Example of unusual detected signal type likely to have an impact on GNSS performance. (Figures courtesy of Nottingham Scientific Ltd.)
Presented at the European Navigation Conference, Switzerland, May 2017
This paper summarizes major findings from the first year of monitoring by the International Knowledge Exchange, Experimentation and Exploitation (STRIKE3), a new European initiative to support the increasing use of GNSS within safety, security, governmental and regulated applications and addressing concerns about GNSS denial of service attacks. STRIKE3 monitors the international GNSS threat scene to capture the scale and dynamics of the problem and works with international GNSS partners to develop, negotiate, promote and implement standards for threat reporting and receiver testing through an international GNSS interference monitoring network.
European economies are now dependent on uninterrupted access to GNSS services. At the same time, GNSS vulnerabilities are being exposed, and threats to denial of GNSS service are increasing. We must ensure that there is a common standard for GNSS threat monitoring and reporting, and a global standard for assessing the performance of GNSS receivers and applications under threat. This will ensure the dominance of GNSS as the backbone to our positioning, navigation and timing needs.
STRIKE3 has built a network of more than 20 interference monitoring sites in 14 countries. This enables STRIKE3 to assess the incidence of deliberate jamming versus unintentional interference to be estimated, as well as comparisons of the most common types of interference at different types of location. Detailed data about the interference signals is collected and used in the creation of test standards. Common signal types as well as unusual ones that are likely to have a major impact on GNSS performance are extracted from the database and added to a test methodology. These will be used to test different types of receivers to better understand impact and help improve mitigation, finally leading to an international test specification.
Working well after midnight on July 19, 1977, a Rockwell Collins engineer named David Van Dusseldorp sat on the rooftop of a company building in Cedar Rapids, Iowa, adjusting an antenna every five minutes to receive a signal from the world’s first Global Positioning System (GPS) satellite, known as NTS-2.
Within a small window of time, the satellite was turned on and the message was successfully received and decoded by the team working the GPS receiver below.
The receiver station used by Rockwell Collins in 1977 was about six feet tall and had two seats, becoming a part of history for receiving and decoding the world’s first GPS signal. (Photo: Rockwell Collins)
Since then, the technology has grown to be the standard of navigation around the world and touches nearly every part of our daily lives. To commemorate the 40-year anniversary, Rockwell Collins invited retirees involved in the project to share their firsthand stories at an event held in Cedar Rapids today.
“We had leaders and team members working together and I knew we could meet the challenge put before us,” said Van Dusseldorp. “The future of GPS was uncertain at the time, but I really felt like we had just accomplished something important.”
Soon after successfully receiving the signal, the U.S. Air Force awarded Rockwell Collins the NAVSTAR GPS user equipment contract. This was the first of many wins that would position the company as a market leader in GPS products for aerospace and defense.
Since that time, Rockwell Collins has continued to pioneer advancements in GPS such as being the first to complete a transatlantic flight using GPS navigation in 1983. In 1994, a secure, military-grade Precision Lightweight GPS Receiver (PLGR) was first fielded that provided warfighters a tactical navigational advantage on the battlefield.
In 2014, Rockwell Collins achieved another milestone in navigation technology by successfully developing a prototype to track a satellite in the Galileo navigation system being created by the European Union to provide global coverage for its nations.
The Rockwell Collins GPS-4000S.
A modern version of the GPS receiver used in 1977 is the Rockwell Collins GPS-4000S, which has the ability to process the transmissions of up to 10 GPS satellites and two Space-Based Augmentation Systems (SBAS) geostationary satellites simultaneously. Compared to the first GPS receiver station that was six feet tall, the GPS-4000S receiver is only 7.87 inches tall.
Size and power of receivers have evolved for different applications, like the Micro GPS Receiver Application Module (MicroGRAM). The receiver is only one inch tall, can use data from up to 12 GPS satellites and consumes the least power of any receiver in its class. Other advancements in receivers include anti-jamming and anti-spoofing technologies crucial to security and efficiency when used within critical military and aircraft operations.
Since that historic day 40 years ago, Rockwell Collins has introduced more than 50 GPS products including GPS anti-jam and precision landing systems, and has delivered more than one million GPS receivers for commercial avionics and government applications, helping shape how the world navigates both on the ground and in the air.
After four years of work, the European Space Agency (ESA) team tasked with keeping the world informed on the status of the Galileo satellite navigation system has formally passed on its responsibility to a European Union agency.
This shift is part of a wider transfer of responsibilities, as this month see the official handover of the running of the Galileo system from ESA to the European Global Navigation Satellite System Agency (GSA).
“Our job — working with the European Commission and GSA — has been to inform Galileo users in an official, transparent way of any system changes that could affect Galileo satellites,” explains Rafael Lucas Rodriguez, ESA’s Galileo services engineering manager.
“Keeping our users in the picture on planned activities that might lead to satellite unavailability, or any unplanned outages, has helped them to plan their own test activities around Galileo signals and to prepare future products.”
The very first Notice Advisory to Galileo Users (NAGU) was issued in June 2013, just three months after the first Galileo positioning fix was achieved, to a then small community of researchers and industrial users, interested in making tests with the newborn four-satellite constellation.
A total of 189 NAGUs were issued under ESA oversight in the last four years, as the constellation grew to its current 18 satellites. The user base increased dramatically from 86 to 774 registered users on the European GNSS Service Centre website as companies worked to prepare Galileo-ready products and then, on 15 December 2016, Galileo’s Initial Services began operating.
GSC web portal 2013.
Throughout this period, the NAGUs, published on the website of the European GNSS Service Centre and sent to subscribers via email, gave the user community a reliable overview of Galileo’s overall status and that of individual satellites.
NAGUs are issued as new satellites are launched and when satellites become ready for service provision, or to give advance warning of signal unavailability owing to planned maintenance or testing activities, or to notify users of unplanned outages and then to inform them when satellites become active again.
“Broadcom is a regular consumer of the NAGUs released by the Galileo Service Centre,” says Javier de Salas, R&D Director at GNSS receiver chipset manufacturer Broadcom.
“Not only do they help us to organise our engineering activities and tests but, more importantly, they are used as input into our orbit prediction engine for our Long Term Orbits products, which in turn are used by hundreds of millions of consumers worldwide.”
Rafael Lucas of the ESA team adds, “Around a dozen people at ESA worked to begin defining, setting up and operationalising the NAGU process, modelled after the well-established Notice Advisory to Navstar Users of GPS.
GPS expert Scott Pace has been chosen by the White House to serve as executive secretary of the National Space Council. Pace is currently director of the Space Policy Institute and Professor of Practice of International Affairs at George Washington University (GWU).
He also serves as a special counselor to the National Space-Based Positioning, Navigation and Timing (PNT) Advisory Board.
Pace has a long career in space policy and is well known and highly respected in the community. Ever since the Trump Administration indicated that it would reestablish the Space Council, his is virtually the only name rumored to be in the running to serve as the head of its staff, according to the announcement on Space Policy Online.
The council was officially reestablished on June 30, and is chaired by Vice President Mike Pence. Pace was spotted at Kennedy Space Center last week where Pence addressed the KSC workforce, further fueling speculation that he would be appointed as head of the Space Council.
In its announcement, the White House said Pace has “honed his expertise in the areas of science, space, and technology” citing his career at GWU, NASA, the White House Office of Science and Technology Policy (OSTP), and the RAND Corporation’s Science and Technology Policy Institute.
Pace received a bachelor’s degree in physics from Harvey Mudd College, a master’s in Aeronautics and Astronautics and Technology and Policy from MIT, and a Ph.D. in policy analysis from the RAND Graduate School.
During the George W. Bush Administration’s second term, Pace was NASA’s Associate Administrator for Program Analysis and Evaluation under then-NASA Administrator Mike Griffin. He was closely involved in formulating the Constellation program to return humans to the surface of the Moon and then going on to Mars.
His expertise is much broader, however. He was deputy director and acting director of the Office of Space Commerce at the Department of Commerce from 1990 to 1993, when that office reported to the Deputy Secretary of Commerce (instead of being part of NOAA as it is today).
He has been very active on GPS issues for many years, including protecting GPS spectrum at World Radiocommunications Conferences (WRCs) organized by the International Telecommunication Union (ITU). He was a member of the U.S. delegation to the WRCs in 1997, 2000, 2003 and 2007.
He also has served as a member of the U.S. delegation to the United Nations Committee on Peaceful Uses of Outer Space (2009 and 2011-2015). Today he is vice-chair of NOAA’s Advisory Committee on Commercial Remote Sensing, of which he has been a member for several years.
John Logsdon, who founded GWU’s Space Policy Institute and is Professor Emeritus there, said via email that he could think of “no one more qualified” to take on the “essential task of crafting a strategic approach to using U.S. space capabilities to advance this country’s geopolitical interests and to forge productive collaboration among all government space actors and the private sector.”
Mary Lynne Dittmar, president and CEO of the Coalition for Deep Space Exploration (CDSE), also praised the announcement.
“Dr. Pace’s unique combination of experience in government, the private sector, and academia, and his internationally-recognized expertise in space policy, make him an exemplary selection” for the position. She added that CDSE looks forward to working with “the Council, its staff, and the vice president’s office to support U.S. leadership and strategic interests in space.”
CDSE is an alliance of space industry businesses and advocacy groups that support deep space human exploration and science.
Here there be dragons. That phrase (or a variation of it) was used by early mapmakers to designate the unknown — and alert sailors to the danger of traveling into uncharted waters.
I’ve always admired explorers who dared to push the boundaries of the known world. We’ve moved from the Age of Exploration to the Age of Information, but exploration continues on frontiers big and small.
Today, of course, most people think of the world as having been mapped. They can simply call up Google maps on their smartphone and see not only the world, but their town, their street and their house — in representational cartography (traditional map), satellite imagery, or even street-view imagery.
Professionals in geographic information systems (GIS) know better. The world is still a mystery in uncounted areas. For one thing, it’s not static: Volcanoes form new land masses, storms change coastlines, the sea-level is rising. For another, there’s more to exploration than a basic map.
That’s where the GIS professional takes center stage, assessing an area beyond what is already known, using a variety of tools to collect and analyze data. As Esri defines it, a GIS lets us “visualize, question, analyze and interpret data to understand relationships, patterns and trends. GIS benefits organizations of all sizes and in almost every industry.” A software-based profession, GIS experts use GPS, GNSS and inertial to gather data, which is where this magazine comes in.
At GPS World, we share GIS developments in our Mapping Market Watch, Mapping Launchpad and at geospatial-solutions.com.
Navigation, a journal published by The Institute of Navigation, has experienced continued growth according to the latest Journal Impact Factor (JIF) report.
The JIF of an academic journal is a measurement tool used to calculate the yearly average number of citations to recent articles published in a journal and is an indication of the relative importance of the journal within its field. It is generally recognized that journals with higher impact factors are deemed more important than those with lower ones due to its citation rate.
Navigation’s Journal Impact Factor is now 1.604, an increase from 0.979 last year and 0.562 the year before. Total citations have increased by more than 270 percent over the past two years.
“We are especially pleased with our strong performance,” said Boris Pervan, Navigation‘s editor. The increase in Navigation‘s impact factor is reflective of ION’s commitment to improve the quality and content of the papers published in the journal.
ION extends its gratitude to its esteemed editorial board, which includes: Penina Axelrad, Pau Closas, Paul Groves, Christopher Hegarty, Changdon Kee, Jiyun Lee, Gary McGraw, Michael Meurer, Thomas Pany, Boris Pervan (editor), Jason Rife, Andrey Soloviev, Maarten Uijt de Haag, Todd Walter, Lisa Beaty (managing editor) and Fiona Walter (administrative editor).
Navigation is indexed in the Thomson Reuters Science Citation Index Expanded (also known as SciSearch), Thomson Reuters Journal Citation Reports/Science Edition and Thomson Reuters Current Contents/Engineering Computing and Technology.
Additionally, Navigation is abstracted in Electrical and Electronics Abstracts. Citations and abstracts of articles in Navigation can be found using the INSPEC online database. Navigation is published by ION in partnership with Wiley.
The Institute of Navigation is the world’s premier professional society dedicated to the advancement of the art and science of positioning, navigation and timing. The institute is a national organization whose membership spans worldwide.
Esri President Jack Dangermond describes the value of GIS at the plenary session of the Esri UC.
“Maps are alive,” declared Jack Dangermond, Esri founder and president, on the plenary stage at the world’s largest GIS event. The 38th annual Esri User Conference is taking place July 10–14 at the San Diego Convention Center.
We are on the cusp of a data and information explosion, Dangermond explained while introducing the conference theme “The Science of Where.”
“We are about to launch in to a different scale,” he predicted. GIS is changing rapidly with numerous new information streams and advances in real-time data, and maps are central to understanding our changing world. GIS provides a platform for managing, analyzing and applying that data and information, he said.
His advice? “Share, collaborate. Communicate so we collectively can learn all bout world. Let’s take our work collectively to scale.”
GIS is vital to understanding developments in numerous areas: population growth, climate change, social changes, natural disasters and political polarization, to name a few. “We have to do everything we can to better understand and form collaborations to address these areas,” he said.
“Today’s businesses and governments require new ways of thinking,” said Dangermond. “Our users are leading the charge, using mapping and analytics to empower digital transformation, accelerate understanding of big data, and democratize technology. It is an inspiration to see how so many different organizations are applying the science of geography and the technology of GIS to gain insight into their data and reveal hidden patterns and spatial relationships.”
Dangermond presented numerous examples of organizations using GIS in new ways. For instance, Oak Ridge National Laboratory has created an “energyshed” map similar to a watershed map. An orchard is using GIS and GPS tracking to collect data on cherry picking. The Democratic Republic of Congo is making use of crowdsourcing to generate maps.
Story Maps are aiding what Dangermond calls “geo-journalism,” telling stories about new developments in virtually every field.
A screenshot of “Washington’s Ice Age Floods” story map from the Washington Geological Survey.
Dangermond also presented the following awards:
Ice Age Floods, by the Washington Geological Survey, won Best Story Map.
The GIS Digital Transformation Award went to Abu Dhabi, which “has taken GIS to new frontiers” in every government agency with every citizen, Dangermond said.
The Enterprise GIS Award went to the U.S. National Geospatial-Intelligence Agency for maintaining the largest GIS database in the world, with daily updates and a user-friendly portal.
The President’s Award, chosen personally by Dangermond, was given to the United Parcel Service (UPS), which saves up to $400 million a year with its location-enabled Orion system. It puts the ability to update maps in the hands of supervisors, who constantly are optimizing routes. Now deployed in the U.S., the Orion system is going worldwide.
Other speakers and their topics at the first-day plenary included:
Renowned author and theoretical physicist Geoffrey West — His book Scale: The Universal Laws of Growth, Innovation, Sustainability, and the Pace of Life in Organisms, Cities, Economies, and Companies, explores dynamic growth and the challenges of achieving that growth sustainably.
Oakland County, Michigan — Making government services more cost-effective
Chesapeake Conservancy — Analyzing imagery and sensor data to protect watershed areas
Taylor Shellfish Farms — Transforming the family-run business by implementing cloud GIS solutions so staff can perform spatial data collection in the field
Severe Trauma Air Rescue Service (STARS), Calgary, Canada — Powering real-time decision support systems to improve emergency services
Smart Dubai — Empowering one of the smart cities of the future with citizen engagement and smart growth
Walt Disney Animation Studios — Behind the scenes of Zootopia.
GIS provides the means for users to apply “the Science of Where” everywhere, according to Esri President Jack Dangermond. (Photo: Esri)
“Maps are alive,” declared Jack Dangermond, Esri founder and president, on the plenary stage at the world’s largest GIS event. The 38th annual Esri User Conference is taking place July 10–14 at the San Diego Convention Center.
We are on the cusp of a data and information explosion, Dangermond explained while introducing the conference theme “The Science of Where.”
Esri President Jack Dangermond describes the value of GIS at the plenary session of the Esri UC. (Photo: GPS World)
“We are about to launch in to a different scale,” he predicted. GIS is changing rapidly with numerous new information streams and advances in real-time data, and maps are central to understanding our changing world. GIS provides a platform for managing, analyzing and applying that data and information, he said.
His advice? “Share, collaborate. Communicate so we collectively can learn all bout world. Let’s take our work collectively to scale.”
GIS is vital to understanding developments in numerous areas: population growth, climate change, social changes, natural disasters and political polarization, to name a few. “We have to do everything we can to better understand and form collaborations to address these areas,” he said.
“Today’s businesses and governments require new ways of thinking,” said Dangermond. “Our users are leading the charge, using mapping and analytics to empower digital transformation, accelerate understanding of big data, and democratize technology. It is an inspiration to see how so many different organizations are applying the science of geography and the technology of GIS to gain insight into their data and reveal hidden patterns and spatial relationships.”
Dangermond presented numerous examples of organizations using GIS in new ways. For instance, Oak Ridge National Laboratory has created an “energyshed” map similar to a watershed map. An orchard is using GIS and GPS tracking to collect data on cherry picking. The Democratic Republic of Congo is making use of crowdsourcing to generate maps.
Story Maps are aiding what Dangermond calls “geo-journalism,” telling stories about new developments in virtually every field.
A screenshot of “Washington’s Ice Age Floods” story map from the Washington Geological Survey.
Dangermond also presented the following awards:
Ice Age Floods, by the Washington Geological Survey, won Best Story Map.
The GIS Digital Transformation Award went to Abu Dhabi, which “has taken GIS to new frontiers” in every government agency with every citizen, Dangermond said.
The Enterprise GIS Award went to the U.S. National Geospatial-Intelligence Agency for maintaining the largest GIS database in the world, with daily updates and a user-friendly portal.
The President’s Award, chosen personally by Dangermond, was given to the United Parcel Service (UPS), which saves up to $400 million a year with its location-enabled Orion system. It puts the ability to update maps in the hands of supervisors, who constantly are optimizing routes. Now deployed in the U.S., the Orion system is going worldwide.
UPS took home the President’s Award for innovative use of GIS. (Photo: Esri)
Other speakers and their topics at the first-day plenary included:
Renowned author and theoretical physicist Geoffrey West — His book Scale: The Universal Laws of Growth, Innovation, Sustainability, and the Pace of Life in Organisms, Cities, Economies, and Companies, explores dynamic growth and the challenges of achieving that growth sustainably.
Walt Disney Animation Studios — Behind the scenes of Zootopia. (Read more here.)
Oakland County, Michigan — Making government services more cost-effective
Chesapeake Conservancy — Analyzing imagery and sensor data to protect watershed areas
Taylor Shellfish Farms — Transforming the family-run business by implementing cloud GIS solutions so staff can perform spatial data collection in the field
Severe Trauma Air Rescue Service (STARS), Calgary, Canada — Powering real-time decision support systems to improve emergency services
Smart Dubai — Empowering one of the smart cities of the future with citizen engagement and smart growth.
When someone utters the words “I’m nearly perfect,” get on your toes. Such self-appraisal usually masks something. It could be insecurity, denial, ignorance or simply fear. At the very least, some level of illusion, if not delusion, is involved.
The press release actually says, “The U.S. Air Force released two technical reports demonstrating that the Global Positioning System (GPS) continues to deliver exceptional performance to civilian users around the world….The 2014 and 2015 performance reports confirm that the GPS Standard Positioning Service (SPS) satisfied nearly all measurable performance commitments documented in the GPS SPS Performance Standard.”
Fair enough. Those are demonstrable facts. Nowhere does the release — other than in its headline — employ the words “perfect” or “near-perfect.”
The problem is, as current events repeatedly show, people remember only the headline. That may be all that they read or register in the first place.
Affixing the label “near-perfect” to GPS is “potentially dangerous,” points out Dana Goward of the Resilient PNT Foundation, “because it could exacerbate the public’s growing over-reliance on, and often blind faith in, GPS. Even if GPS did always perform perfectly, all kinds of things can happen to signals after they leave the satellites and before they get to receivers. Personal privacy devices, other jammers, spoofers, solar activity, other electromagnetic interference, even the local geography can significantly degrade or disable a receiver’s performance. That’s why in the GPS System Performance Standard the Air Force specifically says its responsibility ends once signals are in space.”
Perfection might exist in space, but it doesn’t down here.
Even in space, accidents sure will happen. The Air Force release documents GPS performance for 2014 and 2015. This conveniently draws up short of January 2016, when several GPS satellites broadcast a timing error that triggered equipment faults and failures globally for nearly 12 hours. Thus demonstrating something far from perfection.
Issuing a statement in the manner done on June 16 perpetuates a dangerous myth, keeps users in the dark about the actual state of affairs, cultivates a What-Me-Worry? approach to positioning, navigation and timing, and abets the lack of political will and understanding of GNSS vulnerabilities.
We have expanded the focus of this magazine to cover other technologies relevant and applicable to the field precisely because GPS, and by extension GNSS, great though they may be, are not perfect. Not even nearly.
At the end of 2016, the DemoGRAPE consortium observed, for the first time ever, ionospheric scintillations on Galileo signals in Antarctica, using Septentrio’s PolaRx5S GNSS reference receiver.
DemoGRAPE investigates improvement of high-precision satellite positioning with a view to developing scientific and technological applications in Antarctica. At higher latitudes, GNSS signal degradation due to ionospheric activity is more pronounced.
Septentrio’s PolaRx5S reference receiver.
The more precise phase-based positioning modes are particularly vulnerable to ionosphere disturbance such as scintillations. Elevated ionospheric activity can cause a loss of precise-positioning mode or, in more extreme cases, a total loss of signal lock.
Monitoring the movement and evolution of ice shelves and glaciers as well as geodetic prospecting require highly precise positioning. Besides this scientific interest, accurate positioning is important from a safety standpoint.
When visibility is limited and travel is restricted, designated routes between remote locations have to be strictly followed to avoid dangers such as falling into a crevasse during a snowstorm.
DEMOGrape is an international project lead by Istituto Nazionale di Geofisica e Vulcanologia (INGV), Rome, Italy in partnership with the Politecnico di Torino, the South African National Space Agency (SANSA) and the National Institute for Space Research, São Paulo, Brazil (INPE).
Septentrio’s PolaRx5S is the benchmark for GNSS space weather applications. It provides data for scintillation analysis (I&Q correlations, phase, code and carrier-to-noise) at up to 100 Hz for all GNSS L-band frequencies. SBF, RINEX and BINEX data logging is possible on both a built-in 16 GB memory and on an externally connected device. Up to 24 independent data archives can be defined. Logged data can be accessed via the web UI server or automatically pushed to a FTP server.
“We are really very happy of the fruitful collaboration with Septentrio colleagues that supported our measurements in the extreme environment of Antarctica,” the team said in an article published in Space Weather. “The first Galileo scintillations observed in the DemoGRAPE sites are attracting the attention of space weather communities, also beyond the European borders.” (Alfonsi, L., P. J. Cilliers, V. Romano, I. Hunstad, E. Correia, N. Linty, Fabio Dovis et al. “First Observations of GNSS Ionospheric Scintillations From DemoGRAPE Project.” Space Weather14, no. 10 (2016): 704-709).
“We are really proud to have enabled our colleagues and friends from INGV and the DEMOGrape consortium to make this first of a kind scintillation measurement on the Galileo signals,” said Bruno Bougard, director of R&D at Septentrio. “Galileo added value on high-precision application resides in its ability to increase the position availability and reliability compared to traditional GPS+GLONASS systems. Demonstrating its resilience to scintillation is key for operations at high latitudes.”
GPS signals are so weak, they cannot be used reliably where they are obstructed such as indoors or in concrete canyons. But if the satellites were much closer, their signals would be much stronger. The low Earth orbit Iridium constellation is already orbiting and providing a PNT service. This month we learn about its current capability and future promise.
By David Lawrence, H. Stewart Cobb, Greg Gutt, Michael O’Connor, Tyler G.R. Reid, Todd Walter and David Whelan
(A shortened version of “Innovation Insights” appeared in the magazine.)
INNOVATION INSIGHTS with Richard Langley
WHOA CANADA! July 1st marks Canada’s sesquicentennial. In 1867, four Canadian provinces, Ontario and Quebec (up to then known as the single Province of Canada), Nova Scotia and New Brunswick, joined together to form The Dominion of Canada — the name suggested by New Brunswick’s Sir Leonard Tilley. Other provinces came on board later with the last, Newfoundland and Labrador, joining in 1949.
Apart from my interest in educating all and sundry about the origins of the “true north, strong and free,” what has this got to do with GNSS or allied technologies? Well, it turns out that Canada has played and continues to play an important role in the development of communications and navigation technologies.
It started on Christmas Eve, 1906, when Canadian inventor Reginald Fessenden carried out the first amplitude modulation radio broadcast of voice and music. And in 1925, Edward “Ted” Rogers, a Canadian pioneer in the radio industry, invented a radio tube using alternating current that became a worldwide standard in radio circuits.
Many other developments in terrestrial communications took place in Canada over the years including microwave repeater technology and shortwave radio broadcasting from the famed transmitter plant (now defunct, unfortunately) established near Sackville, New Brunswick, during World War II.
There have also been significant Canadian advances in satellite technology. The first Canadian satellite, Alouette (French for “skylark”), was launched in September 1962 to study the ionosphere. Launched by the United States, it was the first satellite to be constructed by a country other than the U.S. or the Soviet Union. Several other Canadian ionospheric research satellites have been orbited since including CAScade, Smallsat and IOnospheric Polar Explorer or CASSIOPE, launched in September 2013. CASSIOPE carries eight instruments for studying the ionosphere including the University of New Brunswick’s GPS Attitude, Positioning, and Profiling instrument.
Canada has also been a leader in satellite communications technology. The first Anik geostationary satellite was launched in November 1972. (Anik means “little brother” in Inuktitut.) Eight more Anik satellites were launched subsequently including Anik F1R, which is also used to broadcast Wide Area Augmentation System information to GPS receivers. And the first satellite to explore the 14/12-GHz band for direct broadcasting to homes and businesses was Canada’s Communications Technology Satellite, dubbed Hermes, launched in January 1976.
And, of course, we don’t need to mention the Remote Manipulator System on the International Space Station, commonly known as Canadarm, nor the work of celebrity Canadian astronaut Col. Chris Hadfield.
In the area of satellite navigation, Canada is known for its development of techniques to use the U.S. Navy Navigation Satellite System or Transit for one-meter positioning accuracy permitting establishment of geodetic control points such as in Canada’s far north. Canada was also an early adopter of GPS and with software and hardware developments by industry, government and academia has made its mark in the world of precision positioning, navigation and timing.
Another Canadian initiative is the Aerion satellite-based air traffic surveillance system that will use the enhanced low Earth orbit Iridium constellation.
And we shouldn’t forget that Canada is slated to provide the search and rescue package for the GPS III satellites.
Speaking of GPS, we all know what a great technology it is, providing the “gold standard” in global satellite navigation. But it does have one dominant problem: the weakness of the signals. The signals are so weak that they cannot be used reliably where they are obstructed such as indoors or in concrete canyons. The problem stems from the fact that these medium Earth orbit satellites are far away and their energy is significantly spread out during their passage to Earth. If the satellites were much closer to the Earth, their signals would be much stronger. Mind you, you would need more satellites to provide global coverage. Fantasy? No. There is already a constellation of satellites in orbit providing such a PNT service. It is Iridium–the same constellation that will provide the Canadian-initiated aircraft tracking system–and in this month’s column we will learn about is current capability and future promise. Pretty neat, eh?
With the advent of smartphones, there are now more than four billion devices that make use of GNSS. These satellite navigation systems provide not just the blue dot representing location on our phones, but also support the critical infrastructure we rely upon.
The U.S. Department of Homeland Security recognizes that all 16 sectors of U.S. critical infrastructure depend on GPS — 13 of which have critical dependence. A recent report by London Economics estimates the cost of a GNSS outage to the U.K. alone would be over £1B per day.With autonomous systems on the rise, our reliance on GNSS will only be increasing.
As we become more dependent on this technology, we become vulnerable to its limitations. One major shortcoming is signal strength. Designed to work in an open-sky environment, GNSS is severely limited in deep attenuation environments, with little or no service in dense cities or indoors. Furthermore, we are susceptible to jamming where a 20-watt GNSS jammer can deny service over a city block.
The proximity of low Earth orbit (LEO) has the potential to provide much stronger signals than the distant GNSS core-constellations like GPS in medium Earth orbit (MEO). Today, the only LEO system with global coverage is the Iridium constellation used primarily for communications.
FIGURE 1 shows the 31-satellite GPS constellation in contrast with the 66-satellite Iridium network. The scale of the difference in distance (several Earth radii) is extraordinary. The result is that Iridium signals are 300 to 2,400 times stronger than GNSS signals on the ground, making them attractive for use in position, navigation and timing (PNT) applications where GNSS signals are obstructed.
FIGURE 1. The 66-satellite Iridium constellation in low Earth orbit and 31-satellite GPS constellation in medium Earth orbit.
LEO-based PNT is now mainstream, in the form of real-time signals that have been delivered over the Iridium satellite network since May 2016. This service is made possible by Satelles in partnership with Iridium Communications Inc. in a service called Satellite Time and Location (STL), a non-GNSS solution for assured time and location that is highly resilient and physically secure. Consumers, businesses and governments are already using these LEO-based signals in environments with high GNSS interference or occlusion.
The security features of these signals are also used to reliably validate GNSS PNT solutions in real time to help mitigate potential spoofing. Furthermore, the fast LEO orbits of Iridium generate Doppler-frequency-shift signatures significantly stronger than GPS, increasing the utility of the STL signal for positioning applications.
STL field tests demonstrate a positioning accuracy of 20 meters and timekeeping to within 1 microsecond, all in deep attenuation environments indoors. This adds substantial robustness in augmenting the GNSS core constellations like GPS and also allows for a standalone backup in many applications.
LEO Constellations: Past, Present, Future
In 1964, Transit (or the U.S. Navy Navigation Satellite System) became the first operational satellite navigation system. This constellation typically consisted of five to 10 satellites placed in polar orbits with an altitude of about 1,100 kilometers. Unlike many terrestrial radio navigation systems, a position fix was not instantaneous. It required 10 to 16 minutes of observation as a satellite passed overhead to achieve the needed geometric diversity. There was also latency; users had to wait for a satellite to come into view, which could take from 30 to 100 minutes.
The trade-off was accuracy; early performance was a few hundred meters and was later improved to 20 meters (and even down to about 1 meter for multiple-pass fixed-site surveys), the best performance of its day. In 1967, Transit became open for civilian use and remained operational until 1996 when GPS was at full operational capability.
The Soviet Union developed a system similar to Transit known as Parus/Tsikada, with first satellites on orbit in 1967. Parus/Tsikada operated on the same passive Doppler observation principle as Transit, on similar frequencies and in similar polar orbits.
Today, the largest satellite constellation with constant global coverage is Iridium. With 66 LEO satellites delivering worldwide satellite connectivity, including the poles, this system has tenfold more satellites than Transit had. Along with its strong signals compared to the GNSS core-constellations in MEO, Iridium’s global coverage makes it ideal for use in PNT applications where GNSS is obstructed.
Figure 1 shows the scale of the difference in altitude with Iridium at 780 kilometers and GPS at 20,200 kilometers. This has substantial implications not only for signal strength, but also for coverage.
Though Iridium has twice as many satellites as GPS, at the Equator users can often only see one satellite at a time, whereas they can see 10 from GPS. This was one of the fundamental trades considered in the design of the GPS constellation. The higher the altitude, the more each launch cost; the lower, the more satellites had to be built to provide coverage. To put this in perspective, global coverage for one satellite in view at all times requires fewer than 10 satellites in MEO, but requires closer to 100 in LEO.
Future LEO Constellations
The hundreds of LEO satellites needed to match the coverage of GPS may be coming. In late 2014 and early 2015, the International Telecommunication Union reported a half-dozen filings for spectrum allocation for large constellations of LEO satellites.
In January 2015, OneWeb announced a partnership with Virgin and Qualcomm to produce a constellation of 648 LEO satellites to deliver broadband Internet globally. This represents the next order of magnitude, with tenfold more satellites than Iridium.
Within days of this announcement, SpaceX, with support from Google, announced a similar ambition for a constellation of more than 4,000 LEO satellites.
In August 2015, Samsung expressed interest with a proposal for a LEO constellation of 4,600. Boeing joined the race in June 2016, announcing plans for a LEO constellation of nearly 3,000 satellites.
These LEO constellations are being proposed to keep up with the rising demand for broadband, not to replace ground infrastructure, and will provide Internet access to the 54% of the global population that lack that access.
TABLE 1 compares the GNSS core constellations in MEO to the big (Iridium), broadband (OneWeb, SpaceX, Boeing) and early navigation (Transit, Parus/Tsikada) LEO constellations.
TABLE 1. Constellation comparison.
LEO versus MEO
Low and medium Earth orbit each have their individual strengths and weaknesses in the context of navigation as summarized by TABLE 2.
TABLE 2. Comparison of LEO and MEO systems for navigation.
Closer to Earth, LEO offers less spreading loss and improved signal strength on the ground. FIGURE 2 shows that the signal spreading (or space) loss for Iridium is between –140 and –130 dB compared to GPS at –160 dB.
This stems from Iridium being 25 times closer to Earth than GPS, resulting in a gain in the neighborhood of 252, which is approximately 30 dB (1,000 fold). This is confirmed by field tests where the carrier-to-noise-density ratio (C/N0) is typically 45 dB-Hz for GPS but closer to 80 dB-Hz for Iridium.
FIGURE 2. Slant range and spreading loss as a function of orbital altitude and user elevation angle (GSO = geostationary orbit).
Now, we face the drawback of LEO proximity: coverage. Being closer to Earth means that satellites have much smaller footprints as shown in FIGURE 3.
FIGURE 3. Comparison of medium and low Earth orbit satellite distance and footprints (drawn to scale).
FIGURE 4 shows the satellite-footprint radius as a function of orbital altitude and user elevation mask angle. This plot shows the GPS footprint to be threefold larger than Iridium’s, corresponding to nine times more area covered. Hence, to achieve the same coverage as GPS with Iridium’s altitude, a LEO constellation requires an order of magnitude more satellites.
FIGURE 4. Satellite footprint radius as a function of orbital altitude and elevation angle (GSO = geostationary orbit).
Another major difference between LEO and MEO is speed. A GPS satellite completes one Earth revolution every 12 hours, while Iridium does so in only 100 minutes. The shorter the orbital period, the faster the angular rate (also called mean motion) and the more quickly satellites pass overhead. The Earth-centered angular rate of Iridium is seven times faster than GPS.
As a result, users on Earth’s surface see LEO Iridium satellites traverse the local sky in just over 10 minutes compared to hours with satellites in MEO. This characteristic gives rapid changes in geometry and several benefits for navigation.
The swift motion whitens multipath (making it more random, like white noise) as reflections are no longer effectively static over short averaging times. Geometric diversity also leads to effective Doppler positioning as was once leveraged by Transit and now by STL using Iridium. Geometric diversity is also desirable for carrier-phase differential GNSS, allowing for much more rapid resolution of integer cycle ambiguities.
Iridium-Satelles STL Service
As previously mentioned, the STL service has been in operation since May 2016. Many from industry and government are already using this service to achieve a more robust PNT solution. This service will only continue to improve with the Iridium NEXT satellites under deployment — the first 10 were successfully launched in January.
STL is a non-GNSS solution for assured time and location that is highly resilient and physically secure. STL utilizes the Iridium constellation to transmit specially structured time and location broadcasts. Due to their high RF power and signal-coding gain, the STL broadcasts are able to penetrate into difficult attenuation environments, including deep indoors. Like GNSS signals, these broadcasts are specifically designed to allow an STL receiver to obtain precise time and frequency measurements to derive its PNT solutions.
STL is able to augment or serve as a back-up to existing GNSS PNT solutions by providing secure measurements in the presence of high attenuation (deep indoors), active jamming and malicious spoofing. Unlike the MEO GNSS satellites, Iridium uses 48 spot beams to focus its transmissions on a relatively small geographic area. The complex overlapping spot beams of Iridium combined with randomized broadcasts give a unique mechanism to provide location-based authentication that is extremely difficult to spoof.
Two main technical innovations are applied to the existing Iridium quadrature phase-shift keying (QPSK) transmission scheme to facilitate precision measurements. First, the QPSK data at the beginning of an STL burst is manipulated to form a continuous wave (cw) marker, which can be used for burst detection and coarse measurement. Second, the remaining QPSK data in the burst is organized into pseudorandom sequences, reducing the effective information data rate while providing a mechanism for precise measurement via correlation with locally generated sequences.
The processing gain of the sequence correlation operation also enhances the capability of the STL signal to penetrate buildings and other occlusions. STL is designed such that a receiver can reliably decode the bursts and perform precise Doppler and range measurements at attenuations of up to 39 dB relative to unobstructed reception. This is sufficient to penetrate buildings and other occlusions, providing coverage in most deep indoor and urban canyon environments.
In environments where both GNSS and STL time and location fixes are available, the GNSS fixes will generally be more accurate. The key advantage of STL is its ability to provide time and position fixes where GNSS is not available because of occlusions, spoofing or other reasons. In this respect, GNSS and STL can be seen as complementary technologies, and it is apparent that receivers supporting both are highly desirable when practical. An example of a combined GNSS + STL receiver board is shown in FIGURE 5 and is available from Satelles.
To test the signal penetration of STL, trials of the system were undertaken at multiple locations inside an urban high-rise building. For these tests, locations with little or no GPS reception were chosen to measure the impact of such an environment on STL signal reception.
Two GPS receivers were used, a smartphone with assisted GPS and a standalone consumer receiver using Bluetooth communications without assistance data. Similarly, STL was used with and without assistance. For these tests, STL assistance included real-time, out-of-band delivery of satellite clock and orbit data and message payload contents. These test locations ranged from the top (13th) to the bottom (2nd) floor as shown in FIGURE 6.
FIGURE 6. Iridium-based STL test locations. These are indoor and deep attenuation environments where GPS is unavailable.
The results show that only upper floors near windows were able to track at most one to two GPS satellites while lower floors could see none. STL, on the other hand, always experienced strong signals. Even on the lowest floor, with many layers of steel and concrete between the antenna and the sky, the C/N0 from Iridium was between 35 and 55 dB-Hz. GPS, by comparison, is typically between 35 and 50 dB-Hz in an open sky environment.
Indoor Time-Transfer Capability
To evaluate the timing performance of STL in a static, indoor environment, a custom STL receiver board was configured to generate a pulse-per-second (PPS) output. The difference in timing between the STL PPS was then compared to the timing output of a GNSS “truth” reference — in this case, a timing receiver that has nominal timing performance at least an order of magnitude better than the STL-based timing we were attempting to measure.
FIGURE 7 shows the timing difference between the PPS signals generated by the STL receiver and the GNSS receiver, showing the STL ability to provide sub-microsecond timekeeping even in a deep attenuation environment.
FIGURE 7. Iridium-based STL timekeeping results based on data from a 30-day indoor trial. This compares indoor STL timing with a GPS feed from outdoors. This shows STL’s timekeeping to be within 1 microsecond in a deep attenuation environment.
While sub-microsecond timing is sufficient for many applications, higher timing accuracy is desired by some. It has been further demonstrated that STL is capable of achieving sub-100-nanosecond timekeeping in a stand-alone configuration with a rubidium-based STL receiver with an unknown static location indoors.
Indoor Positioning Performance
Unlike the time-transfer capability of STL, positioning requires satellite motion over time to achieve a reasonable 4D time-and-location fix. Therefore, understanding the convergence properties of STL positioning accuracy over time is important to understanding the applicability of STL for various potential uses.
To study these convergence properties, STL data was collected over a 24-hour period in a one-story office environment. The data was then post-processed in a series of trials that each represented a different starting time in the data set — each trial offset to begin 5 seconds ahead of the previous trial’s start time. In this way, the 24-hour data set could be used to generate a statistically significant set of trial runs in which positioning convergence characteristics could be evaluated.
We found out from the results of the post-processed trials that after 10 minutes of convergence, the STL solution had converged to an accuracy of better than 35 meters for 67% of the trials. After sufficient time, typically an accuracy of 20 meters can be achieved in deep attenuation environments such as indoors. The vertical accuracy of STL, in the absence of other measurements or vertical constraints, is comparable to the horizontal accuracy.
Looking Forward
We see the benefit of LEO in navigation with the operational STL using Iridium, where stronger signals allow for operation deep indoors and in other GNSS-challenged environments. Though extremely valuable as a complement to GPS, Iridium lacks the numbers to fully replace GPS as a standalone navigation system in all capacities as only one satellite at a time is typically in view.
However, these numbers may be coming in LEO with the unprecedented scale of the recently announced Broadband constellations of OneWeb, SpaceX, Boeing and others summarized in Table 1. OneWeb’s constellation is nearly as large as the total number of operational satellites in LEO today and is an order of magnitude larger than Iridium. SpaceX’s and Boeing’s proposed constellations each have more than twice the total number of operational satellites in orbit in 2017.
The unparalleled number of satellites in these proposed broadband LEO constellations gives rise to better geometry than any of the GNSS core-constellations in MEO by at least threefold, as shown by FIGURE 8.
FIGURE 8. Comparison of geometric dilution of precision (98th percentile) as a function of constellation size and altitude (MEO = medium Earth orbit; GSO = geostationary orbit).
This plot represents the 98th percentile geometric dilution of precision a user would experience on Earth as a function of constellation size and altitude, assuming a 5-degree elevation mask angle. This stronger geometry allows for relaxation of the signal-in-space user range error, while still matching the user position accuracy of GPS. This enables the use of lower than traditional cost satellite clocks and more amenable orbit determination levels.
When combined with the more benign LEO radiation environment compared to MEO, satellite navigation payloads could be built using commercial off-the-shelf components in place of specialized space-hardened ones, greatly reducing cost. By partnering with these LEO constellation providers, much like Satelles has done with Iridium, a PNT service comparable to GPS could be achieved though with the added benefits of LEO including stronger signals and rapid changes in geometry.
Conclusion
Robust PNT services from LEO are here today, providing augmentation to GPS where GPS isn’t available. The addition of navigation signals from LEO provides a number of benefits. The faster LEO motion provides geometric diversity, giving rise to multipath whitening, faster initialization times for carrier-phase differential GNSS, and Doppler-based positioning.
Perhaps most importantly, LEO constellations have the advantage of being closer to the Earth than the GNSS core constellations in MEO, experiencing less path loss and delivering signals 1,000 times (30-dB) stronger. This makes them more resilient to jamming and more capable in deep attenuation environments such as in urban canyons and indoors.
This extra power allows the LEO-based Satelles STL using Iridium to achieve timekeeping within 1 microsecond and a positioning accuracy of 20 meters, all while deep indoors where GNSS is unavailable. This adds indispensable resilience and security to GNSS that we are increasingly reliant upon, creating a comprehensive satellite navigation system that truly works everywhere.
This PNT service using Iridium is perhaps a sign of things to come. We’ve seen a progression in LEO use since the dawn of the Space Age, namely, an order of magnitude increase in constellation size every 30 years. Transit first offered an occasional position update based on a constellation of six satellites in the 1960s.
Built in the 1990s, Iridium, with an order of magnitude more satellites at 66, now offers global coverage. On the horizon are constellations like OneWeb, which promise the next order of magnitude with 648+ satellites, slated for the 2020s. This most recent scale gives rise to better satellite geometry than GPS today with the added benefits of LEO.
The STL signal using Iridium sets a precedent that could lead to unparalleled navigation services that are robust due to the improved signal strength and precise due to the huge number of LEO satellites coming, each moving quickly and giving the geometric diversity needed to enable fast carrier-phase differential GNSS.
The need for such a service is already clear. It would enable a diversity of future technologies and applications, such as safety-critical autonomous vehicles under development that must operate in challenging urban environments.
Acknowledgments
This article is based on a book chapter to be released in a new generation of GPS “Blue Books” entitled 21st Century Navigation Technologies: Integrated GNSS, Sensor Systems, and Applications to be published by Wiley-IEEE.
The article was also based on the following Institute of Navigation conference publications by the authors:
“Differential and Rubidium Disciplined Test Results from an Iridium-Based Secure Timing Solution” by S. Cobb, D. Lawrence, G. Gutt and M. O’Connor in Proceedings of the 2017 International Technical Meeting of The Institute of Navigation, Monterey, California, 2017.
“Test Results from a LEO-Satellite-Based Assured Time and Location Solution” by D. Lawrence, H.S. Cobb, G. Gutt, F. Tremblay, P. Laplante and M. O’Connor in Proceedings of the 2016 International Technical Meeting of The Institute of Navigation, Monterey, California, 2016.
“Orbital Diversity for Satellite Navigation” by D. Lawrence, H.S. Cobb, G. Gutt, F. Tremblay, P. Laplante and M. O’Connor in Proceedings of ION GNSS 2012, the 25th International Technical Meeting of the Satellite Division of The Institute of Navigation, Nashville, Tennessee, 2012.
“Leveraging Broadband LEO Constellations for Navigation” by T.G.R. Reid, A.M. Neish, T.F. Walter and P.K. Enge in Proceedings of ION GNSS+ 2016, the 29th International Technical Meeting of the Satellite Division of The Institute of Navigation, Portland, Oregon, 2016.
Manufacturers
The unassisted Bluetooth receiver used was a Dual Electronics XGPS150A Universal Bluetooth GPS Receiver; the assisted-GPS smartphone used was a Samsung Galaxy S4. Timing output was evaluated with a Trimble Thunderbolt GNSS timing receiver.
DAVID LAWRENCE is the principal navigation architect for Satelles. In addition to authoring over 20 papers and over 30 patents, Lawrence has developed high-performance navigation software that has been deployed in aircraft landing, precision agriculture, mining, transportation, and machine automation.
H. STEWART COBB is the principal hardware architect for Satelles. Dr. Cobb has made a diverse range of contributions to the PNT community, including inventing and delivering the first commercial implementation of pseudolites as a principal hardware engineer at Novariant.
GREG GUTT is the president and chief technology officer of Satelles. As a graduate student, Gutt Developed ultra-low-noise superconducting sensors for NASA’s Gravity Probe B program. He later went on to become a Boeing technical fellow and is the original principal inventor of the Satelles time and location technology.
MICHAEL O’CONNOR is the chief executive officer of Satelles. As a graduate student, O’Connor developed the world’s first GPS-based precision steering system for farm vehicles. He went on to bring this technology to market with Novariant and helped launch the precision agriculture industry.
TYLER G.R. REID just completed his Ph.D. in the GPS Research Laboratory in the Department of Aeronautics and Astronautics at Stanford University. He is an alumnus of the International Space University and will soon be starting as a research scientist at Ford Motor Company on their autonomous driving team.
TODD WALTER is a senior research engineer in the Department of Aeronautics and Astronautics at Stanford University where he received his Ph.D. in applied physics. His research focuses on implementing high-integrity air navigation systems.
DAVID WHELAN was the vice president and chief technologist for Boeing Defense, Space & Security. Whelan earned his Ph.D. and MS in physics from the University of California Los Angeles and his B.A. from the University of California San Diego.
FURTHER READING
Authors’ Conference Publications
“Differential and Rubidium Disciplined Test Results from an Iridium-Based Secure Timing Solution” by S. Cobb, D. Lawrence, G. Gutt and M. O’Connor in Proceedings of the 2017 International Technical Meeting of The Institute of Navigation, Monterey, California, Jan. 30 – Feb. 1, 2017, pp. 1111–1116.
“Leveraging Commercial Broadband LEO Constellations for Navigation” by T.G.R. Reid, A.M. Neish, T.F. Walter and P.K. Enge in Proceedings of ION GNSS+ 2016, the 29th International Technical Meeting of the Satellite Division of The Institute of Navigation, Portland, Oregon, Sept. 12–16, 2016, pp. 2300–2314 (best presentation award).
“Test Results from a LEO-Satellite-Based Assured Time and Location Solution” by D. Lawrence, H.S. Cobb, G. Gutt, F. Tremblay, P. Laplante and M. O’Connor in Proceedings of the 2016 International Technical Meeting of The Institute of Navigation, Monterey, California, Jan. 25–28, 2016, pp. 125–129.
“Orbital Diversity for Satellite Navigation” by P. Enge, B. Ferrell, J. Bennet, D. Whelan, G. Gutt and D. Lawrence in Proceedings of ION GNSS 2012, the 25th International Technical Meeting of the Satellite Division of The Institute of Navigation, Nashville, Tennessee, 17–21 Sept., 2012, pp. 3834–3846 (best presentation award).
Global Navigation from Low Earth Orbiting Satellites
“Analysis of Iridium-Augmented GPS for Floating Carrier Phase Positioning” by M. Joerger, L. Gratton, B. Pervan and C. E. Cohen in Navigation, Vol. 57, No. 2, Summer 2010, pp. 137–160, doi: 10.1002/j.2161-4296.2010.tb01773.x.
“Overview of IRIDIUM Satellite Network” by K. Maine, C. Devieux and P. Swan in Proceedings of IEEE WESCON’95, the Microelectronics Communications Technology Producing Quality Products Mobile and Portable Power Emerging Technologies Conference (formerly Western Electronics Show and Convention), San Francisco, California, Nov. 7–9, 1995, pp. 483–490, doi: 10.1109/WESCON.1995.485428.
Transit, the U.S. Navy Navigation Satellite System
The Legacy of Transit, a special edition of the Johns Hopkins APL Technical Digest edited by V.L. Pisacane, Vol. 19, No. 1, Jan.–March 1998.
“A History of Satellite Navigation” by B.W. Parkinson, T. Stansell, R. Beard and K. Gromov in Navigation, Vol. 42, No. 1, Spring 1995, pp. 109–164, 10.1002/j.2161-4296.1995.tb02333.x.
“The Navy Navigation Satellite System: Description and Status” by T.A. Stansell, Jr. in Navigation, Vol. 15, No. 3, Fall 1968, pp. 229–243, 10.1002/j.2161-4296.1968.tb01612.x.
GPS and other Global Navigation Satellite Systems
Springer Handbook of Global Navigation Satellite Systems, edited by P.J.G. Teunissen and O. Montenbruck, published by Springer International Publishing AG, Cham, Switzerland, 2017.
Northrop Grumman Corporation has been awarded a contract from the U.S. Air Force for technology maturation and risk reduction in support of next-generation navigation systems.
Under the $49 million contract from the Air Force Life Cycle Management Center, Northrop Grumman will provide the preliminary hardware and software architecture design for the Embedded GPS/Inertial Navigation System (INS)-Modernization, or EGI-M, technology. The modernized system is expected to be available for platform integration starting in 2019.
Northrop Grumman’s EGI-M will be based upon modular, open systems architecture to support the rapid insertion of new capabilities and adaptability based on unique platform requirements. Additionally, EGI-M will incorporate M-code-capable GPS receivers, which will help to ensure the secure transmission of accurate military signals.
“We are dedicated to ensuring mission success and the safety of warfighters by providing an EGI-M solution that offers robust, accurate and reliable positioning, navigation and timing [PNT] information, even in GPS-denied conditions,” said Dean Ebert, vice president, navigation and positioning systems business unit, Northrop Grumman Mission Systems.
EGI-M technology is designed for compatibility with current systems on legacy aircraft, allowing ease of integration and rapid adoption of new capabilities.
EGI-M will also comply with the Federal Aviation Administration’s NextGen air traffic control requirements that aircraft flying at higher altitudes be equipped with Automatic Dependence Surveillance-Broadcast (ADS‑B) Out by January 2020.
ADS-B Out transmits information about an aircraft’s altitude, speed and location to ground stations and to other equipped aircraft in the vicinity.
