Finding Mobile GPS Jammers using ad-hoc networks

GPS/GNSS jamming systems (sometimes referred to as personal privacy devices) are illegal, and for good reason - they're potentially dangerous.

As reported by InsideGNSS: GPS/GNSS technology constitutes a fundamental element for new intelligent transport systems (ITSs) and their applications, such as advanced driver assistance, dangerous goods tracking, and distance- based toll systems. Due to the weak strength of navigation signals from distant satellites, however, these applications are threatened by malicious as well as unintentional interference.

In particular, so-called in-car jammers — also known as “personal privacy devices” — represent a serious threat for GNSS-based systems and applications.

A common Chinese made GPS Jammer - illegal in the USA
purchasable in the UK, but illegal to use.

These jammers are cheap devices able to obscure, partially or totally, the navigation signals received not only by the operator’s vehicle but also by other receivers in the vicinity.

The introduction of standards for vehicular ad-hoc networks (VANETs) sometimes referred to Car2Car or V2V systems, enables the exchange of data regarding detected interference events. This data exchange can be used to enhance the awareness of interference sources, allowing their localization and mitigation, thus increasing the reliability of future ITSs.

Jamming devices could be thwarted using ad-hoc
vehicle networks - which are being developed in the USA
as well as the EU

GNSS Interference Detection and Localization 
Interest in developing GNSS interference detection and localization capabilities has increased steadily in the last few years. The first efforts in this direction have come for military applications, like the jammer detection and location (JLOC) system developed and propsed by Dr. Alison Brown with NAVSYS. This system provides situational awareness on GPS interference events to U.S. military personnel and predicts effects worldwide to enhance battlefield situational awareness and mission planning.

In the case of identified GPS threats, the system disseminates alerts and reports to subscribed JLOC users through the SIPRNet (Secure Internet Protocol Router Network), a system of interconnected computer networks used by the U.S. departments of defense and state to transmit classified information. The core element is the JLOC master station, operated by the U.S. National Geospatial-Intelligence Agency (NGA), which collects information on interference events through dedicated sensors incorporating GPS receivers. These sensors generate reports when they detect signal degradation as measured by carrier-to-noise ratio (C/N0) readings.

For the actual localization of the interference source, angle-of-arrival (AOA) information is collected from receivers capable of digital beam-forming, while time-difference-of-arrival (TDOA) measurements are computed with snapshots of data from multiple locations.

Further studies have been done to integrate mobile devices, such as cell phones, into the network of sensors. Also airborne sensors that can be carried on small unmanned aerial vehicles (UAVs) are envisaged for possible use in future jammer location systems.

Small UAV (drones) could be used to identify GPS jamming
sources in the USA

Interference monitoring and localization systems have been developed to protect safety critical aviation services as required by the International Civil Aviation Organization (ICAO) for GPS-based approach procedures.

In this application, location of interference sources is commonly based on direction-finding sensors. For example, in the United States the localization of interference is performed by the combined use of airborne (AIMDS), transportable (TIMDS), portable (PIMDS), handheld (HIMDS), and fixed (FIMDS) interference monitoring and detection systems. In Europe, similar systems are operated, such as the so-called GIMOS (GNSS Interference Monitoring System) in Germany.

A GBAS reference station outside of an airport.

The problem that can be caused for aviation by GPS jammers became very visible in November 2009 at the Newark Liberty International Airport (New York City). Without an appropriate interference localization system in place, it took more than three months to find the reason for periodic outages of the airport’s ground-based augmentation system (GBAS) reference stations: a GPS jammer transmitting from a vehicle passing near the airport. The airport eventually tackled the problem by making infrastructural changes, such as relocating the GBAS reference antennas over a wider area and enhancing interference detection and localization capabilities.

For maritime applications, the threat represented by jammers became evident in 2008, when the General Lighthouse Authorities of the United Kingdom and Ireland (GLA) conducted a series of sea-trials with the aim of characterizing the full effects of GPS jamming on safe navigation at sea. The test unveiled serious effects on GLA differential GPS (DGPS) reference stations and GPS receivers on ships, as well as radar systems using GPS as their time reference.

These results gave rise to the GAARDIAN/SENTINEL projects. The GAARDIAN project developed and deployed probe sensors at various locations around the United Kingdom and Ireland to continuously report on the integrity, continuity, accuracy, and reliability of GPS signals. The monitoring network was then further expanded by including the Ordnance Survey’s OS Net, consisting of more than 100 continuously operating GNSS receivers. This system bases detection of anomalies on a mask for C/N0 measurements.

The SENTINEL project later added interference localization capability to this network through the use of handheld GPS interference detection devices. AOA, TDOA, and differential-received-signal-strength (DRSS)–based geolocation are currently under investigation.

A down-to-earth alternative

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 favor of satellite-based alternatives, under a modernization program 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.

In a paper presented at the NAV10 conference in London in December, Mitch Narins, chief systems engineer at the FAA, and colleagues described the Newark jamming incident as “a valuable lesson” because it highlighted the risks of becoming too dependent on satellite-based systems that were vulnerable to disruption. Mr Narins and his team are now investigating whether the old-style terrestrial systems can be modernized and extended to provide a backup that could take over in the event of GPS failures. They expect to make their recommendations in 2013 or 2014, in time for implementation to begin in 2016.

An eLoran reference station

Elsewhere, eLoran is another non-satellite-based alternative which has many cheerleaders. It is an enhanced version of Loran-C, which is itself an improved version of the original Loran (“long-range navigation”) system developed in the 1940s. Once widely used in America, Japan and parts of Europe, Loran fell out of favor with the emergence of satellite-based systems. But its proponents have continued to develop the technology, and eLoran is now accurate to within 10 meters, which is comparable to GPS. “It is terrestrial as opposed to spaced-based, uses very high-powered signals rather than low-powered ones and it's very low frequency instead of high,” says Sally Basker, president of the International Loran Association. “All of which means its failure mechanisms are different to GPS and other satellite-navigation systems.”

Enthusiasm for eLoran is strongest in Britain, where the government awarded a 15-year contract in 2007 to develop eLoran for use by shipping in western Europe. A ministerial decision to move from the development to the operational phase is expected shortly. In the United States and Canada, however, Loran-C transmitters were switched off last year. After a long debate about the merits of keeping the system going, Barack Obama declared it outdated. The House of Representatives has given the Department of Homeland Security until April to decide whether a single, national GPS backup system is required. Which technology would be used to build such a system remains to be seen.

In a way, GPS has become a victim of its own success. Because it is used for such a wide range of civilian purposes, when somebody wishes to disable one GPS-based system, their actions can also disrupt other, unrelated systems. The benefits of satellite positioning are undeniable, and they are only likely to increase in future. But it is now clear that fully realizing those benefits depends on putting systems in place to mitigate against deliberate and accidental interference, and to provide an independent backup that does not rely on the delicate trilling of distant satellites. 

GPS jamming affects everyone, even the London Stock Exchange

As reported by The Economist: Every day for up to ten minutes near the London Stock Exchange, someone blocks signals from the global positioning system (GPS) network of satellites. Navigation systems in cars stop working and time-stamps on trades made in financial institutions can be affected. The incidents are not a cyber-attack by a foreign power, though. The most likely culprit, according to Charles Curry, whose firm Chronos Technology covertly monitors such events, is a delivery driver dodging his bosses’ attempts to track him.

The signals are weak. Mr Curry likens them to a 20-watt light bulb viewed from 12,000 miles (19,300 km). And the jammers are cheap: a driver can buy a dashboard model for about £50 ($78 USD). They are a growing menace. The bubbles of electromagnetic noise they create interfere with legitimate GPS users. They can disrupt civil aviation and kill mobile-phone signals, too. In America their sale and use is banned. In Britain they are illegal for civilians to use deliberately, but not, yet, to buy: Ofcom, a regulator, is mulling a ban. In recent years Australian officials have destroyed hundreds of jammers.

In the right (or wrong) hands, they are potential weapons. Britain’s armed services test the devices in the Brecon Beacons in Wales, a military training area. North Korea uses big lorry-mounted versions to block GPS signals in South Korea. Starting with a four-day burst in August 2010, the attacks, which come from three positions inside the North, have lengthened. In early 2012 they ran for 16 days, causing 1,016 aircraft and 254 ships to report disruption.

North Korea GPS jamming systems

Mr Curry worries that criminals or terrorists could knock out GPS for an entire city or shipping lane anywhere in a flash. Even without North Korean-sized contraptions, the jamming can be substantial. Suitcase-sized devices on sale on the internet claim a range of 300-1,000 metres.

Malfunctioning satellites and natural interference from solar activity have hit GPS signals and sent ships off course. David Last, a navigation expert, says an accidental power cut, perhaps caused by a jammer taken on board a car ferry, could cause a shipwreck. Generating a false signal—spoofing—is another threat. In December 2011 Iran said it had spoofed an American drone before capturing it (most experts dismiss the claim). So far effective spoofing seems confined to laboratories, but Mr Last says some governments are already taking countermeasures.

One solution is a different means of navigation. In April South Korea announced plans for a network of 43 eLoran (enhanced long-range navigation) ground-based radio towers, based on technology first used in the second world war. It uses a far stronger signal than GPS, and should give pilots and ships’ captains a safer alternative by 2016. With Chinese and Russian help, South Korea hopes to expand coverage across the region.

Britain’s General Lighthouse Authorities (GLA) are following suit with seven new eLoran stations. Martin Bransby, an engineer with the GLA, says this will replace visual navigation as the main backup for GPS. It will be working by mid-2014, and cost less than £700,000 ($1.08M USD); receivers cost £2,000 ($3,077 USD) per vessel. By 2019 coverage should reach all big British ports.

America’s military-research agency DARPA has an experimental “single-chip timing and inertial measurement unit” (TIMU). When finished, according to the project’s boss, Andrei Shkel, it will use tiny gyroscopes and accelerometers to track its position without using satellites or radio towers. America’s White Sands missile range in New Mexico is installing a “Non-GPS Based Positioning System”, using ground-based antennae to provide centimeter-level positioning over 2,500 square miles. In May the Canadian government said it would splash out on anti-jam upgrades for military aircraft.

A new version of the US air force’s bunker-busting bomb, designed in part to destroy Iranian nuclear facilities, includes technology to prevent defenders from blocking its satellite-based guidance systems. MBDA, a European missile firm, is working on similar lines.

But for many users, GPS and other space-based navigation systems—which include Russia’s GLONASS, China’s partly complete Beidou, and an as-yet unfinished project by the European Union (Galileo)—remain indispensable and ubiquitous. They are also vulnerable. For those whose lives or livelihoods depend on knowing where they are, more resilient substitutes cannot come fast enough.

Hybrid location technologies: MEMS Sensor Positioning

Most smart phones include several MEMS sensors. The data they provide
helps make location possible when GPS signals are compromised.

As continued from our previous report: Many smart phones are equipped with sensors that track device orientation and movement to enable a host of applications, such as gaming and compasses (Table 6). These sensors usually include microelectromechanical systems (MEMS).

For example, accelerometers measure acceleration based on user movement. Generally, a three-axis accelerometer measures the change in user velocity position in a variety of cases, such as walking, running, falling, and vibration.

Gyroscopes measure rotational velocity. They also are implemented across three axes. Gyroscope measurements provide orientation. A combination of accelerometer and gyroscope measurements in three dimensions can be used to continuously track user position.

Magnetometers measure the earth’s magnetic field as well as any ambient magnetic influences. They are used for mapping and compass functions (potentially in conjunction with accelerometers). And, barometers measure the altitude based on air pressure changes and can be used to find a user’s position while moving up in altitude (Fig. 4).

Physical readings from the sensors are typically sent to the inertial measurement unit (IMU), which collects data from the inertial sensors, formats them, and delivers them to the sensor location subsystem—the inertial navigation solution (INS). Yet there’s a key difference in the positioning technique used by the INS compared to other location methods.

A-GNSS and Wi-Fi positioning and cellular positioning methods feature an absolute position computation process. The INS uses dead reckoning. It’s given a starting position (perhaps from an A-GNSS fix) and then uses sensor data such as speeds and angular direction to advance the position over time. Eventually, the uncertainties in the reported sensor data add up, and a new, accurate reference position is required to start the dead reckoning process over.

While GPS, Wi-Fi, and cellular technologies provide the user’s position on the map, sensors can provide an idea of how the mobile device itself is moving—whether it’s being turned, set on a table, or thrown. This fine-grade information can be very useful for enabling applications such as gaming. It also presents a challenge.

If purely position calculation is of interest, then the positioning engine must be able to intelligently filter out extraneous effects such as the rhythmic motions of walking or running and holding the handset in different positions while talking. Different people have different usage profiles, so the sensor’s positioning engine must be able to robustly handle a variety of different scenarios.

DARPA Seeks to Eliminate GPS Dependence

As reported by GPSWorld: Call it irony, poetic justice, or just the nature of the beast. The same impulse that led to the invention of GPS now has engendered a drive to beget non-GPS.

In the 1970s, the U.S. military began putting together a program “to drop five bombs in the same hole.” The program office, to the wall of which that mission statement was tacked, went on to develop the first satellite navigation positioning system: GPS. In 2012, the U.S. Defense Advanced Research Projects Agency (DARPA) declared that this system no longer sufficed for reliable delivery of precision munitions under every circumstance.

“More than 98 percent of the missiles currently in the U.S. arsenal have mission durations of less than 20 minutes, and today, almost all of these missions are critically dependent on GPS for achieving the required level of delivery accuracy,” a communiqué stated.

Because of vulnerability to jamming, spoofing, and other intentional or unintentional modifications of position, orientation, and time information, the agency has put forth a new goal “to completely eliminate dependence on GPS or any other external signals during the mission and rely solely on self-contained solutions such as inertial navigation,” which is immune to such extrinsic forces.

The Chip-Scale Combinatorial Atomic Navigator (C-SCAN) program has made 10 exploratory grants to investigate and develop this concept, to large corporations, a small start-up, national labs, and academic groups. Only one has been announced, by contracting agent Wright Patterson Air Force Base, to AOSense. DARPA wishes to emphasize that this is a sample of what is happening in C-SCAN, and should not been viewed by readers as the only technical approach paving the way.

The company, located in Sunnyvale, California, has gotten busy building an experimental navigation-system-on-a-chip that combines traditional, solid-state, and atomic inertial guidance technology. Their goal: create a sensor on a chip that works reliably, without drift, over considerable distances for at least 20 minutes.
AOSense is exploring how to shrink and fabricate atomic sensors together with high-performance solid-state inertial sensors. DARPA hopes the C-SCAN program will lead to a breed of inertial microsystems, with a wider range of operating conditions and greater immunity to the environment, reduced start-up time, increased sensitivity, and improved bias and scale factor stability. Oh, and not cost too awful much per piece.

Another project at Northrop Grumman seeks to develop a  micro-gyro for personal and unmanned vehicle navigation.

Despite impressive micro-PNT work to date, current mechanisms remain complex, bulky, power-hungry — and pricey. They have limited resolution and poor long-term stability. Alternative forms give excellent resolution and bias stability, but are limited in bandwidth and generally do not allow high-frequency measurements.

Make no mistake, however. Yankee (and whatever other forms that can be brought to bear) ingenuity will, eventually, win the day. Where then will GNSS find itself?

NTSB calls for wireless technology to let all vehicles 'talk' to each other

As reported by NBC: Federal safety authorities Tuesday called for all U.S. cars, trucks and buses to come equipped with technology that would allow them to "talk" to one another to help avoid accidents.

The proposal was one of three the National Transportation Safety Board (NTSB) made Tuesday in its investigation of two school bus accidents last year. The main focus was an accident near Chesterfield, N.J., that killed an 11-year-old girl, but the board also looked at evidence from a similar accident in Port St. Lucie, Fla., that also killed a student. In both accidents, the school buses collided with trucks at intersections.

In a summary report, the board recommended that the National Highway Traffic Safety Administration (NHTSA) develop standards for "connected-vehicle technology" — wireless components that would let vehicles communicate on the road. The full final report is expected in about three weeks.

With those standards in place, "NHTSA can then require this technology to be installed on all highway vehicles," Deborah Hersman, chairman of the NTSB, said at the board's meeting Tuesday. "This technology more than anything else holds great promise to protect lives and prevent injuries."

The Alliance of Automobile Manufacturers, the trade group for most of the major automakers — which is working with the NHTSA on research and development of connected-vehicle technology — didn't immediately respond to a request for comment.

But in testimony before the Senate Transportation Committee in May, Mitch Bainwol, the alliance's president and chief executive, raised doubts that such systems could be feasible in the near term.
Aftermarket component systems would need to be overhauled, a patchwork of state and federal laws would have to be unified and legal questions of liability surrounding operating cars with automated systems would have to be hashed out, he said.

"The question of who is responsible — when (and) for what — will need to be addressed," Bainwol said.
Last August, the NHTSA began conducting a yearlong study of 3,000 connected vehicles in Ann Arbor, Mich., using WiFi-like components that send electronic data messages back and forth and translate the data into a hazard warnings for the drivers. The test is focusing on safety at intersections, lane changes and rear-end accidents involving vehicles stopped at intersections.

"Vehicle-to-vehicle communication has the potential to be the ultimate game-changer in roadway safety — but we need to understand how to apply the technology in an effective way in the real world," NHTSA Administrator David Strickland said when the test was launched.

Regarding the two school bus crashes, the NTSB also recommended tougher qualifications for agencies that oversee the medical certification of commercial drivers. The summary report found that the driver of the bus in the New Jersey crash was fatigued and was using sedatives, and it said he likely wouldn't have been issued a license had he disclosed all the medications he was taking.

In an animated reconstruction of the New Jersey crash, NTSB investigators depicted the truck's speeding into the intersection just as the school bus was leaving it. The reconstruction shows the truck ramming into the left rear side of the bus, which spins off the road.

The truck driver was speeding and was carrying an overweight load in a truck that had defective brakes, the NTSB said.

And the NTSB also looked at the effectiveness of the seat belts on the bus in New Jersey — one of only six states that require school buses to have them.

The board said seat belts and shoulder belts would have helped to reduce flailing injuries, but it stopped short of recommending their mandatory use nationwide.

Instead, it recommended that school districts offer training to bus drivers, students and parents to drive home "the importance of wearing seat belts" in the states that do require them: California, Florida, Louisiana, New Jersey, New York and Texas.

The National Association for Pupil Transportation said it was eager to work with the NTSB and the NHTSA "to evaluate the practicability of implementing the recommendations that have been offered today."

Lockheed Martin Prototype to Help Prep for GPS III Launch

As reported by GPSWorld: Lockheed Martin has delivered a full-sized, functional prototype of the next-generation GPS satellite to Cape Canaveral Air Force Station to test facilities and pre-launch processes in advance of the arrival of the first GPS III flight satellite.

The GPS III Non-Flight Satellite Testbed (GNST) arrived at the Cape on July 19 to begin to dry run launch-base space-vehicle processing activities and other testing that future flight GPS III satellites will undergo. The first flight GPS III satellite is expected to arrive at the Cape in 2014, ready for launch by the U.S. Air Force in 2015.

The GNST arrived at the Cape by Air Force C-17 aircraft from Buckley Air Force Base near Lockheed Martin’s GPS III Processing Facility (GPF) in Denver, Colorado. Prior to shipment, the GNST was developed and then completed a series of high-fidelity activities to pathfind the integration, test and environmental checkout that all production GPS III satellites undergo at Lockheed Martin’s new satellite manufacturing facility.

An innovative investment by the Air Force under the original GPS III development contract, the GNST has helped to identify and resolve development issues prior to integration and test of the first GPS III flight space vehicle (SV 01).  Following the Air Force’s rigorous “back-to-basics” acquisition approach, the GNST has gone through the development, test and production process for the GPS III program first, significantly reducing risk for the flight vehicles, improving production predictability, increasing mission assurance and lowering overall program costs.

“We call the GNST a ‘pathfinder’ because it has truly blazed the trail for every one of our GPS III processes from initial development, production, integration and test, and now pre-launch activities,” explained Keoki Jackson, vice president for Lockheed Martin’s Navigation Systems mission area. “All future GPS III satellites will follow this same path, so the GNST was a smart initiative to help us discover and resolve any issues in advance, implement production efficiencies, and ultimately save a tremendous amount of time and money in the long run.”

GPS III is a critically important program for the Air Force, affordably replacing aging GPS satellites in orbit, while improving capability to meet the evolving demands of military, commercial and civilian users. GPS III satellites will deliver three times better accuracy, include enhancements which extend spacecraft life 25 percent further than the prior GPS block, and a new civil signal designed to be interoperable with international global navigation satellite systems.

Lockheed Martin is currently under contract for production of the first four GPS III satellites (SV 01-04), and has received advanced procurement funding for long-lead components for the fifth, sixth, seventh and eighth satellites

Adaptive Filtering for Errant GPS Data in Smartphone and Vehicle Tracking Systems

loop of errant position data - only about
5.2km was actually traveled.

The route shown to the left is for a pedometer application on my iPhone; one of the many free applications available.  You'll note a loop in the middle of the run - where in fact there was no actual loop; I followed streets and highways and took the same path back that I took out.  When I posted the data on Facebook, my friends and family congratulated me on such a long distance over a short time period - I had to explain that the data wasn't accurate, which I only knew from experience on this route - and by looking closer at the actual trail that the application created for me on a separate page.

So what happened?  GPS data (which is a key source of how the pedometer generates it's data) from time to time can lose accuracy - it's a fact of life; nothing is infallible.  This can be attributed to several potential factors: inadvertent or intentional signal jamming, loss of signal strength in heavy tree foliage, multipathing, an impaired view of the sky combined with a poor satellite constellation, ionospheric interference, space weather interference or signal degredation, GNSS systemic issues, etc.

This reminded me of the reason we developed adaptive filtering processes into our vehicle tracking software.

Big Data - Real-time position data
Smartphone and vehicle tracking systems are a kind of 'Big Data' system that is continuously absorbing position data from the field - pre-processing some of the data, but storing it away for use and forwarding to customers; either in near-real-time, or at a later date.  Some errant data can be identified and eliminated immediately, but most data must be evaluated later for cohesiveness.  Data errors are not always multidimensional: in some cases all but one particular portion of the data is correct.

Adaptive GPS Filtering

A position taken under an overpass inadvertently increased
the estimated speed of the vehicle to 99MPH, which triggered
an over-speed alert, which in turn warranted an investigation.
The driver was cleared of any wrong doing after the analysis.

By looking at moving 'windows' of patterned data, the system can evaluate positions and select those that seem to be out of sync with prior patterns, by evaluating significant speed deviation, sudden direction changes, sudden changes in available satellites for a location calculation and position data that appears 'out of place'; or combinations of the prior conditions.  The larger the data-set to work from, especially when looking backward and forward, the better these types of analyses perform - and the more likely they are to find and remove the errant data while leaving valid data in-place.

Endpoints and window size of data
Errant data at the beginning or end of a reported sequence of data can be more difficult to detect - but one easy way to fix that is by changing the time window; by choosing an earlier start or stop time for the report.  As the window narrows, this gets more and more difficult to determine - such as in instantaneous alert reporting - i.e. over-speed alerts.

Fleet Managers - the human brain as a Big Data Engine
In a prior report we discussed how fleet managers can act a a 'Big Data' Engine, evaluating data in order to determine if it's valid, and to give it proper meaning.  In the above example, it was difficult to tell from the position report or the over-speed alert if this was an actual violation by the driver or not. Though positions prior to and after the report looked normal, it was possible for the driver to have increased their speed long enough to reach the alert trip - but by pairing the data with the satellite map data, we were able to determine that there was an impaired view of the sky, and possible multipathing - eliminating the point as a possible traffic violation.  This kind of analysis would be difficult or impossible with today's technology; there is still a place for humans as part of the critical evaluation of events.

In the future, use of inertial measurement unit technology will be able to help 'fix' the problem at the source by providing an estimate that the GPS signal can corroborate with or can identify as 'challengable'.

In the original example, it appears that there is an intermittent wide-band jamming source in the area that I happened to be traveling.