During the past 80 years, ground-penetrating radar (GPR) has evolved from a skeptically received glacier sounder to a full multicomponent 3D volume-imaging and characterization device. The tool can be calibrated to allow for quantitative estimates of physical properties such as water content. Because of its high resolution, GPR is a valuable tool for quantifying subsurface heterogeneity, and its ability to see nonmetallic and metallic objects makes it a useful mapping tool to detect, localize, and characterize buried objects. No tool solves all problems; so to determine whether GPR is appropriate for a given problem, studying the reasons for failure can provide an understanding of the basics, which in turn can help determine whether GPR is appropriate for a given problem. We discuss the specific aspects of borehole radar and describe recent developments to become more sensitiveto orientation and to exploit the supplementary information in different components in polarimetric uses of radar data. Multicomponent GPR data contain more diverse geometric information than single-channel data, and this is exploited in developed dedicated imaging algorithms. The evolution of these imaging schemes is discussed for ground-coupled and air-coupled antennas. For air-coupled antennas, the measured radiated wavefield can be used as the basis for the wavefield extrapolator in linear-inversion schemes with an imaging condition, which eliminates the source-time function and corrects for the measured radiation pattern. A handheld GPR system coupled with a metal detector is ready for routine use in mine fields. Recent advances in modeling, tomography, and full-waveform inversion, as well as Green's function extraction through correlation and deconvolution, show much promise in this field.

/pdf/surface-and-borehole-ground-penetrating-radar-developments-2qckwgquor.pdf

Surface and borehole ground-penetrating-radar developments

The magnetic dipole polarizability tensor is an object-specific property possessing information about the size, shape, and material. This information could be used by electromagnetic induction sensors typically used for demining operations to discriminate between buried mines and clutter, reducing false alarm rates, and improving demining throughput and safety. This paper presents a methodology capable of obtaining the spectroscopic tensors of small metallic objects and low metal anti-personnel mine surrogates. The experimental results are validated against simulated and analytical solutions to ensure that the obtained tensor truly represents the absolute object tensor. Absolute tensors for a number of typical clutter items and mine surrogates are presented, with significant variance observed between those of mine and clutter.

Magnetic Polarizability Tensor Spectroscopy for Low Metal Anti-Personnel Mine Surrogates

This paper describes a study carried out into the discrimination and classification of anti-personnel landmines using the MINEHOUND GPR. Other techniques, well reported in the literature, are not considered in this study. The techniques investigated enabled the classification of landmines to be achieved on a restricted set of targets. The approach proposes a method whereby a library of radar signatures of landmines is acquired under controlled conditions and then used to classify unknown signatures. Initial results show that this method enables clutter targets to be well separated from landmine targets, with the exception of air voids, such as pipes. The technique offers the potential of a reduction in false alarm rate to 10% of the current performance.

Classification of landmines using GPR

7. Ground-Penetrating Radar

GPR has been thought a useful sensor for detection of buried land mines, but no GPR has been practically deployed in humanitarian demining. Since 2002, we have developed a new hand-held land mine detection dual-sensor ALIS. ALIS is equipped with a metal detector and a GPR, and it has a sensor tracking system, which can record the GPR and Metal detector signal with its location. It makes possible to process the data afterwards, including migration. The migration processing drastically increases the quality of the image of the buried objects. ALIS uses two different GPR systems, namely VNA (Vector Network Analyzer) based GPR and an Impulse GPR. VNA based GPR can provide better quality GPR images, although the impulse GPR is faster and light weight. ALIS evaluation tests have been held in mine affected courtiers including Afghanistan, Croatia, Egypt and Cambodia. In the two-month evaluation test in Cambodia, ALIS worked without any problem. After some demonstrations and evaluation, we got many useful suggestions. Using these advises, we have modified the ALIS and it is now more easy to use. ALIS will be commercialized in 2007.

Development of the Hand held dual sensor ALIS and its evaluation

This paper describes the further engineering development and performance of the MINEHOUND affordable humanitarian mine detector, sponsored by the UK Department for International Development and developed by ERA Technology. Using a radically different patented approach from conventional ground penetrating radar (GPR) designs, in terms of the man machine interface, MINEHOUND offers simplicity of use and affordability, both key factors in humanitarian demining operations. Trials were carried out during the period 2002-2004 and have been reported at SPIE 2002 and SPIE 2004. MINEHOUND has the capability of detecting completely non-metallic mines and offers an affordable solution to hand held mine detection. The GPR is a time-domain radar transmitting 1ns duration impulses at a repetition frequency of 1MHz. The GPR transmitter- receiver and associated control and signal processing is mounted on a compact purpose designed printed circuit board 220mm by 100mm. A dedicated state of the art “Blackfin” DSP processor is used to provide all control and signal processing functions. Trials of batches of MINEHOUND are planned for 2005 in the Cambodia and Angola as well as the Balkans.

MINEHOUND production development

A single board ultra-wideband (UWB) radar has been developed to provide a compact, rugged, high performance capability for hand held applications such as anti-personnel landmine detection. This paper discusses the radar system developed by ERA Technology, which provides the radar functionality of the MINEHOUND dual sensor detector. (4 pages)

A High Performance Time Domain UWB Radar Design

The UK Department for International Development (DfID), in collaboration with the German Foreign Ministry (Auswartiges Amt), contracted ERA Technology to carry out extensive field trials in Cambodia, Bosnia and Angola of an advanced technology, dual sensor, and hand-held landmine detector system called MINEHOUND This detector combines a metal detector with a Ground Penetrating Radar (GPR) As a result of extremely successful trials MINEHOUND was developed as a product by ERA Technology and Vallon GmbH and has been available for sale since late 2006 This paper describes the transition to production of the detector Keywords: Landmine detection, humanitarian, de-mining, ground penetrating radar, multi sensor INTRODUCTION MINEHOUND - VMR2 is an advanced, dual sensor, mine detector comprising a Ground Penetrating Radar (GPR) developed by ERA Technology Ltd (UK) and an induction Metal Detector (MD) based on the VMH3 manufactured by Vallon GmbH (FRG) MINEHOUND is designed to meet the user requirements for ease of use, ruggedness and functionality Both the MD and GPR provide audio outputs, which give the operator information on the size of the target; the GPR also provides information on the depth and symmetry of the target As the GPR will only respond to targets with a significant radar cross-section, and hence, physical dimensions, sources of false alarm to the metal detector, such as bullets, casings and fragmentation are rejected This results in a significant reduction in the false alarm rate that deminers typically suffer from when using a metal detector alone Field trials in Cambodia, Bosnia and Angola in 2005 and 2006 showed that MINEHOUND could reduce false alarms in real minefields by up to 7:1 and typically 5:1as described in [1]

MINEHOUND: transition to production

http://ieeexplore.ieee.org/iel5/4126071/4126072/04126085.pdf

Hand-Held Microwave Search Detector

This paper describes a vehicle mounted 8-channel radar system suitable for buried landmine and IED detection. The
system is designed to find Anti Tank (AT) landmines and buried Improvised Explosive Devices (IEDs). The radar uses
field-proven ground penetrating radar sub-system modules and is scalable to 16, 32 or 64 channels, for covering greater
swathe widths and for providing higher cross track resolution. This offers the capability of detecting smaller targets
down to a minimum dimension of 100mm. The current rate of advance of the technology demonstrator is 10 kph; this
can be increased to 20 kph where required. The data output is triggered via shaft encoder or via GPS and, for each
forward increment; the data output is variable from a single byte per channel through to the 512 samples per channel.
Trials using an autonomous vehicle, combined with a COFDM wireless link for data and telemetry back to a base
station, have proven successful and the system architecture is described in this paper. The GPR array can be used as a
standalone sensor or can be integrated with off-the-shelf software and a metal detection array.

Nigel Hunt

Papers

MINEHOUND production development

A High Performance Time Domain UWB Radar Design

MINEHOUND: transition to production

Hand-Held Microwave Search Detector

An affordable modular vehicle radar for landmine and IED detection