CAIMAN Experiment

Non-acoustic detection systems can be used in combination with Sonar systems to determine the presence of an underwater threat, such as terrorist divers. The goal of the CAIMAN (Coastal Anti Intruders MAgnetometers Network) joint experiment (Italian Navy, NATO Undersea Research Centre and INGV Marine Geophysics) is the application of High Definition Geophysics Magnetic techniques in a port protection scenario, where conventional measurements of very low magnetic sources, like intruder swimmers, are strongly disturbed by ambient, natural and artificial, background noise and other time-variant magnetic anomalies. Two tri-axial fluxgate magnetometers were deployed on the sea bottom and connected to a shore side measurement station. A team of navy divers, wearing both COTS and EOD equipment, performed some coastal approach runs on each magnetometer alternatively. Magnetic signature data were logged and post processed using MATLAB®. Results demonstrated the effectiveness of high definition time reduction techniques using a self-referred integrated array design

A Preliminary Study on SVM based Analysis of Underwater Magnetic Signals for Port Protection

People who attend to the problem of underwater port protection usually use sonar based systems. Recently it has been shown that integrating a sonar system with an auxiliary array of magnetic sensors can improve the effectiveness of the intruder detection system. One of the major issues that arise from the integrated magnetic and acoustic system is the interpretation of the magnetic signals coming from the sensors. In this paper a machine learning approach is proposed for the detection of divers or, in general, of underwater magnetic sources. The research proposed here, by means of a windowing of the signals, uses Support Vector Machines for classification, as tool for the detection problem. Empirical results show the effectiveness of the method

A realistic inversion algorithm for magnetic anomaly data: the Mt. Amiata volcano test

The aim of this work is the formulation of a 3D model of the Mt. Amiata volcanic complex (Southern Tuscany) by means of geomagnetic data. This work is shown not only as a real test to check the validity of the inversion algorithm, but also to add information about the structure of the volcanic complex. First, we outline briefly the theory of geomagnetic data inversion and we introduce the approach adopted. Then we show the 3D model of the Amiata volcano built from the inversion, and we compare it with the available geological information. The most important consideration regards the surface distribution of the magnetization that is in good agreement with rock samples from this area. Moreover, the recovered model orientation recall the extension of the lava flows, and as a last proof of validity, the source appears to be contained inside of the topographic contour level. The credibility of the inversion procedure drives the interpretation even for the deepest part of the volcano. The geomagnetic signal appears suppressed at a depth of about 2 km, but the most striking consequence is that sub-vertical structures are found even in different positions from the conduits shown in the geologic sections. The results are thus in good agreement with the information obtained from other data, but showing features that had not been identified, stressing the informative power of the geomagnetic signal when a meaningful inversion algorithm is used

Marine geomagnetic high definition metrology; possible archaeological applications

The marine geomagnetism is often used to solve geological problems at a regional scale: structural, volcanological or mining problems, for instance (Faggioni et al., 1995). In recent time, the development of the “high definition (HD) metrology” (Faggioni et al., 2001) has made the marine geomagnetic method suitable for detecting short wavelength and low amplitude geomagnetic anomalies. This type of signal may be often related to environmental and/or archaeological sources......

The revised aeromagnetic anomaly map of Italy

This paper presents the revised aeromagnetic anomaly map of Italy and its surrounding seas, projected at reference altitude of 2500 m and geomagnetic epoch 1979.0. The magnetic data set used for the map compilation is composed of the total intensity field data acquired partly during the aeromagnetic surveys performed by the Italian National Oil Company (Agip - Direzione Esplorazione Idrocarburi) between 1971 and 1980, and during the new surveys committed by the Geophysical Corporate Services of Eni Spa - Exploration & Production Division in the years 2001-2002. In both campaigns the recorded data were very dense and uniformly distributed over the examined area. A detailed re-processing of this data set and a re-organization into a new digital database were carried out. The re-processing was done using modern adequate techniques, obtaining a remarkable exploitation of the data information content. The result is a colour shaded relief map that shows on a large scale many of the structural lineaments of the Italian area. The inclusion of a larger number of data and the subtraction of an appropriate magnetic reference field are the main reasons of an enhancement in the anomaly definition. This new map replaces the previous Agip version, and aims to become the reference aeromagnetic cartography of the Italian area. We think this work will be useful both for researchers interested in large scale tectonic studies, and for anyone interested in the investigation of smaller scale structures, such as volcanic complexes or infra-sedimentary magnetic bodies, as well as for mining research

Misure ambientali in mare aperto: sviluppo di tecnologie per l'acquisizione e l'analisi di dati meteo-mareografici misurati da una boa oceanografica in Mar Ligure

Obiettivo del presente lavoro è lo sviluppo di un metodo di analisi in grado di stimare i parametri fondamentali del moto ondoso, a partire dai dati acquisiti da tre altimetri acustici installati a bordo di una boa meteo-oceanografica operante in mare aperto. Il metodo di analisi sviluppato compie opportune operazioni di filtraggio sulle sequenze temporali delle misure effettuate dai tre altimetri, quindi, elaborando tali sequenze, fornisce le stime di alcuni parametri caratteristici del moto ondoso (tra cui l’altezza e la direzione di propagazione). I diversi tipi di filtraggio ed il metodo di stima sviluppati si basano sul calcolo di alcuni parametri statistici (tra cui media, mediana e deviazione standard) delle serie temporali di dati acquisiti, sulla conoscenza delle loro densità spettrali di potenza (calcolate mediante FFT), e sul calcolo delle funzioni di crosscorrelazione delle sequenze di dati prese a due a due. Il procedimento di stima realizzato è stato sperimentato su una notevole quantità di dati reali acquisiti in Mar Ligure tramite l’utilizzo della stazione di misura fissa su cui sono montati gli altimetri acustici, ed ha fornito risultati soddisfacenti per quanto riguarda affidabilità e precisione. Nell’ambito della valutazione delle prestazioni del sistema di acquisizione dati e del metodo di stima, i risultati ottenuti sono stati confrontati con misure provenienti da altri sensori a bordo della stazione e con stime analoghe effettuate a partire dai dati acquisiti da un’altra stazione di misura, operante anch’essa in Mar Ligure, ma dotata di strumentazione di altro tipo

Anti-intruder port protection “MAC (Magnetic ACoustic) System”: advances in the magnetic component performance

In the following, we report the advances made in the development of a magnetic component for peripheral monitoring of port environments for anti-intruder systems. The project was initiated by the Office of Research and Development, COMFORDRAG, Italian Navy, in 2004, with the aim of improving the detection performance of current acoustic-based anti-intruder systems, in the vicinity of quays or the seabed or in acoustic-shadow zones behind natural or artificial objects. In the five-year period from 2004 to 2008, the system has been subjected to detection-performance tests in experiments involving divers equipped with air tanks and rebreather kits in real port environments and, at the same time, the associated signal processing has been subjected to development, to enhance detection performance. In tests involving simulated diver attacks against a vessel moored alongside a quay in the port of La Spezia, the system has been proved particularly effective by detecting 9 divers out of 9. The processing of the magnetic signal has been enhanced by implementing an amplitude threshold, as a means of filtering the passive energy components, termed Passive Energy Cutting (PEC), that is, the elimination of components that comprise no useful information regarding diver transits. The use of PEC boosts the reliability of the system in terms of detection versus false alarm rate, as evidenced by the comparison of the ROC curves for the system with and without PEC

Clearance Operation of Teulada Site (Italy): A Novel Approach for Short Term MCM Missions in Seafloor Hard Conditions

In May 2007, following a request by Italian Navy (ITN), NURC agreed to provide the technology, developed during the port protection studies and 2006 MCM ops. in Baltic sea for Estonian Navy, to survey part of the Capo Teulada firing range (Sardinia Island, Italy), used by NATO Armed Forces. The goal of the service, fully funded by ITN, was to survey part of the firing range with acoustic, magnetic and optical instruments in order to detect and classify the ordnance laying on the seafloor. The team operated from CRV Leonardo to produce a detailed acoustic and magnetic map of the area. The positions of the targets of interest have been provided to Italian Navy for further identification and disposal. The activities have demonstrated that the NURC Autonomous Underwater Vehicles (AUVs) Remus type equipped with high frequency side scan sonar can detect and classify targets of the dimensions of unexploded ordnance laying proud on the sea floor. A multiple sonar images technique has also been used to improve the classification performances. However, in some areas, targets that were completely buried or concealed in Posidonia fields wouldn’t have been detectable with AUV sonar. To overcome this limitation, INGV supported the NURC team by using a new high definition magnetometer technique to detect and classify buried metal targets. A proton Overhauser sensor was towed from Leonardo vessel and a magnetometer reference station was set ashore in an appropriate site. A subset of interesting contacts (acoustic and magnetic) have been identified optically by means of the video camera installed on the ROV (Pluto Plus type by Gaymarine) operated from Leonardo. The positioning accuracy achieved was fully compatible with the reacquisition by ROV and then by divers or mine hunters for future disposal ops. The survey has also produced an accurate map of the Posidonia fields and a detailed bathymetry of the area. More than 300 contacts have been acquired and more than 200 were classified in less than 15 days. The success of Teulada operation has convinced ITN to ask NURC for a common development programme with the aim to validate at sea a fully integrated multi-sensor approach (sonar, magnetic and optical) in MCM short term ops. using USV/AUV platforms

Harbour water managment for port structures and sea bottom design, coast proximity navigation managment, water quality control.

Tide is a sea level up-down water motion basically depending on three different phenomena: the Earth-Moon-Sun gravitational relationship, the water surface fluid reaction to atmospheric meteorological dynamic action and the Newtonian vertical adjustment of the sea surface due to atmospheric pressure variations. The first tide component (astro-tide) is periodic and well known in all points of the Earth surface; the second one is directly related to the meteorological phenomenon and then it is foreseeable; the Newtonian component, on the contrary, is not readily predictable by a general hydrostatic law, because the factor “J” that represents the Newtonian transfer (from the atmospheric weight to the consequent sea level) is variable in each harbour area. A statistical study and the related numerical data interpretation of the measurements performed in the Ports of Genoa, La Spezia, Marina di Carrara, Livorno, Piombino, Civitavecchia and Ravenna (belonging to the Italian Newtonian Meteotide Network) show port values of Jph (from 1.4-1.6 cm/hPa to > 2 cm/hPa, on the contrary of the off-shore areas where Jph is about 1 cm/hPa). This phenomenon (hydrobarometric tide wave) produces even double values of harbour sea level fluctuations amplitude in comparison to astronomic tide sea level oscillations, and is characterized by a wavelength from 8-12 h to same days and a 10-25 days/year as mean temporal occurrence in the Northern Tyrrhenian Sea. This is the most relevant ordinary risk factor for our ports activity and structures design. The present note shows a quantitative method to define the values of Jph factor for ports and its use in the Harbour WaterSide Management (HWSM) based on the joined use of barometers, hydrometers and clocks, the preliminary results related to the use of the gravimeters as hydrobarometric predictor in La Spezia Port and two examples of use of Jph factor in the port management: refloating of a landing ship and optimisation of a dock performance as pleasure boats mooring

Harbour Sea-floor Clearance: “HD” High Definition Magnetic Survey Performance

Seafloor clearance methods based on acoustic, direct-inspection, and single-sensor magnetic approaches suffer from limitations in controlling the target-sensor distance, and may prove ineffective when the small size or the dangerous nature of targets requires high accuracy in localization. Moreover, random magnetic variations over time bring about spatial decorrelation phenomena, and hinder the application of double-sensor methods in noisy harbour environments. The new High Definition (HD) magnetic survey protocol tackles the measurement-distance problem in two ways: first, by varying the sensor depth dynamically, and secondly by backprojecting the measured field according to seafloor data and vertical incremental factors associated with the bandwidth characteristics of targets. The method to make up for timeinduced loss in spatial localization ability exploits the local behaviour of a coherence function, which correlates local observations to a set of spatially-stabilized reference stations. The consequent normalization of measured magnetic signals allows one to assign the monitored areas with a specific level of confidence in the detection results, ranging from 100% (certainty) to 0% (random events). The principles of HD detection have been fully applied in the seafloor clearance of the firing test site located south of Cape Teulada (Sardinia, Italy), where very weak signal sources such as cartridge cases, mines, and small objects down to 1 Kg mass values (lobster pots) have been successfully localized, even when covered by extensive colonies of Posidonia