New Technology for Landmine Detection

Estimated reading time: 6 minutes

Even though antennae operating at the required frequency range of 500 megahertz to 4 gigahertz are available in the market, many of them are big and heavy and therefore unsuitable for handheld devices. This is why the RUB researchers constructed their own model, incorporating as few metal elements as possible. One advantage of the system is weight reduction, but it offers yet another benefit: the plastic surface reflects the signals sent back from the ground to a significantly lesser extent than a metal surface. Systematic measurement errors can thus be avoided.

The radar system was optimised by the project partners at the Technical University Ilmenau. The engineers utilised the technology developed at RUB for positioning. In addition to hardware, algorithms are crucial for signal processing. They must be able to identify which objects in the ground are mines and which are not.

“We knew that we needed test objects,” points out Baer. “Therefore, we assembled mines from everyday items.” Not with real explosives, of course, but with empty detonators.

Subsequently, the researchers created computer models of the real mines and simulated the radar signals that would be generated by each mine, the so-called radar cross section. They searched the models for elements that are characteristic for mines, but not for objects such as stones or screws.

The metal detonator strongly reflects the incoming antenna signals, and the radar cross section is additionally determined by the surrounding explosive and other components. Consequently, each mine type generates a characteristic radar cross section. As a result, the improvised explosive devices in the ground can be distinguished from other objects.

The important thing is that the detection algorithm knows as many different types as possible. This is why Jan Barowski and Christoph Baer assigned a special task to their students and colleagues: “We asked them to bring a random container from home and turn it into a mine. Had we built all mines ourselves, they would have ended up looking the same,” says Baer. Moreover, new combinations can be virtually created based on the computer-simulated mines, ensuring greater diversity.

However, mine detection requires more than this. Prior to identifying a signal with a specific radar cross section using ground penetrating radar, raw data must be processed. “Conducting measurements with our radar is initially like looking through a camera without a lens,” explains Jan Barowski. “The optics required for focusing is lacking.” Actually punctual objects look like curved lines. Researchers can convert those lines into point objects using digital signal processing. Since the depth of focus differs from object to object that would not be possible if only one lens was used.

The challenge is to apply the technology in real time. Barowski: “The person holding the radar device should see an image instantly.” That means it shouldn’t be necessary to first painstakingly edit data at a computer. The researchers intend to solve the problem with a field programmable gate array, a piece of hardware that they can adapt to a specific function.

In the first step, the engineers use signal processing to remove interferences caused by layers of earth from the images, focus on point objects, and compare the properties of their signals with known radar cross sections of different mine types or other objects. This is how they intend to distinguish relevant objects from irrelevant ones in the ground. Finally, they have to include the information supplied by the positioning system.

The German research team had transported the antennae and one radar detector for initial tests to Colombia in October 2015. In order to prevent damage to the antennae during transport, the researchers from Bochum sent the disassembled components to South America. Together with Colombian students, they reassembled them back to an antenna at their destination.

“Our aim is to share the expertise with our Colombian partners in the course of the project,” points out Christoph Baer. “This is why we have been performing all steps in close collaboration with the students on location.”

The RUB researchers have likewise acquired new insight on their journey to South America – especially during the visit to the training grounds where mine clearance exercises are conducted by the military. Baer: “Afterwards, we were certain that even though we might be able to build a mine detection device, it is out of the question that we would go minesweeping on location.”

The Medici team is now hoping to receive a follow-up grant in order to continue the project until a functional prototype is developed. A representative of the German embassy in Colombia and the Colombian government have declared to write a letter, in order to make third parties understand how important the project is for the country.

“All mines must be found, because it is a matter of humanitarian mine clearance,” stresses Christoph Baer. “Consequently, our project will not produce any patents.” It is bad enough that this kind of research is necessary at all. The researchers do not want to make a profit from their work. “Helping people is what matters to us.”

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