Localization of anti-personnel landmines using multi-bistatic ground-coupled ground penetrating radar

Summary form only given. Ground-penetrating radar is a mature technology which has a promising application in humanitarian demining. The technology is fast, inexpensive, and capable of detecting both metallic and non-metallic target casings. However, the efficacy of conventional air-coupled GPR has been limited by the rough air-soil interface, below which landmines are typically buried. Much of the recent literature focuses on advanced signal processing techniques in an attempt to remove the effects of the rough surface. Conversely, this work proposes the use of ground-contact antennas, which greatly improves signal penetration and reduces the rough ground clutter, thereby simplifying data analysis. Achieving contact between the surface and antennas can be done by integrating the antennas onto the feet of a non-articulated walking robotic platform. Finally, rather than imaging the subsurface, this localization method implements a robust geometric analysis to detect and localize a target with a minimal number of GPR scans. By using fewer scans and simpler data processing techniques, this method is capable of increasing the surveying speed of traditional GPR methods. Experimental data is collected using an ultra-wideband radar from Time Domain (Huntsville, AL, USA), which has a bandwidth of 3.1 to 5.3GHz. The antennas are circularly polarized compact spiral antennas, which operate from 2GHz to 6GHz. These antennas were designed and fabricated for this application, and the diameter of only 2cm achieves complete contact with the ground for each GPR scan. Additionally, the polarization and directivity of the antennas minimizes the direct signal, and therefore simplifies the identification of target reflections. The time-of-flight is determined by the maximum correlation between the reflection and a reference signal. Scans which satisfy both an amplitude and correlation threshold are analyzed with a localization algorithm, which utilizes time-difference of arrivals to geometrically determine the target location. A minimum of four unique bistatic GPR scans are necessary to evaluate for the target's position in three-space in soil with unknown permittivity, and an increased number of GPR scans improves the accuracy and reliability of the results. Using the proposed localization method, metallic cylindrical targets, 4cm in height and 4cm in radius buried in dry sand at depths varying between 5 and 15cm, were successfully located. Although this method has not yet been evaluated experimentally for non-metallic targets, previous computational work shows evidence that this method can be viable for plastic mine targets as well. Furthermore, theoretical simulations have demonstrated acceptable localization results for dispersive and wet soils for both casing types.