scholarly journals Real magnetic stripping method in unexploded ordnance detection and remediation – a case study from Rohožník military training range in SW Slovakia

2021 ◽  
Vol 51 (3) ◽  
pp. 277-294
Author(s):  
Roman PAŠTEKA ◽  
Miroslav HAJACH ◽  
Bibiana BRIXOVÁ ◽  
Ján MIKUŠKA ◽  
John STANLEY
Keyword(s):  
Military Training ◽  
High Amplitude ◽  
Magnetic Data ◽  
Unexploded Ordnance ◽  
High Definition ◽  
Near Surface ◽  
3D Euler Deconvolution ◽  
Explosive Ordnance Disposal ◽  
Deep Source

In this contribution we present results from a case-study, which was performed in collaboration between geophysicists and explosive ordnance disposal technicians at the Rohožník military training range in SW Slovakia. The aim of this study was to locate a deep-penetrated unexploded Mk-82 aerial bomb using high-definition digital magnetometry. The location where this bomb had entered the ground was known but its final position needed to be determined so that a safe excavation and disposal could be conducted. However, the detection of this unexploded ordnance object was complicated by the presence of intense magnetic interference from a number of near surface ferrous items including non-explosive test bombs, fragmentation and other iron junk. These items contributed a localised, high amplitude of magnetic clutter masking any deeper source. Our strategy was to approach the problem in three stages. First, we used magnetic data to locate the near surface items. After the detection and before the excavation of the searched objects, two quantitative interpretation methods were used. These involved an optimised modelling of source bodies and the application of a 3D Euler deconvolution. Both methods yielded acceptable results, but the former was found to be more accurate. After the interpretation phase, many of the items were then safely excavated and removed individually. A second magnetic mapping was then performed and from this data which was now significantly less cluttered, we were able to identify but not quantify, two deep source items and to confirm that all remaining near surface items were significantly smaller in size than a Mk-82 bomb. As the remaining near surface sources were interpreted as being contained within the surface one metre of soil and being small they could be assured to be non-explosive, it was considered most practical to mechanically excavate and remove this soil and the remaining objects contained.

scholarly journals Interpretation of high resolution airborne magnetic data (HRAMD) of Ilesha and its environs, Southwest Nigeria, using Euler deconvolution method

2017 ◽  
Vol 64 (4) ◽  
pp. 227-241
Author(s):  
Oluwaseun Tolutope Olurin
Keyword(s):  
High Resolution ◽  
High Amplitude ◽  
Sharp Contrast ◽  
Magnetic Data ◽  
Magnetic Intensity ◽  
Euler Deconvolution ◽  
Southwestern Nigeria ◽  
Near Surface ◽  
Low Amplitude ◽  
Airborne Magnetic

AbstractInterpretation of high resolution aeromagnetic data of Ilesha and its environs within the basement complex of the geological setting of Southwestern Nigeria was carried out in the study. The study area is delimited by geographic latitudes 7°30′–8°00′N and longitudes 4°30′–5°00′E. This investigation was carried out using Euler deconvolution on filtered digitised total magnetic data (Sheet Number 243) to delineate geological structures within the area under consideration. The digitised airborne magnetic data acquired in 2009 were obtained from the archives of the Nigeria Geological Survey Agency (NGSA). The airborne magnetic data were filtered, processed and enhanced; the resultant data were subjected to qualitative and quantitative magnetic interpretation, geometry and depth weighting analyses across the study area using Euler deconvolution filter control file in Oasis Montag software. Total magnetic intensity distribution in the field ranged from –77.7 to 139.7 nT. Total magnetic field intensities reveal high-magnitude magnetic intensity values (high-amplitude anomaly) and magnetic low intensities (low-amplitude magnetic anomaly) in the area under consideration. The study area is characterised with high intensity correlated with lithological variation in the basement. The sharp contrast is enhanced due to the sharp contrast in magnetic intensity between the magnetic susceptibilities of the crystalline and sedimentary rocks. The reduced-to-equator (RTE) map is characterised by high frequencies, short wavelengths, small size, weak intensity, sharp low amplitude and nearly irregular shaped anomalies, which may due to near-surface sources, such as shallow geologic units and cultural features. Euler deconvolution solution indicates a generally undulating basement, with a depth ranging from −500 to 1000 m. The Euler deconvolution results show that the basement relief is generally gentle and flat, lying within the basement terrain.

A solution to unexploded ordnance detection problem from its magnetic anomaly using Kaczmarz regularization

2016 ◽  
Vol 4 (3) ◽  
pp. SH61-SH69 ◽  
Author(s):  
Maha Abdelazeem ◽  
Mohamed M. Gobashy
Keyword(s):  
Test Site ◽  
Precise Determination ◽  
Magnetic Data ◽  
Normal System ◽  
Unexploded Ordnance ◽  
Geophysical Research ◽  
Severe Problem ◽  
Near Surface ◽  
Development Plans ◽  
New Processing

Old military events pose a critical and severe problem for many countries, including the Egyptian northwestern coast. These result in extensive areas of surface/subsurface landmines that affect the economic development plans of many countries. Detection of these landmines becomes a target for many geophysical research teams. Currently, unconventional near-surface flight technologies, such as quad-hexacopters instead of regular land surveys, are used for safety reasons in the acquisition phase. We have introduced a new processing and modeling technique of magnetic data conducted over mines or near-surface geophysical targets for accurate and precise determination of location and depth. The technique is based on the application of the Kaczmarz regularization method to the ill-posed magnetic inverse problem. The advantage of this method is the optimum transformation of regularized normal equations to an equivalent augmented regularized normal system of equations. The condition number of the updated system, which determines the degree of ill posedness, is greatly lower than the original one; this improves and guarantees a good solution to the system. The method is applied to an unexploded ordnance (UXO) test site in the United Kingdom. Our results have determined that the technique is appropriate and promising in efficiently addressing a wide number of problems that are important to near-surface geophysicists, including UXO detection.

A multi-scale ground and drone-borne magnetic survey approach for the detection and investigation of archaeological structures

2021 ◽  
Author(s):  
Bruno Gavazzi ◽  
Hugo Reiller ◽  
Marc Munschy ◽  
Gilles Pierrevelcin ◽  
Florian Basoge ◽  
...  
Keyword(s):  
Vertical Component ◽  
High Amplitude ◽  
Magnetic Survey ◽  
Rhine River ◽  
Near Surface ◽  
Multi Scale ◽  
Electric Power Line ◽  
Frequency Magnetic Field ◽  
Ground Magnetic

<p><span>Ground magnetic surveys are commonly used for imaging near-surface structures in archaeological studies. Usually, surveys are conducted using vertical component gradiometers or scalar gradiometers to produce a vertical pseudo-gradient map. Scalar magnetometers can also be used, albeit less frequently, to produce maps of the total magnetic anomaly. In all these cases, the equipment is pushed or pulled by an operator or carried behind a vehicle. Here we present a third approach made available by the use of three-component fluxgate magnetometers: fast surveys over large areas using a compact lightweight drone flying automatically 1 to 2 m above the ground and high precision surveys acquired by an operator 0,2 to 1 m above the ground. A case study on the gallo-roman site of Oedenburg, </span><span>located</span><span> along the Rhine River in its upper valley, illustrates the results that can be obtained with the approach. A comparison with previously acquired pseudo-gradient surveys show</span><span>s</span><span> that the presented method allows a faster coverage, a greater resolution for the imaging of short wavelength structures (such as walls) and a better capacity of imaging large wavelength structures (such as pathways, palaeochannels or soil composition variations). As the site is crossed by a high voltage electric power line, a method to suppress the high-amplitude 50 Hz frequency magnetic field is presented.</span></p>

scholarly journals Synthetic Case Study: Discrimination of Unexploded Ordnance (UXO) and non-UXO Sources with varying Remanent Magnetization Strength using Magnetic Data

2021 ◽  
Author(s):  
Mark David Wigh ◽  
Thomas Mejer Hansen ◽  
Arne Døssing
Keyword(s):  
Magnetic Moment ◽  
Remanent Magnetization ◽  
Prior Information ◽  
Forward Model ◽  
Magnetic Data ◽  
Unexploded Ordnance ◽  
The North ◽  
Discrimination Rate ◽  
High Discrimination

Summary We investigate if it is theoretically possible to discriminate between unexploded ordnance (UXO) and non-UXO sources by modelling the magnetic dipole moment for ferrous objects of different shapes and sizes. This is carried out by approximating the volumetric demagnetization factors of rectangular prisms, representing shapes similar to a long rod or flat steel plate. By modelling different UXO as prolate spheroids the demagnetization factors can be determined which can be compared with the magnetic response of a prism. The inversion is carried out in a probabilistic framework, where the UXO forward model and the non-UXO forward model are assigned individual prior models in terms of shape, size, orientation and remanent magnetization of the object. 95 independent realizations of the prism prior model are generated to make 95 synthetic anomalies exemplifying non-UXO objects, which are inverted for using the UXO model. It is investigated if an identical magnetic moment can be produced between the two models and how well resolved the magnetic moment is in terms of the measured anomaly. The case study is carried out in two steps where we first have little prior information of expected UXO properties and another where a UXO prior is introduced with expected values of aspect ratio and size of 24 different UXO, that are often encountered in the North Sea. With no prior information of expected UXO, discrimination is at many times implausible, unless elongated rod prism objects are considered, where the magnetic moment often can not be reproduced by a spheroid. Introducing the UXO prior we achieve a much better discrimination rate when using the list of expected UXO properties. By using the UXO prior we can account for a much higher remanent magnetization allowed in the prior, and still achieve high discrimination capabilities in comparison to a case with no UXO prior.

scholarly journals Model-Based Probabilistic Inversion Using Magnetic Data: A Case Study on the Kevitsa Deposit

Geosciences ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 150
Author(s):  
Nilgün Güdük ◽  
Miguel de la Varga ◽  
Janne Kaukolinna ◽  
Florian Wellmann
Keyword(s):  
Structural Parameters ◽  
Rock Properties ◽  
Magnetic Data ◽  
Geological Model ◽  
Borehole Data ◽  
Likelihood Functions ◽  
Different Types ◽  
Geophysical Information ◽  
Different Sources

Structural geological models are widely used to represent relevant geological interfaces and property distributions in the subsurface. Considering the inherent uncertainty of these models, the non-uniqueness of geophysical inverse problems, and the growing availability of data, there is a need for methods that integrate different types of data consistently and consider the uncertainties quantitatively. Probabilistic inference provides a suitable tool for this purpose. Using a Bayesian framework, geological modeling can be considered as an integral part of the inversion and thereby naturally constrain geophysical inversion procedures. This integration prevents geologically unrealistic results and provides the opportunity to include geological and geophysical information in the inversion. This information can be from different sources and is added to the framework through likelihood functions. We applied this methodology to the structurally complex Kevitsa deposit in Finland. We started with an interpretation-based 3D geological model and defined the uncertainties in our geological model through probability density functions. Airborne magnetic data and geological interpretations of borehole data were used to define geophysical and geological likelihoods, respectively. The geophysical data were linked to the uncertain structural parameters through the rock properties. The result of the inverse problem was an ensemble of realized models. These structural models and their uncertainties are visualized using information entropy, which allows for quantitative analysis. Our results show that with our methodology, we can use well-defined likelihood functions to add meaningful information to our initial model without requiring a computationally-heavy full grid inversion, discrepancies between model and data are spotted more easily, and the complementary strength of different types of data can be integrated into one framework.

A hydrochemical and isotopic case study around a near surface radioactive waste disposal

2007 ◽  
Vol 95 (1) ◽  
Author(s):  
Zs. Szántó ◽  
É. Svingor ◽  
I. Futó ◽  
L. Palcsu ◽  
M. Molnár ◽  
...  
Keyword(s):  
Radioactive Waste ◽  
Waste Treatment ◽  
Radioactive Waste Disposal ◽  
Ion Chemistry ◽  
Continuous Transition ◽  
Near Surface ◽  
Disposal Facility ◽  
Treatment And Disposal ◽  
Site Characterisation

As part of the site characterisation program for the near surface radioactive waste treatment and disposal facility (RWTDF) at Püspökszilágy, Hungary, water quality and environmental isotope investigations have been carried out. Water samples for major ion chemistry, tritium,The chemical composition of groundwaters presented a continuous transition from waters situated on one side to waters on the top and on the other slope of the disposal suggesting the mixing of the three hydrochemical “endmembers”.Most of δ

Computer Application in Geosciences: Imaging of the Subsurface by Structural Coupled Inversion of Potential Field Data

2014 ◽  
Vol 644-650 ◽  
pp. 2670-2673
Author(s):  
Jun Wang ◽  
Xiao Hong Meng ◽  
Fang Li ◽  
Jun Jie Zhou
Keyword(s):  
Potential Field ◽  
Field Data ◽  
Gravity Data ◽  
Computer Application ◽  
Magnetic Data ◽  
Imaging Method ◽  
Inversion Algorithm ◽  
Constant Property ◽  
Near Surface ◽  
Potential Field Data

With the continuing growth in influence of near surface geophysics, the research of the subsurface structure is of great significance. Geophysical imaging is one of the efficient computer tools that can be applied. This paper utilize the inversion of potential field data to do the subsurface imaging. Here, gravity data and magnetic data are inverted together with structural coupled inversion algorithm. The subspace (model space) is divided into a set of rectangular cells by an orthogonal 2D mesh and assume a constant property (density and magnetic susceptibility) value within each cell. The inversion matrix equation is solved as an unconstrained optimization problem with conjugate gradient method (CG). This imaging method is applied to synthetic data for typical models of gravity and magnetic anomalies and is tested on field data.

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