Three-dimensional imaging of buried objects in very lossy earth by inversion of VETEM data

Abstract

The very early time electromagnetic system (VETEM) is an efficient tool for the detection of buried objects in very lossy earth, which allows a deeper penetration depth compared to the ground-penetrating radar. In this paper, the inversion of VETEM data is investigated using three-dimensional (3-D) inverse scattering techniques, where multiple frequencies are applied in the frequency range from 0-5 MHz. For small and moderately sized problems, the Born approximation and/or the Born iterative method have been used with the aid of the singular value decomposition and/or the conjugate gradient method in solving the linearized integral equations. For large-scale problems, a localized 3-D inversion method based on the Born approximation has been proposed for the inversion of VETEM data over a large measurement domain. Ways to process and to calibrate the experimental VETEM data are discussed to capture the real physics of buried objects. Reconstruction examples using synthesized VETEM data and real-world VETEM data are given to test the validity and efficiency of the proposed approach.Index Terms-Buried objects, singular value decomposition (SVD), three-dimensional imaging, three-dimensional inversion, Tikhonov regularization, very lossy earth, very early time electromagnetic (VETEM) data.

A two-step iterative inexact-Newton method for electromagnetic imaging of dielectric structures from real data

“…Since (4) involves Fredholm integral operators of the first kind onto the infinite dimensional space of all the contrast functions χ , equation ( 5) gives rise to an ill-posed inverse problem. It follows that any Newton step (equation ( 9)) can be ill-posed, too, since it is a linear approximation of the ill-posed equation ( 5) under linearization (6) [27,28].…”

“…In the past few years, the electromagnetic inverse scattering problem for the imaging of dielectric targets has been addressed by using several different approaches (see, for example, [1][2][3][4][5][6][7][8][9][10][11] and references therein). These reconstruction methods can be grouped into two main categories.…”

Reconstruction of two-dimensional buried objects by a differential evolution method

“…Another approach involves the partitioning of the test area and mutual coupling between the reduced investigation areas is assumed to be negligible. This approach has been successfully applied for example in [4].…”

“…There are several applications (e.g., nondestructive evaluation and testing, civil engineering, subsurface prospecting, medical imaging, etc), which could strongly benefit from the development of new and efficient detection procedures. Recently, a lot of inversion methods have been proposed [1][2][3][4][5][6][7][8][9][10][11]. Among them, there are very interesting methods based on electromagnetic inverse scattering, whose equations constitute the relationships between the unknown parameters of the targets and the 'input' data (i.e., samples of the scattered electric field, which are collected in a suitable measurement domain).…”

3D near-to-surface conductivity reconstruction by inversion of VETEM data using the distorted Born iterative method

“…For the EMI data, BA, the Born iterative method (BIM) [11][12][13] as well as the distorted BIM (DBIM) [14,15] are used more often than DT. Using BIM and DBIM, images with higher resolution are often obtained than using BA or DT.…”