Improved Permittivity Calibration Method for Wideband In Situ Permittivity Probe
This letter discusses about an improved permittivity probe calibration method for calculating the complex permittivity of soils from reflection data over a very wide bandwidth. The accuracy of this method is demonstrated using reflection data collected from a unique wideband (10-1000 MHz) permittivity probe specifically designed for quick in situ permittivity measurements of soils at different depths. The improved calibration method is based on the traditional capacitance model, which suffers from errors caused by the assumption that the capacitance is independent of the frequency and the permittivity of the ambient medium under test. The improved capacitance model is introduced here to account for the frequency- and permittivity-dependent effects. Thus, it produces more accurate permittivity estimation over a much wider frequency and permittivity ranges. This letter will discuss about the accuracy of this improved permittivity probe calibration method and a wideband in situ soil probe design.
Prediction of the effects of soil and target properties on the antipersonnel landmine detection performance of ground-penetrating radar: A Colombian case study
The performance of ground-penetrating (GPR) radar is determined fundamentally by the soil electromagnetic (EM) properties and the target characteristics. In this paper, we predict the effects of such properties on the antipersonnel (AP) landmine detection performance of GPR in a Colombian scenario. Firstly, we use available soil geophysical information in existing pedotransfer models to calculate soil EM properties. The latter are included in a two-dimensional (21)), finite-difference time-domain (FDTD) modeling program in conjunction with the characteristics of AP landmines to calculate the buried target reflection. The approach is applied to two soils selected among Colombian mine-affected areas, and several local improvised explosive devices (IEDs) and AP landmines are modeled as targets. The signatures from such targets buried in the selected soils are predicted, considering different conditions. Finally, we show how the GPR can contribute in detecting Iow- and non-metallic targets in these Colombian soils. Such a system could be quite adequate for complementing humanitarian landmine detection by metal detectors. (c) 2007 Elsevier B.V. All rights reserved.
Geophysical mapping of ground ice using a combination of capacitive coupled resistivity and ground-penetrating radar, Northwest Territories, Canada
[1] The nature and distribution of ground ice are two of the most unpredictable geological variables in near-surface deposits characterized by continuous permafrost. Subsurface information about ground ice distribution and structure can be obtained either by invasive and environmentally destructive techniques like drilling and excavation or by noninvasive low-impact geophysical methods. In this study, coordinated measurements by two complementary geophysical tools, capacitive-coupled resistivity (CCR) and ground-penetrating radar (GPR) were used to map ground ice in a variety of locations in the Mackenzie Delta region of the western Canadian Arctic. Both CCR and GPR systems are highly portable (especially on snow covered surfaces) and very effective in collecting data under winter conditions when cold ground temperatures ensure that nearly all liquid water is frozen and signal penetration is enhanced. CCR and GPR readily detect stratigraphic differences including the contacts between massive ice deposits and enclosing sediments. GPR is widely used in permafrost research, but CCR has been used in only a few studies. This is the first study to combine results from both systems by collecting complementary data sets along coincident transects. We demonstrate that when combined, these data increase the quality and interpretation of subsurface information beyond what could be determined by either of the instruments alone. The complementary nature of these two geophysical tools facilitated the detection and mapping of massive ground ice, ice-rich sediments, ice wedges, thermokarst, and basic stratigraphic relationships. This study breaks new ground by documenting the benefits of using these techniques together in permafrost investigations.