A Novel 3-D Imaging Method for Subsurface Targets Based on Time-Domain Electromagnetic Induction System

In recent years, the time-domain electromagnetic (TEM) method has played an important role in the detection and identification of subsurface targets, but the imaging of underground limited volume targets has always been a major problem. In this letter, we propose a novel 3-D imaging method to image subsurface targets using the TEM induction (TEMI) system. The method is based on the discretization of the underground into several grids which represent the independent magnetic dipoles contribution to the measured responses collectively. The strength of every dipole is obtained by minimizing the mismatch between computed and observed secondary response from the targets using the iterative optimization method. Then, the simulation and field experiments are done to verify the feasibility of this method. The results show that the method proposed herein has a small amount of computation and strong robustness, which help visualize the underground targets in three dimensions accurately and rapidly.