15 Nov 2012

Humanitarian De-Mining: Radar and Acoustic Detection Methods

Dr. Timothy D. Bechtel, P.G., Franklin and Marshall College, University of Pennsylvania, and Enviroscan, Inc., and Marian J. Bechtel, Bryn Mawr College

Since the signing of the Ottawa (mine ban) Treaty, great progress has been made in humanitarian de-mining. However, many influential countries are still not signatories, and mines continue to be used by some states and non-state armed groups. In addition, many countries are infested from conflicts that ended decades ago. In nearly all mined areas, the mines are mixed with ubiquitous battlefield debris or “clutter,” and many mines are intentionally minimum-metal to avoid detection.

Our international research group (The RASCAN Group from Russia, UK, Italy, Japan, and USA) has been developing holographic radar as a tool to address the problem of distinguishing buried minimum-metal landmines from clutter in arid environments. The system produces high-resolution, two-dimensional images of the subsurface, which are suitable for both human interpretation and computer analysis (using scanned receptive fields for object location, and trained neural networks for object identification). In recent experiments, minimally trained humans identified mines with 90% success and a false alarm rate of 0.74 per correct identification. For the computer analysis, mine detection success was 100%, with zero false alarms, and the test clutter objects were identified with around 75% success rate.

Although this is spectacular success, the holographic radar method is severely limited by wet soils of the type that are common in countries with the worst mine infestations (e.g. Cambodia). Luckily, a student familiar with the RASCAN Group, and possessing a background in both physics and music, conceived and developed a prototype seismo-acoustic device that functions well in wet soils. The seismo-acoustic method uses a remote seismic vibrator to induce
resonance in compliant objects (such as plastic mines), and a system of noise-canceling microphones to detect the weak but characteristic acoustic field above a resonating mine.

The variations in soil mineralogy, compaction, moisture content, moisture chemistry, and surface roughness across the world’s minefields probably preclude development of a single universally effective device. We hope to add holographic radar and seismo-acoustics to the de-miner’s toolkit, making the process potentially safer and cheaper.