Yogadhish Das’s research while affiliated with Medicine Hat College and other places

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Publications (62)


The Detection of Buried Explosive Objects
  • Article
  • Full-text available

August 2014

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403 Reads

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15 Citations

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Yogadhish Das

There is a need for methods which can be used to detect buried objects, most prominently in the fields of archaeology, forensics, geophysics, submarine and mine detection. This article reviews methods of detecting and identifying small buried explosive-filled objects, with emphasis on mines and artillery shells. The approaches, which span a number of intertwined disciplines, are in many cases directly adaptable to these other applications of remote sensing.RÉSUMÉDes méthodes de détection des objets enfouis sont nécessaires dans des domaines tels que l'archéologie, la prospection, la détection sous-marine et celle des mines. Le présent article fait la revue des méthodes de détection et d'identification des petits objets enfouis et bourrés d'explosifs— nommément les mines et les obus d'artillerie. Ces méthodes, qui touchent à un certain nombre de disciplines souvent reliées entre elles, sont, dans plusieurs cas, directement applicables à l'un ou l'autre de ces domaines.

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Influence of dispersive soil electromagnetic properties on hand-held time domain electromagnetic sensors

May 2013

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36 Reads

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4 Citations

Geophysical Prospecting

Although metal detectors remain the workhorses of humanitarian demining, it is well established that the performance of both continuous wave (frequency domain) and pulsed induction (time domain) detectors can be severely compromised by so‐called ‘soil‐effects’. Generally, problem soils reduce the signal‐to‐noise ratio and increase the false‐detection rate. In certain locations, the soil‐effect is so severe as to render the detector practically inoperable. The current study is part of an ongoing international effort to establish and quantify the influence of soil electromagnetic properties on the operation of metal detectors and related sensor technologies. In particular, we examine the relative influence of soil electrical conductivity, magnetic susceptibility and associated frequency dependence on the time domain electromagnetic (TDEM) response of pulsed induction metal detectors and related small‐scale TDEM sensors.


Modeling the Response of Electromagnetic Induction Sensors to Inhomogeneous Magnetic Soils With Arbitrary Relief

September 2009

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80 Reads

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28 Citations

IEEE Transactions on Geoscience and Remote Sensing

A general model to compute the response of an electromagnetic induction sensor to a magnetic soil, in both time and frequency domains, is developed. The model requires modest computational resources and can be applied to arbitrary soil inhomogeneities and relief, and to arbitrary sensor coil shapes, orientations, and positions. Central to the model is the concept of a head sensitivity map, which can be used to characterize the sensor head as a function of the shape, size, and position of the sensor coils. Two further concepts related to the head sensitivity are presented, which are the zero equisensitivity surface and the volume of influence. We demonstrate that these concepts aid the understanding of the detector behavior. The general model is based on the Born approximation, which is valid if the soil magnetic susceptibility is sufficiently small. A simpler model, which is only valid for homogeneous half-space soils but does not require the Born approximation, is also developed. The responses predicted by both models are shown to be in good agreement with each other and also with available analytic solutions. Comparing the two models also enabled an expression for the error incurred when using the Born approximation to be established. We shown that, for most soils of relevance to mine clearance, the corresponding error is negligible.


Study of the influence of the plastic casing on the electromagnetic induction response of a buried landmine

May 2008

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19 Reads

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2 Citations

Proceedings of SPIE - The International Society for Optical Engineering

Most studies of the electromagnetic induction (EMI) response of a low-metal landmine buried in soil ignore any influence that the plastic casing may have on such response. In most cases such treatment is adequate since only the metal components of a landmine are expected to contribute to such a response. However, when the landmine is buried in a soil that has significant conductivity and/or magnetic susceptibility, the electromagnetic void created by the casing may have an influence on the EMI response of the landmine. That possibility is investigated using a simple analytical model and an experiment. A sphere is chosen as a simple prototype for the small metal parts in low-metal landmines, and a concentric spherical shell, made of foamed polystyrene, encasing the sphere is used to represent the plastic landmine body. The time-domain EMI response is measured using a purpose-designed system based on a modified Schiebel AN19/2 metal detector. Responses of the metallic sphere, the polystyrene shell and the metal-polystyrene composite target are measured with the targets buried in magnetic soil half-spaces. The particular soil type for which data are presented in this paper is Cambodian "laterite" with dispersive magnetic susceptibility, which serves as a good model for soils that are known to affect the performance of metal detectors. The metal sphere used has a diameter of 0.0254 m and is made of 6061-T6 aluminum, and the polystyrene shell has an outer diameter of 0.15 m. For the specific soil and targets used, theoretical results show that a small effect on the time-domain response is expected from the presence of the polystyrene casing. Experimental results confirm this for the case of the buried polystyrene shell. However the small difference in the example of the composite target is masked by experimental errors.


Effects of magnetic soil on metal detectors - Preliminary experimental results

May 2007

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25 Reads

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5 Citations

Proceedings of SPIE - The International Society for Optical Engineering

In a series of previous papers, analytical results dealing with the effects of soil electromagnetic properties on the performance of induction metal detectors were reported. In this paper experimental data are provided to verify some previously reported results. The time-domain response of a magnetic soil half-space and a small metallic sphere situated in air as well as buried in the soil were measured using a purpose-designed system based on a modified Schiebel AN19/2 metal detector. As in the previous work, the sphere is chosen as a simple prototype for the small metal parts in low-metal landmines. The soil used was Cambodian "laterite" with dispersive magnetic susceptibility, which serves as a good model for soils that are known to adversely affect the performance of metal detectors. The metal object used was a sphere of diameter 0.0254 m made of 6061-T6 aluminum. Experimental data are in good agreement with theoretical predictions. Data also show that for the weakly magnetic soil used in the experiments, the total response of the buried sphere is the sum of the response of the soil and that of the sphere placed in air. This finding should simplify the prediction or measurement of response of buried targets as one can separately measure/compute the response of an object in air and that of the host media and simply add the two. This simplification may not be possible for soils that are more strongly magnetic.


Effects of soil electromagnetic properties on metal detectors

July 2006

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494 Reads

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82 Citations

IEEE Transactions on Geoscience and Remote Sensing

This paper presents an analysis, based on existing work in geophysics and nondestructive testing, of the effects of soil electromagnetic properties on the functioning of metal detectors widely used to detect buried landmines. The host soil is modeled as a half-space having real and frequency-independent electrical conductivity but frequency-dependent complex magnetic susceptibility. The analysis technique has been applied to three examples of soil of practical importance, namely, nonconducting soil with frequency-independent susceptibility, nonconducting soil with frequency-dependent susceptibility, and nonmagnetic soil with constant conductivity. Simplifications are made to clearly explain a number of previous field and experimental observations, for example, the greater influence of magnetic properties than of electrical conductivity on the performance of metal detectors. Results also show that soil magnetic properties affect continuous wave and pulsed-induction detectors differently. The effect that electrical conductivity and magnetic susceptibility of the host soil have on the signal produced by a target is investigated by computing the response of a buried small metallic sphere. Computations show that in some cases, which could represent practical landmine detection scenarios, the signal from the soil can dominate that due to the target, making it hard to detect the target. Further, it is shown that magnetic soil can alter a target's spectral response, which implies that, contrary to present practice, object identification techniques should take into account the electromagnetic parameters of the host medium.


Physical model of soil and its implications for landmine detection interference - art. no. 62170N

June 2006

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100 Reads

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1 Citation

Proceedings of SPIE - The International Society for Optical Engineering

T. J. Katsube

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Y. Das

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[...]

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N. Scromeda

Many soil physical and chemical properties interfere with landmine detection. Prior knowledge of these properties would improve detection technology selection and increase demining safety and efficiency. Developments in rapid mapping of these properties over wide areas is essential to meet military and economic constraints. Fusion of multiple detection technologies is also essential to overcome detection signal interferences. For these purposes, rapid mapping by use of remote sensing is being tested, starting with electrical conductivity mapping by radar remote sensing. Laboratory induced-polarization (IP) is also being tested to develop techniques to discriminate between electromagnetic signals from metallic particles in landmines and in soil, for regions with detection interference. Key physical models of soil are being developed for fusion of various landmine detection systems and to explain remote sensing responses to soil. Radar satellite tests carried out over the Canadian Forces Base Suffield (CFBS; Alberta, Canada) in 2004 and 2005 indicated 10 areas for possible high clay content and electrical conductivity. Eight of these were validated by soil maps and Landsat clay images. Two had high organic content with physical characteristics not known at present. Studies on soil with fine-grained iron-oxide powder and on iron with varied degrees of corrosion show that spectral-IP is sensitive to iron or iron-oxides regardless of their state. Soil has layered structure consisting of various grain-size combinations, but its physical characteristics are significantly influenced by whether its clay content is above or below a critical clay content (15 to 25 %). Results of these tests are discussed in this paper with explanations using the soil physical model.


Time-domain response of a metal detector to a target buried in soil with frequency-dependent magnetic susceptibility

June 2006

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103 Reads

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7 Citations

Proceedings of SPIE - The International Society for Optical Engineering

The work reported in this paper is a part of on-going studies to clarify how and to what extent soil electromagnetic properties affect the performance of induction metal detectors widely used in humanitarian demining. This paper studies the specific case of the time-domain response of a small metallic sphere buried in a non-conducting soil half-space with frequency-dependent complex magnetic susceptibility. The sphere is chosen as a simple prototype for the small metal parts in low-metal landmines, while soil with dispersive magnetic susceptibility is a good model for some soils that are known to adversely affect the performance of metal detectors. The included analysis and computations extend previous work which has been done mostly in the frequency domain. Approximate theoretical expressions for weakly magnetic soils are found to fit the experimental data very well, which allowed the estimation of soil model parameters, albeit in an ad hoc manner. Soil signal is found to exceed target signal (due to an aluminum sphere of radius 0.0127 m) in many cases, even for the weakly magnetic Cambodian laterite used in the experiments. How deep a buried target is detected depends on many other factors in addition to the relative strength of soil and target signals. A general statement cannot thus be made regarding detectability of a target in soil based on the presented results. However, computational results complemented with experimental data extend the understanding of the effect that soil has on metal detectors.


Effect of the soil on the metal detector signature of a buried mine - art. no. 62170Q

May 2006

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41 Reads

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4 Citations

Proceedings of SPIE - The International Society for Optical Engineering

This paper analyzes the effect of the soil on the response of a metal detector (MD). The total response is first decomposed in a direct coupling between the transmitter and the receiver, the mine contribution and the soil contribution. The mine contribution is further related to its free space signature by introducting a number of transfer functions (TFs). Those TFs characterize the effect of the soil on the field propagation, from the transmit coil to the mine and back to the receiver, and on the mine signature. The expressions derived are quite general. However the TFs and other quantities of interest can only be computed if the scattering problem has been solved. For this it is usually necessary to resort to numerical techniques. Such techniques are computationally expensive, especially to analyze the various effects of the soil as they require to compute the solution for a large set of parameters. Therefore, we propose to model a buried mine by a multilayered sphere. From outside to inside, the layers represent the air, the soil, the mine explosive and the mine metallic content. Further, the analytic solution for such a multilayered sphere is used to compute the mine and soil responses, the mine free space signature and the various TFs as a function of the parameters of interest such as the soil electromagnetic (EM) properties or the mine depth. Finally, the validity domain of a number of practical approximations is discussed.


The Canadian Forces ILDS - A militarily fielded, multi-sensor, vehicle-mounted, teleoperated landmine detection system - art. no. 62172G

May 2006

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643 Reads

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3 Citations

Proceedings of SPIE - The International Society for Optical Engineering

The Improved Landmine Detection System (ILDS) is intended to meet Canadian military mine clearance requirements in rear area combat situations and peacekeeping on roads and tracks. The system consists of two teleoperated vehicles and a command vehicle. The teleoperated protection vehicle precedes, clearing antipersonnel mines and magnetic and tilt rod-fuzed antitank mines. It consists of an armoured personnel carrier with a forward looking infrared imager, a finger plow or roller and a magnetic signature duplicator. The teleoperated detection vehicle follows to detect antitank mines. The purpose-built vehicle carries forward looking infrared and visible imagers, a 3 m wide, down-looking sensitive electromagnetic induction detector array and a 3 m wide down-looking ground probing radar, which scan the ground in front of the vehicle. Sensor information is combined using navigation sensors and custom navigation, registration, spatial correspondence and data fusion algorithms. Suspicious targets are then confirmed by a thermal neutron activation detector. The prototype, designed and built by Defence R&D Canada, was completed in October 1997. General Dynamics Canada delivered four production units, based on the prototype concept and technologies, to the Canadian Forces (CF) in 2002. ILDS was deployed in Afghanistan in 2003, making the system the first militarily fielded, teleoperated, multi-sensor vehicle-mounted mine detector and the first with a fielded confirmation sensor. Performance of the prototype in Canadian and independent US trials is summarized and recent results from the production version of the confirmation sensor are discussed. CF operations with ILDS in Afghanistan are described.


Citations (42)


... Low rainfall results in less carbonic acid dissolution in soil which is another factor that may result in high pH (Singh et al. 2014a). The results of EC indicate that soils are non-saline and the concentration of soluble salts is less, similar to the results obtained in other studies (Katsube et al. 2003). A few samples had high EC attributed to soil pollution and leachate (Kumar et al. 2023a). ...

Reference:

Soil quality under different tree species in an urban university campus: a multidimensional study
Prediction and validation of soil electromagnetic characteristics for application in landmine detection

... One of the major security threats to the communities of civilians and security agencies in our current societies is BEDs (Besaw, 2016), which are sometimes very difficult to detect during and after conflicts. Due to the electromagnetic and magnetic properties of most of the BEDs, some studies identify some geophysical methods such as magnetic, very low frequency (VLF) and ground penetrating radar (GPR) as excellent phenomenology for detecting BEDs (McFee & Das, 1980;Besaw, 2016). Recently, a report showed that more than seventy (70) countries have about 80 to 110 million BEDs as explosive weapons, which damage over 70 people per day (Brito-da-Costa, et al., 2021). ...

The Detection of Buried Explosive Objects

... 22 Електромагнітна індукція ("еlectromagnetic induction" (EMI))важлива технологія у сфері гуманітарного розмінування, оскільки вона дозволяє виявляти металеві об'єкти, такі як міни та нерозірвані боєприпаси, які залишилися в ґрунті після збройних конфліктів, а її використання забезпечує високий рівень точності, дозволяючи визначати підземні об'єкти без необхідності фізичного втручання у ґрунт. Розглянуто вплив характеристик ґрунту на електромагнітну індукцію 27,28 , використання для зниження ризиків при розмінуванні, розроблено мобільний EMI-детектор для роботи на гусеничній платформі 29 . ...

Soil Information Requirements for Humanitarian Demining: The Case for a Soil Properties Database

Proceedings of SPIE - The International Society for Optical Engineering

... A single unit was constructed to be part of the original DRDC-designed POC vehicle-mounted mine detector system, then called ILDP. 2 The requirements imposed by the application had a significant impact on the design. Beyond the obvious constraints of size, mass and power consumption, the two most significant requirements were interrogation time and field of view (FOV). ...

Multisensor vehicle-mounted teleoperated mine detector with data fusion
  • Citing Article
  • January 1998

Proceedings of SPIE - The International Society for Optical Engineering

... The range of ECa at the study site is small and would imply a uniform soil type based on traditional soil classification. For example, clay-rich soil has an electrical conductivity of 2.5-10 mS/m, and topsoil has an electrical conductivity of 5-25 mS/m (Katsube et al., 2004). However, such conjecture makes it difficult to explain the trends in ECa. ...

Soil moisture and electrical conductivity prediction and their implication for landmine detection technologies

Proceedings of SPIE - The International Society for Optical Engineering

... This response is believed to be due to the magnetic response of the soil which is not completely removed by the down-track filter since the magnetic properties of the soil vary with position. This response is very similar to that due to a magnetic material with a uniform logarithmic distribution of relaxation times789. ...

Effects of magnetic soil on metal detectors - Preliminary experimental results
  • Citing Article
  • May 2007

Proceedings of SPIE - The International Society for Optical Engineering

... The team of DRDC started in 1997 a project testing the combination of various detection technologies called Improved Landmine Detector Project ILDP. Since a single detection technique will not be able to detect all types of landmines in all conditions, the fusion of various techniques can be more effective [29], [30]. The authors tested a small teleoperated vehicle carrying four types of detectors: Forward Looking Infrared imager, down looking electromagnetic induction detector, down-looking Ground Penetrating Radar (GPR) and finally a thermal neutron activation detector used as confirmatory detector of suspected targets. ...

The Canadian Forces ILDS - A militarily fielded, multi-sensor, vehicle-mounted, teleoperated landmine detection system - art. no. 62172G

Proceedings of SPIE - The International Society for Optical Engineering

... Such systems allow the most usual missions of robotic systems which require both locomotion and manipulation abilities. This way, they offer multiple applications in different industrial and productive areas as mining and construction or for people assistance [19,20]. The proposed tele-operation system integrates switching of control signals generated by the master to control the whole mobile manipulator system, or to control the robotic arm only. ...

Articulated robotic scanner for mine detection: a novel approach to vehicle-mounted systems
  • Citing Article
  • August 1999

Proceedings of SPIE - The International Society for Optical Engineering

... The measurements from a nonconductive nonviscous but susceptible ferrite bead sample (Figure 9b) show a zero-quadrature response and an in-phase measurement that does not vary from the low-frequency value. Samples that show viscous magnetization (Figure 9c) are expected to have an in-phase magnetization that decreases as frequency increases, with a nearly constant out-of-phase component (Das, 2005;Bailey and West, 2007). ...

Electromagnetic induction response of a target buried in conductive and magnetic soil
  • Citing Article
  • June 2005

Proceedings of SPIE - The International Society for Optical Engineering

... Based on these and previous studies [10], [50], some of which focused on tropical countries [51], [52], we shall assume a maximum magnetic susceptibility (12) of the order of 0.01-0.1, acknowledging that even higher values are possible in areas of extreme ferromagnetic mineral concentration, e.g., in the form of magnetic pebbles or rocks [48]. Magnetic viscosity effects will be neglected for the time being. ...

Electromagnetic characteristics of Cambodian soil: Implication for landmine detection in soil containing ferromagnetic minerals
  • Citing Article
  • August 2002

Proceedings of SPIE - The International Society for Optical Engineering