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1

Parametric classification of ferromagnetic bottom objects based on an image analysis of magnetic anomaly map

Bodus-Olkowska Izabela, Uriasz Janusz

Annual of Navigation

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2022

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No. 28

18--28

EN

The magnetic properties of ferromagnetic objects or naturally occurring minerals such as ores can be detected and mapped using magnetic field theory studies. Magnetometry water area survey are commonly used for the purposes of detecting the oil or gas pipelines, shipwrecks and their equipment (i.e. anchors or engines), wrecks of airplanes or cars, barrels, containers, unexploded ordnances and mines and other metal debris. It is possible by detecting the magnetic anomalies they induce. The following article is presenting the stages of geoclassification of the bottom objects based on the analysis of a magnetic anomaly map. In order to determine the conditions and parameters of geoclassification, a catalog of ferrous seabed bottom features was previously developed. The catalog is dedicated to inland water areas and contains the characteristics of features potentially possible to meet in these waters along with the parameters of the magnetic anomaly they induce: e.g. spatial dimensions (length, width, area, perimeter, value ratio) together with the value of the generated anomaly itself. The further part of the article presents the map segmentation process, carried out for the purpose of detecting the areas covered by an anomaly and then dimensioning it along with the classification procedure. The whole process is summarized with the verification of the correctness of the method's operation on modeled and real anomalies.

2

Ferromagnetic Underwater Target Detection Based on a Magnetic Anomaly Map

Bodus-Olkowska Izabela, Uriasz Janusz

Geomatics and Environmental Engineering

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2020

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Vol. 14, no. 1

35--45

EN

A magnetic anomaly map of an underwater area indicates the places where the distortion of a magnetic field has occurred. Through the interpretation procedures, a hydrographer can easily indicate the places where the ferromagnetic objects are, then calculate the level of each distortion – by the value of total anomaly – and initially, based on their own knowledge, try to classify the sources of distortion. Objects that induce micro anomaly changes (>30 nT) – like industrial infrastructure, such as pipelines and cables; to unintendingly located targets with ferromagnetic characteristics: wrecks (vessels, planes, cars), military mines, UXO, lost anchors and chains. Interpretation of such a map with the attempt to identify the source of magnetic field distortion, requires a specific knowledge as well as experience. In this article the author presents the research results of dimensioning and location of potential ferromagnetic underwater objects based on a magnetic anomaly map. For further consideration an anchor of buoyage system is taken into account. Geolocation of ferromagnetic sources, contours extraction and dimensioning algorithms of ferromagnetic targets have been carried out in Matlab software. The map of magnetic anomaly enhanced with extracted information was developed in ArcGIS. The analysis was carried out for the purpose of the dissertation thesis and the results are used in further research.

PL

Mapa anomalii magnetycznych obszaru podwodnego wskazuje miejsca, w których występuje zniekształcenie ziemskiego pola magnetycznego. Za pomocą procedur interpretacyjnych hydrograf może łatwo wskazać miejsca, w których znajdują się obiekty ferromagnetyczne, a następnie obliczyć poziom każdego zniekształcenia – według wartości całkowitej anomalii – i na podstawie własnej wiedzy spróbować sklasyfikować źródła zniekształceń. Obiekty, które indukują zniekształcenie pola magnetycznego na obszarach wodnych, mogą być różne. Te wywołujące zmiany pola magnetycznego (anomalia >30 nT) to między innymi infrastruktura przemysłowa, np.: rurociągi i kable, a także nieumyślnie zlokalizowane cele o charakterystyce ferromagnetycznej: wraki (statków, samolotów, samochodów), miny wojskowe, niewybuchy, kotwice i łańcuchy statków. Interpretacja takiej mapy w celu zidentyfikowania źródła zniekształcenia pola magnetycznego wymaga specjalistycznej wiedzy i doświadczenia. Całkowita wartość anomalii magnetycznej określa wielkość poziomu ferromagnetyzmu obiektu, a wymiar powierzchni objętej anomalią umożliwia geolokalizację celu i ustalenie jego wymiarów. W artykule autorzy przedstawiają wyniki badań wymiarowania i lokalizacji potencjalnych ferromagnetycznych podwodnych obiektów na podstawie mapy anomalii magnetycznych. Przeanalizowano anomalię magnetyczną spowodowaną przez kotwicę oznakowania nawigacyjnego. Geolokalizacja źródeł ferromagnetycznych, ekstrakcja ich konturów i algorytmy wymiarowania celów ferromagnetycznych zostały przeprowadzone za pomocą oprogramowania Matlab. Porównano i podsumowano wyniki działania różnych filtrów stosowanych do przetwarzania obrazów. Mapa anomalii magnetycznej wzbogacona o wyodrębnione informacje została opracowana w ArcGIS. Analiza została przeprowadzona na potrzeby pracy doktorskiej, a jej wyniki wykorzystano w dalszych badaniach

3

Segmentacja obrazu mapy anomalii magnetycznej akwenu dla celów detekcji i lokalizacji podwodnych obiektów ferromagnetycznych

Bodus-Olkowska Izabela, Uriasz Janusz

Roczniki Geomatyki

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2019

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T. 17, z. 1(84)

27--40

PL

Mapa anomalii magnetycznych akwenu ilustruje miejsca, w których występują zakłócenia pola magnetycznego. Przez interpretację tego rodzaju mapy użytkownik może łatwo wskazać miejsca występowania zakłóceń oraz obliczyć poziom każdego z nich. Obiekt, który indukuje zniekształcenie pola magnetycznego na obszarach wodnych, może być różnego pochodzenia: od warstw geologicznych obszaru badań, przez obiekty takie jak infrastruktura przemysłowa: rurociągi i kable, do niezamierzonych obiektów o właściwościach ferromagnetycznych: wraki (wraki, wrak samolotu ), miny wojskowe, utracone kotwice i łańcuchy. Omówione powyżej aspekty interpretacji mapy anomalii magnetycznej wymagają konkretnej wiedzy i doświadczenia w tej dziedzinie. Przez całkowitą wartość anomalii magnetycznej można oszacować jak bardzo ferromagnetyczne jest ciało zakłócające. Poprzez wymiar obszaru występowania anomalii można określić położenie i wymiary obiektu. Przyjmuje się, że zastosowanie procedur segmentacji i wymiarowania obszarów jest bardzo wygodne w pracy przy interpretacji map, zarówno dla tych, którzy nie mają styczności bezpośredniej z mapami anomalii magnetycznej, ale także dla specjalistów zajmujących się tego rodzaju analizą danych. W artykule autor przedstawia koncepcję segmentacji obrazu mapy anomalii magnetycznej, detekcję miejsc występowania ciała zakłócającego pole magnetyczne oraz jego zwymiarowanie. Metody segmentacji ujęte w analizie są powszechnie stosowanymi w analizach obrazów, m.in. zdjęć lotniczych czy satelitarnych, obrazów z kamer video czy radarowych. W analizie uwzględniono dwa rodzaje źródeł zniekształceń pola magnetycznego: kotwicy od pławy i wraku. Mapa anomalii została opracowana przy użyciu oprogramowania hydrograficznego Hypack, a badania nad segmentacją mapy przeprowadzono w środowisku Matlab.

EN

The magnetic anomaly map of the water areas illustrates locations of the magnetic field distortions. By analyzing this kind of map, the user can easily indicate places of interference and calculate their levels. The objects which induce the magnetic field distortions in water areas, can be of various origins: from geological layers, through objects such as industrial infrastructure (e.g. pipelines and cables), to unintentional objects with ferromagnetic properties, like wrecks (ship wrecks, plane wrecks, car wrecks), military mines, lost anchors and chains. The aspects of magnetic anomaly map interpretation discussed above, require specific knowledge and experience. Through the total value of the magnetic anomaly, it is possible to estimate ferromagnetic properties of a disturbing body. The location and dimensions of the object can be determined by dimensions of the anomaly area. It is assumed that the use of segmentation and area dimensioning procedures is very useful in map interpretation, both for those who do not have direct contact with magnetic anomaly maps, but also for specialists involved in this kind of data analysis.The author of this paper presents the concept of segmentation of the magnetic anomaly map image, detection of locations of the interfering body and its dimensioning. Segmentation methods applied for the analysis are commonly used in image analysis, including aerial or satellite imagery, video or radar images. Two types of sources of distortion of the magnetic field in water areas: an anchor buoy and a ship wreck were considered in the analysis. The anomaly map was developed using the Hypack software, and the map segmentation in the Matlab.

4

Magnetic interpretation utilizing a new inverse algorithm for assessing the parameters of buried inclined dike‑like geological structure

Essa Khalid S., Elhussein Mahmoud

Acta Geophysica

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2019

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Vol. 67, no. 2

533--544

EN

A new algorithm has been established to interpret magnetic anomaly data due to inclined dike-like structure. This algorithm uses first horizontal derivative anomalies attained from magnetic anomaly data utilizing filters of sequential window lengths. The final estimated parameters are the half-width, the depth, angle of magnetization and amplitude factor of an inclined dike-like geological structure. A minimum variance criterion is used for selecting the most suitable variables. This algorithm has been realized to theoretical data without and with random noise. The effects of interference due to near structures have additionally been studied. The method was then applied to two field examples from Turkey and Peru, which demonstrate its effectiveness and accurateness. Thus, it is a respectable correspondence among the model parameters retrieved from this approach, drilling information, and the outcomes published in the literature. For example, in Turkey, we applied the technique to gauge the source variables and also the results were precise to w = 64.74 m and h = 87.65 m (2% and 3% errors, respectively) based on information from Aydin and Gelişli (Jeofizik 10:41–49, 1996).

5

Magnetic investigation and 2½ D gravity profile modelling across the Beattie magnetic anomaly in the southeastern Karoo Basin, South Africa

Baiyegunhi Ch., Gwavava O.

Acta Geophysica

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2017

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Vol. 65, no. 1

119--138

EN

The southeastern Karoo Basin is considered to be one of the most prospective areas for shale gas exploration in South Africa. An interesting magnetic anomaly, the Beattie magnetic anomaly (BMA), and geologic intrusions are seen on the magnetic map. To date, the source of the BMA and interconnectivity of the igneous intrusions are not well understood. In this study, we investigate the interconnectivity of the igneous intrusions and possible location of the source of the BMA using gravity and magnetic methods. The gravity model results showed that igneous intrusions are interconnected at depth, which probably pose threat by increasing the risk of fracking the Karoo for shale gas exploration. The magnetic results revealed that the BMA becomes stronger with depth. The average depths to the top of the shallow and deep magnetic sources were estimated to be approximately 0.6 and 15 km, respectively.

6

Interpretation of magnetic anomalies using a genetic algorithm

Kaftan İ.

Acta Geophysica

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2017

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Vol. 65, no. 4

627--634

EN

A genetic algorithm (GA) is an artificial intelligence method used for optimization. We applied a GA to the inversion of magnetic anomalies over a thick dike. Inversion of nonlinear geophysical problems using a GA has advantages because it does not require model gradients or welldefined initial model parameters. The evolution process consists of selection, crossover, and mutation genetic operators that look for the best fit to the observed data and a solution consisting of plausible compact sources. The efficiency of a GA on both synthetic and real magnetic anomalies of dikes by estimating model parameters, such as depth to the top of the dike (H), the half-width of the dike (B), the distance from the origin to the reference point (D), the dip of the thick dike (δ), and the susceptibility contrast (k), has been shown. For the synthetic anomaly case, it has been considered for both noise-free and noisy magnetic data. In the real case, the vertical magnetic anomaly from the Pima copper mine in Arizona, USA, and the vertical magnetic anomaly in the Bayburt–Sarıhan skarn zone in northeastern Turkey have been inverted and interpreted. We compared the estimated parameters with the results of conventional inversion methods used in previous studies. We can conclude that the GA method used in this study is a useful tool for evaluating magnetic anomalies for dike models.

7

Geologiczno-geofizyczna ocena perspektyw złożowych pierwotnych i wietrzeniowych minerałów tytanowych w rejonie ofiolitowego masywu Ślęży w Sudetach (SW Polska)

Wiszniewska J., Petecki Z.

Przegląd Geologiczny

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2016

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Vol. 64, nr 9

650--656

EN

Miocene aged heavy mineral (HMin) alluvial cones and regolith sands above ore-bearing gabbro and amphibolite/diabase rock zone were considered as a prospective metallotect in the area of Devonian ophiolite Ślęża Massif in the Sudets (SW Poland). The available research data from the Sobótka region indicated that the ultramafic gabbro intrusion has an interesting titanium ore enrichment with minerals such as ilmenite and titanomagnetite in the Strzegomiany-Kunów primary ultramafic rocks. The mean composition of ore gabbro samples taken from the surface contained eg; Fe -14.21%, TiO2 - 4.92%, V2O5 - 0,15. Conducted geophysical surveys in the vicinity of the presumed gabbroic rocks at thin Quaternary sediments cover, suggested the variable content ofa primary mineralization, which could be related to the increased content of heavy minerals fractions over the bed in the form of regolith or as a secondary deposit. Titanium minerals such as ilmenite, sphene, were enriched during the oxidation process and created secondary bed, where the concentrates of titanium oxides: rutile, leucoxene or oxidized ilmenite may have a high titanium content as high as 70-90%. Placer HMin sands are at present a major source of titanium deposits worldwide and the largest industrial value due to their large resources, simplicity and purity of exploitation and the ability to yield concentrates of HMin: ilmenite, rutile, pseudobrookite, anatase and leucoxene, sometimes in the company of valuable zircon, monazite or garnet. These deposits in the world are mainly used in metallurgical and chemical industries, eg; the production ofpaints and pigments used in the pharmacy, paper and paint industry. Similar observations have been reported from the region of Spain, Portugal, western Australia andfrom the south of India. Preliminary results of presented study indicate that the Strzegomiany-Kunów region can be considered as prospective not only because of the presence ofprimary titanium mineralization in gabbro, especially in diallage gabbro, amphibolite (diabase) and serpentinite, but also a presence of enriched titanium mineralization in regolith over gabbro and in clastic sediments on the foreland of Ślęża Massif.

8

Geological setting of the Milejowice-Janowice diabase intrusion: insights into post-Caledonian magmatism in the Holy Cross Mts., Poland

Kowalczewski Z.

Geological Quarterly

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2004

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Vol. 48, No 2

135--146

EN

Near Milejowice and Janowice in the eastern part of the Łysogóry Unit of the Holy Cross Mts., Poland, a SW-NE trending diabase has been identified intruding Lower Palaeozoic strata. This intrusion causes amagnetic anomaly, with delta T values of 48-112 gamma. It is orientated perpendicular to the regional strike. Boreholes encountered one to three component dykes 2.0 to more than 10.0 m thick inclined at 75-90 degrees Celsius, generally towards the east. They are hydrothermally altered and affected by surface weathering. The intrusion is located along two independent transverse faults, "skipping" from one to another irrespective of their strike. The intrusive zone is strongly tectonically disturbed, S-curved and disrupted by faults into segments and sub-segments. Most of the diabases are slicken-sided, and locally cataclased and mylonitized. The Milejowice-Janowice diabases probably formed in the Early Devonian, i.e. late Lochkovian-early Pragian, as post-tectonic igneous rocks belonging to within-plate, continental basalts according to Krzemiński (2004). Their origin may be referred tomagmatism triggered by the extension of the Baltica passivemargin during the final Late Silurian-Early Devonian phase of its collision with eastern Avalonia. A complex and at least two-phase development ofmagmatism in the Holy Cross Mts. is envisaged.