It’s no secret: A key development of Operation Protective Edge has been the discovery of Hamas’ tunnels emerging into Israel from Gaza. While many Hamas rockets have been neutralized by Iron Dome missiles, the tunnels boost Hamas’ efforts to kill or abduct civilians, and on the way, to attack soldiers. The tunnels are also good for hiding weapons.

The Israel Defense Forces has discovered lots of tunnels and is destroying them. Some are quite sophisticated with electricity and telephone lines, often as deep as 20 meters below ground. Hamas men use Gaza’s sandy soil to create a credible military threat.

Even though the tunnels aren’t a new issue, no technology has been found to locate them. On Sunday, the IDF talked about its programs to solve the problem, but for the time being basic intelligence is the main weapon. By 2006 more than 100 proposals and ideas had been sent on the problem to the Defense Ministry’s Administration for the Development of Weapons and Technological Infrastructure.

As things stand now, a number of technological systems are in various stages of development and testing. Among them is a system of underground sensors, developed by graduates of the IDF’s Talpiot technology program at an estimated cost of 200 million shekels ($59 million). But no new information has been released on this project — it’s not even clear if testing has been completed.

There are three main types of technology for locating tunnels; the most common is based on listening for digging. In 2009, scientists at the Technion technology institute’s Faculty of Civil and Environmental Engineering presented a method for identifying tunnels using a fiber-optic cable.

The Technion’s Assaf Klar and Raphael Linker say the system can even locate narrow tunnels more than 60 feet (18 meters) deep while keeping a lid on false alarms.

“Tunnel excavation is accompanied by the release of stresses that cause permanent — though very tiny — displacements and strains in the ground,” Klar says. “If you can measure these strains in the soil with sensitive equipment, you can find a tunnel’s location.” Tunnel excavation produces a very distinctive signal, he adds.

Just a few shekels per meter

The research lays the groundwork for an underground fence based on existing technology called BOTDR — Brillouin optical time domain reflectometry. This makes it possible to measure fiber distortion along 30 kilometers using a single device and a standard fiber-optic cable — a cable that costs only a few shekels a meter.

The system is based on so-called wavelet decomposition of the BOTDR signal, a process that breaks down the signal into simpler shapes and filters out irrelevant noise. The signals that remain are then classified by a network that locates tunnels using the computer simulation of tens of thousands of profiles, including disturbances not related to tunneling; for example, raindrops.

“The ability of the BOTDR approach to supply a continuous profile of soil distortions along the fiber-optic line — and the ability of the neural network to identify the relevant profile — are the keys to the system’s success,” Linker says.

In recent days, geology experts have made their own claims; they say technologies indeed exist to locate the tunnels, it’s just that the IDF hasn’t adopted them. “It’s not a challenge and it’s not difficult; solutions are already at hand,” says Dov Frimerman, the former geologist at the Public Works Department.

Frimerman was one of the geologists behind the research into the sinkholes near the Dead Sea. He describes another method for locating underground spaces via radar, which he used to find sinkholes at the Dead Sea.

“If I drive a car or armored personnel carrier with underground radar attached, technically there’s no tunnel I can’t identify up to 10 meters deep,” he says. “You can go over the entire border at 5 kilometers an hour and within three hours mark every tunnel.”

The radar sends electromagnetic waves into the ground and creates a picture of the soil layers — “for example, if there’s a fault. That’s how we found the [hollow] spaces under the parking lot of what was the resort village at Ein Gedi,” Frimerman says.

This American-made radar is relatively simple to use. Frimerman notes that even Hamas’ tunnels more than 10 meters deep can be found by this method when the tunnels slope up into Israeli territory. Also, sealed- and concrete-walled tunnels can be identified this way.

The NASA way

A third method for locating tunnels more than 10 meters deep is microgravimetry, which measures very small variations in gravity.

“The level of precision of this test is in parts of a billion, so there’s no hole or space in the ground up to 100 to 150 meters that can’t be identified with it,” Frimerman says. The equipment was originally developed by NASA and was used to test gravity variations to determine the distribution of minerals in the ground.

The method for locating tunnels by listening for sounds underground is called geo-seismology. It’s based on the use of microphones as underground sensors.

“When you don’t know if there are tunnels you can dig two pits 10 centimeters in diameter and 10 meters deep. You place microphones there, which cost $80 to $100 each, and connect them to equipment that costs $2,500. It’s impossible to reach a distance 100 meters from the microphones without hearing movement in the headphones,” Frimerman says.

“If the tunnel is ready, you can hear whoever is walking in it; you can distinguish between the steps of a person and the steps of a fox, for example. It’s impossible to dig at a distance of 100 to 150 meters from the microphones without noticing the digging.”

For a relatively low price the IDF could spread microphones 100 meters apart and cover the entire Gaza border, Frimerman says. If the position where soldier Gilad Shalit was abducted in 2006 had two microphones near the fence 100 meters apart, no one could have walked through the tunnel without being heard, he adds.

“The technology exists; it’s not clear why they aren’t using it,” he says. “We proposed it 30 years ago.”

Frimerman’s claims are also backed up by one of Israel’s best known geologists, Col. (res.) Yossi Langotsky, the man behind Israel’s massive oil-and-gas discoveries off the coast. He also set up Military Intelligence’s special-operations division and is a two-time winner of the Israel Defense Prize.

Langotsky says it was a mistake not to give Military Intelligence and the IDF’s technological units responsibility for finding a solution to the tunnel problem. Instead, too much money has been wasted, he says.

For secrecy’s sake, the IDF, the Defense Ministry and the defense contractors developing the technology — such as Elbit Systems and Rafael Advanced Defense Systems — declined to answer TheMarker’s queries on the matter. Scientists from the Technion, where two teams are working on the tunnel problem, also declined to comment.

The Defense Ministry said: “All the technologies mentioned in the story are very well known to the defense establishment and have been examined in depth in light of the threat and soil conditions in the sector. For reasons of classified information, we are prevented from providing details on the use of each of these technologies.”

According to a senior officer, the IDF has tried almost every technology in an attempt to locate the tunnels, with the help of both geologists and the U.S. military. But as a senior officer in Southern Command put it: “Not a single system that is capable of locating tunnels is being created.”

The U.S. Department of Homeland Security has made tunnel-location technology a high priority, too — to stop the smuggling of people, drugs, cash and weapons from Mexico. In recent years, the Americans have also used microphones in a system known as Border Tunneling Activity Detection.

Defense contractor Lockheed Martin is developing a radar system to identify tunnels, but in the meantime the United States is largely relying on good-old-fashioned informers — and luck.