We are in the process of developing a high-resolution landmine scanning system “ALIS” which produces horizontal slices of the shallow subsurface for visualization of buried explosives and inert clutter. As many AP mines contain minimum amounts of metal, metal detectors need to be combined with a complimentary subsurface imaging sensor. Ground Penetrating Radar (GPR) is widely accepted for subsurface sensing in the fields of geology, archaeology and utility detection. The demining application requires real-time imaging results with centimetre resolution in a highly portable package. The key requirement for sharp images of the subsurface is the precise tracking of the geophysical sensor(s) during data collection. We should also notice that GPR system is a very wide band radar system, and equivalent to UWB radar, which has recently been developed for short-range high-accuracy radar. We are testing simplified but effective signal processing for imaging mines. We are currently testing a dual sensor ALIS which is a realtime sensor tracking system based on a CCD camera and image processing. In this paper we introduce the GPR systems which we have developed for detection of buried antipersonnel mines and small size explosives. ALIS has been deployed in Cambodia since 2009 and detected more than 70 mines in mine fields, and returned more than 13ha cleaned fields to local farmers. We also report the current status of ALIS in Cambodia.
Dual sensor is one of the most promising sensors for humanitarian demining operations. Conventional landmine
detection depends on highly trained and focused human operators manually sweeping 1m<sup>2</sup> plots with a metal detector
and listening for characteristic audio signals indicating the presence of AP (Anti-personnel) landmines. In order to
reduce the time of plodding detected objects, metal detectors need to be combined with a complimentary subsurface
imaging sensor. i.e., GPR(Ground Penetrating Radar). The demining application requires real-time imaging results with
centimetre resolution in a highly portable package. We are currently testing a dual sensor ALIS which is a real-time
sensor tracking system based on a CCD camera and image processing. In this paper we introduce ALIS systems which
we have developed for detection of buried antipersonnel mines and small size explosives. The performance of ALIS has
been tested in Cambodia since 2009. More than 80 anti-personnel mines have been detected and removed from local
agricultural area. ALIS has cleared more than 70,000 m<sup>2</sup> area and returned it to local farmers.
In order to demonstrate the possibility of Ground Penetrating Radar (GPR) for detection of small buried objects such as
landmine and UXO, conducted demonstration tests by using the 3DGPR system, which is a GPR system combined with
high accuracy positing system using a commercial laser positioning system (iGPS). iGPS can provide absolute and better
than centimetre precise x,y,z coordinates to multiple mine sensors at the same time. The developed " 3DGPR" system is
efficient and capable of high-resolution 3D shallow subsurface scanning of larger areas (25 m<sup>2</sup> to thousands of square
meters) with irregular topography . Field test by using a 500MHz GPR system equipped with 3DGPR system was
conducted. PMN-2 and Type-72 mine models have been buried at the depth of 5-20cm in sand. We could demonstrate
that the 3DGPR can visualize each of these buried land mines very clearly.
Metal detectors are used not only to detect but also to locate targets. The location performance has been evaluated
previously only in laboratory. The performance probably differs that in the field. In this paper, the evaluation of the
location performance based on the analysis of pinpointing error is discussed. The data for the evaluation were collected
in a blind test in the field. Therefore, the analyzed performance can be seen as the performance under field conditions.
Further, the performance is discussed in relation to the search head and footprint dimensions.
Metal detector has commonly been used for landmine detection and ground-penetrating radar (GPR) is about to be
deployed as dual sensor that is in combination with metal detector. Since both devices employ electromagnetic
techniques, they are influenced by magnetic and dielectric properties of soil. To observe the influence, various soil
properties as well as their spatial distributions were measured in four types of soil where a field test of metal detectors
and GPRs took place. By analyzing soil properties these four types of soil were graded based on the estimated amount of
influence on the detection techniques. The classification was compared to the detection performance of devices obtained
from the blind test and a clear correlation between the difficulty of soil and the performance was observed; the detection
and identification performance were degraded in soils that were classified as problematic. Therefore, it was demonstrated
that the performance of metal detector and GPR for landmine detection can qualitatively be assessed by geophysical
Tohoku University, Japan is developing a new hand-held land mine detection dual-sensor (ALIS) which is equipped
with a metal detector and a GPR. ALIS is equipped with a sensor tracking system, which can record the GPR and Metal
detector signal with its location. The Migration processing drastically increases the quality of the imaging of the buried
objects.Evaluation test of ALIS has been conducted several test sites. Tests in real mine fields in Croatia has been
conducted between December 2007 and April 2008. Under different soil and environment conditions, ALIS worked
well. Then ALIS evaluation test started in Cambodia in February 2009 and we could find discrimination capability of
ALIS in test lanes, and we are planning to start evaluation test in real mine fields in Cambodia.
Since 2002, our research group at Tohoku University has 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 evaluation test was conducted in Croatia in October 2007. Then after, we stared a half-year evaluation test of ALIS in QC test in Croatia in December 2007. This test will be conducted in various soil and environmental conditions in Croatia.
We are developing a new hand-held land mine detection dual-sensor (ALIS) which is equipped with a metal detector
and a GPR. ALIS is equipped with a sensor tracking system, which can record the GPR and Metal detector signal with
its location. It makes possible to process the data after the data was acquired, including migration. The migration
processing drastically increases the quality of the images of the buried objects. Evaluation test of ALIS has been
conducted in several test sites. In February 2006, a one-month evaluation test was conducted in Croatia, and in October-
December 2006, a two-month evaluation test was conducted in Croatia. Since the dual-sensor is a new landmine
detection sensor, and the conventional evaluation procedure developed for metal detectors cannot directly be applied for
the dual sensor. In Croatia, the detection probability was comparable to that by a metal detector operated by local
deminers. In addition, we showed that ALIS provides image of buried objects by GPR, which can be used for
identification. Therefore, their performances were sufficiently high. Then the test was also conducted in Cambodia. The
test was carried out by 2 local deminers independently, which allows studying the influence of different operators and
increases the statistical value of the results.
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. The new system, we do not need any standard mark on the
ground. Also, ALIS uses two different GPOR systems, including 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 were 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.
We are developing a new landmine detection sensor (ALIS) which is equipped with a metal detector and a GPR. Although this is a hand-held system, we can record the metal detector and GPR signal with the sensor position information. Therefore, signal processing for 2-D signal image is possible. For the metal detector, we apply cross-correlation algorism for sharpening the image and estimation of the depth of the target. For GPR signal, we can apply migration algorithm, which drastically reduce the clutter and we can obtain 3-D image of the buried targets. At first, linear interpolation and cubic interpolation are used respectively to deal with the problem of random data position. Comparing results, we find the image quality of two kinds of interpolations is almost same. Then the migration is used to refocus the scattered signals and improve the image quality for reconstructed landmine image. ALIS demonstration were held in Afghanistan in December 2004 and other countries including Egypt and Croatia in 2005. After some demonstrations and evaluation, we received many useful suggestions. Using these advises, we have modified the ALIS and it is now more easy to use. In this paper, we describe the latest characteristics of the ALIS and summarize its operation.
We developed a hand-held landmine detection sensor system, ALIS (Advanced Landmine Imaging System), combined with a metal detector and GPR (Ground penetrating radar). The system has a CCD camera attached on the sensor handle and can record the MD and GPR signal with the sensor position information. Therefore, it can offer the visual MD image and GPR image, which is used to define targets. But because ALIS is a hand-held system, the sensor position is random when it is operated in the field by human being. Also GPR normally suffers from very strong clutter. To deal with these problems, the interpolation is a common choice for both MD and GPR to create grid data set firstly and migration was used to improve the quality of GPR image. But generally the interpolation can not improve the quality of data set, although it can offer grid data set for visualization. Also for 3D GPR data set, it will consume much processing time. In fact, the migration can not only improve the quality of GPR data but also interpolate data to offer grid data set. It is a kind of 2.5D interpolation and just uses related data in the diffraction trajectory surface. So it can offer directly the visual GPR image and save the processing time. We will discuss two procedures for GPR, interpolation + migration or only migration, in this paper. Lastly, we also will report some results of evaluation test in 2006 February in Croatia.
SAR-GPR is a sensor system composed of a GPR and a metal detector for landmine detection. The GPR employs an array antenna for advanced signal processing for better subsurface imaging. This system combined with synthetic aperture radar algorithm, can suppress clutter and can image buried objects in strongly inhomogeneous material. SAR-GPR is a stepped frequency radar system, whose RF component is a newly developed compact vector network analyzers. The size of the system is 30cm x 30cm x 30cm, composed from 6 Vivaldi antennas and 3 vector network analyzers. The weight of the system is less than 30kg, and it can be mounted on a robotic arm on a small unmanned vehicle. In the signal processing of the SAR-GPR has a unique future. It can be used with an algorithm for strong clutter suppression. The sensor has about 10cm offset from the ground surface, and it can even image the ground surface topography. It will be implemented for more advanced imaging algorithm, which can be used for the ground surface with a large roughness. Field tests of SAR-GPR were carried out in March 2005 in Japan. Then after, it was also evaluated in the Netherlands and Croatia. We report the results of these evaluation and demonstration.