In this paper, the characterization of the electromagnetic soil properties of a blind lane used in a trial for a dual-sensor mine detector is presented. Several techniques are used and are compared here; Time Domain Reflectometry, gravimetric techniques and Frequency Domain Reflection and Transmission methods. The derived soil properties are mapped by interpolation and the resulting maps are compared with the recorded deminers' performance on the lane. Recurrent and non-predicted results from the performance of the dual-sensor detector are explained as the results of variability of certain properties.
In this paper results are presented of a study on the performance of a dual-sensor landmine detector and its dependency on soil moisture. The detector was used on a trial site in the K5 mine belt in Cambodia. Soil samples were taken from the trial lane, as well as GPR measurements. The data obtained from these soil samples and field measurements are integrated into a model for soil moisture content that is correlated with the land mine detector performance.
With the emergence of commercially available multisensor mine detection systems, the need for standardised test and evaluation procedures becomes more pressing. For metal detectors this already has been established and is laid down in the CEN workshop document CWA14747:2003. The ITEP multisensor working group has taken the first step towards a similar document, by means of a so called "best practice" document, which would ultimately lead to a proper standard. In this paper we address various issues important for multisensor mine detection testing and evaluation and in this way hope to contribute to a draft version of the "best practice" document encouraging other parties to do the same and hence speed up the process of standardisation.
In previous work we have shown that GPR signatures are affected by
soil texture and soil water content. In this contribution we will
use a three dimensional electromagnetic model and a hydrological
soil model to explore in more detail the relationships between GPR
signatures, soil physical conditions and GPR detection performance.
First, we will use the HYDRUS2D hydrological model to calculate a
soil water content distribution around a land-mine. This model has
been verified against measured soil water distributions in previous
work. Next, we will use existing pedotransfer functions (e.g. Topp,
Peplinski, Dobson, Ulaby) to convert the predicted soil water
contents around the land-mines as well as known soil textures and
bulk densities into soil parameters relevant to the electromagnetic
behaviour of the soil medium. This will enable a mapping between the
hydrological model and the electromagnetic GPR model. Using existing
and new laboratory and field measurements from the land-mine test
facilities at TNO-FEL we will make a first attempt to verify our
modelling approach for the prediction of GPR signatures in field
soils. Finally a detection algorithm is used to evaluate the GPR
detection performance with respect to changing environmental soil
Soil water content, relative permittivity, electrical conductivity, thermal conductivity and heat capacity, directly or indirectly affect the detection capabilities of sensors used for land mine detection. The most important of these is water content since it also influences the other properties. Therefore an experiment was set up where water was applied to a test area and the water content was monitored over time. Simultaneously, measurements with a ground penetrating radar (GPR) were carried out. Subsequently the measurements of both the water content reflectometers (WCR) and GPR were compared against the outcome of a soil water content model and a model relating soil water content with medium relative permittivity. We find that the introduction of water in a dry sand soil, increases the impedance contrast of the land mine with respect to its surrounding (i.e. stronger electromagnetic signatures) which may result in better detection. Alternative effects also seem play a role in finding and identifying features of potential targets.
The contrast in relative dielectric constant between landmines and the surrounding soil is one of the most important elements for radar detection purposes. For most geologic materials the relative dielectric constant lies within the range of 3-30, with dry sand at the lower end of this range at about 3-5. Nonmetallic landmines have a dielectric constant range of 3.2-9.8 whereas metallic landmines have a much higher relative dielectric constant. In previous work, literature data were used to compose a MATLAB model that determines whether or not field conditions are appropriate for use of GPR instruments. This model has been verified for dry and moist sand, silt, and clay soils in New Mexico. The objective of this paper is to validate this model over a wider range of soil texture and soil moisture conditions. Therefore, GPR measurements will be taken on experimental test facilities for landmine detection at Yuma Proving Grounds in Arizona and at the TNO Physics and Electronics Laboratory in The Netherlands. These facilities cover a wide range of soil textures from ferruginous sand to clay and peat as well as many levels of soil moisture.