The Special Case of Sea Mines

In this chapter, work carried out at the Royal Military Academy regarding sea mines and mine countermeasures is summarized. Three sensors used for the detection and identification of sea mines are studied here: sonar, gradiometer and infrared camera. These sensors can be applied to detect different types of sea mines. Some signal and image processing techniques developed to extract relevant information for the detection of underwater objects are presented in this chapter. These techniques are validated using data collected in the frame of different European and NATO projects

Magnetic sensors and gradiometers for detection of objects

Disertační práce popisuje vývoj nových detekčních zařízení s anizotropními magnetorezistoryThis thesis describes development of innovative sensor systems based on anisotropi

Atomic magnetometers and their application in industry

In modern detection techniques, high-precision magnetic field detection plays a crucial role. Atomic magnetometers stand out among other devices due to their high sensitivity, large detection range, low power consumption, high sampling rate, continuous gradient measurements, and good confidentiality. Atomic magnetometers have become a hot topic in the field of magnetometry due to their ability to measure not only the total strength of the Earth’s magnetic field, but also its gradients, both slow- and high-velocity transient magnetic fields, both strong and weak. In recent years, researchers have shifted their focus from improving the performance of atomic magnetometers to utilizing their exceptional capabilities for practical applications. The objective of this study is to explore the measurement principle and detection method of atomic magnetometers, and it also examines the technological means and research progress of atomic magnetometers in various industrial fields, including magnetic imaging, material examination, underwater magnetic target detection, and magnetic communication. Additionally, this study discusses the potential applications and future development trends of atomic magnetometers

Remote Detection Optical Magnetometry

Sensitive magnetometers have been applied in a wide range of research fields, including geophysical exploration, bio-magnetic field detection, ultralow-field nuclear magnetic resonance, etc. Commonly, magnetometers are directly placed at the position where the magnetic field is to be measured. However, in some situations, for example in near space or harsh environments, near nuclear reactors or particle accelerators, it is hard to place a magnetometer directly there. If the magnetic field can be detected remotely, i.e., via stand-off detection, this problem can be solved. As optical magnetometers are based on optical readout, they are naturally promising for stand-off detection. We review various approaches to optical stand-off magnetometry proposed and developed over the years, culminating in recent results on measuring magnetic fields in the mesosphere using laser guide stars, magnetometry with mirrorless-lasing readout, and proposals for satellite-assisted interrogation of atmospheric sodium.Comment: 68 pages, 19 figure

Gravity Gradiometry and Map Matching: An Aid to Aircraft Inertial Navigation Systems

Inertial navigation systems (INS) offer passive, all-weather, and undeniable navigation information, which military customers often view as especially appealing strengths. Unfortunately, Airmen and engineers still struggle with INS’s drifting position errors, and navigation aids generally detract from INS’s strengths. At this year’s Air, Space, and Cyberspace in the 21st Century Conference, the Chief of Staff of the Air Force identified the Global Positioning System (GPS) as a widely-known and exploitable vulnerability, saying that it’s critical the Joint force reduce GPS dependence. Recent advances provide an opportunity for gravity gradient instruments (GGI), which measure spatial derivatives of the gravity vector, to aid an INS and preserve its strengths. This thesis shows that a GGI and map matching enhanced (GAME) INS improves navigation accuracy, presents the conditions that make GAME feasible for aircraft, and identifies opportunities for improvement. The methodology includes computer models and algorithms, where a GGI and map matching aid an INS through a Kalman filter. Simulations cover different terrains, altitudes, velocities, flight durations, INS drifts, update rates, components of the gravity gradient tensor, GGI and map noise levels, map resolutions, and levels of interpolation. Although GAME with today’s technology only appears worthwhile for long range and long endurance flights, the technologies expected in 10 years promise a broad spectrum of scenarios where GAME potentially provides great returns on investments and dominates the market for secure and covert navigation

Perimeter Security and Intruder Detection Using Gravity Gradiometry: A Feasibility Study

Changes in the mass distribution around some point on the Earth’s surface induce corresponding changes to the magnitude and direction of the gravity vector at that location. The nine-tensor derivative of the gravity vector, or gravity gradient, is sensitive to very small changes in the gravity vector. With some assumptions, continuous measurement of the gravity gradient using a gravity gradiometer (GGI) is used to determine the location of a mass change in the local area near the instrument. This investigation sought to determine the effectiveness, operating characteristics, and limitations of a physical perimeter security system that uses an array of GGIs to detect and locate a human intruder. Results are obtained via computer simulations utilizing the closed form solution for calculating a gravity gradient given an object’s size and mass, as well as industry-predicted future GGI performance characteristics

OBJECT PERCEPTION IN UNDERWATER ENVIRONMENTS: A SURVEY ON SENSORS AND SENSING METHODOLOGIES

Underwater robots play a critical role in the marine industry. Object perception is the foundation for the automatic operations of submerged vehicles in dynamic aquatic environments. However, underwater perception encounters multiple environmental challenges, including rapid light attenuation, light refraction, or backscattering effect. These problems reduce the sensing devices’ signal-to-noise ratio (SNR), making underwater perception a complicated research topic. This paper describes the state-of-the-art sensing technologies and object perception techniques for underwater robots in different environmental conditions. Due to the current sensing modalities’ various constraints and characteristics, we divide the perception ranges into close-range, medium-range, and long-range. We survey and describe recent advances for each perception range and suggest some potential future research directions worthy of investigating in this field

An electromagnetic imaging system for metallic object detection and classification

PhD ThesisElectromagnetic imaging currently plays a vital role in various disciplines, from engineering to medical applications and is based upon the characteristics of electromagnetic fields and their interaction with the properties of materials. The detection and characterisation of metallic objects which pose a threat to safety is of great interest in relation to public and homeland security worldwide. Inspections are conducted under the prerequisite that is divested of all metallic objects. These inspection conditions are problematic in terms of the disruption of the movement of people and produce a soft target for terrorist attack. Thus, there is a need for a new generation of detection systems and information technologies which can provide an enhanced characterisation and discrimination capabilities. This thesis proposes an automatic metallic object detection and classification system. Two related topics have been addressed: to design and implement a new metallic object detection system; and to develop an appropriate signal processing algorithm to classify the targeted signatures. The new detection system uses an array of sensors in conjunction with pulsed excitation. The contributions of this research can be summarised as follows: (1) investigating the possibility of using magneto-resistance sensors for metallic object detection; (2) evaluating the proposed system by generating a database consisting of 12 real handguns with more than 20 objects used in daily life; (3) extracted features from the system outcomes using four feature categories referring to the objects’ shape, material composition, time-frequency signal analysis and transient pulse response; and (4) applying two classification methods to classify the objects into threats and non-threats, giving a successful classification rate of more than 92% using the feature combination and classification framework of the new system. The study concludes that novel magnetic field imaging system and their signal outputs can be used to detect, identify and classify metallic objects. In comparison with conventional induction-based walk-through metal detectors, the magneto-resistance sensor array-based system shows great potential for object identification and discrimination. This novel system design and signal processing achievement may be able to produce significant improvements in automatic threat object detection and classification applications.Iraqi Cultural Attaché, Londo

Design modifications of a UAV wing for optimal integration of a magnetic anomaly detection sensor

Supervisors: Prof. Afzal Suleman. Examination Committee: Chairperson: Prof. Filipe Szolnoky Ramos Pinto Cunha; Supervisor: Prof. Afzal Suleman; Member of the Committee: Major Dr. Luís Filipe da Silva FélixThis work describes the conceptual design of a Unmanned Air Vehicle (UAV) wing with a Magnetic Anomaly Detection (MAD) sensor for submarine detection operations. Nowadays, underwater marine vessels are able to evade conventional detection methods such as sonar. Therefore, it is necessary to integrate MAD sensors in modern Anti-Submarine Warfare theatres. UAVs typically generate a magnetic field due to the electrical systems on board, causing interference noise on the MAD sensor data analysis and compromising its performance. To address these issues, a characterization of the aircraft’s magnetic signature was conducted, and it was found that the wing tip and a tail stinger boom are the best options to minimize the magnetic noise. A structural and aerodynamic analysis of the aircraft showed the wing tip configuration was the best option since the amount of mass required to counter the moment of a tail stinger boom would require major modifications on the UAV. Also, the aircraft magnetic signature is minimum at the wing tip, with an intensity of -2.9nT. An aerodynamic characterization of the aircraft was carried to evaluate the effect of the MAD pods on the wingtips. A parametric optimization of the wing was conducted. Given the dimensional constraints on the wing structure and a target magnetic noise of 2nT at the wing tip, the optimizer objective function was to minimize the total fuel consumption. The optimum solution allowed a decrease of 30% on the magnetic noise and a fuel consumption of 8.71 kg of fuel for an 8-hour search operation.Este trabalho descreve o processo de projeto conceptual de uma asa de um Veículo Aéreo Não-Tripulado (VANT) com um sensor de anomalias magnéticas (AM) para ser usado em deteção de submarinos. Atualmente, estes veículos estão dotados com capacidades que diminuem as hipóteses de detecão por métodos convencionais, como o sonar. Assim, torna-se necessário integrar sensores de AM em cenários atuais de Guerra Anti-Submarina. Os sistemas aviónicos destas aeronaves geram um campo magnético que causa interferência no sensor de AM, causando ruído nos dados da análise e comprometendo a sua eficiência. Para evitar este problema, realizou-se uma caracterização da assinatura magnética da aeronave, concluindo que as pontas das asas e uma configuração de arpão na cauda seriam as melhores soluções para colocar o sensor, a fim de minimizar a interferência magnética. Estudos estruturais e aerodinâmicos revelaram que a primeira seria a melhor opção, pois a massa necessária para anular o momento gerado na segunda requeria alterações substanciais na estrutura da aeronave. A ponta da asa era também o local com menor nível de assinatura magnética. Realizou-se uma otimização paramétrica da asa da aeronave, considerando os efeitos aerodinâmicos dos invólucros do sensor. Atendendo às restrições no dimensionamento da estrutura da asa e a um valor de interferência magnética, o otimizador teria como objetivo minimizar o consumo total de combustível. A solução ótima permitiu reduzir em 30% o valor da assinatura magnética na ponta da asa e obter uma configuração que, numa missão de patrulha de 8 horas, consome 8.71 kg de combustível.N/

Theoretical Developments in Electromagnetic Induction Geophysics with Selected Applications in the Near Surface

Near-surface applied electromagnetic geophysics is experiencing an explosive period of growth with many innovative techniques and applications presently emergent and others certain to be forthcoming. An attempt is made here to bring together and describe some of the most notable advances. This is a difficult task since papers describing electromagnetic induction methods are widely dispersed throughout the scientific literature. The traditional topics discussed herein include modeling, inversion, heterogeneity, anisotropy, target recognition, logging, and airborne electromagnetics (EM). Several new or emerging techniques are introduced including landmine detection, biogeophysics, interferometry, shallow-water electromagnetics, radiomagnetotellurics, and airborne unexploded ordnance (UXO) discrimination. Representative case histories that illustrate the range of exciting new geoscience that has been enabled by the developing techniques are presented from important application areas such as hydrogeology, contamination, UXO and landmines, soils and agriculture, archeology, and hazards and climat