The objectives of this project consisted of both hardware and software goals. On the hardware side, the goal was to develop an innovative vector (multi-axis) handheld ultra-wideband (UWB) electromagnetic induction (EMI) sensor in the time domain (TD) with precise three-dimensional (3-D) positioning for close interrogation of anomalies. This new instrument would allow a new, higher level of unexploded ordnance (UXO) discrimination in the vicinity of a noteworthy magnetic response or in the presence of metallic clutter. Data processing software accompanying the new instrument would also be developed. The goal was to develop clutter-tolerant signal processing for UXO discrimination using the data provided by the new sensor, based on new, high-fidelity, physically complete forward modeling (the Standardized Excitation Approach [SEA] and the Normalized Surface Magnetic Source [NSMS] approach), rigorous instrument characterization, and new processing techniques.
Researchers constructed the Man-Portable Vector (MPV) instrument along with a positioning system with sub-centimeter accuracy at a range of about two meters. This new instrument was successfully used to acquire data under lab conditions and in both static and dynamic modes. Initially, positioning of the MPV sensor head was accomplished through a laser positioning system. However, due to considerations such as the added weight and the bulky setup procedure, a novel “beacon” positioning system, which uses the primary field of the MPV itself to locate the sensor head, was developed and successfully deployed.
Results from all blind tests indicated the MPV can acquire diverse and accurate vector data with a signal to noise ratio (SNR) similar to or better than previous TD handheld instruments. Single target inversion results for laboratory blind tests were 100% accurate. The MPV also successfully acquired three axis data of the secondary field at five locations within the 75cm sensor head disk. Researchers developed algorithms and models which accompanied the development of the MPV hardware. These algorithms include Support Vector Machine (SVM) classification models, extensions of the SEA, and improvements to the NSMS model.
The MPV is now a fully functioning EMI instrument capable of vector sensing of magnetic anomalies while being well-located within a limited range. For precise, cued interrogation of anomalies, the MPV provides diverse, accurate, TD data of the secondary EMI field suitable for inversion and discrimination with high-fidelity, rigorous models. At the same time, as the project progressed, it was determined that the MPV instrument was too large and heavy to be used for a long period of time regardless of the data quality. Therefore, the MPV has been redesigned with these issues in mind.