Predicting Soil Influence on the Performance of Metal Detectors: Magnetic Properties of Tropical Soils

Mine detection and clearance are costly and time-consuming procedures necessary to benefit the communities these weapons affect. A complication surrounding mine detection is the influence of the soil on landmine detection, but little research has been done on the subject. This article discusses how soil can affect mine detectors and research plans to improve mine-detection efficiency

Modeling of GPR Clutter Caused by Soil Heterogeneity

In small-scale measurements, ground-penetrating radar (GPR) often uses a higher frequency to detect a small object or structural changes in the ground. GPR becomes more sensitive to the natural heterogeneity of the soil when a higher frequency is used. Soil heterogeneity scatters electromagnetic waves, and the scattered waves are in part observed as unwanted reflections that are often referred to as clutter. Data containing a great amount of clutter are difficult to analyze and interpret because clutter disturbs reflections from objects of interest. Therefore, modeling GPR clutter is useful to assess the effectiveness of GPR measurements. In this paper, the development of such a technique is discussed. This modeling technique requires the permittivity distribution of soil (or its geostatistical properties) and gives a nominal value of clutter power. The paper demonstrates the technique with the comparison to the data from a GPR time-lapse measurement. The proposed technique is discussed in regard to its applicability and limitations based on the results

Influence of Soil Properties on the Performance of Metal Detectors and GPR

This article examines the effects of four soil types on metal detector and GPR performance and proposes the development of a classification system based on soil type to aid in the selection of effective methods for manual demining

Vorhersage des Einflusses der magnetischen Suszeptibilität des Bodens auf die Funktionsweise von Metalldetektoren bei der Landminensuche – Fallbeispiel Angola

Zur Räumung der als Relikte bewaffneter Konflikte im Boden liegenden Landminen werden wegen geringer Kosten und leich-ter Anwendbarkeit vor allem Metalldetektoren eingesetzt. Tropische Böden bereiten dabei häufig Probleme, da ihre magnetische Suszeptibilität zu starken Einschränkungen wie z.B. Fehlalarmen führt. In einer Studie an 511 Proben von lateritischen Böden aus 15 tropischen Ländern konnten PREETZ et al. (2008) ein Klassifikationssystem entwickeln, das die magnetische Suszeptibilität nach dem Ausgangsgestein und dem Verwitterungsgrad des Bodens einzu-schätzen erlaubt. Um die in vielen Ländern vorliegenden Bodenkarten nutzen zu können, wurde nach einem Algorithmus gesucht, der die Zielgröße direkt zu Bodentypen nach dem FAO- oder WRB-System in Beziehung setzt. Als regionales Fallbeispiel diente Angola. Auf der Grundlage vorhandener Bodenkarten und der Definitionen diagnostischer Horizonte nach dem FAO-/WRB-System wurde ein zusätzliches Schema entwickelt, das die örtlich verbreiteten Ferralsols, Plinthosols, Acrisols und sonstigen Bodentypen nach dem prognostizierten Grad der magnetischen Suszeptibilität in 4 Klassen unterschiedlichen Einflusses auf die Funktionsweise von Metalldetektoren einteilt. Das Ergebnis besteht in landesweiten Karten, die die Medianwerte und die 90 %-Quantile der prognostizierten magnetischen Suszeptibilität darstellen und als Hilfsmittel bei der Planung der Landminensuche eingesetzt werden können

Modeling of GPR Clutter Caused by Soil Heterogeneity

In small-scale measurements, ground-penetrating radar (GPR) often uses a higher frequency to detect a small object or structural changes in the ground. GPR becomes more sensitive to the natural heterogeneity of the soil when a higher frequency is used. Soil heterogeneity scatters electromagnetic waves, and the scattered waves are in part observed as unwanted reflections that are often referred to as clutter. Data containing a great amount of clutter are difficult to analyze and interpret because clutter disturbs reflections from objects of interest. Therefore, modeling GPR clutter is useful to assess the effectiveness of GPR measurements. In this paper, the development of such a technique is discussed. This modeling technique requires the permittivity distribution of soil (or its geostatistical properties) and gives a nominal value of clutter power. The paper demonstrates the technique with the comparison to the data from a GPR time-lapse measurement. The proposed technique is discussed in regard to its applicability and limitations based on the results

Relationship between magnetic properties and reddening of tropical soils as indicators of weathering

This study evaluates the use of magnetic properties as an indicator of weathering of tropical soils. Soil samples collected across the tropical belt were analysed for magnetic susceptibility and its frequency dependence. Frequency dependence is caused by superparamagnetic (SP) ferrimagnetic nanoparticles, which are commonly attributed to neoformation during soil forming processes. Magnetic properties are compared to the redness rating of soil colour, which is related to the hematite content and is an established proxy for soil weathering. The investigated samples comprise material of different weathering stages from unweathered and weathered rock to subsoil and strongly weathered topsoil. They cover a broad variety of parent materials: ultrabasic, basic, intermediate, acid igneous rocks, clays and clay slates, phyllites and sandstones. The results show that soil reddening, magnetic susceptibility and in particular frequency-dependent susceptibility generally increase with proceeding weathering. However, there is a lithologic overprint and the parent material has to be taken into consideration. Soils stemming from acid igneous rocks, clays, clay slates and phyllites show a positive correlation between reddening and susceptibility or frequency dependent susceptibility, rendering these properties suitable for indicating weathering. In contrast, soils stemming from ultrabasic, basic and intermediate igneous rocks and sandstones show no significant correlation. The reason is the strong lithogenic overprint of ferrimagnetic minerals including SP particles, which commonly occur in these rock types