Home News Combat against GPS jammers

Combat against GPS jammers

UK: GNSS Availability, Accuracy, Reliability and Integrity Assessment for Timing and Navigation (GAARDIAN) Consortium has developed an equipment to provide real-time information about the reliability of GPS at airports or other sensitive locations using networks of probes, The Economist reports. Each probe can pick up GPS signals and signals from eLoran, an enhanced version of Loran, the ground-based terrestrial radio-navigation system first used by the American and British navies during the Second World War. The probes also contain a small atomic clock. By comparing the GPS and eLoran time signals with its internal clock, each probe can detect interference and determine whether it is natural or man-made.

Development of this equipment was funded by the UK Government’s Technology Strategy Board and the Engineering and Physical Sciences Research Council. Member of the Consortium are Imperial College London, University of Bath, BT Design, Chronos Technology, and the Department for Innovation, Universities and Skills, the General Lighthouse Authority, the National Physical Laboratory, and Ordnance Survey. As the uses of satellite positioning technology continue to grow, in a bid to stop deliberate and dangerous jamming of GPS signals, the Consortium was assigned this GBP 2.2 million project.

This equipment was presented during GNSS Interference, Detection and Monitoring Conference 2011 in Teddington, UK. And, The Economist has explored many similar activities in rest of the world. For instance, in America there is already a military system to spot GPS interference: the GPS Jammer Detection and Location (JLOC) system run by the National Geospatial Intelligence Agency. According to Navsys, the company that developed JLOC, it involves a network of GPS receivers capable of detecting regions of higher than normal signal levels and low signal-to-noise ratios, either of which can indicate interference. But it is unknown how many sensors there are in the JLOC system, or how accurately it can determine the location of a jammer.

Earlier, at a GNSS conference in Portland, Oregon, Phil Ward, president of Navward GPS Consulting in Dallas, Texas, proposed an innovative solution. Even low-power jammers could be detected, he suggested, if legislation was passed requiring smartphones, many of which now contain GPS receivers, to look out for jammers and warn other phones nearby if one is detected. The phones would then collectively determine the jammer’s location and report it. It is a clever idea, but it would take years to implement.

Another way to cope with jammers is to deploy backup systems that do not depend on satellite signals, but rely on terrestrial signals instead. In America radio-navigation and air-traffic-control systems based on terrestrial beacons, which predate GPS, were supposed to be phased out by 2018 in favour of satellite-based alternatives, under a modernisation programme called NextGen, overseen by the Federal Aviation Administration (FAA). Switching to satellite-based air-traffic control would, for example, allow more direct routes and save fuel, because aircraft would no longer have to follow a wiggly route from one ground-based beacon to another.

Meanwhile, it also has been observed that the ability to detect man-made interference is not much use unless the source can be located. That is where SENTINEL comes in. It is a new research project announced by Chronos Technology, the British firm that leads the GAARDIAN consortium. The idea is to use probes similar to those used in GAARDIAN, but interconnected in such a way that the position of a jamming device can be determined by triangulation. “If there is a power loss on one probe, and weaker power losses in other probes, that could help us pinpoint the source of the problem,” said Andy Proctor of Chronos to The Economist.

Source: The Economist