Applications and vulnerabilities of satellite navigation systems in global freight transportation

Part of a series on complexity and risk in freight transportation

Note: This post is part of a series on complexity and risk in freight transportation systems. Part 1 (Evolution) is divided into two posts: Global Freight and Land-Based Freight (coming soon). Part 2 (Risks) is divided into multiple posts including: this one, Globalization, Trade Policy, Giant Ships, and GHG Emissions, Ship Lifecycle (coming soon), Cybersecurity (coming soon), and others to come. Part 3 (Leverage Points) will follow.

The Jin Nui Zou is an oil tanker owned by the China Shipping Tanker Company Ltd. [1] On September 5th, 2019 the vessel entered the Port of Dalian oil terminal in Northeast China. Dalian is the headquarters of two subsidiaries of COSCO shipping which were sanctioned by the U.S. government for importing Iranian crude oil. [2] Like all large cargo and passenger vessels, the Jin Nui Zou is equipped with an automatic identification system (AIS). This system transmits the ship's identity, location, direction, speed and other characteristics to nearby vessels and a network of AIS stations and satellites. AIS tracking of the Jin Nui Zou shows it entered the Port of Dalian on a normal course. [3] As the ship approached the terminal from the southeast, however, the vessel's AIS positions suddenly scatter throughout the port with some showing the vessel traveling at a very high speed. Eventually the vessel's AIS positions settle into a circular pattern centered around a location inside of the oil terminal tank field—on land.

AIS is a cornerstone of modern marine navigation. It is used by vessel operators to avoid collisions with other vessels, and by shipping companies to track and manage their fleet. AIS also is used by a number of authorities to monitor the activities of cargo and fishing fleets, for search and rescue operations, for aids to navigation and for other applications. AIS does not work, however, without the precise location and time provided by GPS and other global navigation satellite systems (GNSS). Global positioning, navigation and timing (PNT) provided by GNSS forms the foundation of marine navigation, railroad operations, trucking operations, military operations, cellular communication, financial exchanges, power systems, driving with Google Maps, Uber, DoorDash, and countless other applications. GPS and the other GNSS constellations are the only true global utility—free, ubiquitous and essential. The economic value of GPS is estimated in the trillions of dollars. And in the U.S. we do not have a backup system.

GPS is one of four global systems—BeiDou (China), Galileo (E.U.), GLONASS (Russia) and GPS (U.S.)—and three regional systems (RNSS)—NavIC (India), BeiDou Compass (China) and QZSS (Japan). Over 75 percent of GNSS devices can use signals from multiple constellations. [4] Developed by the U.S. military in the 1970s, GPS consists of a core constellation of 27 satellites—31 are currently in service—which fly in medium Earth orbit approximately 20,200 km (12,550 miles) above sea level. [5] The satellites and other infrastructure are managed by the U.S. Space Force—a new branch of the military under the Secretary of the Air Force. Each satellite has a precise atomic clock and broadcasts a radio signal providing its location, status and time. Civilian users were given access to the full, non-degraded signal in 2000. GPS has a new, more secure M-Code signal nearing completion that will be restricted to military use. [6] Encryption with M-Code will combat the increasing threat of GPS interference.

The tracking phenomenon seen with the Jin Nui Zou is one of tens of thousands of GNSS "spoofing" incidents documented over the last decade. Similar circular patterns were seen near 15 other Chinese oil terminals in the summer and fall of 2019. [7] A 2019 report by C4ADS—an organization that researches global conflict and security issues—documented 9,883 instances across 10 locations that affected 1,311 civilian vessel navigation systems near Russian occupied territories and overseas military facilities. [8] It also found a correlation between GNSS interference events and movements of the Russian head of state, interference emanating from a Russian airbase in Syria and interference along the Russian coast and Crimea in the Black Sea emanating from a "palace" reported to be built for President Putin.

Interference with GNSS signals is not a new phenomenon. Devices that are able to overpower faint GPS signals ("jamming") were used in the 1991 Persian Gulf War several years before GPS was fully operational and almost a decade before the non-degraded signal was made available to civilian users. Jamming GNSS radio frequencies blocks reception to a receiver, preventing it from calculating a geographic location or accessing the timestamp. The incidents at Chinese oil terminals and Russian facilities used a more sophisticated device with the ability to mimic or "spoof" a legitimate GNSS signal in order to manipulate position and time data. Both jamming and spoofing are a threat to any service relying on PNT. Spoofing, however, poses a more serious threat and there are few countermeasures for the billions of devices in use today.

GPS was originally developed for military navigation and pinpoint weapons delivery—to "drop 5 bombs in the same hole." [9] Today, there is almost one device with a GNSS receiver for every person on the planet. [10] The vast majority of these devices are smartphones, followed in a distant second by wearable devices. [11] While smaller in number, GNSS is used for navigation and timing in transportation, energy, financial markets and other segments of the economy. GNSS satellites are equipped with extremely precise atomic clocks which serve as the reference time for power grids, cellular communications networks, financial markets and other applications. To determine its location, a GNSS device compares the time it receives a signal to the time the satellite sent it and calculates a geometric sphere. With signals from four separate satellites, a precise location can be determined by calculating the point where the spheres intersect.

The accuracy of positioning based on GNSS depends on satellite geometry, signal blockage, atmospheric conditions and the receiver's design/capabilities. To improve accuracy, ground-based and satellite-based augmentation systems have been developed. There are four primary satellite-based augmentation systems (SBAS) serving specific geographic areas including the U.S. Wide Area Augmentation System (WAAS) and European Geostationary Navigation Overlay System (EGNOS). SBAS satellites broadcast correction signals that are used for signal integrity, wide area corrections and as an extra navigation signal in some cases.

Ground-based augmentation systems use a network of stations with precise known locations. These stations continuously compare their position based on GNSS signals with their known location, and broadcast a correction signal that can be used by differential GNSS receivers to improve the accuracy of their position. The U.S. Coast Guard operated a ground-based differential GPS (DGPS) with 85 broadcast stations that provided nationwide coverage for land navigation and 50 nautical miles offshore. Developed in the late 1980's and early 1990's, DGPS improved positioning accuracy from several meters to less than one meter. With the improved accuracy of un-augmented GNSS and the use of satellite-based augmentations systems, however, DGPS was no longer need. After more than 25 years of service, the Coast Guard switched off the final four stations located in the Great Lakes and the St. Lawrence Seaway in June of last year. [12]

Marine Applications

The origin of navigational techniques and technologies is the ocean. Around three thousand years ago, humans began exploring the Pacific crossing hundred of miles of open ocean in boats made from hollowed-out trees with leaves woven together for sails. [13] They accomplished these voyages long before the compass, sextant and other modern navigational tools would be developed. "In seafaring and navigational terms, while the Europeans were discovering fire, the Polynesians had already split the atom." [14]

Three thousand years later, ocean navigation would be one of the earliest applications of most modern navigation aids. The first commercial GPS devices made by Trimble and Magellan were targeted to the recreational sailing market. Today, GNSS-based technologies are used for many applications in the maritime industry including vessel monitoring, traffic management, port operations and search and rescue (SAR). Most vessels are equipped with augmented GNSS devices for more accurate positioning. New equipment leverages SBAS—including WAAS and EGNOS—and a number of countries in Europe and around the world continue to provide DGNSS coverage in coastal areas. The International Association of Marine Aids to Navigation and Lighthouse Authorities (IALA) established the standard used for DGNSS radar beacons. LORAN, another ground-based system, can be used for harbor entrance and approach maneuvers where these systems are available as well. [15]

Since December of 2004, the use of automatic identification systems (AIS) with GNSS receivers is required by the International Maritime Organization (IMO) for all ships 300 gross tonnes or larger on international voyages, cargo ships 500 gross tonnes or larger not engaged in international voyages and all passenger ships regardless of size. [16] The IMO also requires large passenger and cargo ships to be equipped with electronic chart display and information systems (ECDIS), which plot and monitor a ship's voyage with real-time information. [17]

AIS is a bidirectional system. The transponder automatically broadcasts a ship's position, identity, type, course, speed, navigational status and other safety-related information to other vessels, shore-based AIS stations and a growing network of AIS satellites. The transceiver simultaneously receives similar information from nearby vessels and shore-based stations. Since AIS is not required for all vessels, ship operators use a combination of AIS, radar and other tools for navigation and collision avoidance. Shipping companies use AIS to track vessels and mange fleet operations. AIS also is used by a number of authorities to track and monitor the activities of cargo and fishing fleets, for search and rescue operations, for aids to navigation and other applications. [18]

Rail Applications

Railways are a difficult environment for GNSS reception, and the industry has been slow to adopt the technology. Tunnels, cuttings and urban canyons all block or degrade signals. GNSS may not meet the level of reliability required for safety-critical rail systems as well. To compensate for these limitations, rail applications use hybrid systems that combine GNSS with track sensors, Doppler radar, Lidar and other technologies. Most railways use some form of mapping system based on GNSS and GIS technologies to track train locations and network infrastructure. GNSS-based technologies also are now being tested and deployed in automatic train control (ATC) systems, track control systems, passenger information systems and fleet management systems. [19]

One of the first applications of GNSS for ATC is enhanced odometry—measuring distance travelled. Traditionally trains are tracked using devices that detect the presence or absence of a train on the track (track circuits) or count the number of axles entering and leaving sections of track (axle counters). These devices are installed within the track network and provide a course determination of the position of trains within track segments. High-speed trains in Europe are monitored using more advanced on-board sensors—Doppler radar, tachometers and inertial sensors—and radio frequency transponders installed within the track network (balises). Train odometers calculate distance traveled based on signals from these transponders and the speed of the train—a technique known as dead reckoning—which is more precise than track circuits and axle counters. Radar-based sensors, however, do not perform well in winter conditions or with slab track. Slab track is a rail embedded within a solid—typically concrete—underlayment rather than loose gravel. It is increasingly common for high-speed railways, in tunnels and on bridges. Balises, axle counters and other sensors embedded in the track network are expensive to install and maintain as well. Mobile GNSS-based receivers, in contrast, are affordable and provide more accurate, real-time positioning—as long as the receiver has reception. [20]

Augmented GNSS has been tested within railway control systems for automatic level crossings (ALX). These systems detect when a train approaches a road crossing, and activate road traffic signals and barriers. Traditional ALX systems use fixed sensors within the track and activate traffic controls based on the maximum speed a train is allowed to travel in the segment of track. Trains equipped with augmented GNSS receivers, however, can track their real-time position and speed. The ECORAIL project in Europe demonstrated how a signal sent from an approaching train can be used by the ALX system to time road closure based on the speed of the train and improve traffic flow. [21]

In the U.S., positive train control (PTC) technology—most equipped with GPS receivers—is now required on 40% of the nation's Class I rails. PTC technology tracks a train's position and automatically deploys braking to prevent collisions, over speeding, and movement into closed work zones or past switches in the wrong position. The Rail Safety Improvement Act of 2008 mandates installation of interoperable PTC on main lines which move passengers, hazardous materials or a significant amount of freight. [22] The mandate came after a head-on collision between a freight train and a commuter train in Chatsworth, California in 2008. The accident killed 25 and injured 135. Railroads have struggled to meet the timetable set by the Act and received multiple extensions. According to the NTSB, 20 incidents could have been prevented by PTC since the 2008 legislation was passed. In December of 2017, a speeding Amtrak passenger train derailed at a curve along a recently completed section of track in DuPont, WA killing three passengers. [23] Two months later an Amtrak passenger train collided with a stationary CSX freight train in Cayce, SC killing two Amtrak crewmembers. [24] According to the NTSB, both incidents could have been prevented by PTC.

All railroads regulated by the Federal Railroad Commission (FRA) use the same PTC software and hardware standards for interoperability. There are three systems that comprise the technology including: an onboard locomotive system which monitors the train's position and speed—with GPS—and can activate braking; a wayside communications system which operates on a dedicated radio frequency and monitors track signals, switches and circuits; and a central back office server which oversees the rail network and authorizes trains to move into new segments of track. Most onboard systems are equipped with a GNSS receiver for signals from the GPS and Galileo satellite constellations. As with other GNSS applications, this forms the foundation of the PTC system providing the train's location, direction and speed. After railroads invested over $11 billion over the last decade, the FRA announced that PTC was successfully deployed for all 57,536 miles of required track on December 29, 2020. [25]

Trucking Applications

GNSS technologies are used extensively in road transportations systems as well. In the 1980s, Trimble and Qualcomm began developing systems for truck fleet management. Qualcomm launched Omnitracs in 1988 and within three years was tracking almost 15,000 trucks for 100 trucking companies. [26] Within a decade one in ten commercial trucks were tracked electronically. Today, the U.S. Federal Motor Carrier Safety Administration (FMCSA) requires most commercial trucks moving interstate freight to use electronic logging devices (ELD). The ELD requirement is part of the FMCSA's Hours of Service (HOS) regulations designed to promoting driver and public safety. It also simplifies requirements for commercial drivers with a single set of federal rules superseding a patchwork of state-level regulations. ELDs digitize and automate record keeping that was previously done with paper log books. While a vehicle is in service, ELDs automatically record date, time and location—with GPS—as well as engine hours, vehicle miles and identity of the driver. [27] Canada adopted a similar ELD requirement, which will be enforced in June of this year. [28]

Beyond tracking and navigation, GNSS and related technologies are integral to autonomous vehicles and intelligent transportation systems (ITS). Similar to automatic train control systems, autonomous vehicle systems pair GNSS-based positioning with inertial navigation and other sensor systems allowing the vehicle to operate in areas with poor GNSS reception. ITS extends these capabilities with wireless communication to surrounding infrastructure and other vehicles. Other applications that rely on GNSS-based PNT include: fleet management, traffic monitoring services, dangerous goods tracking, tolling and congestion management, insurance telematics, emergency services and other applications. [29]


Despite the vulnerability to interference, there are few alternatives or backup systems to GNSS. Land-based long range navigation (LORAN) is still available in some countries. LORAN was developed by the U.S. government in World War II and the U.S. operated a nationwide system until 2010. E-LORAN (enhanced) is a low-frequency navigation system that uses terrestrial transmission stations. Each station emits precisely timed and shaped radio pulses centered at 100 kHz. The stations are grouped into chains with a single master station and two or more secondary stations. Since E-LORAN is transmitted by terrestrial stations, the signal is much stronger than satellite-based GNSS signals, and so receivers are less susceptible to interference. [30] In response to GPS vulnerabilities, the federal National Timing Resilience and Security Act of 2018 established a mandate—but no appropriations—for an alternative land-based timing system, which may resurrect LORAN in the U.S. [31]

There are new satellite-based technologies in development to mitigate spoofing interference as well. The European Global Navigation Satellite Systems Agency (GSA) is adding authentication capabilities to the Galileo constellation based on the timed efficient stream loss-tolerant authentication (TESLA) protocol, which only requires public keys for decryption. It also will be backward compatible with existing Galileo receivers. [32] Similarly, the U.S. has launched 23 of 24 satellites needed to deploy encrypted M-Code for military GPS users. The U.S. also is planning to launch Navigation Technology Satellite – 3 (NTS-3), the first experimental PNT satellite in more than 40 years. [33] NTS-3 will test a number of new technologies including a new digital signal generator that can be reprogrammed while it is in orbit. This capability will allow it to broadcast new signals to avoid and defeat interference, and add signatures to the signals to counter spoofing.

Interested in more? I’m working on a more comprehensive report on GNSS vulnerabilities that will be published by the Seattle Institute in a few months.


[1]: FleetMon (2021). Vessel JIN NIU ZUO (Oil tanker) IMO 9303699, MMSI 413136000. Retrieved January 23, 2021.

[2]: Gardner, T., & Mohammed, A. (2019, October 16). U.S. “deeply concerned” about untrackable China ships carrying Iran oil. Reuters. Retrieved January 24, 2021.

[3]: Bergman, B. (2019, December 12). Systematic GPS Manipulation Occurring at Chinese Oil Terminals and Government Installations. SkyTruth. Retrieved December 8, 2020.

[4]: European GSA (2020). GNSS User Technology Report: 2020. European Global Navigation Satellite Systems Agency.

[5]: NCO for Space-Based PNT (2021, January 24). Space Segment. Retrieved January 24, 2021.

[6]: Hitchens, T. (2020, December 7). GPS Anti-Jam M-Code Takes Two Steps Forward. Retrieved December 19, 2020.

[7]: Bergman, 2019

[8]: C4ADS (2019). Above Us Only Stars: Exposing GPS Spoofing in Russia and Syria.

[9]: Milner, G. (2017). Pinpoint: How GPS is Changing Technology, Culture, and Our Minds. New York: W. W. Norton & Company, p. 58.

[10]: European GSA (2019). GSA GNSS Market Report: 2019. European Global Navigation Satellite Systems Agency.

[11]: Fredrickson, C. K. (2020, June 29). Coast Guard Discontinues Differential GPS Broadcast. Retrieved January 20, 2021.

[12]: Fredrickson, 2020

[13]: Kiste, R. C., Suggs, R. C., Kahn, M., Augustyn, A., Kuiper, K., Lotha, G., et al. (2020, November 16). Polynesian culture. Retrieved January 20, 2021.

[14]: Milner, 2017, p. 5.

[15]: Kealy, A., & Moore, T. (2017). Land and Maritime Applications. In P. J. G. Teunissen & O. Montenbruck (Eds.), Springer Handbook of Global Navigation Satellite Systems (pp. 841–875). Cham: Springer International Publishing.

[16]: IMO (2021a). AIS transponders. Retrieved January 20, 2021.

[17]: IMO (2021b). Electronic Nautical Charts (ENC) and Electronic Chart Display and Information Systems (ECDIS). Retrieved January 20, 2021.

[18]: Kealy & Moore, 2017

[19]: Kealy & Moore, 2017

[20]: González, E., Prados, C., Antón, V., & Kennes, B. (2012). GRAIL-2: Enhanced Odometry based on GNSS. Procedia - Social and Behavioral Sciences, 48, 880–887.

[21]: ESA (2005, July 5). ECORAIL - successful demonstration of EGNOS for railway control applications. Retrieved January 20, 2021.

[22]: FRA (2009). Overview and Highlights of the Railway Safety Improvement Act of 2008. Federal Railroad Administration.

[23]: NTSB (2019a). Amtrak Passenger Train 501 Derailment in DuPont, Washington on December 18, 2017: Accident Report (No. NTSB/RAR-19/01). National Transportation Safety Board.

[24]: NTSB (2019b). Amtrak Passenger Train Head-on Collision With Stationary CSX Freight Train in Cayce, South Carolina on February 4, 2018: Accident Report (No. NTSB/RAR-19/02). National Transportation Safety Board.

[25]: FRA (2020, December 29). Federal Railroad Administration Announces Landmark Achievement with Full Implementation of Positive Train Control. Federal Railroad Administration.; AAR (2020, December 29). America’s Railroads Meet PTC Mandate, Look to the Future. Association of American Railroads.

[26]: Milner, 2017

[27]: FMCSA (2015). 49 CFR Parts 385, 386, 390, and 395: Electronic Logging Devices and Hours of Service Supporting Documents, 80 Federal Register 78292–78416.

[28]: Transport Canada (2019). Canada Gazette, Part 2, Volume 153, Number 12: Regulations Amending the Commercial Vehicle Drivers Hours of Service Regulations (Electronic Logging Devices and Other Amendments), 153 Canada Gazette.

[29]: Kealy & Moore, 2017

[30]: Kealy & Moore, 2017

[31]: NCO for Space-Based PNT (2021). LORAN-C Infrastructure & E-LORAN. Retrieved January 24, 2021.

[32]: European GSA, 2020

[33]: AFRL (2021). Navigation Technology Satellite – 3 (NTS-3). Retrieved January 19, 2021.