling of the scattered magnetic field response from targets for improved characterization. Previous research has shown that enhanced capability may be achieved by extending the temporal or spectral information. Theoretically, received signals measured during the transmit period provide information about the instantaneous magnetization and current gathering in objects within the presence of the illuminating field. Although some work has been conducted to examine designs that provide for on-time signal reception, few, if any, efforts have concentrated on optimal methodologies for processing associated signals. Through a combination of modeling and analysis of experimental data, this project examined the potential of on-time EMI data to improve the detection and discrimination of UXO and aid in rejecting anthropogenic and soil-related clutter and noise.
This project determined that on-time data provide a number of theoretical and practical enhancements to aid in UXO characterization. This work also supported a more thorough understanding of the physical mechanisms being exploited by existing on-time instruments and their capabilities and limitations. The research provides a theoretical basis that links the understanding of existing off-time pulsed induction and always-on frequency-domain responses to the full waveform response. This approach provides for estimation of the magnetic properties of targets (e.g., demagnetization factors and bulk magnetic susceptibility) that are not obtainable with conventional off-time pulsed induction methods.
A synthesis of the results of this exploratory investigation suggests that a handheld prototype full waveform system that combines the best designs and methods can be developed. The researchers initiated integrated system design tradeoffs that compare candidate configurations and quantify performance and suitability with respect to maximizing the information content from on-time signals as well as cost and logistical considerations. Both data and theory provide evidence that there is potential to extract useful and unique information about targets and the ground in which they are buried from on-time signals. In particular, new processing methods show potential to improve target detection and discrimination, especially when on-time and off-time signals are used in conjunction with one other.