Magnetic properties of soils have adverse effects on metal detectors, particularly hampering operations during clearance
of landmines and unexploded ordnance. Although there is well established research in soil magnetism and modeling
electromagnetic induction systems these have tended to exist in disparate disciplines. Hence, a workshop was organized
to bring together researchers, academics, stakeholders and manufacturers to discuss key priorities for research and
technology in a unique multidisciplinary environment. Key knowledge gaps identified include limited information on the
spatial heterogeneity of soil magnetic properties in 2D and 3D, whether current models describing soil responses are
appropriate for all soils and the need for compensation mechanisms in detectors to be improved. Several priorities were
identified that would maximize future developments for multidisciplinary research in soil magnetism and detector
technology. These include acquiring well constrained empirical data on soil electromagnetic properties and detector
response over the frequency range of detectors; development of predictive models of soil magnetic properties;
investigating variability of soil magnetic properties in two and three dimensions across a range of scales. Improved
communication between disciplines is key to effective targeting and realization of research priorities. Possible platforms
include a multidisciplinary pilot study at an appropriate site and the development of an online repository to assist
dissemination of results and information.
The ability to interrogate objects buried in soil and ascertain their chemical composition in-situ
would be an important capability enhancement for both military and humanitarian demining. Laser
Induced Breakdown Spectroscopy (LIBS) is a simple spark spectrochemical technique using a
pulsed laser. Recent developments in broadband and man-portable LIBS provide the capability for
the real-time detection at very high sensitivity of all elements in any target material because all
chemical elements emit in the 200-940 nm spectral region. This technological advance offers a
unique potential for the development of a rugged and reliable man-portable or robot-deployable
chemical sensor that would be capable of both in-situ point probing and chemical sensing for
landmine detection.
Broadband LIBS data was acquired under laboratory conditions for more than a dozen different
types of anti-personnel and anti-tank landmine casings from four countries plus a set of antitank
landmine simulants. Subsequently, a statistical classification technique (partial least squares
discriminant analysis, PLS-DA) was used to discriminate landmine casings from the simulants and
to assign "unknown" spectra to a mine type based upon a library classification approach. Overall, a
correct classification success of 99.0% was achieved, with a misclassification rate of only 1.8%.
This performance illustrates the potential that LIBS has to be developed into a field-deployable
device that could be utilized as a confirmatory sensor in landmine detection. The operational
concept envisioned is a small LIBS system that is either man-portable or robot-deployed in which a
micro-laser is contained in the handle of a deminer's probe, with laser light delivered and collected
through an optical fiber in the tapered tip of the probe. In such a configuration, chemical analysis
could be readily accomplished by LIBS after touching the buried object that one is interested in
identifying and using real-time statistical signal processing techniques to accomplish "mine/no-mine"
discrimination and even object identification if a material library could be constructed prior
to analysis.
One of the Department of Defense's most pressing environmental problems is the efficient detection and identification
of unexploded ordnance (UXO). In regions of highly magnetic soils, magnetic and electromagnetic sensors often detect
anomalies that are of geologic origin, adding significantly to remediation costs. In order to develop predictive models for
magnetic susceptibility, it is crucial to understand modes of formation and the spatial distribution of different iron
oxides. Most rock types contain iron and their magnetic susceptibility is determined by the amount and form of iron
oxides present. When rocks weather, the amount and form of the oxides change, producing concomitant changes in
magnetic susceptibility. The type of iron oxide found in the weathered rock or regolith is a function of the duration and
intensity of weathering, as well as the original content of iron in the parent material. The rate of weathering is controlled
by rainfall and temperature; thus knowing the climate zone, the amount of iron in the lithology and the age of the surface
will help predict the amount and forms of iron oxide. We have compiled analyses of the types, amounts, and magnetic
properties of iron oxides from soils over a wide climate range, from semi arid grasslands, to temperate regions, and
tropical forests. We find there is a predictable range of iron oxide type and magnetic susceptibility according to the
climate zone, the age of the soil and the amount of iron in the unweathered regolith.
KEYWORDS: Land mines, Soil science, Sensors, Thermography, Mining, General packet radio service, Vegetation, Temperature metrology, Magnetism, Infrared cameras
Modeling studies and experimental work have demonstrated that the dynamic behavior of soil physical properties has a significant effect on most sensors for the detection of buried land mines. An outdoor test site has been constructed allowing full control over soil water content and continuous monitoring of important soil properties and environmental conditions. Time domain reflectometry sensors and thermistors measure soil water1 content and temperature, respectively, at different depths above and below the land mines as well as in homogeneous soil away from the land mines. During the two-year operation of the test-site, the soils have evolved to reflect real field soil conditions. This paper compares visual observations as well as ground-penetrating radar and thermal infrared measurements at this site taken immediately after construction in early 2004 with measurements from early 2006. The visual observations reveal that the 2006 soil surfaces exhibit a much higher spatial variability due to the development of mini-reliefs, "loose" and "connected" soil crusts, cracks in clay soils, and vegetation. Evidence is presented that the increased variability of soil surface characteristics leads to a higher natural spatial variability of soil surface temperatures and, thus, to a lower probability to detect landmines using thermal imagery. No evidence was found that the soil surface changes affect the GPR signatures of landmines under the soil conditions encountered in this study. The New Mexico Tech outdoor Landmine Detection Sensor Test Facility is easily accessible and anyone interested is welcome to use it for sensor testing.
Laser Induced Breakdown Spectroscopy (LIBS) is an emerging, minimally-destructive sensor technology for in-situ, real-time chemical species identification and analysis. The Army Research Laboratory has been engaged in LIBS analysis for over a decade and recently has been investigating the potential to apply broadband LIBS analysis to specific military problems, one of which is as a handheld, confirmatory sensor for landmine detection. Laboratory tests with a prototype man-portable LIBS system demonstrate a high degree of success in identifying landmine casings.
Laser-induced breakdown spectroscopy (LIBS) is an emerging atomic emission spectroscopic technique that offers the prospect highly- selective, sensitive, and of real-time detection and analysis of both natural and man-made materials. Because LIBS is simultaneously sensitive to all chemical elements due to detector response in the 200-980nm range with 0.1 nm spectral resolution, the technique has many attributes that make it an attractive tool for a variety of military, security, and environmental applications.
Laser-induced breakdown spectroscopy (LIBS) spectra were collected under laboratory conditions and compiled in a library for a suite of plastic landmine casings and a variety of non-mine plastic materials on two occasions during 2004 using a Nd-YAG laser and a high-resolution broadband spectrometer to collect the full 200-980 nm LIBS spectrum.. The landmine casings examined included a broad selection of anti-personnel and anti-tank mines from different countries of manufacture. Two 'blind' tests were conducted in which LIBS spectra for the landmine casings and plastics were compared with a previously-constructed material spectral library. Using a linear correlation software, 'mine/no mine' determinations were correctly made for >90% of the samples in both tests.
KEYWORDS: Land mines, Sensors, Soil science, Mining, Temperature metrology, Infrared cameras, General packet radio service, Thermography, Infrared radiation, Metals
Previous modeling studies and experimental work have demonstrated that soil physical properties have a significant effect on most sensors for the detection of buried land mines. While a modeling approach allows for testing of the effects of a wide range of soil variables, most experimental work is limited to (field) soils with poorly known or controlled properties. With this in mind, we constructed a new outdoor test site with full control of soil water content and continuous monitoring of important soil properties and environmental conditions. In three wooden frames of 2 x 2 x 1 meter, filled with different soil types (sand, loam, and clay), we buried low-metal anti-tank and anti-personnel land mine simulants. We installed time domain reflectometry (for measurement of soil water content) and temperature probes at different depths above and below the land mines as well as in homogeneous soil away from the land mines. In this paper we document the features of this new test site and present results from the monitoring equipment.
Ground penetrating radar and thermal sensors hold much promise for the detection of non-metallic land mines. In previous work we have shown that the performance of ground penetrating radar strongly depends on field soil conditions such as texture, water content, and soil-water salinity since these soil parameters determine the dielectric soil properties. From soil physics and field measurements we know that the performance of thermal sensors also strongly depends on soil texture and water content. There is it critical that field soil conditions are taken into account when radar and thermal sensors are employed. The objectives of this contribution are (i) to make an inventory of readily available soil data bases world wide and (ii) to investigate how the information contained in these data bases can be used for derivation of soil dielectric and thermal properties relevant for operation of land mine sensors.
Laser Induced Breakdown Spectroscopy (LIBS) is an atomic emission spectroscopic technique that utilizes a pulsed laser to create a microplasma on the target together with an array spectrometer to capture the transient light for elemental identification and quantification. LIBS has certain important characteristics that make it a very attractive sensor technology for military uses. Such attributes include that facts that LIBS (1) is relatively simple and straightforward, (2) requires no sample preparation, (3) generates a real-time response, and (4) only engages a very small sample (pg-ng) of matter in each laser shot and microplasma event, (5) has inherent high sensitivity, and (6) responds to all forms of unknowns, and, therefore, is particularly suited for the sensing of dangerous materials. Additionally, a LIBS sensor system can be inexpensive, configured to be man-portable, and designed for both in-situ point sensing and remote stand-off detection with distances of up to 20-25 meters. Broadband LIBS results covering the spectral region from 200-970 nm acquired at the Army Research Laboratory (ARL) under laboratory conditions for a variety of landmine casings and explosive materials. This data will illustrate the potential that LIBS has to be developed into a hand-deployable device that could be utilized as a confirmatory sensor in landmine detection. The concept envisioned is a backpack-size system in which an eyesafe micro-laser is contained in the handle of a deminer's probe and light is delivered and collected through an optical fiber in the tapered tip of the probe. In such a configuration, analyses can be made readily by touching the buried object that one is interested in identifying.
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