According to the UN Mine Action Service, landmines kill 15,000–20,000 people every year (mostly children) and maim countless more across 78 countries. Demining efforts cost US 300–1000 USD per mine, and, for every 5000 mines cleared, one person is killed and two are injured. Thus, clearing post-combat regions of landmines has proven to be a difficult, risky, dangerous and expensive task with enormous social implications for civilians.
The demining has two contexts, the military and the humanitarian. The main aim of the military is cleaning the path where the soldiers are going to walk through. Instead the humanitarian must clear the zone of mines to ensure the life of every member of the community who lives close to the danger region. “There are literally millions of anti-personnel mines in the ground in places where people need to grow food, or need to walk to the nearest well, or simply go about their daily business – shelter under a tree from the Sun,” explains Bill Lionheart, a mathematician at the University of Manchester in the UK.
Many technologies have been employed in detection of landmines. Military has been mainly using metal detectors to search for booby traps. However, the landmines are increasingly being constructed from plastic. Mine search also suffers from false alarms, “Only one in 2,000 found objects is a mine,” says Dr Christoph Baer from the Institute of Electronic Circuits in Bochum, who collaborates with Jan Barowski and Jochen Jebramcik from the Institute of Microwave Systems at the Ruhr-Universität. This renders the search extremely difficult.
Researchers in physical, chemical, and biological sciences are studying and developing new methods that could reduce the false alarm rate and maintain or increase the probability of detection for mine clearance. Vapor Sensors detect very small amount of explosive material that manages to escape in the form of vapors from the shield structures of mines. By using techniques like molecular diffusion and turbulence processing, these vapors can be transported. And then these can be detected by Chemical sensors by employing electromechanical, espectorpial or piezoelectric principles. Biological methods employ animals with sensitive sniffing powers like dogs, rats, insects and microorganisms to detect the presence of explosives.
Robotic vehicles and drones are also being increasingly employed for mind detection and clearing, to reduce the risk to the personnel.
Rats Are Being Trained to Sniff Out Land Mines
Apopo’s African giant pouched rats—or “hero” rats—are being trained to sniff out and detect TNT vapor in the ground. They’re bred and raised at the organization’s headquarters in Tanzania, and those used to detect land mines have already worked in Mozambique and Angola.
“They have a very keen sense of smell and there is no problem for them to find the land mines,” says TeKimiti Gilbert, head of mine action at Apopo, a Belgian organization that trains rats for humanitarian purposes. “The advantage of the rats is that they don’t look for metal, they look for explosives.”
Landmine detection schemes
One of the most common and mature systems are metal detectors, which consist of coils that generate electromagnetic field, the induced eddy currents in metal mines generate opposing current in the coils of metal detector that leads to their detection. The metal detectors fail to detect the landmines made up of plastic or which may have a very small amount of metal.
A GPR system consists of an antenna or series of antennas that emit the waves and then pick up the return signal. The GPR analyzes the return signals generated by reflections of the waves at the boundaries of materials with different indexes of refraction caused by differences in electrical properties. Generally, reflections occur at discontinuities in the dielectric constant, such as at the boundary between soil and a landmine or between soil and a large rock. A small computerized signal-processing system then interprets the return signal to determine the object’s shape and position.
In collaboration with partners from South America, engineers at the German Ruhr-Universität Bochum and Technical University Ilmenau are developing a new mine clearance technology, based on ground penetrating radar. In the long run, they are aiming at creating a handheld device that will detect different mine types on rough terrain without fail and which can be used in the same way as metal detectors.
While ground-penetrating detection techniques such as radar or metal detectors may be more mature, anti-personnel landmines manufacturers have moved to using plastic instead of metal, both for economical and stealth reasons, which makes their detection increasingly difficult.
Find A Better Way – a charity that supports the development of improved techniques for detecting landmines. The hope is that this work will speed up the process of clearing landmines, which can be an intensely risky and laborious process. Lionheart and his team are developing ways to reduce the number of false-positives when searching for mines. “So in a way, our challenge is not so much to find mines, but to detect that something’s not a mine,” he says.
For example, it is common for landmine clearance teams to use metal detectors to locate the firing pin and metal percussion caps present in many landmines. Currently, all those bits of metal have to be dug out of the ground before an area can be declared safe and, according to Lionheart, this approach would mean of the order of hundreds of years before people could get their land back.
To improve the situation, Lionheart and his colleagues have developed the technology and the underlying maths of metal detectors to develop devices that can not only detect, but also characterize metal objects in the ground. This makes it possible to disregard the signals that relate to harmless bits of scrap metal.
Similarly, Lionheart’s team is developing a form of ground-penetrating radar with multiple sensors. This enables a far more detailed picture of the subsurface to be pieced together than is possible with conventional radar techniques.
Acoustic sensors can detect landmines by projecting the acoustic waves generated by acoustic sensors and then analyzing the reflected waves the location and identity of the target body can be found. The study of these sensors has revealed that it is very powerful in the wet and heavy ground such as clay while it is inefficient in sandy soils.
Infrared Imaging Systems
IR imaging can detect the difference between the IR radiation emitted by the landmines and the background. However thermal signature fades with long periods of time and presence of vegetation also affects the detection.
Electric Impedance Tomography (EIT)
EIT uses bi-dimensional array of electrodes to generate electricity and capture signals, the conductivity distribution and anomalies of mines generate an image that can be analysed to detect metallic as well as non-metallic mines. The biggest disadvantage is that sensors must be in close contact with the surface which increases the risk of triggering the explosion of the mine.
No single technique is powerful enough to provide good performance. But if used to combine two or more techniques the desired performance can be achieved.
3D Integrated Imaging to Tackle Landmine Detection
The three-year research project lead by Dr. Manuchehr Soleimani at the Engineering Tomography Lab of the University of Bath aims to provide technology that can differentiate between images of plastic and metallic elements within a single explosive device, at depths of up to 10 cm underground on varied terrain.
“We aim to develop an integrated technology to detect both metallic and non-metallic landmines and to improve the speed and reliability of this process,” Soleimani said.
That integrated technology includes two different types of array, so that older, metal landmines can be detected, as well as the newer plastic landmines that have begun to proliferate.
For the Electrical Capacitance Tomography part, his team used a set of 12 copper electrodes arranged in a 4×3 matrix array (250 by 250mm in total, 4mm thin) and a 12-channel capacitance measurement instrument to image the dielectric permittivity properties of objects placed in front of the sensor array. He was able to image dielectric solids at a depth of just over half the full sensor arrays length.
For the Magnetic Induction Tomography part, inductive coils and eddy currents were used to map the passive electromagnetic properties of the objects to be detected, in 3D. Here the sensors (16 air-core cylindrical coils, each 4cm in diameter) were placed in a circular shape with their axes perpendicular to the plate. 3D image reconstruction was performed based on the analysis of sequential coil excitations and responses.
“The idea is to use both imaging techniques across a range of frequencies and get a spectroscopic signature of the materials being imaged”, Soleimani said. “In effect, we could build a library of material signatures so the imaging of buried dielectric materials could yield their precise compositions. This could be associated with a matching table of known landmines to speed their identification, based on their shape and composition.”
US army awards USD$26.1 million contract to develop improved Husky Mine Detection Systems (HMDS)
Minelab Electronics, a company renowned for its metal detectors, and an American company NIITEK that makes ground penetrating radar, have partnered together to win a contract to produce a mine sweeping system for US military in two years.
The NIITEK® HMDS is a multi-panel high-performance Ground Penetrating Radar (GPR) system when mounted on manned, blast-resistant vehicles, provides a rapid 3D subsurface visualization of anti-vehicular landlines or any other type of buried explosive hazard.
Minelab’s STMR advanced version system has a dual coil configuration embedded in a rigid 2.2m wide structure and is based on its BiPolar Pulse Induction technology. Its vehicle mounted metal detection system, provides a reliable, effective and fast means of detecting landmines, unexploded ordnance and explosive remnants of war, and has been used in humanitarian demining operations for the past eight years.
The combination of Single Transmit Multiple Receive (STMR) array NIITEK’s radar would allow the system to detect anti-personnel landmines, anti-tank landmines and Improvised Explosive Devices with high probability of detection and low false alarm rates.
DTU to Work on New Mine Detection Drone
Researchers at Technical University of Denmark – DTU have received DKK 11 million from Innovation Fund Denmark to develop a drone with magnetometers capable of mapping mines in former war zones. The new demining system consist of developing a ‘magnetometer bird’, a frame with embedded magnetometer, which is attached to the drone and hangs approx. 5-10 metres below it.
“The plan is for our drone and its unique magnetometer module to make demining more precise than the current method of using off-road vehicles on land and special divers in coastal areas. It will also minimize the risk of injuries for the people involved, as the drone can be operated from a safe position outside the mined areas,” explains Arne Døssing, senior research, DTU Space, who heads the project of developing the new technology.
“It will be the first drone in the world to fly with a ‘bird’ underneath it. This construction is absolutely necessary to ensure the ultra-sensitive magnetometers are as close to the surface as possible, at the same time as minimizing exposure to magnetic disturbances from other instruments and from the flying drone,” says Døssing..
The drone has been developed by Sky-Watch, and in addition to the ability to fly like a regular aircraft, it allows for vertical take-off and landing in the same way as a helicopter.
Initially, the researchers will be focusing on the need to clear mines from World War II. The magnetometer drone will furthermore be tested in the mountains of Greenland, where it may have an impact on the search for mineral deposits or military waste, and it will also be tested from a vessel in relation to its ability to detect large mines in deeper waters. In both cases, the drone’s ability to take off and land vertically is significant.
However Mine clearance requires much more than the latest technologies
How we made Mozambique mine-free
“Mozambique – once one of the most heavily mined countries in the world – is now mine-free is a culmination of 22 years’ work, but the results will last forever. It is a beacon of hope for other countries living with a legacy of landmines,”said Calvin Ruysen the southern African regional director at the Halo Trust.
“I feel proud to see Mozambique realise this incredible achievement. It’s been a massive concerted effort from so many people: the de-miners, the survey teams, the donors and the Mozambique government,” said Calvin Ruysen the southern African regional director at the Halo Trust.
“Our challenge now is to seize the momentum towards achieving a mine-free world by 2025. This means focusing on other heavily mined countries such as Angola, Zimbabwe, Afghanistan and Cambodia.
It’s not going to be easy: the de-mining sector relies on continued political will and resources. But Mozambique’s achievement is compelling and an example to other nations of what can be achieved.”
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