Experimental time-domain controlled source electromagnetic induction for highly conductive targets detection and discrimination

The response of geological materials at the scale of meters and the response of buried targets of different shapes and sizes using controlled-source electromagnetic induction (CSEM) is investigated. This dissertation focuses on three topics; i) frac- tal properties on electric conductivity data from near-surface geology and processing techniques for enhancing man-made target responses, ii) non-linear inversion of spa- tiotemporal data using continuation method, and iii) classification of CSEM transient and spatiotemporal data. In the first topic, apparent conductivity profiles and maps were studied to de- termine self-affine properties of the geological noise and the effects of man-made con- ductive metal targets. 2-D Fourier transform and omnidirectional variograms showed that variations in apparent conductivity exhibit self-affinity, corresponding to frac- tional Brownian motion. Self-affinity no longer holds when targets are buried in the near-surface, making feasible the use of spectral methods to determine their pres- ence. The difference between the geology and target responses can be exploited using wavelet decomposition. A series of experiments showed that wavelet filtering is able to separate target responses from the geological background. In the second topic, a continuation-based inversion method approach is adopted, based on path-tracking in model space, to solve the non-linear least squares prob- lem for unexploded ordnance (UXO) data. The model corresponds to a stretched- exponential decay of eddy currents induced in a magnetic spheroid. The fast inversion of actual field multi-receiver CSEM responses of inert, buried ordnance is also shown. Software based on the continuation method could be installed within a multi-receiver CSEM sensor and used for near-real-time UXO decision. In the third topic, unsupervised self-organizing maps (SOM) were adapted for data clustering and classification. The use of self-organizing maps (SOM) for central- loop CSEM transients shows potential capability to perform classification, discrimi- nating background and non-dangerous items (clutter) data from, for instance, unex- ploded ordnance. Implementation of a merge SOM algorithm showed that clustering and classification of spatiotemporal CSEM data is possible. The ability to extract tar- get signals from a background-contaminated pattern is desired to avoid dealing with forward models containing subsurface response or to implement processing algorithm to remove, to some degree, the effects of background response and the target-host interactions

A Multidisciplinary Analysis of Frequency Domain Metal Detectors for Humanitarian Demining

This thesis details an analysis of metal detectors (low frequency electromagnetic induction devices) with emphasis on Frequency Domain (FD) systems and the operational conditions of interest to humanitarian demining. After an initial look at humanitarian demining and a review of their basic principles we turn our attention to electromagnetic induction modelling and to analytical solutions to some basic FD direct (forward) problems. The second half of the thesis focuses then on the analysis of an extensive amount of experimental data. The possibility of target classification is first discussed on a qualitative basis, then quantitatively. Finally, we discuss shape and size determination via near field imaging

Exploitation and Mitigation of Multipath in Complex Wave Propagation Environments for Target Detection, Tracking, and Communication.

This thesis introduces novel wave propagation models and RF based techniques for detection, tracking, and communication in highly cluttered environments. The applications of interest include localization of deeply submerged targets such as UXO and clandestine tunnels, real-time positioning and tracking of small robotic platforms for search and rescue missions, and enhanced situational awareness in urban warfare. First, an accurate near-ground wave propagation model for indoor and urban scenarios that is based on a hybrid physical optics and asymptotic expansion of dyadic Green's function for a half-space dielectric medium is presented. This model and other full-wave solvers are then used to: 1) investigate direction finding in highly cluttered environments, and 2) analyze the performance of compact antenna diversity systems. Second, a novel sub-wavelength RF source tracking system for applications in GPS-denied environments is realized and measured. The system utilizes a highly miniaturized transmit antenna and a biomimetic circuit that mimics the hearing mechanism of a fly to achieve a compact system. It is shown that tracking with absolute positioning of better than 70cm in complex buildings through multiple layers of walls is achievable from outside in a standoff distance. The third part of the work focuses on a physics-based analysis technique for compact and co-located antenna diversity systems that takes into account the complex radiation pattern of the diversity antennas in conjunction with an accurate near-ground propagation model. A co-located, co-polarized radiation pattern diversity system prototype is realized and characterized. Based on the above analysis technique and measurement results, a diversity gain of 8dB is achieved. In the last part of the work, a subsurface imaging radar system based on distributed near-ground sensor networks that utilize ultra-wideband waveforms in the VHF range is described. Numerical models and laboratory scale model measurements are used to demonstrate high resolution synthetic aperture imaging of deeply submerged targets under a layered medium using an ad hoc network of mobile transceivers.PHDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/96112/1/fikadu_1.pd

DETERMINE: Novel Radar Techniques for Humanitarian Demining

Today the plague of landmines represent one of the greatest curses of modern time, killing and maiming innocent people every day. It is not easy to provide a global estimate of the problem dimension, however, reported casualties describe that the majority of the victims are civilians, with almost a half represented by children. Among all the technologies that are currently employed for landmine clearance, Ground Penetrating Radar (GPR) is one of those expected to increase the efficiency of operation, even if its high-resolution imaging capability and the possibility of detecting also non-metallic landmines are unfortunately balanced by the high sensor false alarm rate. Most landmines may be considered as multiple layered dielectric cylinders that interact with each other to produce multiple reflections, which will be not the case for other common clutter objects. Considering that each scattering component has its own angular radiation pattern, the research has evaluated the improvements that multistatic configurations could bring to the collected information content. Employing representative landmine models, a number of experimental campaigns have confirmed that GPR is capable of detecting the internal reflections and that the presence of such scattering components could be highlighted changing the antennas offset. In particular, results show that the information that can be extracted relevantly changes with the antenna separation, demonstrating that this approach can provide better confidence in the discrimination and recognition process. The proposed bistatic approach aims at exploiting possible presence of internal structure beneath the target, which for landmines means the activation or detonation assemblies and possible internal material diversity, maintaining a limited acquisition effort. Such bistatic configurations are then included in a conceptual design of a highly flexible GPR system capable of searching for landmines across a large variety of terrains, at reasonably low cost and targeting operators safety

Summary of Research 1994

The views expressed in this report are those of the authors and do not reflect the official policy or position of the Department of Defense or the U.S. Government.This report contains 359 summaries of research projects which were carried out under funding of the Naval Postgraduate School Research Program. A list of recent publications is also included which consists of conference presentations and publications, books, contributions to books, published journal papers, and technical reports. The research was conducted in the areas of Aeronautics and Astronautics, Computer Science, Electrical and Computer Engineering, Mathematics, Mechanical Engineering, Meteorology, National Security Affairs, Oceanography, Operations Research, Physics, and Systems Management. This also includes research by the Command, Control and Communications (C3) Academic Group, Electronic Warfare Academic Group, Space Systems Academic Group, and the Undersea Warfare Academic Group

Radar Technology

In this book “Radar Technology”, the chapters are divided into four main topic areas: Topic area 1: “Radar Systems” consists of chapters which treat whole radar systems, environment and target functional chain. Topic area 2: “Radar Applications” shows various applications of radar systems, including meteorological radars, ground penetrating radars and glaciology. Topic area 3: “Radar Functional Chain and Signal Processing” describes several aspects of the radar signal processing. From parameter extraction, target detection over tracking and classification technologies. Topic area 4: “Radar Subsystems and Components” consists of design technology of radar subsystem components like antenna design or waveform design

The development of integrated high-resolution geophysical, photogrammetric and GPS surveying applied to landslides in the South Wales coalfield

The aim of this research is to develop an integrated and cost-effective site investigation approach for slow moving landslides or potentially unstable slopes found within the South Wales Coalfield, an area of complex geology and hydrogeology. The research was based on the use and assessment of a wide range of surface geophysical techniques, supported by GPS and Digital Photogrammetry surveying, and the joint interpretation of the results which such techniques provide. The South Wales Coalfield has one of the highest concentrations of urban landslides in the UK due to its layered Carboniferous geology. Quaternary / Holocene geomorphology, coal mining history and relatively high rainfall. Mynydd yr Eglwys landslide (Ystrad, Rhondda Cynon Taff) was selected as the field study site because it can be considered representative of the active landslides found within the area. In autumn 1998, following an exceptional heavy rainfall period, a new compound deep- seated failure developed in a previously mined hillslope. This deep-seated failure then caused the reactivation of ancient periglacial debris slides downslope creating a serious risk to the modern housing estate located close to the toe. Electromagnetic (GEM-2), self potential, electrical resistivity tomography, seismic refraction tomography, MASW and induced polarization geophysical data were all acquired on the landslide. This combination of techniques provided information on lithology, faulting, degree of rock fracturing/weathering, thickness of displaced material, spatial distribution of areas with high water/clay content and the direction of groundwater flow. The repetition of a few ERT and SP profiles showed the applicability of geophysical monitoring in detecting changes in groundwater content and defining preferential groundwater pathways within the hillslope. Digital Photogrammetry from Helium balloon can provide a 3D landslide topographic model with 10cm-level accuracy. Topcon HiPer Pro GPS+ instrument can be used in RTK mode to monitor movement with 12mm and 15mm horizontal and vertical precision respectively.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

The development of integrated high-resolution geophysical, photogrammetric and GPS surveying applied to landslides in the South Wales coalfield

The aim of this research is to develop an integrated and cost-effective site investigation approach for slow moving landslides or potentially unstable slopes found within the South Wales Coalfield, an area of complex geology and hydrogeology. The research was based on the use and assessment of a wide range of surface geophysical techniques, supported by GPS and Digital Photogrammetry surveying, and the joint interpretation of the results which such techniques provide. The South Wales Coalfield has one of the highest concentrations of urban landslides in the UK due to its layered Carboniferous geology. Quaternary / Holocene geomorphology, coal mining history and relatively high rainfall. Mynydd yr Eglwys landslide (Ystrad, Rhondda Cynon Taff) was selected as the field study site because it can be considered representative of the active landslides found within the area. In autumn 1998, following an exceptional heavy rainfall period, a new compound deep- seated failure developed in a previously mined hillslope. This deep-seated failure then caused the reactivation of ancient periglacial debris slides downslope creating a serious risk to the modern housing estate located close to the toe. Electromagnetic (GEM-2), self potential, electrical resistivity tomography, seismic refraction tomography, MASW and induced polarization geophysical data were all acquired on the landslide. This combination of techniques provided information on lithology, faulting, degree of rock fracturing/weathering, thickness of displaced material, spatial distribution of areas with high water/clay content and the direction of groundwater flow. The repetition of a few ERT and SP profiles showed the applicability of geophysical monitoring in detecting changes in groundwater content and defining preferential groundwater pathways within the hillslope. Digital Photogrammetry from Helium balloon can provide a 3D landslide topographic model with 10cm-level accuracy. Topcon HiPer Pro GPS+ instrument can be used in RTK mode to monitor movement with 12mm and 15mm horizontal and vertical precision respectively.EThOS - Electronic Theses Online ServiceGBUnited Kingdo