The objective of this work was to combine a Small Area Inertial Measurement Tracking System (SAINT) with an advanced hand-held, time-domain electromagnetic sensor (TEM-HH) and document classification performance at the Standardized unexploded ordnance (UXO) Test Site at Aberdeen Proving Ground (APG), Maryland. The TEM-HH has a single, circular, 35-cm diameter transmit coil and an inner, circular, 25-cm diameter receive coil. The SAINT integrates an inertial measurement unit and a digital magnetic compass. The two data streams were collected separately and merged during post processing. Cued data collections occurred over APG’s Calibration Lanes and the Blind Grid Area at an average rate of 27 per hour. Target classification was based on a comparison of principal axis polarizabilities from a dipole fit for each anomaly to a known signature library. This project’s classification objectives were met; 97% of the UXO was identified as UXO (the other 3% were not detected) while rejecting 77% of the clutter.
The TEM-HH was a single transmit/receive coil system based on the same electronics developed for the NRL TEMTADS 5x5 and 2x2 arrays. The sensor had a circular, 35-cm diameter transmit coil and an inner, circular, 25-cm diameter receive coil.
The SAINT system was contained in a triangular, yellow case that attached to the pole of an EM61- HH. For this test, the EM61-HH coil had been removed and replaced by the TEM-HH coil. The SAINT system contained an inertial measurement unit (IMU) and an embedded data acquisition computer. An external battery supplied power. The IMU data for each data collection was saved to an SD memory card and downloaded to a PC computer later. The IMU data was post-processed on the PC computer to give the EMI coil trajectory. There had been no effort to integrate the TEM and SAINT data streams. Each was collected separately with no common time stamp. The TEM data and the IMU position data were matched up in time with a time shift parameter in the inversion algorithm.
The goal of this demonstration was to repeat the Blind grid portion of the APG Standardized Test Site using the TEM-HH with the SAINT and to achieve equal or improved results in UXO
characterization compared to the TEM-HH with template on the same area, but to do it in significantly less time. It should be noted that this was done as a proof-of-concept and that nothing was done to integrate or improve the two systems. A time shift parameter was added to the inversion algorithm to match the positioning data to the TEM data.
CORRECT CLASSIFICATION OF TARGETS OF INTEREST
This was one of the two primary measures of the classification value of this sensor. The goal was to properly classify a large percentage of the seeded munitions items. By collecting high-quality, precisely-located data, researchers expected to be able to discriminate munitions from scrap and frag with reasonable efficiency. The objective was considered met if more than 95% of the seeded munitions items were correctly classified. This criterion was met; 97% of the UXO was identified as UXO. The other 3% were not detected.
REDUCTION OF FALSE ALARMS
This was the other primary measure of the classification value of this technology. Researchers expected to properly classify a large percentage of the clutter as such. By collecting high-quality, precisely-located data, they expect to be able to discriminate munitions from scrap and frag with some efficiency. The objective was considered met if more than 50% of the non-munitions items were labeled as no dig while retaining 95% of the munitions items on the dig list. This criterion was met; 77% of the clutter was rejected.
CUED PRODUCTION RATE
Even if the performance of the technology on the metrics above was satisfactory, there was an
economic metric to consider. Survey efficiency was the metric that was tracked in this demonstration. This objective was considered met if the production rate was at least 150 anomalies per day. Previously with the TEM-HH and the template, the goal was 50 targets a day and an average rate of 67 per day was achieved. This criterion was met. On one good day, over 200 flags were measured in an 8-hour day
The goal of this demonstration was to show that the TEM-HH combined with SAINT positioning could provide UXO classification performance comparable to the TEM 5x5 array and 2x2 array. Overall, this goal was met. There were several issues noted that should be addressed before trying to use this system at any future ESTCP Munitions Response Live Site Demonstrations.
The SAINT system would require several fixes/improvements. The intermittent data acquisition glitch would need to be fixed. A batch processing mode is needed. Finally, some means of time synchronizing its data with the TEM-HH needs to be implemented. All of these would allow for rapid acquisition and analysis of the data.
For the TEM-HH, the small backpack electronics should be repaired. Additional receive coils should be studied and the best (fewest coils / unambiguous inversion) configuration implemented.
Given these updates, the researchers feel that the TEM-HH combined with SAINT positioning is a viable system for cued UXO characterization and would be ready for testing on Live Sites under more rigorous terrain conditions.