A new underground sensor, based on a buried fiber-optic cable and powerful computer analysis, is many times more sensitive than anything currently available. The new system, called Adelos, can detect vegetation moving above ground, or underground. Many different types of pedestrians or vehicles can be identified. As Adelos developers put it, their system is sensitive enough to hear tree roots growing. Tests have also shown Adelos can detect changes in the movement of natural gas or oil in buried pipelines.
Adelos was developed from work the U.S. Navy has done to produce more effective sonar. Decades ago, the navy found that sorting out all the noise your sonar hears was a data processing job best handled by a computer. A powerful computer and a library of sounds enables you to classify sounds quickly and accurately most of the time. The simplest sonar puts a blip on a TV screen to show the contact. The more powerful your sonar transmitter is, the farther away you will detect targets. With the computer, you could more accurately identify what you had detected. This signal processing system relies on collecting as much data as possible on temperature layers, salinity and other aspects of the underwater geography as well as recordings of sea noises and other ships. Identify and classify as many of these as possible. Take into account whatever noise your own ship makes. Put all of this in an electronic library that works with the sonar. When you use the sonar, it compares the signals it received with its signal library and makes a more accurate estimate of what is out there and where it is. This only worked instantaneously with very powerful computers. Individual ships and submarines can be identified by their noise "signature". At least until they undergo some modification which changes their sound. This use of a sound library became most useful with passive (just listening) sonar. Increasingly powerful computers made it possible to use passive sonar most of the time. In the 1990s, the navy did research on a system like Adelos, but never got beyond the prototype stage. It was all this work that Adelos is using now for a land based sonar using a very sensitive fiber-optic cable as a sensor.
Adelos would work well for high security installations, like military bases, nuclear plants or laboratories. But for guarding, say, the Mexican border, or locations in combat zones (Iraq, Afghanistan), it would run into the same problems other electronic sensors have encountered. That is to say, the enemy would constantly attack the system, often eventually rendering it useless. This can be overcome in a combat zone by covering the sensor zones with weapons. Israel does this on the sensor fence around Gaza, by using remotely controlled machine-gun turrets. If the sensors pick up something, there are vidcams (with magnification) there to confirm what it is, and the remotely controlled machine-guns to fire on anyone trying to disable the sensors. In Afghanistan and Iraq, there are troops available to fire on anyone messing with the sensors.
But on the Mexican border, there is no such armed deterrent to those damaging the sensors. Adelos is buried 45 cm (18 inches) underground, easily reachable by someone with a shovel, or some explosives. But aside from situations like the Mexican border, systems like Adelos are an advance in perimeter security. Companies that run oil and natural gas pipelines are also interested, as a way to better monitor performance and catch problems early.