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Introduction
I am a Chartered Engineer and am passionate about improving learning and teaching for the next generation of engineers.
I carry out research on remote sensing technologies for infrastructure and geophysical applications. I have specific interest in computational modelling and optimisation of EM sensing systems. I am the lead developer of gprMax (http://www.gprmax.com), widely used EM simulation software.
I also publish in the fields of engineering education and technology enhanced learning.
Current institution
Publications
Publications (73)
gprMax is open source software that simulates electromagnetic wave propagation, using the Finite-Difference Time-Domain (FDTD) method, for the numerical modelling of Ground Penetrating Radar (GPR). gprMax was originally developed in 1996 when numerical modelling using the FDTD method and, in general, the numerical modelling of GPR were in their inf...
gprMax (http://www.gprmax.com) was originally developed in 1996 when electromagnetic numerical modelling using the FDTD method was in its infancy. Since then a number of commercial and other freely-available FDTD-based solvers have become available, but over the past 18 years gprMax has been one of the most widely used simulation tools in the GPR c...
The way in which electromagnetic fields are transmitted and received by ground penetrating radar (GPR) antennas is crucial to the performance of GPR systems. Simple antennas have been characterized by analyzing their radiation patterns and directivity. However, there have been limited studies that combine real GPR antennas with realistic environmen...
MATLAB is a software package used by engineers for design, optimisation, visualisation of data, and to simulate and control hardware. There are many important skills that engineering students develop through learning to use MATLAB – the most significant of which is the ability to distil a problem so that it can be solved using a computer algorithm...
Very few researchers have developed numerical models of Ground-Penetrating Radar (GPR) that include realistic descriptions of both the antennas and the sub-surface. This is essential to be able to accurately predict responses from near-surface, near-field targets. This paper presents detailed three-dimensional (3D) Finite-Difference Time-Domain (FD...
Ground-penetrating radar (GPR) is a mature geophysical method that has gained increasing popularity in planetary science over the past decade. GPR has been utilised both for Lunar and Martian missions providing pivotal information regarding the near surface geology of Terrestrial planets. Within that context, numerous processing pipelines have been...
Chang'E-4 and its rover Yutu-2 are the first artificial objects that soft-landed on the far side of the Moon. Yutu-2 is also the second planetary rover equipped with a set of ground-penetrating radar 2 (GPR) systems; two with 500 MHz (Channel-2A&2B), and one with 60 MHz (Channel-1) central frequency. GPR is a near surface geophysical technique capa...
Chang'E-3, E-4 and E-5 were the first planetary missions with in-situ ground-penetrating radar (GPR) in their scientific payloads. Apart from the Chang'E missions, in-situ GPR has also been used in the Martian missions Tianwen-1 and Perseverance, establishing GPR as a mainstream and pivotal tool in the new era of planetary exploration. Despite its...
Radio-echo sounding reveals patches of high backscatter in basal ice units, which represent distinct englacial features in the bottom parts of glaciers and ice sheets. Their material composition and physical properties are largely unknown due to their direct inaccessibility but could provide significant information on the physical state as well as...
Determining subsurface electromagnetic (EM) wave velocity is critical for Ground‐penetrating radar (GPR) data analysis, as velocity is used for the time‐to‐depth conversion, and hence leads to obtaining the precise location of the objects of interest. Currently, the way to acquire detailed subsurface EM wave velocity models involves employing multi...
Hyperbola fitting is a mainstream interpretation technique used in ground-penetrating radar (GPR) due to its simplicity and relatively low computational requirements. Conventional hyperbola fitting is based on the assumption that the investigated medium is a homogeneous half-space, and that the target is an ideal reflector with zero radius. However...
Ground-penetrating radar (GPR) systems with multiconcurrent sampling receivers can rapidly acquire dense multioffset GPR data, which are not feasible using typical common-offset (CO) GPR systems with a single fixed offset transmitter-receiver pair. Multioffset GPR data from these new multiconcurrent receiver systems have the potential to be used to...
There is a need to accurately simulate materials with complex electromagnetic properties when modelling Ground Penetrating Radar (GPR), as many objects encountered with GPR contain water, e.g. soils, curing concrete, and water-filled pipes. One of widely-used open-source software that simulates electromagnetic wave propagation is gprMax. It uses Ye...
General full-wave electromagnetic solvers, such as those utilizing the finite-difference time-domain (FDTD) method, are computationally demanding for simulating practical GPR problems. We explore the performance of a near-real-time, forward modeling approach for GPR that is based on a machine learning (ML) architecture. To ease the process, we have...
There is a need to accurately simulate materials with complex electromagnetic properties when modelling Ground Penetrating Radar (GPR), as many objects encountered with GPR contain water, e.g. soils, curing concrete, and water-filled pipes. One of widely-used open-source software that simulates electromagnetic wave propagation is gprMax. It uses Ye...
Plain Language Summary
The landing site of Chang’E‐4 is at the Von Kármán (VK) crater at the South Pole‐Aitken (SPA) basin. The SPA basin is the oldest and biggest basin on the Moon created at the early stages of its evolution by an impact that is, believed to have penetrated the lunar crust and uplifted materials from the top mantle. Understanding...
Full-waveform inversion (FWI) is considered one of the most promising interpretation tools for hydrogeological applications using ground-penetrating radar. However, FWI has had limited practical uptake for several reasons: large computational requirements, an inability to reconstruct loss mechanisms of soil, and the need for a good initial starting...
Full-waveform inversion (FWI) of cross-borehole Ground Penetrating Radar (GPR) data is a technique with the potential to investigate subsurface structures. Typical FWI applications transform the 3D measurements into a 2D domain via an asymptotic 3D to 2D data transformation, widely known as a Bleistein filter. Despite the broad use of such a transf...
Ground penetrating radar (GPR) is a well-established tool for detecting and locating reinforcing bars (rebars) in concrete structures. However, using GPR to quantify the diameter of rebars is a challenging problem that current processing approaches fail to tackle. To that extent, we have developed a novel machine learning framework that can estimat...
Horizontally stratified media are commonly used to represent naturally occurring and man-made structures, such as soils, roads, and pavements, when probed by ground-penetrating radar (GPR). Electromagnetic (EM) wave scattering from such multilayered media is dependent on the roughness of the interfaces. In this paper, we developed a closed-form asy...
The simulation, or forward modeling, of ground penetrating radar (GPR) is becoming a more frequently used approach to facilitate the interpretation of complex real GPR data, and as an essential component of full-waveform inversion (FWI). However, general full-wave 3-D electromagnetic (EM) solvers, such as the ones based on the finite-difference tim...
The Finite-Difference Time-Domain (FDTD) method is a popular numerical modelling technique in computational electromagnetics. The volumetric nature of the FDTD technique means simulations often require extensive computational resources (both processing time and memory). The simulation of Ground Penetrating Radar (GPR) is one such challenge, where t...
Finite-difference time-domain forward modeling of ground-penetrating radar (GPR) is becoming regularly used in model-based interpretation methods, such as full-waveform inversion (FWI) and machine learning schemes. Oversimplifications in such forward models can compromise the accuracy and realism with which real GPR responses can be simulated, whic...
Numerical artifacts affect the reliability of computational dosimetry of human exposure to low-frequency electromagnetic fields. In the guidelines of the International Commission of Non-Ionizing Radiation Protection, a reduction factor of 3 was considered to take into account numerical uncertainties when determining the limit values for human expos...
This paper presents two electromagnetic simulators based on the Finite-Difference Time Domain (FDTD) technique and Boundary Element Method (BEM), for Ground Penetrating Radar applications. The first simulator is the new open-source version of the software gprMax, which employs Yee's algorithm to solve Maxwell's equations by using the FDTD method an...
This work aims at offering an overview on the scientific results stemming from a selection of three Short-Term Scientific Missions (STSMs) carried out in 2016 and funded by the COST Action TU1208 “Civil Engineering Applications of Ground Penetrating Radar.” The research activities focused on the development and use of electromagnetic modelling and...
In this paper we compare current implementations of commonly used numerical techniques — the Finite-Difference Time-Domain (FDTD) method, the Finite-Integration Technique (FIT), and Time-Domain Integral Equations (TDIE) — to solve the canonical problem of a horizontal dipole antenna radiating over lossless and lossy half-spaces. These types of envi...
GPR full-waveform inversion (FWI) is a challenging high-resolution inversion approach for GPR data that can return simultaneously the electromagnetic wave velocity and attenuation. In recent years, crosshole GPR FWI has been applied to a wide range of applications, where it has been mostly implemented in the computationally attractive 2D domain. Th...
Development of accurate models of GPR antennas is being driven by research into more accurate simulation of amplitude and phase information, improved antenna designs, and better-performing forward simulations for inversion procedures. Models of a simple dipole antenna, as well as more complex models similar to a GSSI 1.5GHz antenna and a MALA Geo-s...
2D crosshole ground penetrating (GPR) full-waveform inversion (FWI) has shown superior resolution compared to ray-based inversion tomograms for synthetic and experimental data. To invert measured 3D data with a 2D model that has a reduced geometrical spreading and assumes infinite source and receiver dimensions perpendicular to the 2D inversion pla...
Directly measuring the radiation characteristics of Ground Penetrating Radar (GPR) antennas in environments typically encountered in GPR surveys, presents many practical difficulties. However it is very important to understand how energy is being transmitted and received by the antenna, especially for areas of research such as antenna design, signa...
Directly measuring the radiation characteristics of Ground Penetrating Radar (GPR) antennas in complex environments, typically encountered in GPR surveys, presents many practical difficulties. However it is crucial to be able to understand how energy is being transmitted and received by the antenna. This in turn is important for areas of research s...
Understanding how energy is transmitted and received by Ground Penetrating Radar antennas is crucial to many areas of the industry: antenna design, data processing and inversion algorithms, usage of antennas in GPR surveys, and interpretation of GPR responses. The radiation characteristics of antennas are usually investigated by studying the radiat...
A three-dimensional (3-D) finite-difference time-domain (FDTD) algorithm is used in order to simulate ground penetrating radar (GPR) for landmine detection. Two bowtie GPR transducers are chosen for the simulations and two widely employed antipersonnel (AP) landmines, namely PMA-1 and PMN are used. The validity of the modeled antennas and landmines...
A numerical modelling case study is presented aim- ing to investigate aspects of the applicability of artificial neural networks (ANN) to the problem of landmine detection using ground penetrating radar (GPR). An essential requirement of ANN and machine learning in general, is a coherent training set. A good training set should include data from as...
gprMax is a freely-available set of electromagnetic wave simulation tools based on the Finite-Difference Time- Domain (FDTD) numerical method. gprMax was originally written in the mid-1990s and has primarily been used to simulate Ground Penetrating Radar (GPR). Current computing resources offer the opportunity to build detailed and complex FDTD mod...
Models of antennas have been included in numerical simulations of ground penetrating radar (GPR) intermittently over the past 20 years with varying degrees of realism. Those antenna models that have been published have been mainly of antennas used in academia or for research purposes, and not regularly used commercial antennas. This is, of course,...
This paper presents an investigation of the radiation characteristics and sensitivity of a high-frequency Ground-Penetrating Radar (GPR) antenna using radiation patterns obtained from both physical measurements and a three-dimensional (3D) Finite-Difference Time-Domain (FDTD) numerical model. The aim was to develop an understanding of how electroma...
Research on the characterisation and optimisation of Ground Penetrating Radar (GPR) antennas will be presented as part of COST Action TU1208 “Civil Engineering Applications of Ground Penetrating Radar”. This work falls within the remit of Working Group 1 – “Novel GPR instrumentation” which focuses on the design of innovative GPR equipment for Civil...
There have been a number of studies using theoretical predictions, numerical solutions, and measured data for analysing the radiation patterns of Ground-Penetrating Radar (GPR) antennas in free-space and over lossless and low-loss half-spaces. These studies demonstrated that theoretical far-field patterns do not apply in the near-field, and that re...
In this study, we numerically evaluated a full-wave antenna model for near-field conditions using GprMax3D. The antenna is effectively characterized by a series of source and field points and global reflection/transmission coefficients, which enables us to take the maximum benefit of using analytical solutions of Maxwell' equations to noticeably re...
Ground-Penetrating Radar (GPR) is a non-destructive electromagnetic investigative tool used in many applications across the fields of engineering and geophysics. The propagation of electromagnetic waves in lossy materials is complex and over the past 20 years, the computational modelling of GPR has developed to improve our understanding of this phe...
This paper presents three-dimensional (3D) numerical models of commercially used Ground-Penetrating Radar (GPR) antennas from Geophysical Survey Systems, Inc. (GSSI) and Mala Geoscience. GprMax, an electromagnetic simulator based on the Finite-Difference Time-Domain (FDTD) technique, is used along with ParaView (an open-source visualisation ap-plic...
Ground Penetrating Radar (GPR) antennas are often not well described and hence modeled in the majority of GPR simulators. As a consequence results from these models do not represent reality. In this paper two detailed Finite-Difference Time-Domain (FDTD) models of commercial GPR antennas are presented. The complex geometry, material properties and...
The paper focuses on the use of Ground-Penetrating Radar (GPR) on natural stone surfaces. Experimental and numerical models were created to examine the effectiveness of GPR to detect layer depths beneath natural stone setts.
The experimental models showed that GPR can be used on natural stone constructions however it was essential that the relative...
This paper presents three-dimensional (3D) numerical models of commercially used Ground-Penetrating Radar (GPR) antennas from Mala Geoscience and Geophysical Survey Systems, Inc. (GSSI). GprMax, an electromagnetic simulator based on the Finite-Difference Time-Domain (FDTD) technique, is used along with ParaView (an open-source visualisation applica...
Ground Penetrating Radar (GPR) antennas are often not well described and hence modeled in the majority of GPR simulators. As a consequence results from these models do not represent reality. In this paper two detailed Finite-Difference Time-Domain (FDTD) models of commercial GPR antennas are presented. The complex geometry, material properties and...
