Abstract
Location and characterization of a buried target from its electromagnetic induction response is a key problem for unexploded ordnance (UXO) detection. This article focuses on the influence of target size, depth, and orientation on its location and characterization on the basis of single dipole model with differential evolution (DE) algorithm against data collected by a portable transient electromagnetic (TEM) system. The sensor of the portable TEM system is composed of a single-layer transmitting coil and five three-component receiving coils. The diameter and current of transmitting coil are 0.5 m and 5 A. The length and resonant frequency of receiving coil are 5.6 cm and 180 kHz. The results of test-stand experiment show that the errors in location and characterization an underground target depend not only on the signal-to-noise ratio of the response, but also on the orientation of the target. For large target vertically (tail down) oriented, the estimated depth and characteristic response only represent the part of target close to the sensor, which are smaller than the real ones. For target flat-lying oriented, the algorithm overestimates both the depth and the characteristic response for the nonuniform primary field throughout the target. Finally, field experiment has been conducted. In general, the target can be located and characterized well even if the response of two targets is superimposed. The errors in estimated positions of about 5-7 cm support the conclusions from our test-stand experiment. These errors are especially critical when excavating targets.
Highlights
Unexploded ordnance (UXO) contamination has become a serious humanitarian and environmental problem worldwide, because it prevents land use by civilians, threatens public safety, and causes serious civilian casualties [1, 2]
Based on the early time response with high signal-to-noise ratio (SNR), the differential evolution (DE) algorithm with 100 iterations is used to complete the inversion within 15 s
With the structure and parameter of a portable transient electromagnetic (TEM) system for UXO detection described, the influence of target size, depth, and orientation on its location and characterization based on the single dipole model with DE algorithm is discussed in detail
Summary
Unexploded ordnance (UXO) contamination has become a serious humanitarian and environmental problem worldwide, because it prevents land use by civilians, threatens public safety, and causes serious civilian casualties [1, 2]. Developed TEM systems, such as the Oak Ridge Airborne Geophysical System [16, 17], the vehicle systems MetalMapper [18, 19], the Berkeley UXO discriminator [20, 21], the Time-Domain Electromagnetic Multisensor Towed Array Detection System [22, 23], and the portable systems [24,25,26,27] have been applied to detect and discriminate UXOlike targets efficiently Because of their large size and weight, it is difficult to use vehicular systems in mountainous or jungle areas.
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