Underground Diagnosis Based on GPR and Learning in the Model Space

Ground Penetrating Radar (GPR) has been widely used in pipeline detection and underground diagnosis. In practical applications, the characteristics of the GPR data of the detected area and the likely underground anomalous structures could be rarely acknowledged before fully analyzing the obtained GPR data, causing challenges to identify the underground structures or abnormals automatically. In this paper, a GPR B-scan image diagnosis method based on learning in the model space is proposed. The idea of learning in the model space is to use models fitted on parts of data as more stable and parsimonious representations of the data. For the GPR image, 2-Direction Echo State Network (2D-ESN) is proposed to fit the image segments through the next item prediction. By building the connections between the points on the image in both the horizontal and vertical directions, the 2D-ESN regards the GPR image segment as a whole and could effectively capture the dynamic characteristics of the GPR image. And then, semi-supervised and supervised learning methods could be further implemented on the 2D-ESN models for underground diagnosis. Experiments on real-world datasets are conducted, and the results demonstrate the effectiveness of the proposed model

Imaging reinforced concrete: A comparative study of Ground Penetration Radar and Rebarscope

Geophysical techniques have been playing a very vital role in subsurface imaging in the recent past. Technology has been making it both reliable and convenient to utilize non-destructive geophysics techniques like Ground Penetration Radar, Induction current based Rebarscope, Seismic methods, ERT, etc. The applications range from shallow subsurface investigation of Bridge decks to old tunnels, mapping of rabars in a pre-existing construction and analyzing the concrete strength. The thesis constitutes of a comparative study and analysis of a Ground Penetration Radar system and a Rebarscope. Individual parameters obtained directly from the study and obtained indirectly from the study shall be analyzed for a better quantitative understanding of their variation and errors to optimize the utility of the instruments individually. Data obtained from both Ground Penetration Radar system and Rebarscope would be compared for accuracy in determining the rebar depth. For the experiments, pre-designed concrete slabs are constructed with rebars at various depths and defects in concrete. Furthermore, a combination of both the instruments is used to minimize errors and to achieve better control over the intrinsic and extrinsic errors of the instruments to undertake real world studies with better dependency. A calibration, comparative and combination study of Ground Penetration Radar and Rebarscope is important for the very purpose of better understanding of the quality of concrete, especially in its initial stages of degradation. The amplitude variation in the signal and dielectric permittivity of the concrete indicates concrete quality. The study illustrate the superiority of the Ground Penetration Radar system, but in cases of highly varying degradation and construction errors Rebarscope plays key role in accurate depth estimation of the reinforcement rebars. The study highlights some limitations of GPR surveys and proceeds to address the limitations by utilizing a Rebarscope in combination with GPR system --Abstract, page iii

Investigating Mechanisms of Hydraulic Conductivity Transience in Sandy Streambeds

Streambed hydraulic conductivity (K) is known to be spatially and temporally heterogeneous, but few attempts to understand the controls on temporal variability have been made. This study documents temporal K transience and demonstrates how hydraulic, geophysical, and sedimentological methods can be combined to understand the processes that give rise to changes in streambed K. Falling head permeameter tests and slug tests were conducted to determine vertical K (Kv) and K (slug test K), respectively. These tests were repeated three times over a twelve-week period on the same grid at a depth of 0.5 meters below the bed of the Loup River in east-central Nebraska during the summer of 2017. This grid included (1) a stationary braid bar where diagenetic pore clogging is expected to control K transience, and (2) mobile sediments of the adjacent stream channel where deposition and erosion are thought to be the dominant controls. Sediment samples were collected at the site of each hydraulic test to determine grain size distributions and estimate K. Ground penetrating radar surveys at 450 MHz and frequency domain electromagnetic geophysical surveys provided high resolution images of subsurface structure. Kv ranges between 0.1 and 45 meters/day, and K ranges between 15 and 55 meters/day. Kv and K changed significantly only between the second and third sampling events. K declined 14-20% in both environments while Kv declined 27% on the bar, but was unchanged in the channel. Despite evidence of scour and fill in the channel captured by GPR, deposition and erosion did not exert a dominant influence on K transience. The results of this study suggest that processes other than physical sediment transport, such as bioclogging or gas ebullition, were responsible for the decrease in K. Advisor: Jesse T. Koru

New Global Perspectives on Archaeological Prospection

This volume is a product of the 13th International Conference on Archaeological Prospection 2019, which was hosted by the Department of Environmental Science in the Faculty of Science at the Institute of Technology Sligo. The conference is held every two years under the banner of the International Society for Archaeological Prospection and this was the first time that the conference was held in Ireland. New Global Perspectives on Archaeological Prospection draws together over 90 papers addressing archaeological prospection techniques, methodologies and case studies from 33 countries across Africa, Asia, Australasia, Europe and North America, reflecting current and global trends in archaeological prospection. At this particular ICAP meeting, specific consideration was given to the development and use of archaeological prospection in Ireland, archaeological feedback for the prospector, applications of prospection technology in the urban environment and the use of legacy data. Papers include novel research areas such as magnetometry near the equator, drone-mounted radar, microgravity assessment of tombs, marine electrical resistivity tomography, convolutional neural networks, data processing, automated interpretive workflows and modelling as well as recent improvements in remote sensing, multispectral imaging and visualisation

Convolutional Autoencoder for Landmine Detection on GPR Scans

Buried unexploded landmines are a serious threat in many countries all over the World. As many landmines are nowadays mostly plastic made, the use of ground penetrating radar (GPR) systems for their detection is gaining the trend. However, despite several techniques have been proposed, a safe automatic solution is far from being at hand. In this paper, we propose a landmine detection method based on convolutional autoencoder applied to B-scans acquired with a GPR. The proposed system leverages an anomaly detection pipeline: the autoencoder learns a description of B-scans clear of landmines, and detects landmine traces as anomalies. In doing so, the autoencoder never uses data containing landmine traces at training time. This allows to avoid making strong assumptions on the kind of landmines to detect, thus paving the way to detection of novel landmine models

Surface and Sub-Surface Analyses for Bridge Inspection

The development of bridge inspection solutions has been discussed in the recent past. In this dissertation, significant development and improvement on the state-of-the-art in the field of bridge inspection using multiple sensors (e.g. ground penetrating radar (GPR) and visual sensor) has been proposed. In the first part of this research (discussed in chapter 3), the focus is towards developing effective and novel methods for rebar detection and localization for sub-surface bridge inspection of steel rebars. The data has been collected using Ground Penetrating Radar (GPR) sensor on real bridge decks. In this regard, a number of different approaches have been successively developed that continue to improve the state-of-the-art in this particular research area. The second part (discussed in chapter 4) of this research deals with the development of an automated system for steel bridge defect detection system using a Multi-Directional Bicycle Robot. The training data has been acquired from actual bridges in Vietnam and validation is performed on data collected using Bicycle Robot from actual bridge located in Highway-80, Lovelock, Nevada, USA. A number of different proposed methods have been discussed in chapter 4. The final chapter of the dissertation will conclude the findings from the different parts and discuss ways of improving on the existing works in the near future

Long-Short-Term Memory in Active Wavefield Geophysical Methods

The PhD thesis discusses the application of Long Short-Term Memory (LSTM) networks in active wavefield geophysical methods. In this work we emphasizes the advantages of Deep Learning (DL) techniques in geophysics, such as improved accuracy, handling complex datasets, and reducing subjectivity. The work explores the suitability of LSTM networks compared to Convolutional Neural Networks (CNNs) in some geophysical applications. The research aims to comprehensively investigate the strengths, limitations, and potential of recurrent neurons, particularly LSTM, in active wavefield geophysics. LSTM networks have the ability to capture temporal dependencies and are well-suited for analyzing geophysical data with non-stationary behavior. They can process both time and frequency domain information, making them valuable for analyzing Seismic and Ground Penetrating Radar (GPR) data. The PhD thesis consists of five main chapters covering methodological development, regression, classification, data fusion, and frequency domain signal processing.The PhD thesis discusses the application of Long Short-Term Memory (LSTM) networks in active wavefield geophysical methods. In this work we emphasizes the advantages of Deep Learning (DL) techniques in geophysics, such as improved accuracy, handling complex datasets, and reducing subjectivity. The work explores the suitability of LSTM networks compared to Convolutional Neural Networks (CNNs) in some geophysical applications. The research aims to comprehensively investigate the strengths, limitations, and potential of recurrent neurons, particularly LSTM, in active wavefield geophysics. LSTM networks have the ability to capture temporal dependencies and are well-suited for analyzing geophysical data with non-stationary behavior. They can process both time and frequency domain information, making them valuable for analyzing Seismic and Ground Penetrating Radar (GPR) data. The PhD thesis consists of five main chapters covering methodological development, regression, classification, data fusion, and frequency domain signal processing

A generic framework for context-dependent fusion with application to landmine detection.

For complex detection and classification problems, involving data with large intra-class variations and noisy inputs, no single source of information can provide a satisfactory solution. As a result, combination of multiple classifiers is playing an increasing role in solving these complex pattern recognition problems, and has proven to be a viable alternative to using a single classifier. Over the past few years, a variety of schemes have been proposed for combining multiple classifiers. Most of these were global as they assign a degree of worthiness to each classifier, that is averaged over the entire training data. This may not be the optimal way to combine the different experts since the behavior of each one may not be uniform over the different regions of the feature space. To overcome this issue, few local methods have been proposed in the last few years. Local fusion methods aim to adapt the classifiers\u27 worthiness to different regions of the feature space. First, they partition the input samples. Then, they identify the best classifier for each partition and designate it as the expert for that partition. Unfortunately, current local methods are either computationally expensive and/or perform these two tasks independently of each other. However, feature space partition and algorithm selection are not independent and their optimization should be simultaneous. In this dissertation, we introduce a new local fusion approach, called Context Extraction for Local Fusion (CELF). CELF was designed to adapt the fusion to different regions of the feature space. It takes advantage of the strength of the different experts and overcome their limitations. First, we describe the baseline CELF algorithm. We formulate a novel objective function that combines context identification and multi-algorithm fusion criteria into a joint objective function. The context identification component thrives to partition the input feature space into different clusters (called contexts), while the fusion component thrives to learn the optimal fusion parameters within each cluster. Second, we propose several variations of CELF to deal with different applications scenario. In particular, we propose an extension that includes a feature discrimination component (CELF-FD). This version is advantageous when dealing with high dimensional feature spaces and/or when the number of features extracted by the individual algorithms varies significantly. CELF-CA is another extension of CELF that adds a regularization term to the objective function to introduce competition among the clusters and to find the optimal number of clusters in an unsupervised way. CELF-CA starts by partitioning the data into a large number of small clusters. As the algorithm progresses, adjacent clusters compete for data points, and clusters that lose the competition gradually become depleted and vanish. Third, we propose CELF-M that generalizes CELF to support multiple classes data sets. The baseline CELF and its extensions were formulated to use linear aggregation to combine the output of the different algorithms within each context. For some applications, this can be too restrictive and non-linear fusion may be needed. To address this potential drawback, we propose two other variations of CELF that use non-linear aggregation. The first one is based on Neural Networks (CELF-NN) and the second one is based on Fuzzy Integrals (CELF-FI). The latter one has the desirable property of assigning weights to subsets of classifiers to take into account the interaction between them. To test a new signature using CELF (or its variants), each algorithm would extract its set of features and assigns a confidence value. Then, the features are used to identify the best context, and the fusion parameters of this context are used to fuse the individual confidence values. For each variation of CELF, we formulate an objective function, derive the necessary conditions to optimize it, and construct an iterative algorithm. Then we use examples to illustrate the behavior of the algorithm, compare it to global fusion, and highlight its advantages. We apply our proposed fusion methods to the problem of landmine detection. We use data collected using Ground Penetration Radar (GPR) and Wideband Electro -Magnetic Induction (WEMI) sensors. We show that CELF (and its variants) can identify meaningful and coherent contexts (e.g. mines of same type, mines buried at the same site, etc.) and that different expert algorithms can be identified for the different contexts. In addition to the land mine detection application, we apply our approaches to semantic video indexing, image database categorization, and phoneme recognition. In all applications, we compare the performance of CELF with standard fusion methods, and show that our approach outperforms all these methods