Accurate Tree Roots Positioning and Sizing over Undulated Ground Surfaces by Common Offset GPR Measurements

Tree roots detection is a popular application of the Ground-penetrating radar (GPR). Normally, the ground surface above the tree roots is assumed to be flat, and standard processing methods based on hyperbolic fitting are applied to the hyperbolae reflection patterns of tree roots for detection purposes. When the surface of the land is undulating (not flat), these typical hyperbolic fitting methods becomes inaccurate. This is because, the reflection patterns change with the uneven ground surfaces. When the soil surface is not flat, it is inaccurate to use the peak point of an asymmetric reflection pattern to identify the depth and horizontal position of the underground target. The reflection patterns of the complex shapes due to extreme surface variations results in analysis difficulties. Furthermore, when multiple objects are buried under an undulating ground, it is hard to judge their relative positions based on a B-scan that assumes a flat ground. In this paper, a roots fitting method based on electromagnetic waves (EM) travel time analysis is proposed to take into consideration the realistic undulating ground surface. A wheel-based (WB) GPR and an antenna-height-fixed (AHF) GPR System are presented, and their corresponding fitting models are proposed. The effectiveness of the proposed method is demonstrated and validated through numerical examples and field experiments.Comment: 11 pages, 6 figures, accepted by IEEE TI

Buried Object Detection by an Inexact Newton Method Applied to Nonlinear Inverse Scattering

An approach to reconstruct buried objects is proposed. It is based on the integral equations of the electromagnetic inverse scattering problem, written in terms of the Green's function for half-space geometries. The full nonlinearity of the problem is exploited in order to inspect strong scatterers. After discretization of the continuous model, the resulting equations are solved in a regularization sense by means of a two-step inexact Newton algorithm. The capabilities and limitations of the method are evaluated by means of some numerical simulations

Modelling scattering of electromagnetic waves in layered media: An up-to-date perspective

This paper addresses the subject of electromagnetic wave scattering in layered media, thus covering the recent progress achieved with different approaches. Existing theories and models are analyzed, classified, and summarized on the basis of their characteristics. Emphasis is placed on both theoretical and practical application. Finally, patterns and trends in the current literature are identified and critically discussed

Comparative Study of Some Population-based Optimization Algorithms on Inverse Scattering of a Two-Dimensional Perfectly Conducting Cylinder in Slab Medium

[[abstract]]The application of four techniques for the shape reconstruction of a 2-D metallic cylinder buried in dielectric slab medium by measured the cattered fields outside is studied in the paper. The finite-difference time-domain (FDTD) technique is employed for electromagnetic analyses for both the forward and inverse scattering problems, while the shape reconstruction problem is transformed into optimization one during the course of inverse scattering. Then, four techniques including asynchronous particle swarm optimization (APSO), PSO, dynamic differential evolution (DDE) and self-adaptive DDE (SADDE) are applied to reconstruct the location and shape of the 2-Dmetallic cylinder for comparative purposes. The statistical performances of these algorithms are compared. The results show that SADDE outperforms PSO, APSO and DDE in terms of the ability of exploring the optima. However, these results are considered to be indicative and do not generally apply to all optimization problems in electromagnetics.[[incitationindex]]SCI[[incitationindex]]EI[[booktype]]紙本[[booktype]]電子

The Use Of Thin Layer Conditions To Reconstruct Objects Buried In A Layered Medium

Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2010Thesis (M.Sc.) -- İstanbul Technical University, Institute of Science and Technology, 2010Bu çalışmada, tabakalı ortamlar için yüksek mertebeden ince tabaka koşulları, düzgün ve pürüzlü ince ara yüzeyler için geçerli olacak şekilde türetilmiş ve tabakalı bir ortamda gömülü cisimlerin görüntülenmesinde uygulanmıştır. Bu koşulları kullanarak, ince ara yüzeylerin sınırları üzerindeki alan değerleri birbirlerine bağlanabilir. Başka bir deyişle, ince tabakanın alt sınırındaki alan değerleri, ince tabakanın üst sınırındaki alan değerleri cinsinden hesaplanabilir. Alan değerlerinin yaklaşıklığının doğruluğunun arttırılması için kaskat ince tabaka koşulları kullanılmıştır. Sonra gömülü cisimlerin görüntülenmesi için Eşdeğer Aralıklı Lineer Örnekleme Yöntemi uygulanmıştır. Bu yöntem cisimleri içeren ortamın sınırlarındaki alan değerlerini kullanır. Sayısal sonuçlar gömülü cisimlerin tabakalı bir ortamda görüntülenmesi için ince tabaka koşullarının uygulanabilirliğini göstermektedir.In this study, higher order thin layer conditions for layered mediums which are valid for both smooth and rough thin interfaces are derived and applied to image objects buried in a layered medium. Using these conditions, field values only on the boundaries of the thin interfaces can be connected with each other. In other words, the field values at the bottom boundary of the thin layer can be evaluated in terms of the field values at the upper boundary of the thin layer. To improve the accuracy of approximation of field values, cascaded thin layer conditions is employed. Then Reciprocity Gap Linear Sampling Method (RG-LSM) is applied to image buried objects. This method uses the field values on the boundary of the domain which contains objects in its interior. Numerical results show the applicability of thin layer conditions to image buried objects in a layered medium.Yüksek LisansM.Sc

Imaging of Scarce Archaeological Remains Using Microwave Tomographic Depictions of Ground Penetrating Radar Data

The Romano-British site of Barcombe in East Sussex, England, has suffered heavy postdepositional attrition through reuse of the building materials for the effects of ploughing. A detailed GPR survey of the site was carried out in 2001, with results, achieved by usual radar data processing, published in 2002. The current paper reexamines the GPR data using microwave tomography approach, based on a linear inverse scattering model, and a 3D visualization that permits to improve the definition of the villa plan and reexamine the possibility of detecting earlier prehistoric remains

Shape reconstruction of three-dimensional conducting objects via near-field measurements

A general framework for the shape reconstruction of conducting objects is presented with the Newton minimization approach. Using a fully numerical method, the initial-guess object is evolved to reconstruct the target. The object is modeled by triangles such that the vertices are the unknowns of the inverse-scattering problem. The cost function is minimized as the evolving object converges to the actual target in merely tens of iterations. © 2014 IEEE