Historical Development and Performance of Airborne Magnetic and Electromagnetic Systems for Mapping and Detection of Unexploded Ordnance

Abstract

Over the past fifteen years, notable progress has been made in the performance of airborne geophysical systems for mapping and detection of unexploded ordnance in terrestrial and shallow marine environments. For magnetometer systems, the most significant improvements include development of boom-mounted platforms, and implementation of higher sample rates, denser magnetometer arrays, and vertical gradient configurations. Nine magnetometer-based systems are described and their performance summarized. In prototype analyses and recent U.S. Department of Defense Environmental Security Technology Certification Program (ESTCP) assessments using new production systems, the best performance has been achieved with a vertical gradient configuration. As effective as magnetometer systems have proven to be at many sites, they are inadequate at sites where basalts and other ferrous geologic formations or soils produce anomalies that approach or exceed those of target ordnance items. Additionally, magnetometer systems are ineffective where detection of non-ferrous ordnance items is of primary concern. We discuss the development of airborne time-domain electromagnetic systems over the past ten years. Overall, improvements in airborne geophysical systems have led to more consistent detection of smaller ordnance. These trends should continue as additional technological advances are made.