In September 2013, the night before he won the prestigious ION Kepler Award, Dr. John Betz and I were enroute to an ION (Institute of Navigation) dinner when he casually mentioned that he was thinking about writing a book. The natural journalistic inquiries about subject and timing brought a surprising response. The draft of the first chapter was already complete and it would be about PNT space systems or GNSS (Global Navigation Satellites System) if you will. Not just GPS, but all space-borne (satnav) PNT (position, navigation and timing) systems and augmentations.
When I asked John exactly why he was writing the book he replied, “I am writing the book for several reasons. First, there is a shortage of books that uniformly treat all satnav systems, rather than emphasizing a single system. There are a lot of common and complementary characteristics that become clear when all are treated in a uniform and consistent way.
“Second, this is a chance to provide an integrated perspective on satnav systems engineering. Lastly, I’ve learned a lot in the last 17 years, and I want to document it in an organized way.”
I, of course, offered to help in any way I could. I mentioned that I would very much like to review the book when it was finished. Not too much was said about the book until the next year at the very same event, when John mentioned the book would be ready for publication in the first quarter of 2016. Again I offered to review the book, and this column is that promised review.
First of all, there can be no doubt that Dr. John Betz, a MITRE Fellow, is qualified to author this engineering tome about all matters pertaining to space-borne PNT. Indeed, if I were to fully recite his impressive curriculum vitae, it would be longer than the entire space allocated for my column, so I will make do with the short paragraphs that accompanied the Kepler Award.
Dr. John Betz, winner of the ION 2013 Kepler Award.
“Dr. John Betz contributed to the international interoperability and compatibility efforts leading to the design of the GPS L1C civil signal. His Binary Offset Carrier (BOC) technique is used for the GPS M-code signal, and adopted by satellite navigation systems developed by Russia, Europe, China, Japan and India.
“Since 1997, Dr. Betz has worked on the NAVSTAR GPS and also on international negotiations concerning compatibility and interoperability of GPS with the world’s satellite navigation systems. For his role in the United States/European Union negotiations that established compatibility and interoperability between GPS and Galileo in 2004, he received the U.S. State Department’s Superior Honor Award.
“More recently, Dr. Betz provided critical analysis related to GPS modernization, recommending affordable enhancements to address increasing threats and to shape the architecture of military GPS for decades to come. Col. Bernard Gruber, [then] director of the GPS Directorate said, ‘I can think of no one else in the past two decades, military or civilian, who has influenced this critical national asset to the same degree as Dr. Betz’.”
I asked Dr. Betz what he liked most about writing the book, what he disliked the most, and would he do it again?
“Don, some chapters just flew — it was really fun to write them,” he said. “And I really like the color graphics, even in the print edition. It was challenging to find the time, given my work schedule. That was probably the most difficult part. It’s amazing when I look back. It was a little more than two years from start to submitting the manuscript. I had planned on 400 pages and it’s 640 pages. And yes, I would do it all again.”
Scope
The scope of this engineering reference is exhaustive in nature where PNT is concerned. The work is balanced between original content and a compilation of academic papers by numerous expert authors. Certainly, Dr. Betz gives credit where credit is due; he often recommends other volumes, texts and papers for enlightenment. However, for me his personal and professional insights and clear explanations of highly technical issues are what make this a compelling volume.
In his introduction, Dr. Betz describes his effort:
“This book describes satellite-based navigation and timing (satnav), the engineering of systems that transmit radio frequency (RF) ranging signals from a constellation of satellites so that a passive receiver can determine time and its position. The intent of this book is to provide a consistent and integrated depiction of the engineering behind satnav.”
If a PNT or GNSS constellation, or even a small group of satnav vehicles, is in orbit today — such as WAAS, EGNOS and QZSS — John describes their makeup and contribution to the overall PNT solution in great detail that is understandable to both the academic and layman alike.
Insights
I have personally been involved with satnav in one fashion or another for 40 years. Frankly, I thought I was well versed in the subject. Yet, in every chapter of John’s book, I either learned something new or had an issue explained that I obviously did not understand quite as well as I thought. There is something for everyone interested in satnav in this wonderful book, regardless of their level of involvement or sophistication with PNT.
References
The book contains exhaustive tables, references, figures and formulas for all levels, which is why I am sanguine this book will become an invaluable reference and textbook for the military as well as any university dealing with educating students concerning satnav and PNT issues.
When I finished reading the 640-page volume, I had added more than 40 blue “stickies” to mark figures or tables for future reference.
This book is a treasure trove for PNT engineers and satnav experts, but it’s readability is such that even if you are only slightly curious about how space-based PNT works, you will find it an educational and enjoyable read.
For instance, on page 29, Table 2.1 summarizes the nominal constellation characteristics, 16 for each system, between GPS (US), GLONASS (Russian), Galileo (European) and the BeiDou (Chinese) constellations. While this will probably only serve as riveting cocktail repartee at something like an ION function, it is also just good to know, fun facts if you will. It might even serve as a Jeopardy category one day.
Bottom Line
Dr. Betz begins his lengthy but enjoyable tome with an explanation of satnav; takes the reader through the various space-borne PNT systems and augmentations on orbit today; describes the signals, the errors and the various pluses and minuses of each system; and then delves into PNT receiver design and describes how each signal is received and utilized.
After reading the book I asked Dr. Betz if he thought or hoped the book would be used as a textbook. He replied, “I hope it gets used in multiple ways. It can certainly be used by practicing engineers as a reference and for in-depth exploration. I hope its contents and structure make it useful as a textbook, because the book includes theoretical and applied questions at the end of many chapters that should help students learn how to extend and apply the theory and practice laid out in the book. Also, I hope its structure is conducive for use in teaching.”
While the jury is still out on whether this is a engineering textbook, a satnav reference manual, a primer on modernized PNT, or perhaps a compendium of all three, if you care at all about modern-day GNSS and all it enables, this book should be in your library.
Until next time, happy navigating, and I hope you enjoy the book.
The founders of Chronos and UrsaNav have formed a new collaboration, named Taviga, that will focus on preserving and establishing low-frequency (LF) positioning, navigation and timing (PNT) networks in the United Kingdom, Europe and the U.S., using repurposed Loran-C or purpose-built eLoran technology.
Taviga aims to ensure timing and navigation for critical infrastructure, protecting it from cyber and other threats, and addressing the concern that over-dependence on single systems for PNT increases vulnerability.
According to a joint press release, “Taviga combines the founders’ decades of experience specializing in low-frequency (LF) PNT technology and industrial timing applications at national and international levels. Its objective is to provide a commercially operated assured LF PNT service.”
Partner with Government. Charles Curry of Chronos Technology Ltd. in the UK and Charles Schue of UrsaNav Inc. in the U.S. joined forces to launch Taviga Ltd. and Taviga LLC. Taviga anticipates working in partnership with government agencies and other entities that have a vested interest in reducing the vulnerability and improving the resilience of critical national infrastructure with a dependency on the GPS and other GNSS sources of PNT.
“We have been researching the precise timing capability of eLoran transmissions for over 10 years,” Curry said. “During that time, the system has never failed, and most impressively it has continued to deliver sub-microsecond time accuracy traceable to UTC in very challenging locations, including deep inside buildings.
“Our research program was supported by the UK’s Innovation Agency — Innovate UK through two flagship projects, GAARDIAN and SENTINEL,” Curry continued. “These two projects highlighted the vulnerabilities that threaten GPS signals (and in the future, Galileo) such as jamming, interference and spoofing. They also demonstrated how eLoran is a technically dissimilar source of PNT and not vulnerable to the same types of interference. eLoran is a truly complementary source of PNT, ideal for use in critical infrastructure applications such as telecoms, broadcasting, financial services and power utilities.
“Every government, academic and industrial study has resulted in the selection of the LF technology known as Enhanced Loran, or eLoran, as the best wide-area complement to GNSS,” UrsaNav’s Schue added. “There is no doubt that the combination of GNSS and eLoran provides the PNT resilience that most users require.
“Integrated GNSS-eLoran solutions can provide the proof-of-time and proof-of-position necessary to safeguard national infrastructure and for business continuity of operations,” Schue said. “Adding eLoran to the PNT mix enables or enhances capabilities of regional and purpose-built solutions. Overreliance on a single solution is neither prudent nor safe.”
Tests led by Chronos and using UrsaNav’s eLoran receiver engine have consistently demonstrated positioning accuracies of better than 10 m and timing accuracies of less than 100 nanoseconds in the area of differential eLoran reference sites.
Taviga’s goal is the long-term operation of an eLoran system for at least 10 years, a period that provides the necessary service assurance continuity to enable industrial users to invest with confidence in an eLoran-based timing and navigation service that complements their GNSS solutions. As users become accustomed to the capabilities and resilience of a combined GNSS-eLoran solution, Taviga expects to expand the service footprint worldwide.
Timing
Leap second lives on
The International Telecommunication Union (ITU) World Radiocommunication Conference (WRC-15) decided that further studies are required on the impact and application of a future reference time-scale, including the modification of Coordinated Universal Time (UTC) and suppressing the so-called “leap second.”
Leap seconds are added periodically to adjust to irregularities in the Earth’s rotation in relation to UTC, the current reference for measuring time, in order to remain close to mean solar time (UT1). A leap second was added most recently on June 30 at 23:59:60 UTC. The proposal to suppress the leap second would have made continuous reference timescale available for all modern electronic navigation and computerized systems to operate while eliminating the need for specialized ad hoc time systems.
A report will be considered by the World Radiocommunication Conference in 2023. Until then, UTC shall continue to be applied as described in Recommendation ITU‑R TF.460‑6.
Disconnect from the Sun? As a representative of the Lick Observatory of the University of California stated, “a problem is that simply omitting leap seconds would redefine the meaning of the word “day” so that it is not related to the sun in the sky, nor connected with the rotation of the Earth.”
“Modern society is increasingly dependent on accurate timekeeping,” said ITU Secretary-General Houlin Zhao.“ITU is responsible for disseminating time signals by both wired communications and by different radiocommunication services, both space and terrestrial, which are critical for all areas of human activity.”
Further studies will be coordinated by ITU along with several other international organizations.
Inertial/GNSS
Drone rules, registry
The Federal Aviation Administration announced in December an official rule and registration process for hobbyists who own small unmanned aircraft weighing more than 0.55 pounds and less than 55 pounds, including payloads such as on-board cameras.
The online registration system does not yet support registration of small UAS used for any purpose other than hobby or recreation — for example, using an unmanned aircraft in connection with a business. The FAA is developing enhancements that will allow such online registrations by spring of 2016.
The registration procedure is a statutory requirement that applies to all hobby aircraft. Under this rule, any owner of a small UAS who has previously operated an unmanned aircraft exclusively as a model aircraft prior to Dec. 21, 2015, must register no later than Feb. 19, 2016. Owners of any other UAS purchased for use as a model aircraft after Dec. 21, 2015, must register before the first flight outdoors.
Owners may register through a web-based system or paper-based process. There is a $5 registration fee, but the FAA is offering a full rebate for those who register before Jan. 20, 2016.
Under the rule, each aircraft must be marked with a unique number, although not necessarily the serial number. The goal is to help authorities track down an owner if a drone collides with another aircraft, flies too high or encroaches on an airport.
Owners using the model aircraft for hobby or recreation will only have to register once and may use the same identification number for all of their model UAS. The registration is valid for three years.
“We expect hundreds of thousands of model unmanned aircraft will be purchased this holiday season,” FAA Administrator Michael Huerta said. “Registration gives us the opportunity to educate these new airspace users before they fly so they know the airspace rules and understand they are accountable to the public for flying responsibly.”
Space maps of some of 13,986 satellites, below, and some navigation satellites, above (courtesy Esri).Alan Cameron
Advocacy in the U.S. capital urges augmentation of GPS/GNSS with eLoran and other “complementary terrestrial PNT services to increase resilience.” See the Resilient Navigation and Timing Foundation’s website, rntfnd.org. This is assuredly a good thing, a worthy cause.
I’ve come to believe, however, that true resilience goes beyond what we normally think of as position and timing sensors. Stimulus comes from a keynote lecture by Dawn Wright, Esri chief scientist, at the 2015 American Geophysical Union Fall Meeting. I hope Esri or the AGU will publish the lecture or post the video. For now, bear with my limited rendition.
In “Toward a Digital Resilience, with a Dash of Location Enlightenment,” Wright describes the new science of big data: the flood of info from satellites, sensors and other measuring systems; the issues inherent in large data sets; and the insight discovered through their manipulation and exploration. She talks to geographic information systems professionals, software makers and users, but her remarks resonate beyond that associated industry sector and well into that of PNT hardware, where we live.
Integrate, integrate, integrate! Interoperability and crosswalking with other systems and data sets. To make it reproducible, make it virtual — as in virtual, living journals. These are three of the eight ideas toward digital resilience that she espouses, making communities more resilient with tools and data.
I’ll return to this in a later editorial; there’s much around which still to wrap my head. But here’s the moral: resilient PNT will ultimately mean more than complementary sensors. It will entail a seamless mesh of hardware and software, of pre-existing and new data, much of it from sources we don’t currently consider PNT-relevant, of input from amateur app makers and users and more.
Bluvision, a real-time location services (RTLS) provider, will be demonstrating its RTLS solution along with Texas Instruments (TI) at CES 2016.
Bluvision’s location algorithms “continue to redefine how technology can be used for indoor location,” the company stated in a news release. Its RTLS solution uses Bluetooth low-energy and Wi-Fi technology to determine specific positioning, leveraging multiple techniques, including smart machine learning algorithms for accuracy.
The combination of Bluetooth Smart, Wi-Fi and sophisticated algorithms on the cloud allows tracking and monitoring of assets — equipment or people — without the need for a smartphone application and uses minimum hardware that is fast and easy to implement, Bluvision said.
Bluvision’s RTLS solution is accurate down to three feet even in harsh conditions. It can be deployed in a large area within hours. The solution supports creating multiple alerts and policies, including creating multiple virtual geofences that trigger alerts when entering or leaving pre-defined areas.
Bluvision will demonstrate the RTLS solution in the TI Village (#N115-N118) at CES 2016, using TI’s SimpleLink Bluetooth Smart CC2640 wireless microcontroller (MCU).
“Our LBS (location-based service) solution is disruptive,” said Jimmy Buchheim, CEO of Bluvision. “Using TI’s SimpleLink CC2640 wireless MCUs with built-in SDR (software-defined radio) and the combination of our talented data scientists, advanced algorithms team and cloud team, allows us to revolutionize indoor location, achieving what is considered impossible accuracy for Bluetooth-based technology.”
For more information on the demo or Bluvision’s RTLS solution, contact Subhashree Sukhu.
eLoran Antenna Park of 13, 200-meter masts at Anthorn, UK.
Readers of GPS World, its e-newsletters, website — and all interested PNT parties — are invited to register their opinion in the current poll at gpsworld.com/janpoll.
Should the U.S. government install a full eLoran network of broadcast stations to back up GPS in case of jamming, interference or other emergencies?
Yes.
No.
More study is needed before answering this question.
Don’t know.
Voters may enter their name in a drawing to receive a $50 gift card. Vote by Jan. 11, 2016.
Results will be published in the February issue of GPS World magazine.
On Nov. 25, 2015, President Obama signed the National Defense Authorization Act (NDAA) for Fiscal Year 2016, after vetoing a previous version. The enacted NDAA complies with the two-year budget agreement, which called for a reduction in defense spending.
The act reduces the GPS IIF line item by $2 million, citing “unjustified support growth” from the U.S. House of Representatives Committee on Appropriations, but otherwise recommends full funding for the Air Force GPS program ($936.775 million).
The NDAA also includes three GPS-related policy provisions: Reporting Requirement (Section 1621), Oversight Council (Section 1603), and M-Code Equipage (Section 1605).
New Space Law Mentions PNT Coordination Office
On Nov. 25, the president also signed the U.S. Commercial Space Launch Competitiveness Act. Title III of the act codifies the support that the Department of Commerce (DOC) provides to the National Coordination Office for Space-Based PNT.
Specifically, it tasks DOC’s Office of Space Commerce “to provide support to federal government organizations working on Space-Based Positioning, Navigation, and Timing policy, including the National Coordination Office for Space-Based Position, Navigation, and Timing.”
Senator Franken Reintroduces GPS Data Privacy Bill
On Nov. 10, Sen. Al Franken (D-MN) reintroduced the Location Privacy Protection Act, which he also introduced during the 112th and 113th Congresses. According to the Senator, “The Location Privacy Protection Act of 2015 closes legal loopholes that allow stalking applications to exist on smartphones.
Sen. Franken’s bill fixes this problem by requiring companies to get customers’ permission before collecting their location data or sharing it with third parties.” The bill joins several others in the 114th Congress that address geolocation privacy issues, including the Geolocation Privacy and Surveillance Act (“GPS Act”) and the Online Communications and Geolocation Protection Act.
The summaries here are from the GPS Bulletin, which is available through the gps.gov website.
Navigation using High-Frequency Ground Beacons and Ionosphere Model Corrections, by Yoav Baumgarten and Mark L. Psiaki, Cornell University.
A new navigation concept relies on passive one-way ranging using pseudorange measurements of high-frequency (HF) beacon signals reflected off the ionosphere.
This is being developed as a possible alternative to GNSS positioning and timing services, with benefits in costs and system redundancy. The HF signals are transmitted from ground-based beacons, traveling from known locations to the unknown user equipment (UE) location along ray paths that reflect off the Earth and the ionosphere. If a set of beacon signals reaches the UE receiver with sufficient geometric diversity, then the three-dimensional position and the clock offset of the receiver can be determined.
Presented at ION GNSS+ 2015.
Inertial Sensors
Dynamic Stochastic Modeling of Inertial Sensors for INS/GNSS Navigation, by M. Wis, Deimos Space, Spain; Ismael Colomina, GeoNumerics, Spain.
Researchers performed a series of experiments with a low-cost inertial device rigidly attached to a navigation-grade reference IMU and found a direct relationship between the low-cost IMU errors and the high-order dynamics. Preliminary results suggest an approach of low-cost sensor modeling that might help reduce some of the errors inherent to the dynamics applied to the sensors.
Presented at ION GNSS+ 2015.
GNSS-INS Integration
Quasi-Tightly-Coupled GNSS-INS Integration with a GNSS Kalman Filter, by Bruno Scherzinger, Applanix Corporation, Canada.
This method, intended for integration of an existing GNSS navigation engine into a GNSS-INS closed-loop configuration with little/no modification of the navigation engine, uses a range measurement model matrix typically used to compute dilutions of precision (DOP) to identify the observable subspace in the time-space frame generated by the available satellites and project the loosely coupled INS-GNSS Kalman filter position measurement into this subspace.
Coming to a store near you: Wi-Fi’s unparalleled reach means it will locate shoppers
Marketing graphic for Cisco Mobile Concierge shows retail businesses how to engage with their customers “in a targeted contextual manner through their mobile devices within specific venues… Customers can now receive relevant information based on their location” within the store. (Courtesy of Smart Wi-Fi Systems)
Wi-Fi indoor location application revenues will reach $2.5 billion by 2020, according to a report from ABI Research. Wi-Fi Indoor Location Applications and Revenues was released in Q4 2015.
“Wi-Fi, as an indoor location and analytics tool, is in a very precarious position,” said Patrick Connolly, Principal Analyst at ABI Research. “Apple continues to create roadblocks, while Bluetooth low-energy (BLE) beacons have not only taken mindshare but also budgets. However, Wi-Fi is ubiquitous on smartphones and available in over 50 percent of major retail stores in the U.S., giving it unparalleled reach. Previously, it was an expensive and inaccurate technology, but Wi-Fi access point vendors like Zebra and Cisco have all upped their game on retail analytics, while start-ups like Euclid have helped to drive adoption worldwide.”
Wi-Fi’s superior penetration means it is a much better technology than BLE beacons for in-store analytics today, according to ABI. While location-based advertising is stealing the headlines, retailers are finally waking up to in-store analytics, which represent a major evolution on people counting and loyalty programs. This data will streamline store layouts, improve staff management, measure advertising campaign performance, enhance loyalty/reward programs, and form the backbone of new smartphone services.
One company active in this space, Cisco Mobil Concierge, promotes its location capabilities for retail, hotels, transport hubs, museums and more. Its Mobility Services Engine API offers such services as “track-and-trace interferers, rogues, Wi-Fi clients and RF tags; Geofencing and zone-based alerts; Thinksmart Localtion Analytics.”
The latter software suite offers such data as shopper cluster points, dwell times, typical paths and crowding. From the shopper’s viewpoint, the experience begins when a smartphone automatically discovers the venue’s services; a “service available” and a media-access-control service access point (MSAP) pops up. The user clicks on the MSAP icon to view a list of services and can opt in to be tracked within the venue, presumably in exchange for special offers.
According to Cisco, this means “new experiences, new revenue and opportunities for businesses everywhere.”
The founders of Chronos and UrsaNav have formed a new collaboration, named Taviga, that will focus on preserving and establishing low-frequency (LF) positioning, navigation and timing (PNT) networks the United Kingdom, Europe and the United States, using repurposed Loran-C or purpose-built eLoran technology.
Taviga — named for timing and navigation — aims to ensure timing and navigation for critical infrastructure from cyber and other threats, and address the concern that over-dependence on single systems for PNT increases vulnerability.
According to a joint press release, “Taviga combines the founders’ decades of experience specializing in low-frequency (LF) PNT technology and industrial timing applications at national and international levels. Its objective is to provide a commercially operated assured LF PNT service.”
Charles Curry, founder of Chronos Technology Ltd. in the UK, and Charles Schue, founder of UrsaNav Inc. in the United States, joined forces to launch Taviga Ltd. and Taviga LLC. Taviga anticipates working in partnership with government agencies and other entities that have a vested interest in reducing the vulnerability and improving the resilience of critical national infrastructure with a dependency on the GPS and other GNSS sources of PNT.
“We have been researching the precise timing capability of eLoran transmissions for over 10 years,” Curry said. “During that time, the system has never failed and most impressively it has continued to deliver sub-microsecond time accuracy traceable to UTC in some very challenging locations including deep inside buildings.
“Our research program was supported by the UK’s Innovation Agency – Innovate UK through two flagship projects, GAARDIAN and SENTINEL,” Curry continued. These two projects highlighted the vulnerabilities that threaten GPS signals (and in the future, Galileo) such as jamming, interference and spoofing. They also demonstrated how eLoran is a technically dissimilar source of PNT and not vulnerable to the same types of interference. eLoran is a truly complementary source of PNT ideal for use in critical infrastructure applications that demand precise time and timing such as telecoms, broadcasting, financial services and power utilities.
“Every government, academic and industrial study has resulted in the selection of the LF technology known as Enhanced Loran, or eLoran, as the best wide-area complement to GNSS,” Schue said. “There is no doubt that the combination of GNSS and eLoran provides the PNT resilience that most users require.
“Whether the application is timing/frequency, aviation, maritime, land-mobile, or location based, integrated GNSS-eLoran solutions can provide the proof-of-time and proof-of-position necessary to safeguard national infrastructure and for business continuity of operations,” Schue said. “Additionally, adding eLoran into the PNT mix enables or enhances the capabilities of regional and purpose-built solutions. PNT resilience results from an eco-system made up of layered solutions. Over reliance on a single solution is neither prudent nor safe. It’s time for Taviga.”
Tests have been conducted as part of Innovate UK supported research projects GAARDIAN and SENTINEL, which were led by Chronos Technology Ltd and included UrsaNav’s eLoran receiver engine. eLoran transmissions from the UK, Denmark, Germany, France and Norway have consistently demonstrated positioning accuracies of better than ten meters and timing accuracies of less than 100 nanoseconds in the area of differential eLoran reference sites. Taviga will now seek to engage those governments and others in discussions as to how to transition their Loran stations to commercial operation.
Taviga’s goal is the long-term operation of an eLoran system for at least 10 years. This length of time provides the necessary service assurance continuity to enable industrial users to invest with confidence in an eLoran-based timing and navigation service that complements their GNSS solutions. As users become accustomed to the additional capabilities and resilience provided with a combined GNSS-eLoran solution, Taviga expects to expand the service footprint into other countries worldwide.
A Wide-Area Multi-Application PNT Resiliency Solution
By Stephen Bartlett, Gerard Offermans and Charles Schue
INNOVATION INSIGHTS with Richard Langley
WHERE HAVE ALL THE SYSTEMS GONE, long time passing?
Radionavigation systems, that is (and apologies to Pete Seeger). If we look at the 1990 Federal Radionavigation Plan (FRP), published by the U.S. Departments of Transportation and Defense, as I did in this column in March 1992, we see that there were 10 radionavigation systems in use by different user segments: Loran-C, Omega, very high frequency (VHF) Omnidirectional Range/Distance Measuring Equipment, Tactical Air Navigation, the Instrument Landing System, the Microwave Landing System, Transit, aviation radiobeacons, marine radiobeacons and GPS.
The latest FRP, issued in 2014, includes only seven or six and a half when you consider that marine radiobeacons were mostly phased out in the intervening years. Systems were shut down because with the advent of GPS, they were considered to be redundant. While there were attendant cost savings, the closure of the various systems has resulted in a dangerous virtual sole dependence on GPS for navigation without any backup.
Transit, was the first to go. It consisted of a constellation of six or seven active satellites in circular, polar orbits at altitudes of roughly 1,100 kilometers. The satellites transmitted signals on 150 and 400 MHz, and receivers measured the integrated Doppler frequency shift of the received signals. Transit was terminated at the end of 1996.
Transit was followed by the Omega hyperbolic navigation system. Omega consisted of eight stations around the globe transmitting time-shared carrier-wave signals on four frequencies between 10.2 and 13.6 kHz. The Omega system was closed down in September 1997.
The marine radiobeacons have been mostly shut down in recent years, although aeronautical beacons continue to operate. Radiobeacons are nondirectional transmitters that operate in the low- and medium-frequency bands. Some marine radiobeacons became Differential GPS stations and subsequently part of the Nationwide DGPS network. That network is being scaled back to provide only coastal and Great Lakes coverage.
And that brings us to Loran-C. Like Omega, it was also a hyperbolic navigation system. A receiver measured the difference in times of arrival of pulses transmitted at 100 kHz by a chain of three to five synchronized stations separated by hundreds of kilometers. At one time, the operation of Loran-C was the responsibility of the U.S. Coast Guard. Together with a number of host nations, the Coast Guard operated 17 chains of stations around the world, including one jointly operated with Russia. These stations provided coverage of the coastal areas of North America and the U.S. interior, northern Europe, the Mediterranean Sea, the Far East and the Hawaiian Islands. Additionally, several other countries operated Loran-C stations. Although moves were already underway to update the Loran technology, the Obama administration decided to terminate Loran-C in the U.S., considering it to be an unnecessary antiquated system. The Coast Guard terminated the transmission of all U.S. Loran-C signals in February 2010 and began dismantling stations.
So, is there no longer a viable non-GNSS alternative or backup system for GPS navigation? While there are other possibilities for time transfer, one of GPS’s other applications, there is no widely available substitute navigation system. Currently. However, as we will see in this month’s column, a new version of Loran — Enhanced Loran or eLoran — has been developed and is being tested on the U.S. east coast. Not your father’s Loran, eLoran seems to be the perfect solution for PNT resiliency.
Telecommunications, energy, finance and transportation are just four among the many critical infrastructure / key resource sectors that have come to rely solely on GPS for positioning, navigation and timing (PNT). In fact, the U.S. Department of Homeland Security (DHS) has determined that 11 of the 16 critical infrastructure sectors in the U.S. are critically dependent on GPS for timing. While we can start to imagine what a day without GPS might be like, we’d really rather not — it would be somewhat depressing and really quite dangerous. We would rather imagine a day when there is a wide-area complementary solution available that protects and augments GPS. In this article, we will delve into such a solution: Enhanced Loran, or eLoran for short. We will explain how it works, debunk some myths, speculate on how it could be used in the U.S. (and abroad), highlight the state of current technology and discuss the state of the possible. We will also summarize the state of eLoran in the world and where things might go from here.
What Is eLoran?
eLoran is the latest in the longstanding and proven series of low-frequency, LOng-RAnge Navigation (LORAN) systems, one that takes full advantage of 21st-century technology. It meets the accuracy, availability, integrity and continuity performance requirements for maritime harbor entrance and approach maneuvers, aviation non-precision instrument approaches, land-mobile vehicle navigation and location-based services. It’s a precise source of time (phase) and frequency. Additionally, eLoran provides user bearing (azimuth) and has built-in integrity. In full disclosure, however, eLoran is only a 2D positioning solution unless integrated with a simple altimeter.
eLoran is a low-frequency radionavigation system that operates in the frequency band of 90 to 110 kHz. eLoran is built on internationally standardized Loran-C, and provides a high-power PNT service for use by all modes of transport and in other applications. eLoran is an independent dissimilar complement to GNSS. It allows GNSS users to retain the safety, security and economic benefits of GNSS even when their satellite services are disrupted.
eLoran uses pulsed signals at a center frequency of 100 kHz. The pulses are designed to allow receivers to distinguish between the groundwave and skywave components in the received composite signal. This way, the eLoran signals can be used over very long ranges without fading or uncertainty in the time-of-arrival (TOA) measurement related to skywaves.
Although eLoran is based upon Loran-C, it has key differences:
All transmissions are synchronized to UTC (like GPS)
Time-of-transmission control
The ability to use differential corrections (similar to DGPS)
Receivers use “all-in-view” signals
Includes one or more Loran data channels that provide: Low-rate data messaging, added integrity, differential corrections (dLoran and/or DGPS) and other communications including navigation messages.
An eLoran receiver measures the TOA of the eLoran signal:
TOA = TOR – TOT = PF + SF + ASF + ∆Rx
where TOR is time of reception, TOT is time of transmission, PF is the primary factor (propagation delay through air), SF is the secondary factor (propagation delay over sea), ASF is the additional secondary factor (propagation delay over terrain) and ∆Rx is the delay due to receiver electronics and cables.
The primary and secondary factors are well-defined delays and can be calculated as a function of distance. The additional secondary factor delay is mostly unknown at the time of installation. Fortunately, the ASFs remain very stable over time. Any fine changes in ASF over time may be compensated for by one or more differential eLoran reference station sites providing corrections over the Loran data channel.
When eLoran is used for positioning, a minimum of three eLoran transmitting sites are needed to calculate a two-dimensional position fix and time. Time (phase) and frequency can be derived from a single transmitting site as well. With three sites, timing can be derived while a receiver is in motion. An integrated eLoran/GPS receiver can take advantage of combinations of eLoran and GPS transmissions to develop a PNT solution. Any additional measurements provide a means to improve the solution’s accuracy (using weighted least squares) or to protect the solution’s integrity (by receiver-autonomous integrity monitoring).
To achieve the highest accuracy levels, the user receiver corrects its TOA measurements with the published ASF values for the area and differential eLoran corrections received through the Loran data channel. ASF maps for specific geographic areas are distributed to users in a receiver-independent data format that is currently being standardized by the Radio Technical Committee for Maritime Services’ (RTCM’s) Special Committee (SC) 127 on eLoran. The ASF map data would be published by the service provider responsible for aids to navigation.
As described before, the measured ASF values remain stable over long periods of time. Any small changes in the published ASFs due to changes in propagation path characteristics or transmitter-related delays will be compensated for by differential corrections. For this, a differential eLoran reference station site is deployed within 20 to 30 miles (32 to 48 kilometers) of the area of interest. The reference station compares its measured ASFs against the published values and broadcasts corrections to the users through the Loran data channel. Figure 1 shows the principle of differential eLoran positioning in a maritime environment and is representative of its use in other modalities as well.
Figure 1. Overview of a representative eLoran system.
eLoran meets the application requirements shown in Table 1. While unaided, Loran-C does not meet the requirements for a multi-modal, redundant PNT system, specifically the position accuracy requirement. The U.S. first developed eLoran to reduce the positioning error and to enable the system to meet modal performance requirements.
Table 1. eLoran system performance requirements.
eLoran Applications
We are staunch advocates of GPS and believe it should be fully funded, kept technically advanced, protected, toughened and augmented. When GPS is available and trustworthy, it should be used. However, no technology is failsafe, and prudent users should not rely on a sole source for their PNT needs. GPS has been called “a single point of failure” for much of the U.S. economy and critical infrastructure. Applications and requirements vary widely from wireless network communications of ± 1.5 microseconds, to maritime harbor entrance and approach requirements of ± 20 meters, to phasor measurement unit requirements in the electric power grid of ± 500 nanoseconds.
It is important to recognize the challenge of providing assured PNT while also taking advantage of the efficiencies gained by implementing a common solution across all sectors, industries and users. Point solutions can provide complementary PNT for specific individual or modal needs, and any resilient PNT ecosystem includes multiple levels of redundancy.
Some key application areas in which eLoran can provide complementary PNT are telecommunications, energy, finance and transportation. We believe these will be some of the first sectors to adopt and exploit eLoran as a component of their critical infrastructure protection and possibly as a co-primary PNT solution alongside GPS.
Telecommunications Sector. A March 2014 letter from the Alliance for Telecommunications Industry Solutions (ATIS) to the National Security Telecommunications Advisory Committee contained an attached document, Recommended Updates to Telecom Vulnerability to Loss of GPS Signals Documentation, that outlined three areas of concern that ATIS has identified relating to the exposure of commercial communications systems to a loss of the GPS signal. Included in the documentation was the statement: “With the Loran systems decommissioned, GPS is currently the only technology that can meet synchronization requirements for E911 as there is no other widely available access to UTC time of day in the United States.” eLoran’s Loran data channel provides the UTC time-of-day information that the telecommunications industry seeks, as well as providing complementary timing (phase) and/or frequency solutions that would mitigate ATIS’s concerns about: (1) the size of the area and duration effects of a GPS outage, (2) the effects of spoofing, (3) the inability of oven-controlled crystal oscillators (OCXOs) to maintain phase alignment for 24 hours at 1.5 microseconds, and (4) the phase performance of OCXOs in varying temperature environments.
The European Telecommunications Standards Institute Primary Reference Clock mask is one tool used by the telecommunications industry to determine the quality of timing signals in telecommunication applications. Figure 2 shows that eLoran is able to meet maximum time interval error (a measurement of wander or time stability) requirements, often outperforming GPS. Testing was performed independently in a cooperative effort between the United Kingdom National Physical Laboratory and Chronos Technology Ltd., UrsaNav’s reseller in England.
Figure 2. Maximum time interval error plot of eLoran and GPS.
Energy Sector. At present, GPS is the only time source for phasor measurement unit (PMU) (also known as synchrophasor) and frequency data recorder (FDR) sensors used to collect data that measures the state of an electrical system and manages power quality. PMUs/FDRs are a necessary component of the movement to a smart-grid approach to improve energy efficiency on the electrical grid and in businesses and homes. PMUs and FDRs cease to work if the GPS signal is lost or unstable. In 2013, UrsaNav began working with the University of Tennessee at Knoxville (UTK) to demonstrate the capability of eLoran, alongside GPS, to provide the necessary timing accuracy for UTK’s high-precision FDRs to collect synchrophasor data from the U.S. power grid. The required accuracy of the timing reference source is ± 500 nanoseconds, needed by each device performing synchrophasor measurements.
The laboratory setup in Bedford, Mass., used side-by-side FDRs: one using a GPS receiver and one using an eLoran receiver. Other than replacing the GPS receiver with an eLoran receiver in one of the FDRs, no other changes were made. The eLoran signals were being transmitted from a former U.S. Coast Guard (USCG) Loran Support Unit in Wildwood, N.J., more than 300 miles (483 kilometers) from our Bedford laboratory.
“Raw” eLoran was used for the test, that is, with no differential corrections nor continuous receiver antenna calibration. Figure 3 shows the resultant frequency and phase angle comparisons between GPS and eLoran. Green is eLoran; black is GPS. Frequency comparisons are on the left, top and bottom. Phase angle comparisons are on the right, top and bottom. The bottom left graph is a blow-up of the area encircled in red in the top left graph. The bottom right graph is a blow-up of the area encircled in red in the top right graph. In both cases, eLoran performs on par with GPS.
Figure 3. Frequency data recorder outputs from GPS and eLoran.
Financial Sector. A European Securities and Markets Authority (ESMA) report, dated May 22, 2014, indicates that the majority of trading venues are already coordinated with GPS time, and further states that the deployment of these systems might be costly and technically challenging. ESMA’s view is that each trading venue and market participant should rely on an atomic clock to issue timestamps. An eLoran timing alternative would be less costly, less technically challenging, and, when used in concert with other solutions (such as GPS, atomic clocks or Network Time Protocol / Precision Time Protocol) would also provide trusted time. eLoran would provide absolute time over very wide areas, thereby allowing dispersed markets and users to take advantage of this synchronized time solution. Additionally, eLoran can often provide time indoors, using a magnetic field (H-field) antenna, thereby precluding the permits and expense required for a rooftop antenna installation. ESMA has asked for industry comment on its proposed requirement to synchronize clocks to the microsecond level, and invited industry responses to its preliminary view that business clocks be accurate at least up to the microsecond level.
Transportation Sector – Aviation. PNT use in air traffic management is illustrative. In accord with U.S. Federal Aviation Administration (FAA) planning, a principal surveillance source in the U.S. national air space (NAS) by 2020 will be Automatic Dependent Surveillance-Broadcast (ADS-B), where the required positional accuracy of aircraft relies on GPS position. Moreover, the independent validation and backup of GPS-derived positions relies on accurate time-of-arrival measurements at a network of 650 radio stations in the NAS that currently use GPS-disciplined clocks with accuracy down to 30 nanoseconds. These radio stations are critical infrastructure of the Surveillance and Broadcast Services (SBS) system, which provides ADS-B surveillance to FAA air traffic management (ATM).
The FAA recognizes the need for a backup to surveillance and navigation in the event of local, regional and wide-scale GPS outages, and is examining both near-term and long-term strategies for continuity of operations during those outages. Because of the long lead times for ATM technology insertion, near-term mitigation strategies out to at least 10 years are constrained by existing ATM ground infrastructure and current avionics capabilities. Long-term solutions are not so constrained, and may be based on new signals in space, new ground infrastructure and new avionics capabilities.
Surveillance. Beginning in 2020, ADS-B will be a principal surveillance technology. In recognition of the need for a backup if GPS fails, the FAA is planning to maintain a mix of beacon-interrogation radar and wide-area multilateration (WAM) in the near term. The long-term strategy is still very much in the evolutionary stage.
Navigation. Near-term strategies involve a mix of approaches based upon existing infrastructure and the current capability of avionics. A leading approach, referred to as DME/DME/IRU, uses two-way ranging to multiple Distance Measuring Equipment (DME) facilities augmented by the avionics inertial reference unit (IRU). This approach is practical and applicable more to air carrier aircraft than regional jets or general aviation. Other approaches rely to some extent on the use of very high frequency Omni-Directional Range (VOR) facilities. As with surveillance, the long-term strategy is very much evolutionary.
It is instructive to note that near-term solutions rely on existing radar, DME and VOR infrastructure because it is in place and is compatible with existing avionics. In the long-term view, new technologies with less costly infrastructure are likely to be more cost-effective, especially if they provide benefits beyond ATM applications. eLoran is such a technology.
Transportation Sector – Maritime. There is an increasing awareness in the maritime world that no single system can provide PNT resiliently under all circumstances. At this moment, GPS (with augmentations) is used on most commercial vessels, and in many cases integrated into systems we did not expect would need or use GPS-derived position or time. Even though the introduction of GLONASS, Galileo, BeiDou and other GNSS systems will provide some resilience, the underlying (satellite) technology remains the same, only providing relatively weak signals from space at mostly the same or close-by frequencies for compatibility and inter-operability.
The International Maritime Organization (IMO) recognizes the need for multiple PNT systems on board maritime vessels. The organization developed the e-Navigation concept to increase maritime safety and security via means of electronic navigation, which calls for at least two independent dissimilar sources of positioning and time in a navigation system to make it robust and fail safe. As a follow on, IMO’s Navigation, Communications and Search and Rescue Committee is considering performance standards for multi-system shipborne navigation receivers, which includes placeholders for satellite, augmentation and terrestrial systems.
The most viable terrestrial system providing PNT services that meet IMO’s requirements is eLoran. With three eLoran transmitters in good geometry, eLoran can provide sub-10 meter (95 percent probability level) horizontal positioning accuracy and UTC synchronization within 50 nanoseconds, sufficient to be the co-primary PNT solution with GNSS. The General Lighthouse Authorities of the United Kingdom and Ireland (GLAs) have installed UrsaNav’s differential eLoran reference stations to provide the world’s first initial operational capability (IOC) eLoran system.
Together with Loran transmitters in England, France, Germany, Norway and Denmark, the differential eLoran reference stations provide better than 10-meter positioning accuracy at seven ports and port approaches along the English and Scottish east coast. IOC was achieved at the end of 2014, with full operational capability planned for 2018. Other nations have either begun, or are exploring, similar projects.
Figure 4 shows the accuracy of an eLoran position at the differential reference station on the Humber River in England. Figure 5 shows the position accuracy while on board a vessel transiting outbound on the river from Humber to the North Sea.
Figure 4. Zero-baseline accuracy at Humber reference station.Figure 5. Onboard, en route accuracy on the Humber River.
Current State of eLoran Technology
eLoran technology has been available since the mid-1990s and is still available today. In fact, the state-of-the-art of eLoran continues to advance along with other 21st-century technology. eLoran system technology can be broken down into a few simple components: transmitting site, control and monitor site, differential reference station site and user equipment.
Modern transmitting site equipment consists of a high-power, modular, fully redundant, hot-swappable and software configurable transmitter, and sophisticated timing and control equipment. Standard transmitter configurations are available in power ranges from 125 kilowatts to 1.5 megawatts. The timing and control equipment includes a variety of external timing inputs to a remote time scale, and a local time scale consisting of three ensembled cesium-based primary reference standards. The local time scale is not directly coupled to the remote time scale. Having a robust local time scale while still monitoring many types of external time sources provides a unique ability to provide proof-of-position and proof-of-time. Modern eLoran transmitting site equipment is smaller, lighter, requires less input power, and generates significantly less waste heat than previously used Loran-C equipment.
The core technology at a differential eLoran reference station site consists of three differential eLoran reference station or integrity monitors (RSIMs) configurable as reference station (RS) or integrity monitor (IM) or hot standby (RS or IM). The site includes electric field (E-field) antennas for each of the three RSIMs.
Modern eLoran receivers are really software-defined radios, and are backward compatible with Loran-C and forward compatible, through firmware or software changes. ASF tables are included in the receivers, and can be updated via the Loran data channel. eLoran receivers can be standalone or integrated with GNSS, inertial navigation systems, chip-scale atomic clocks, barometric altimeters, sensors for signals-of-opportunity, and so on. Basically, any technology that can be integrated with GPS can also be integrated with eLoran.
Figure 6 shows a resilient PNT receiver that includes GPS, DGPS, eLoran and a dual-band (100/300 kHz) E-field antenna. The left-hand antenna, shown installed on the P&O Ferries’ Pride of Hull, is the resilient PNT antenna. The right-hand antenna is a standard GPS antenna.
Figure 6. Resilient PNT receiver and dual-band antenna.
World View of eLoran
Nine nations are operating Loran-C or eLoran stations, including Russia and China. It is our understanding that the Republic of Korea, India and the Kingdom of Saudi Arabia are pursuing the installation of eLoran technology or upgrading their Loran-C technology to eLoran.
The modernization and upgrade of the U.S. Loran-C system to eLoran was a congressionally mandated program jointly executed by the FAA and USCG from 1997 to 2009, and funded at $160 million. During this time, eLoran was successfully tested and demonstrated in all modes: aviation, maritime, land-mobile, location-based, and timing and frequency. Further, eLoran has been successfully in operation in the U.K. for several years. Every national and international government, industry and academic report has concluded that GNSS is vulnerable and that eLoran is the best complementary solution to help negate those vulnerabilities.
The U.S. terminated its Loran-C service, and thereby its nascent eLoran program, in 2010. Canada followed suit and terminated its Loran-C service as well. Shortly thereafter, DHS/USCG began dismantling or demolishing the modernized infrastructure. However, in December 2014, Congress directed that DHS/USCG preserve the existing, unused U.S. Loran-C infrastructure, unless the Secretary of Homeland Security certifies it is not needed for a system to complement GPS.
In March 2015, U.S. House of Representatives Resolution (H.R.) 1678, a bill that would require establishment of a strong, difficult-to-disrupt terrestrial system to complement GPS, and to serve as another source of PNT when GPS isn’t available, was referred to the Committee on Armed Services. The bill seeks to amend the language that provided for the establishment and management of GPS in Title 10, the section of law that deals with the armed services. We understand that other members of Congress have expressed interest and will be co-sponsoring the bipartisan bill. H.R. 1678 was introduced by Congressman John Garamendi (Democrat, Calif.) with Congressman Duncan Hunter (Republican, Calif.), Congressman Frank LoBiondo (Republican, N.J.) and Congressman Peter DeFazio (Democrat, Ore.) as the initial co-sponsors. In August, the bill was referred to the Subcommittee on Strategic Forces.
Additionally, in May 2015, the DHS and USCG entered into a cooperative research and development agreement with UrsaNav and Exelis (now part of Harris Corp.) to research, evaluate and document at least one alternative to GPS as a means of providing PNT information in the form of eLoran.
It is our understanding that the U.S. Congress is still considerably concerned about the lack of a complementary PNT solution to safeguard U.S. critical infrastructure and key resource sectors, and to protect our economy in the event of a GPS outage. Congress continues to press the administration for a resolution, in the form of a continental U.S. eLoran system, before our nation is placed at further risk.
Acknowledgments
The authors wish to acknowledge the assistance of Dr. Ron Bruno, Harris Corp., and Dr. Paul Williams and Chris Hargreaves, GLAs.
Manufacturers
UrsaNav provided the eLoran receiver and Symmetricom, now Microsemi, provided the GPS receiver for the timing tests shown in Figure 2.
STEVE BARTLETT is vice president of operations at UrsaNav, Inc., North Billerica, Mass.
GERARD OFFERMANS is senior research scientist at UrsaNav engaged in various R&D project work and product development.
CHARLES SCHUE is co-owner and president of UrsaNav.
FURTHER READING
eLoran
“Can eLoran Deliver Resilient PNT?” by N. Ward, C. Hargreaves, P. Williams and M. Bransby in Proceedings of The Institute of Navigation 2015 Pacific PNT Meeting, Honolulu, Hawaii, April 20–23, 2015, pp. 1051–1054.
“eLoran Initial Operational Capability in the United Kingdom – First Results” by G. Offermans, E. Johannessen, S. Bartlett, C. Schue, A. Grebnev, M. Bransby, P. Williams and C. Hargreaves in Proceedings of the 2015 International Technical Meeting of The Institute of Navigation, Dana Point, Calif., January 26–28, 2015, pp. 27–39.
“Implementing a Wide Area High Accuracy UTC Service via eLoran” by G. Offermans, E. Johannessen and C. Schue in Proceedings of the 46th Annual Precise Time and Time Interval Systems and Applications Meeting, Boston, Mass., December 2014, pp. 124–133.
2014 Federal Radionavigation Plan (F, DOT-VNTSC-OST-R-15-01, U.S. Department of Defense, Department of Homeland Security and Department of Transportation, Washington, D.C., available from the National Technical Information Service, Springfield, Virginia, 2015.
1990 Federal Radionavigation Plan, DOT-VNTSC-RSPA-90-3 and DOD-4650.4, U.S. Department of Transportation and U.S. Department of Defense, Washington, D.C., available from the National Technical Information Service, Springfield, Virginia, 1990.
CLEVELAND, Ohio — November 18, 2015 — GPS World relaunched this week with a redesigned print magazine and website, GPSWorld.com. Both feature a new logo, new design and widened coverage.
The GPS World brand has expanded its technical coverage to include all GNSS and Position, Navigation & Timing (PNT) solutions, trends and applications.
“We celebrated GPS World’s 25th anniversary in 2014 by embarking on the brand’s most-comprehensive research project to date,” said Kevin Stoltman, president and CEO of Cleveland-based North Coast Media, GPS World’s parent company.
The GPS World team conducted a research project and used a rebranding/repositioning expert to help better serve its industry-leading family of readers and marketing partners for decades to come.
“After months of comprehensive focus groups and surveys, we discovered readers and advertisers across the globe are fiercely loyal to GPS World,” Stoltman adds. “They love what we do, the information we offer. They just crave more of it: They want us to cover all GNSS and PNT technologies, trends and applications — and that’s exactly what we’re doing now, across all media platforms: print, digital and events.”
GPS World November 2015
The new GPS World publication also features a six-fold increase in segment-specific technical coverage — GNSS/PNT trends, obstacles and opportunities related to: Survey, Mapping, OEM, unmanned autonomous vehicles (UAVs), Defense, Mobile, Transportation and Machine Control. Those increase in segments also are reflected on GPSWorld.com.
“GNSS — and GPS as its leading element — remains at the core of all that we and the industry do,” said Alan Cameron, editor-in-chief and publisher of GPS World. “But it has become abundantly clear that to deliver the everywhere-everytime solution, GPS/GNSS require augmentation, back-up and alternatives. This is the promise of the future for UAVs, critical infrastructure, defense, machine control, surveying, construction and countless other fields: a consistent, highly accurate PNT solution at all times. Our new brand and expanded coverage represent our commitment to the industry in pursuit of this goal.”
The new website features a mobile-responsive design as well as new opportunities for website sponsorship with the Platinum Website Sponsorship option.
About GPS World
Founded in 1990, GPS World has an independently audited total unduplicated reach of 70,650 — delivering the largest audience in the industry. The B2B media brand publishes nine e-newsletters with a combined readership of more than 113,000, and conducts monthly technical webinars for engineers. Its website, GPSWorld.com, draws an industry-dominant 650,000 visitors and 1.5 million page views annually. (Source: June 2015 Verified Audit Circulation Annual Audit Report)
For more information on advertising or sponsorship opportunities with GPS World, please contact International Account Manager Michelle Mitchell at [email protected] or 216-363-7922.
GPS World is published by North Coast Media LLC, the largest B2B publishing company headquartered in Cleveland. NCM’s flagship brands include LP Gas, Pit & Quarry, GPS World, Pest Management Professional, Landscape Management and Golfdom. Ancillary brands include Portable Plants & Equipment, Geospatial Solutions, Athletic Turf, Truman’s Scientific Guide to Pest Management Operations and a host of other leading industry reference books.
