Dense light field coding: a survey

Light Field (LF) imaging is a promising solution for providing more immersive and closer to reality multimedia experiences to end-users with unprecedented creative freedom and flexibility for applications in different areas, such as virtual and augmented reality. Due to the recent technological advances in optics, sensor manufacturing and available transmission bandwidth, as well as the investment of many tech giants in this area, it is expected that soon many LF transmission systems will be available to both consumers and professionals. Recognizing this, novel standardization initiatives have recently emerged in both the Joint Photographic Experts Group (JPEG) and the Moving Picture Experts Group (MPEG), triggering the discussion on the deployment of LF coding solutions to efficiently handle the massive amount of data involved in such systems. Since then, the topic of LF content coding has become a booming research area, attracting the attention of many researchers worldwide. In this context, this paper provides a comprehensive survey of the most relevant LF coding solutions proposed in the literature, focusing on angularly dense LFs. Special attention is placed on a thorough description of the different LF coding methods and on the main concepts related to this relevant area. Moreover, comprehensive insights are presented into open research challenges and future research directions for LF coding.info:eu-repo/semantics/publishedVersio

Advanced Techniques for Ground Penetrating Radar Imaging

Ground penetrating radar (GPR) has become one of the key technologies in subsurface sensing and, in general, in non-destructive testing (NDT), since it is able to detect both metallic and nonmetallic targets. GPR for NDT has been successfully introduced in a wide range of sectors, such as mining and geology, glaciology, civil engineering and civil works, archaeology, and security and defense. In recent decades, improvements in georeferencing and positioning systems have enabled the introduction of synthetic aperture radar (SAR) techniques in GPR systems, yielding GPR–SAR systems capable of providing high-resolution microwave images. In parallel, the radiofrequency front-end of GPR systems has been optimized in terms of compactness (e.g., smaller Tx/Rx antennas) and cost. These advances, combined with improvements in autonomous platforms, such as unmanned terrestrial and aerial vehicles, have fostered new fields of application for GPR, where fast and reliable detection capabilities are demanded. In addition, processing techniques have been improved, taking advantage of the research conducted in related fields like inverse scattering and imaging. As a result, novel and robust algorithms have been developed for clutter reduction, automatic target recognition, and efficient processing of large sets of measurements to enable real-time imaging, among others. This Special Issue provides an overview of the state of the art in GPR imaging, focusing on the latest advances from both hardware and software perspectives

The Rapid Acquisition and Application of Geophysical Data to the Sustainable and Proficient Management of Shallow Aquifers and Cemeteries

Rapidly acquired non-invasive geophysical data is key to reducing the risk inherent in subsurface investigations. It achieves this risk reduction by provision of spatiotemporally dense datasets and new methods to measure the efficacy of acquisition, analysis, and modeling. In a first example, I use two geophysical methods—electrical resistivity tomography and time-domain electromagnetics—to investigate the subsurface in a rapidly urbanizing alluvial floodplain setting. Specifically I focus on the geologic structure of a shallow alluvial aquifer in the Brazos River floodplain of Texas, characterizing dynamic hydrological interactions between the aquifer and the adjacent river. Based on new geophysical insights, I determine how the sedimentary architecture of the shallow alluvial aquifer acts as a control on its recharge and discharge and how bidirectional preferential flow pathways establish hydrologic communication between the aquifer and the river at human and geologic time scales. In a second example, I develop a protocol to improve identification of unmarked graves in a historic African-American cemetery. I show that a geophysicist’s detection proficiency, expressed in terms of true-positive, true-negative, false-positive, and false-negative percentages, can be improved using radar signatures of nearby known targets as a proxy for ground-truth

Spatial priors for tomographic reconstructions from limited data

Tomografie is het reconstrueren van het inwendige van een object a.d.h.v externe metingen, b.v. beelden verkregen met X-stralen of microgolven. Deze thesis bekijkt de specifieke aspecten van microgolftomografie en magnetische resonantie beeldvorming (Magnetic Resonance Imaging – MRI); beide technieken zijn onschadelijk voor de mens. Terwijl het gebruik van MRI wijdverspreid is voor veel klinische toepassingen, is microgolftomografie nog niet in klinisch gebruik ondanks zijn potentiële voordelen. Door de lage kost en draagbaarheid van de toestellen is het een waardevolle aanvulling aan het assortiment