Large Vibrometer Arrays for Seismic Landmine Detection

Inexpensive ground-contacting accelerometers have been demonstrated in field experiments as appropriate vibrometers for a seismic landmine detection system. A thirty-two-element line array of these has been used to detect a variety of anti-tank (AT) landmines under realistic field conditions. Images of data measured by scanning this line array to synthesize a larger plane array have shown that the two-dimensional array offers potential advantages in terms of both measurement speed and landmine image contrast. The simultaneity of measurements with a physical array, as compared to synthetic array measurements that have been performed in the past, presents opportunities for improved landmine detection algorithms. Issues pertaining to the implementation of large arrays of vibrometers include sensor fidelity, array fidelity, scalability, and safety. Experimental measurements with prototype sensors in the laboratory and at a field test site have demonstrated the robust and repeatable ground coupling of the sensor in sand, dirt, gravel, and grass. Ground loading has been investigated with multiple array configurations with the dominant effect being an increase in the wave speeds of the surface waves. While the field experiments with the line array were conducted using commercially available data acquisition hardware and software, a custom data acquisition and processing system has been developed to meet the requirements of a large array of sensors. A lightweight sensor ensures the safety of touching the ground over buried landmines as the contact force is significantly less than the force required to detonate typical antipersonnel (AP) landmines and AT landmines.