Unexploded ordnance (UXO) site characterization is normally best accomplished using both active electromagnetic (EM) induction and magnetometry. Magnetometers typically perform better for large, deep ferrous objects, and EM sensors typically perform better for small shallow objects of all metals. However, simultaneous deployment of these two technologies on a single platform is difficult due to the active nature of EM technology, which generates noise that is picked up by magnetometers operated at close proximity. Economics often restrict site characterization to only one survey, hence the use of only one technology. Thus, for reasons of performance, economy, and safety, a single-platform magnetometer and EM solution would be widely used.
This project developed and demonstrated a proof-of-concept synchronized data acquisition and processing system that allows simultaneous deployment of EM and magnetometer sensors on a common vehicular-towed platform. New sampling electronics were designed and developed that interleave the magnetometer and EM61 data, sampling the magnetometers only after the EM61 pulse has diminished, thereby eliminating the EM61-induced noise. This allows magnetometers and EM61 coils to be co-located on a single towed platform. An existing vehicular Surface Towed Ordnance Location System (STOLS) was employed as a development platform, re-using STOLS' vehicle and system components. A new non-metallic proof-of-concept towed sensor platform was developed to reduce platform noise.
The system was demonstrated at the Standardized UXO Technology Demonstration Site at Aberdeen Proving Ground, Maryland. The system completed the 13-acre Open Site in roughly a day and a half, successfully acquiring high-quality co-located magnetometer and EM61 data in a single survey. The synchronous interleaved magnetometer and EM61 electronics functioned correctly. The system collected high-quality, low-noise magnetometer data while the EM61 array was running. The Simultaneous Multisensor STOLS has been used at several large survey sites since the close of this ESTCP-funded project, and the actual survey costs were calculated to be $708 per acre.
In addition to reducing survey times and human exposure in the field, the collection of spatially co-registered magnetometer and EM data will improve the probability of detection and reduce the false alarm rate. The spatially co-registered data generated by the system can be supplied to UXO researchers and algorithm developers working on feature extraction, automatic target recognition, and information fusion. Modifications to the data processing software to simultaneously view and analyze both magnetometer and EM data sets will enable the incorporation of new feature extraction algorithms. In addition, the use of this technology will result in a 50% cost reduction as compared to other towed array technologies that use magnetometers and EM61s sequentially instead of simultaneously. (Project Completed - 2005)