In April 2017, the U.S. military dropped the most powerful non-nuclear bomb ever used in combat on a tunnel complex in Afghanistan’s Nangarhar province. The airstrike targeted the Islamic State’s Khorasan branch. The use of the GBU-43/B Massive Ordnance Air Blast weapon, the so-called “Mother of All Bombs,” highlighted the growing threat posed by adversaries’ underground structures. Gen. John Nicholson, commander of U.S. Forces-Afghanistan, cited the challenge of dealing with subterranean targets to justify the use of the bomb, also known as the MOAB. “As ISIS-K’s losses have mounted, they are using [improvised explosive devices], bunkers and tunnels to thicken their defense,” he said in a statement released after the attack. Additionally, hostile regimes such as North Korea are believed to be hiding WMD technology and other weaponry in underground facilities that the U.S. military might need to locate.
Meanwhile, drug cartels are using tunnels to smuggle contraband into the United States from Mexico. Sixty-seven of them were discovered from fiscal years 2011 through 2016, according to the Government Accountability Office. “In a lot of cases they start [digging a tunnel] in a building on one side of the border and they end in a building on the other side of the border,” said Mark Kaczmarek, a program manager at the Department of Homeland Security’s science and technology directorate.
Indian Border Security Force (BSF), which is responsible for guarding the borders with Bangladesh and Pakistan is carrying out field trials of high-tech ground-penetrating radar (GPR) that will help in detection of tunnels, anti-tank mines and improvised explosive devices (IEDs) on the border with Pakistan. Equipped with an LCD screen and telescopic rod to “plot the real time threat”, the handheld GPR will be able to conduct “automatic target recognition”. According to the specifications approved by a panel for the GPR, the system should not weigh more than 5 kilograms for it to be a handheld device and should be able to detect all kinds of mines and IEDs in different soil conditions.
The GPR system, according to the officials, will strengthen the counter-infilteration measures and help the security forces in detecting underground tunnels on the India-Pakistan border. Since 2012, the Indian Army and BSF have detected six underground tunnels along the border in Jammu region. These tunnels were being used to push Pakistani terrorists, arms and ammunitions in Jammu and Kashmir.
Seventeen years ago in Worcester, Massachusetts, six firefighters who were dispatched to a smoke-filled warehouse lost their lives as they were unable to find an exit before running out of oxygen. A group of scientists at the Jet Propulsion Laboratory in California are working on a tracking system called “Pointer,” that could save firefighters’ lives around the world. The lead researcher at JPL said the device of this kind could not only help firefighters, but could be used for search-and-rescue efforts, the military and even in space.
Underground detection technologies
There’s a variety of technologies that you can use to detect voids in the ground … but geology plays a major role in that process,” Mark Kaczmarek, a program manager at the Department of Homeland Security’s science and technology directorate said. “Certain types of geology will absorb certain types of radiation whether it’s acoustic, whether it’s electromagnetic, RF energy, etc.,” he explained. “You may find that one technology that you field may be suited for a particular area and its geology [but] may not be suited for another area and its geology. So if you have a place that’s highly rocky versus highly sandy versus clay — all that plays into how well any given technology works in trying to detect tunnels.”
There are several different types of tunnels that U.S. forces need to be able to find, said Lee Perren, a research geophysicist with the Army Engineer Research and Development Center. “We have very rudimentary tunnels — it’s just a hole in the ground, there’s really nothing in it. You can have interconnected tunnels, things that connect legitimate infrastructure — so they’ll go into a sewer system and cut through the wall and go over somewhere else so that they can get to where they’re trying to get to. Or you can have purpose-built, sophisticated tunnels that have all kinds of infrastructure in them,” he explained.
Locating ones that have already been completed sometimes requires different technologies than locating ones that are under construction, he noted during a media engagement in Fort Belvoir, Virginia, hosted by the Joint Improvised-Threat Defeat Organization, also known as JIDO. “When you take those perturbations and start to look at all of those different things, there are a lot of different ways that one needs to go about detecting tunnels,” he said.
ERDC has also developed a less expensive linear sensing system that uses a buried line of fiber-optic cable to monitor and process acoustic and seismic energy associated with tunnel activity. These passive detection technologies work very well if the adversary is in the act of building the tunnel. But if the tunnel already exists other types of capabilities are needed to detect them, Perren noted.
One such technology is the active seismic imager, or ASI, which is a modified Toolcat. “Essentially we have a Bobcat with a thumper,” Perren explained. “It pounds the ground and we have a stream of geophones behind it that listens for that sound to propagate through. … When there’s a hole in the ground the velocity structure changes and we can find that.” The Engineer Research and Development Center developed the border tunneling activity detection system-point, or BTADS-P. It includes an array of buried geophones that listen for construction activities. “This one is very infrastructure rich,” Perren said. “It’s somewhat more expensive to [deploy] but it’s very good at finding localizations.” It can tell operators where the underground activity is taking place, and they can adjust the depth of the array as they conduct their search, he noted.
Ground resistivity is a major area of interest. “We put electricity in the ground using electrodes,” Perren said. “When there’s a void it resists electricity. The electricity goes around it and that allows us to map its location.” Another capability is the electromagnetic induction system, or EIS. Using power and light wires, communication wires and transmitter-receivers it detects buried infrastructure that conducts electricity. It is man-portable and weighs about 30 pounds, according to ERDC officials. ERDC is trying to make the data gleaned from these systems understandable to non-experts, he noted. “We’ve developed processing routines that take that huge amount of strange-looking data — squiggled lines, this and that — and turns it into something that is more likely to be usable by a commander” such as color-coded maps, he added.
Another capability is the electromagnetic induction system, or EIS. Using power and light wires, communication wires and transmitter-receivers it detects buried infrastructure that conducts electricity. It is man-portable and weighs about 30 pounds, according to ERDC officials.
Looking beyond ground-based systems, officials are exploring the use of drones to detect tunnels from the air. Engineers at the MIT Lincoln Laboratory have been working on a new technology for JIDO. It includes an Airborg 10K unmanned aerial system developed by Top Flight Technologies. The platform carries an antenna and electronics payload and weighs about 15 pounds, said Christian Austin, an engineer with the lab. If the UAS is surveying an area and it detects a large change in the magnetic field, that indicates there is something subsurface, he explained.
“It would fly around in circles and it would generate sort of a heat map of what’s in the area — what you’re seeing below the ground — or maybe it would fly lawnmower tracks [and] the output of the system would be some sort of heat map from the algorithm,” he said. A commander could then decide what action to take against any suspected tunnels. The experimental system is currently in the demonstration phase, Austin said.
China develops AI radar for underground space detection in cities
Chinese researchers have developed a new 3D radar with artificial intelligence (AI), offering urban underground space detection a higher accuracy than previous generations. The ground penetrating radar, Eagle Eye-A, was designed and built by a research institute affiliated with the China Aerospace Science and Industry Corp.
Jiao Xiaoliang, director of the institute’s science and technology committee, said the newly-developed radar is capable of detecting soil diseases and pipelines as deep as six meters underground, with a fast response and no harm to the environment. Its detection accuracy rate is over 90 percent and its false alarm rate is less than 5 percent.
Urban underground space is always at risk of road collapses and pipeline leakages. With its AI system, the new radar will greatly boost the efficiency of auto-detection and identification while requiring less manpower in data processing. The radar is equipped with both BeiDou satellite navigation and GPS systems, which can help obtain high precision positioning of underground targets.
Space technology allows precise navigation without GNSS
The German Aerospace research center DLR developed an optical navigation and inspection system for use in environments where position determination is not possible via a satellite navigation system such as GPS or Galileo. The Integrated Positioning System (IPS) can accurately determine one’s own position without additional “prior knowledge” of the environment and without external reference points. Originally developed for missions in outer space, the scientists also see possible applications in tunnels, mines or industrial facilities.
The technology behind the Integrated Positioning System is a multi-sensor system. This draws upon various measurement techniques, which come together as so to minimize the risk of errors. Speaking with EE News Europe, the manager behind the Integrated Positioning System project – Anko Börner – explains: “The system can be used, for example, to inspect industrial plants or mines, but also to support autonomous driving.” Börner adds: “They are, so to speak, the technical eye and provide comprehensive and valuable data. Just as the eye is the most important sensory organ for humans, optical systems are the primary sensor for detecting the surroundings of technical devices.”
To confirm the reliability of the navigation results an indoor experiment was conducted at the DLR offices in Berlin-Adlershof. For this, fifteen 15 independent trials were conducted, each started at a fixed point. The experiment took place under real life conditions, such as with changing lighting, low texturing and optical disturbances generated by moving people along office corridors.
Working models of the Integrated Positioning System have been produced. An example is the DMT PILOT 3D. This technology was produced in cooperation with DLR and it provided accurate altitude determination as well as 3D documentation, to assist with aircraft navigation. As with the core technology, the DMT PILOT 3D, which comes in the form of a portable device, was originally designed for a non-Earth related purpose: to assist with missions to Mars. The technology has also been used with the inspection of mines and ships. Future developments with optical sensor systems include robotics and drones, many of which will be international collaborations.
Currently firefighters use radios, thermal imaging cameras, GPS and an alert system to communicate and find their way when trapped in a structure fire; however each of those devices has limitations. However, GPS and radio signals can often be blocked inside of steel and concrete buildings. “Inside a structure fire, everything is noisy. There is a lot going on. We may or may not be able to hear (a device), and even if we do hear it, we not be able to exactly pinpoint where (the firefighter) is,” Burbank Fire Battalion Chief Ron Barone said.
Arumugam said a device of this type could be a lifesaver for future search-and-rescue teams, but has wide potential application beyond that. “POINTER could be used in space robotics,” he said. “It could be used for tracking robots in underground tunnels, caves or under ice. They need to be able to navigate themselves, and we don’t have sensors today that would be able to track them. For us, this is a great opportunity to develop a technology for NASA and non-NASA uses.” Such technology shall also be used in Urban Warfare like current battle of U.S.-backed Iraq’s forces to retake the city of Mosul from ISIS which requires street by street, house by house, room by room operation through thick concrete jungle.
POINTER is both a technological and a mathematical breakthrough. JPL’s Darmindra Arumugam solved a problem researchers had been looking at since the 1970s. “Most of that research has focused on radio waves, which have the advantage of propagating energy over long distances. That’s made them ideal for communications and sensory technologies like radar. But they’re also notoriously unpredictable indoors: they ricochet off walls and won’t penetrate far underground. This is why you might lose your phone signal when you enter a steel-reinforced building or walk down to a basement,” writes Andrew Good Jet Propulsion Laboratory, Pasadena, Calif.
Instead, Arumugam started looking at electromagnetic fields — quasistatic fields, to be exact. These fields have been largely overlooked by researchers because they have short ranges. They’re limited to just a few hundred yards, or meters, but they don’t behave like waves. They can get around walls, offering increased non-line-of-sight capabilities.
The fields can also be tweaked to different sizes and wavelengths. Whereas waves represent energy in constant motion over time, fields can be stationary, or can change so slowly that they appear stationary (known as quasi-stationary or quasi-static). They can even be used to sense the different orientations of devices.
That last part is important. A tracking device emitting a quasi-static field would tell a receiver where it was in space, plus which way it was facing. It could tell a team commander whether a firefighter is crawling along the ground or is stationary, facing down on the floor — suggesting that person may have stopped moving.
All of this involves complicated mathematics. Arumugam developed the theory, technique and algorithms that can analyze both the electrical and the magnetic components of quasistatic fields. These algorithms are the key to being able to interpret the quasistatic fields and their signaling.
POINTER was successfully demonstrated for top leadership at the Department of Homeland Security (DHS) Science and Technology Directorate, which has funded its development. “To this day, the ability to track and locate first responders is a number one priority for disaster agencies across the country,” said Greg Price, DHS First Responder Technologies Division director. “It’s truly a Holy Grail capability that doesn’t exist today. If the POINTER project continues along its current path of success, first responders will be safer in the future.
Although there is interest in what JPL’s device can do, the technology is being developed further – mainly to make it smaller so it can be placed in a pocket or on a belt buckle. But doing something like that could take a few years.
A pocket-sized lifesaver
The technology is now being developed further so that it can be miniaturized and prepared for commercialization. Besides first responders, the need for this technology spans industrial, military and space applications.
Arumugam and his team put together a field transmitter that fits on a backpack, and they’ve shown it can be shrunk down to a device that weighs 0.4 ounces (11.7 grams). Over the next few years, JPL will be working to shrink POINTER even further, until a transmitter is small enough to fit into a pocket or on a belt buckle.
Ed Chow, manager of JPL’s Civil Program Office and POINTER program manager, said a cellphone-sized tracker would integrate well with another first responder technology called AUDREY. This artificial intelligence system would distribute real-time data across a team of first responders, but distributing relevant information depends on knowing each member’s exact location in the field.
“AUDREY is trying to provide suggested directions for firefighters lost in smoke,” Chow said. “But without knowing each member’s exact position and orientation, you can’t make those kinds of suggestions.”
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