Refraction Tomography Research Articles

A Long-Term Retrospective Natural History Study of EFEMP1-Associated Autosomal Dominant Drusen.

To analyze the natural history of EFEMP1-associated autosomal dominant drusen (ADD). In this retrospective observational study of molecularly confirmed patients with ADD, data and retinal imaging were extracted from an in-house database. The main outcome measurements were best-corrected visual acuity (BCVA), refraction, and retinal imaging, including quantitative analyses of the outer nuclear layer (ONL) thickness and pigmented epithelium detachment area, as well as qualitative analyses. The study included 44 patients (34 females and 10 males). The mean ± SD age of symptom onset was 40.1 ± 6.59 years of age (range, 25-52). Fourteen patients were asymptomatic during their entire follow-up. The most common symptoms at presentation were reduced vision (70%) and distortion in central vision (53%). Most subjects were emmetropic. The mean BCVA (logMAR) at baseline was 0.27 ± 0.41 (range, -0.1 to 2.1) in right eyes and was 0.19 ± 0.32 (range, -0.2 to 1.3) in left eyes. After a mean follow-up of 7.9 years, BCVA was reduced to 0.59 ± 0.66 (range, -0.1 to 2.1) in right eyes and 0.5 ± 0.72 (range, -0.1 to 2.4) in left eyes, values that were significantly different than baseline (P<0.0001 and P<0.0014, respectively). Fifteen eyes showed active or inactive choroidal neovascularization (CNV). BCVA differed significantly (P = 0.0004) between eyes with and without CNV at a comparable mean age. The ONL had a slow rate of thinning longitudinally, which significantly correlated with BCVA. Despite the late onset and relatively good prognosis of ADD, CNVs are more frequent than previously reported and are associated with a worse prognosis. Further research is necessary to elucidate gender associations.

Invertible neural networks for uncertainty quantification in refraction tomography

Uncertainty quantification (UQ) should be an essential ingredient of geophysical inversion because it measures the confidence in the results and enables the assessment of the value of information in the data. However, UQ using established methods ranges from very expensive to prohibitively costly, and estimating noise levels and integrating prior information is challenging, so it is not yet widely undertaken. In this paper, we explore the capabilities of a machine learning-based UQ tool known as the invertible neural network (INN) and focus on its application to a 2D tomography problem within a complex foothills environment. We propose a novel approach to handle realistic problem dimensions that uses variational autoencoders to compress the velocity model and data. The INN relates the respective latent spaces, significantly reducing memory requirements. Our findings reveal that this INN-based workflow can perform tomographic inversion while integrating an implicit prior in the form of a set of velocity models with pertinent features. Furthermore, we can address both epistemic and aleatoric uncertainties by adopting a deep ensemble strategy. This integrated approach yields plausible estimates of relative confidence in the inverted velocities, showcasing the potential of INN as a tool for UQ in geophysical inversion.

Flow Pathways in Fractured Basalt under Challenging Environmental Conditions: A Synergistic Approach of Electrical Resistivity Tomography and Seismic Refraction Imaging

Flow Pathways in Fractured Basalt under Challenging Environmental Conditions: A Synergistic Approach of Electrical Resistivity Tomography and Seismic Refraction Imaging

Assessment of different agricultural soil compaction levels using shallow seismic geophysical methods

A well-developed soil structure is crucial for a fertile soil and rules its influence on the ecosystem. Slight variations in the way soil components are organized and connected can greatly impact the soil mechanical and hydraulic characteristics. However, these features are challenging to measure at a scale that is relevant for agricultural management. In this study, we assess the capability of two seismic geophysical methods, i.e. Seismic Refraction Tomography and Multichannel Analysis of Surface Waves, to monitor the effects of compaction on agricultural bare soil. The purpose is to highlight the different mechanical response caused both by soil plastic deformation and soil water distribution due to increasing compaction. Results demonstrate that both geophysical techniques provide sufficient information to capture the effects of soil compaction and distinguish its significance, while traditional direct measurements, being punctual, lack sufficient spatial coverage. P-wave velocities carry a strong imprint of soil compaction, provided by seismic refraction, incorporating the information given by the multiphase medium in its entirety. On the other hand, S-wave velocity derived from Surface Waves discriminates the effect of solid matrix structure. This work, moreover, aims to pave the way for seismic methods to spatially characterize compaction at field scale, illustrating its potential and suggesting possible developments.

Assessment of Site Effects and Numerical Modeling of Seismic Ground Motion to Support Seismic Microzonation of Dushanbe City, Tajikistan

In the territory of Dushanbe city, the capital of Tajikistan, detailed geological and geophysical data were collected during geophysical surveys in 2019–2020. The data comprise 5 microtremor array measurements, 9 seismic refraction tomography profiles, seismological data from 5 temporary seismic stations for standard spectral ratio calculations, 60 borehole datasets, and 175 ambient noise measurements. The complete dataset for Dushanbe was used to build a consistent 3D geologic model of the city with a size of 12 × 12 km2. The results of the seismological and geophysical surveys were compared and calibrated with borehole data to define the boundaries of each layer in the study area. The Leapfrog Works software was utilized to create a 3D geomodel. From the 3D geomodel, we extracted six 12 km long 2D geological cross-sections. These 2D geological cross-sections were used for 2D dynamic numerical modeling with the Universal Distinct Element Code software to calculate the local seismic response. Finally, the dynamic numerical modeling results were compared with the amplification functions obtained from the seismological and ambient noise data analysis. The 2D dynamic numerical modeling results allowed a better assessment of the site effects in the study area to support seismic microzonation and the determination of local peak ground acceleration changes in combination with regional seismic hazard maps. In addition, our results confirm the strong seismic amplification effects noted in some previous studies, which are attributed to the influence of local topographic and subsurface characteristics on seismic ground motions.

Seismic characterisation of the subsoil under a historic building: Cathedral Church of Saint Mary in Murcia case study

This research focuses on the Cathedral Church of Saint Mary in Murcia, Spain, which is located in a moderate-to-high seismic risk zone in the Spanish context. The study uses geophysical techniques and geotechnical investigation to characterise seismic ground models at the building's scale, aiming to understand the real amplification of the ground under seismic effect in historic buildings. Three soil layers (silt, sand with gravel, and gravel) were identified through core borings. Multichannel Analysis of Surface Waves (MASW) profiles and Mini-array profiles revealed Vs values of 305 ± 32 m/s, 296 ± 62 m/s, and 440 ± 38.5 m/s, respectively, for these materials. Seismic Refraction Tomography (SRT) showed Vp values of 586 ± 73 m/s, 700 m/s, and 1466 ± 489 m/s for the corresponding layers. The horizontal-to-vertical spectral ratio (HVSR) approach identified a ground predominant period ranging from 0.37 to 0.38 s. Another significant peak at 2.3 s is observed, probably associated to the Triassic basement. Three seismic events with magnitudes Mw between 4.9 and 5.1 were used as inputs to determine the amplification factor (AF). The results indicate a PGA amplification factor between 1.7 and 2.1. These results contribute to the conservation and mitigation of seismic risk of this cultural heritage generating input data that enables precise computation of the soil-structure interaction.

Assess the Effectiveness of Multichannel Analysis of Surface Waves Method in Mapping Ancient Structures in Ultrashallow Aquatic Environments: The Case of Agioi Theodoroi, Greece

ABSTRACTThe present geophysical research aims to evaluate the applicability of multichannel analysis of surface waves (MASW) on mapping ultrashallow underwater ancient masonry remnants. The work presents the analysis from a single seismic line using MASW and seismic refraction tomography (SRT) methods and its corresponding electrical resistivity tomography (ERT) section surveyed at the submerged prehistoric site of Agioi Theodoroi area located 10 km eastern of Heraklion, Crete, Greece. The 2D MASW velocity model exhibits significant correspondence with the resistivity structure extracted from the ERT data, showing lateral S‐wave velocity (Vs) variations at the positions where the high resistivity anomalies exist. The analysis of synthetic seismic data calculated from a respective model reproduced a comparable S‐wave velocity pseudo‐section with the real data. However, the investigated targets (submerged buried masonry) appear shallower and wider in MASW sections than in the real world and the corresponding synthetic models, due to insufficient vertical and horizontal resolution of this method. Surface waves travelling through the seafloor sediments (Scholte‐waves) demonstrate very low velocity values. This makes them suitable for the detection of shallow and relatively large (&gt; 0.5 m) underwater manmade structures, providing the enhancement of MASW method resolution, by utilizing a high frequency (&gt; 100 Hz) seismic source, recording short Scholte wavelengths (≤ 1 m) and using shorter (≤ 0.5 m) receiver spacing and array length. Consequently, the results of this work demonstrate the potential in employing conventional seismic techniques in the delineation of underwater antiquities and the revealing of the cultural dynamics in very shallow off‐shore archaeological sites.

Factors Affecting the Stability of Loess Landslides: A Review

The stability of loess landslides affects the production and livelihood of the people in its vicinity. The stability of loess landslides is influenced by various factors, including internal structure, collapsibility, water content, and shear strength. The landslide stability of loesses can be analyzed by several geophysical methods, such as seismic refraction tomography (SRT), electrical resistivity tomography (ERT), micro-seismic technology, and ground penetrating radar (GPR). Geotechnical tests (compression and shear tests) and remote sensing techniques (Global Navigation Satellite System (GNSS), Interferometric Synthetic Aperture Radar (InSAR) and airborne 3D laser technology) are used for studying the landslide stability of loesses as well. Some of the methods above can measure parameters (e.g., fractures, water content, shear strength, creep) which influence the stability of loess landslides, while other methods qualitatively indicate the influencing factors. Integrating parameters measured by different methods, minimizing disturbances to landslides, and assessing landslide stability are important steps in studying landslide hazards. This paper comprehensively introduces the methods used in recent studies on the landslide stability of loesses and summarizes the factors which affect the landslide stability. Furthermore, the relationships between different parameters and methods are examined. This paper enhances comprehension of the underlying mechanisms of the stability of loess landslides to diminish disastrous consequences.

Diopter detection method based on optical imaging.

The peripheral retinal refractive state plays an important role in eye growth and development and is closely related to the development of myopia. Existing methods for measuring the peripheral retinal refractive state are cumbersome and can only detect in a limited range. To address the above shortcomings, this paper proposes a retinal refractive state detection method using optical refractive compensation imaging. First, a series of defocus images is captured using an optical system, and then the images are enhanced and filtered. Subsequently, the Sobel function is applied to calculate sharpness, and the asymmetric Gaussian (AG) model is employed for peak fitting, allowing for the determination of the fundus retina's overall refractive compensation value. We performed consistency analysis on the central and peripheral diopters with autorefractor KR-8900 (Topcon, Japan) and WAM-5500 (Grand Seiko, Japan), respectively. The intraclass correlation coefficients (ICCs) are all greater than 0.9, showing good consistency. This is a promising alternative to the current techniques for assessing the refraction of the peripheral retina.

Computation and Modelling of Seismic Refraction Tomography for Anisotropic Medium Based on Pseudo Bending Method

Seismic refraction tomography is one of the imaging techniques in geophysical methods used to remodel the near-surface velocity layer structure of the Earth. In this study, we carried out a new computational approach and modelling of seismic refraction tomography using the pseudo-bending method. The true model of the near-surface is designed to be anisotropic medium which is having a low velocity anomaly distribution. This anomaly is constructed in such a way as to be similar to a model of liquid waste away spreading, which exhibits seismic velocities ranging from 1600 m/s to 1800 m/s. Based on our computations and numerical modelling results, it was found that the ray tracing path using pseudo-bending method displays an asymmetrical trajectory when the positions of the source and geophone are exchanged. Altering the shooting configuration from direct shoot (DS) to reversed shoot (RS) also reveals a significant difference in travel time values. The results of delay time tomography inversion, which represents the difference between travel times in the true model and the initial model using the SIRT method, indicate the presence of a low velocity anomaly that can be interpreted as the distribution of liquid waste.

Enhanced Screening for Ectasia Risk: Multimodal Refractive Imaging Observations From the Fellow Unoperated Eye of Patients With Post-Laser In Situ Keratomileusis Ectasia

Purpose: The aim of this study was to report multimodal refractive imaging findings that may predict ectasia susceptibility on nonoperated eyes of patients who developed post-LASIK ectasia in the fellow eye. Study Design: This is a retrospective case series. Methods: The nonoperated fellow eyes of 5 patients who had unilateral LASIK with progressive ectasia underwent a comprehensive ophthalmologic evaluation and multimodal refractive imaging (MRI), including Pentacam HR and Corvis ST (Oculus; Wetzlar, Germany), along with segmental OCT (RTVue; Optovue, Inc, Fremont, CA). Different objective indices and parameters from the Pentacam, Corvis ST, and OCT were analyzed. Results: None of the 5 cases showed ectasia detection on the Pentacam TKC (topographic keratoconus classification), and inferior–superior (IS) asymmetry values were lower than 1.0 D in all 5 cases. Corneal thicknesses at the thinnest points measured with the Pentacam were 530, 466, 517, 488, and 511 µ, and with the OCT were 512, 460, 508, 480, and 495 µ, in cases 1to 5, respectively. The keratoconus risk scoring system based on OCT measurements demonstrated a high risk in 2 patients. The BAD-D (Belin-Ambrósio Enhanced Ectasia Deviation) was higher than 1.22 in all 5 cases and higher than 1.6 in 2 cases. Four cases had ARTmax (Ambrósio Relational Thickness to the meridian with maximal progression increase) lower than 390. The PRFI (Pentacam Random Forest Index) was equal or higher than 0.12 in all 5 cases, and enhanced posterior elevation, which is calculated using data from the standard elevation map, excluding a 3.5-mm area centered on the thinnest point, was abnormal in all 5 cases. The value of the current version of the tomographic biomechanical index (TBI V1), derived from artificial intelligence (AI) algorithms, which integrate Scheimpflug-based tomography and biomechanical data, was equal or higher than 0.29 in 3 cases. Conclusions: Signs of ectasia susceptibility were detected in all nonoperated eyes based on multimodal imaging. These findings support the clinical relevance of such analysis when screening for ectasia risk among candidates for refractive surgery.

Impacts of hydrofacies geometry designed from seismic refraction tomography on estimated hydrogeophysical variables

Abstract. Understanding the critical zone processes related to groundwater flows relies on subsurface structure knowledge and its associated parameters. We propose a methodology to draw the patterns of the subsurface critical zone at the catchment scale from seismic refraction data and show its interest for hydrological modelling. The designed patterns define the structure of a physically based distributed hydrological model applied to a mountainous catchment. With that goal, we acquired 10 seismic profiles covering the different geomorphology zones of the studied catchment. We develop a methodology to analyse the geostatistical characteristics of the seismic data and interpolate them over the whole catchment. The applied geostatistical model considers the scale variability of the subsurface structures observed from the seismic data analysis. We use compressional seismic wave velocity thresholds to identify the depth of the soil and saprolite bottom boundaries. Assuming that such porous compartments host the main part of the active aquifer, their patterns are embedded in a distributed hydrological model. We examine the sensitivity of classical hydrological data (piezometric heads) and geophysical data (magnetic resonance soundings) to the applied velocity thresholds used to define the soil and saprolite boundaries. Different sets of hydrogeological parameters are used in order to distinguish general trends or specificities related to the choice of parameter values. The application of the methodology to an actual catchment illustrates the interest of seismic refraction in constraining the structure of the critical zone subsurface compartments. The sensitivity tests highlight the complementarity of the analysed hydrogeophysical data sets.

Reliable extraction of x-ray refraction and dark-field signals with a large field of view, multi-modal scanning system at spectral energies up to 150 kVp

Abstract Multi-modal x-ray scanning allows the simultaneous acquisition of attenuation, refraction and ultra-small angle scattering or dark field images. While many examples of multi-modal x-ray scanning exist in the literature, extension to high x-ray energy, necessary to investigate dense and high-Z materials, still poses challenges. We present the investigation of attenuation, refraction and dark field images taken at 90, 120 and 150 kVp, using a scanning, large field of view multi-modal imaging system. Increases in tube voltage reduce both contrast and signal to noise but still produce satisfactory results suitable for quantitative analysis. On top of benchmarking against phantoms made of known materials, we illustrate this by scanning a 9 V PP3 battery; a highly absorbing sample which causes photon starvation at lower energies.

An assessment of seismicity and near surface geophysical characteristics of potential solid waste landfill sites in the Eastern Black Sea Region of Türkiye.

This study aimed to assess the suitability of the potential solid waste landfill sites in seven provinces (Samsun, Ordu, Giresun, Trabzon, Gümüşhane, Bayburt and Artvin) in the Eastern Blacksea Region of Türkiye. The earthquake hazard analysis for two major earthquakes which occurred in the region was first carried out. Then, the geophysical methods including seismic refraction tomography (SRT), electrical resistivity tomography (ERT) and Multichannel Analysis of Surface Waves (MASW) were conducted to find out the structural and physical properties of the subsurface which include the layering, soil classification based on VS30 and the groundwater content at 25 locations of 13 in target provinces. The integrated interpretation of whole data sets demonstrates that Işıktepe, Esence, Çamburnu and Kazantaş which are characterized by VP > 1200m/s, VS30 ≥ 400m/s, ρ > 70 Ohm-m, low earthquake hazard and seismicity are more suitable among others. Vezirköprü, Şebinkarahisar, Yenice, Bayburt-Center, Balkaynak and Murgul will be suitable after a geotechnical reclamation due to moderate seismic velocities and electrical resistivity which are 900 < VP ≤ 1200m/s, 200 < VS30 < 400m/s and 10 < ρ ≤ 70 Ohm-m representing stiff and wet soils. In addition, Bafra, Ağalık and Ovacık were considered to be unsuitable due to the presence of thick, water-saturated soft soil and extremely weathered rocks. Finally, this study shows that the joint interpretation of seismicity and geophysical data in potential waste landfill sites, extremely important for the planning and development of a city, can provide the valuable information which will enable to prevent possible deformations, environmental problems and economic losses after waste landfill.

Integrating seismic refraction and electrical approaches in determining geophysical properties of near-surface cavities in Calabar-Ikom highway, Odukpani, Cross River State, Nigeria

Integrated seismic refraction tomography (SRT) and electrical resistivity tomography (ERT) were used to study near-surface cavities with the aim of determining their geophysical properties. Five seismic refraction profiles around the study area were carried out using a 24-channel seismograph (ES-3000) while four ERT and ERT profiles were also conducted with IGIS resistivity meter and PLOTREFA software respectively. The data was processed using the RES2DINV software. Travel-time curves and velocity models were generated from the processed SRT data for each survey line, and 2-D inverted apparent resistivity models along the same lines were also generated for the purpose of comparison respectively. The results as obtained from the profiles showed SRT 1 (with a modelled velocity of 1,216 m/s in layer two at a depth of approximately 11 m - 20 m beneath the subsurface and an estimated cavity diameter of 11 m) and ERT 1 (with an apparent resistivity of approximately 826 Ωm and a depth of approximately 12.5 m – 16 m) indicates that the near-surface cavity outcrop links with a close-by mountainous structure in the EW direction. Profiles SRT 2 (with an approximately modeled velocity layer of 980 m/s in layer two at an approximate depth of 3.5 m – 7.0 m) and SRT 3 (with a modeled velocity layer of approx. 1,000 m/s in layer two at an approximate depth of 4.0 m – 7.0 m and 3.0 m – 9.0 m); ERT 2 (with an apparent resistivity of approximately 80 Ωm); and ERT 3 (with apparent resistivities of 116 Ωm and 182 Ωm at depths of approximately 3.5 m to 6.4 m and 4.0 m to 15.8 m) indicates that the surface cavity outcrop extends underneath the road network (Odukpani Central Section of Calabar-Ikom Highway) with a width of approximately 12 m. Profiles SRT 4 and SRT 5 (with an average velocity layer of 1,000 m/s in layer two at an approximate depth of 6.0 m – 13.2 m), and ERT 4 (with apparent resistivity ranging between 121 Ωm and 172 Ωm) at a depth of approximately 9.5 m to 20.0 m reveal that the near-surface cavity extends up to about 11 m across the highway and about 120 m away from the edge of the road. The above result will serve as reliable technical information to Transport and Building Construction Engineers on the presence of cavities along road networks and settlement areas in Odukpani Local Government Area. The recommendation is also made for the use of other geophysical techniques like Ground Penetration Radar (GPR) in conjunction with SRT and ERT to get higher-resolution imagery of the study area.

Reflection seismic imaging of subsurface geologic structures in the Bayan Obo mining area, China

A dense 2D seismic reflection survey was conducted at the Bayan Obo rare-earth-elements-Nb-Fe deposit in China to explore its geologic features and mineral endowment. A composite processing workflow was established for prestack depth imaging of this data set, which involved static correction to compensate for shifts caused by lateral inhomogeneities in near-surface layers and rugged topography. Standard methods were used to attenuate different types of noise and improve the signal-to-noise ratio of the data. A velocity model in the depth domain was obtained from refraction tomography and velocity analysis, and then used in migration. The preliminary interpretation of the final image revealed the mapping of mineralization at its true position in depth, indicating a relatively deep extension (approximately1.5 km). The results demonstrate the potential of seismic imaging as a complementary exploration tool to gravity and electromagnetic methods for mineral exploration purposes in the Bayan Obo mining area, providing a high-resolution seismic image and allowing for depth characterization of the mineral deposits. In addition, the images provide important information for guiding the selection of drilling borehole locations for deep exploration.

Non-invasive Visualization and Characterization of Bile Canaliculus Formation Using Refractive Index Tomography.

The vital role of bile canaliculus (BC) in liver function is closely related to its morphology. Electron microscopy has contributed to understanding BC morphology; however, its invasiveness limits its use in living specimens. Here, we report non-invasive characterization of BC formation using refractive index (RI) tomography. First, we investigated and characterized the RI distribution of BCs in two-dimensional (2D) cultured HepG2 cells. BCs were identified based on their distinct morphology and functionality, as confirmed using a fluorescence-labeled bile acid analog. The RI distribution of BCs exhibited three common features: (1) luminal spaces with a low RI between adjacent hepatocytes; (2) luminal spaces surrounded by a membranous structure with a high RI; and (3) multiple microvillus structures with a high RI within the lumen. Second, we demonstrated the characterization of BC structures in a three-dimensional (3D) culture model, which is more relevant to the in vivo environment but more difficult to evaluate than 2D cultures. Various BC structures were identified inside HepG2 spheroids with the three features of RI distribution. Third, we conducted comparative analyses and found that the BC lumina of spheroids had higher circularity and lower RI standard deviation than 2D cultures. We also addressed comparison of BC and intracellular lumen-like structures within a HepG2 spheroid, and found that the BC lumina had higher RI and longer perimeter than intracellular lumen-like structures. Our demonstration of the non-destructive, label-free visualization and quantitative characterization of living BC structures will be a basis for various hepatological and pharmaceutical applications.

Landslide assessment through integrated geoelectrical and seismic methods: A case study in Thungsong site, southern Thailand

Many landslides can cause significant damage to infrastructure, property, and human life. To study landslide structure and processes, geophysical techniques are most productive when employed in combination with other survey and monitoring tools, such as intrusive sampling. Here, the integration of electrical resistivity tomography (ERT) and seismic refraction tomography (SRT) methods is used to assess landslides in Thungsong district, Nakhon Si Thammarat, the south of Thailand, where is a hilly and seasons of prolonged rainfall region. The 2D cross-plot analysis of P-wave velocity and resistivity values obtained by these two methods is introduced to identify potential landslide-prone zones in this region. The results of the 2D cross-plot model reveal detailed image of the subsurface conditions, highlighting areas of low P-wave velocity (lower than 600 m/s) and low resistivity (lower than 600 Ωm). These areas are indicative of weak zone and are potential to be sliding materials. Moreover, an intrusive sampling data from boreholes is also used for the calibration and validation geophysical data with geological data. This can improve the accuracy of landslide assessment and develop effective mitigation strategies to reduce the risk of landslides in this area. In addition of the 2D cross-plot, the volume of sliding material is also determined from the difference of the surface and slipping plane elevations. The volume calculation of sliding material is roughly 33447.76 m3. This approach provides a preliminary tool for landslide studies and monitoring landslides in this region, thus enabling an improved understanding of slope failure processes in this context, and the basis of a landslide mitigation strategy in the future.

Application of seismic refraction tomography for detecting a hidden potential fault

Seismic refraction technique is an increasingly useful geophysical tool for geotechnical studies in civil engineering work including the mapping of different soil formation of subsoil and detection of the bed rock. Additionally, wave velocity is a key parameter which correlates directly with significant geotechnical parameters of soils and rocks. Today, the evolution of the measurement technique in the field and the data processing allows to obtain tomographic images which increases its potential for applications to evaluate structuration of rock mass. This work describes the basic principles of seismic tomography and a case history of an application in civil works used to evaluate the foundation conditions of a site were a new structure for a spillway for the Gatun lake, north Panama, was projected. The study allowed to detect a destructured band sector in the bedrock which was covered by more modern sediments and vegetation just in the site of interest for the foundation of a project. The magnitude of the destructured bedrock forced to relocate the structure.

An Accurate Calibration Method for Multilayer Refractive Imaging in Underwater 3-D Scanning

An Accurate Calibration Method for Multilayer Refractive Imaging in Underwater 3-D Scanning