Hexagon has joined the Multilateral Memorandum of Understanding (MMoU) on Strengthening the Global Geodesy Supply Chain.
The MMOU is a shared recognition by the United Nations Global Geodetic Centre of Excellence (UN-GGCE) — alongside member state government departments and agencies, private sector companies, organizations, associations, and academic institutions — that action is required to make the foundations of positioning, navigation and timing services robust.
With HxGN SmartNet, Hexagon has built a reliable, scalable GNSS infrastructure that integrates physical reference stations, specialized software such as Leica Spider, and a secure environment for distributing precise positioning data. Supporting tens of thousands of users worldwide, SmartNet delivers the accuracy and continuity essential for daily operations across many sectors.
The MMoU signatories hope to advance resilient positioning services and strengthen geospatial capabilities for nations around the world. Through joint initiatives, they aim to:
Enhance continuity and accuracy of GNSS-based positioning services
Strengthen resilience against signal interference
Support countries in developing and maintaining geodetic infrastructure
Expand education and workforce development in geodesy.
These initiatives ultimately help end users access more consistent accuracy, higher service availability, and stronger resilience against jamming or spoofing.
The MMoU was signed by Henning Sandfort, president, Geosystems Business Area, Hexagon, and Dieter Fritsch, Hexagon’s representative to the UN-GGIM Private Sector Network, on Nov. 17.
“Joining the MMoU underscores our commitment to ensuring that accurate, dependable geospatial information is accessible to governments and organisations worldwide,” Sandfort said.
“Hexagon’s contribution under the MMoU demonstrates the importance of global collaboration between Member States, UN and the geospatial industry,” said Nicholas Brown, head of Office at the UN-GGCE. “Hexagon is a key player of GNSS technology and digital reality solutions and therefore mostly welcomed to contribute the future vision of a strengthened global geodesy supply chain.
Instead, the ANPR-FASTag hybrid system will continue to rely on ground-based high-speed cameras to identify vehicles and radio-frequency-identification FASTag readers to charge them.
The Ministry of Road Transport and Highways is proceeding with corridor projects relying on automatic number-plate recognition (ANPR) and FASTag systems, which don’t require vehicles to stop. A GNSS toll system tracks the exact location of the vehicle and calculates the distance traveled on a toll roll, ensuring that users end up paying for just the distance they actually traveled.
For several years, the Indian government had intended to implement a GNSS-based toll system based on real-time location tracking. Now, it looks like these plans have been scrapped.
Promoting precious pollinators
Washington State University (WSU) is leading the Pacific Northwest Pollen Atlas (bees.wsu.edu) to map and describe pollen. It aims to determine pollinator health and thus food humans eat that depend on pollination. Honey bees and other pollinators collect pollen from plants within a two-mile radius of their hive.
“We hope to create a database of plants and share the nutrient content in their pollen so gardeners can plant a healthy variety,” said Priya Chakrabarti Basu, WSU assistant professor, Entomology.
Researchers will map pollen varieties collected by citizen scientists in every Washington county over a four-year period and colleagues around the Pacific Northwest are also recruiting to increase the project’s scope. Expected to take decades to complete, the efforts are part of Basu’s larger effort to map pollen nutrition across North America.
How’s the weather out there?
High-resolution atmospheric data is the missing link in forecasting weather. A new approach sharpens GNSS tomography, while showing how the model makes decisions — a transparency critical for building trust as AI enters weather forecasting.
By revealing the hidden details of storms and humidity patterns, the new method can give forecasters the tools needed to anticipate extreme events with greater confidence, according to researchers at Wrocław University, Poland. The team described their deep-learning framework in a paper published in Satellite Navigation in August.
With sharper GNSS tomography, meteorologists can feed more accurate humidity fields into both physics-based and AI-driven forecasting models, significantly improving storm prediction and early-warning systems.
Africa is really huge
Photo: Equal Earth, Strebe / CC BY-SA 4.0
A Correct the Map campaign aims to replace the 16th-century Mercator map because it doesn’t show the true size of Africa, which is three times as large as Europe. Supporters say the historic map — created to guide European explorers — promotes a false view of the continent and its size, fostering a false impression that Africa is “marginal.”
In August, the 55-country African Union endorsed the campaign to have organizations around the world replace the Mercator with alternatives such as the 2018 Equal Earth projection. The African Union is expected to make an official decision to adopt the Equal Earth map in February. The campaign also asks the United Nations and the BBC to adopt the Equal Earth map.
“Since February 2022, there has been an increase in jamming and/or possible spoofing of GNSS. This issue particularly affects the geographical areas surrounding conflict zones but is also present in the eastern Mediterranean, Baltic Sea and Arctic area,” the European Union Aviation Safety Agency stated in a Feb. 17 safety information bulletin.
On April 4, the United Kingdom’s Civil Aviation Authority followed with its own advisory adding that, in addition to the year-over-year increase, interference has intensified in recent months citing the same geographic areas of concern.
Both advisories list impacts to aircraft that include:
loss of ability to use GNSS for waypoint navigation
loss of area navigation (RNAV) approach capability
inability to conduct or maintain Required Navigation Performance (RNP) operations, including RNP and RNP Authorization Required (RNP AR) approaches
triggering of terrain warnings, possibly with pull up commands
inconsistent aircraft position on the navigation display
loss of automatic dependent surveillance-broadcast (ADS-B), wind shear, terrain and surface functionalities
failure or degradation of a variety of air traffic management service and aircraft systems that use GNSS as a time reference
potential airspace infringements and/or route deviations due to GNSS degradation.
Airspace infringement can be a real concern, especially in conflict zones or near belligerent nations.
GPS was first authorized for civil use because of just such an incident. In 1983, a Korean airliner accidentally trespassed into Soviet airspace and was shot down. Despite the fact that the GPS constellation had not yet been declared fully operational, in September of that year President Ronald Regan authorized its use in civil applications to help avoid similar tragedies in the future.
GPS-based navigation for aircraft was subsequently found to be so efficient and successful that the Federal Aviation Administration (FAA) planned to eliminate all the terrestrial navigation beacons it maintains for air traffic and rely entirely upon GPS. Despite a 2001 report from the U.S. Department of Transportation’s Volpe Center cautioning against such an action, this plan was not abandoned until several years later when an aircraft crossing the Atlantic lost GPS reception.
In recent years, aviation industry concerns about interference with GPS and other GNSS signals have intensified. These concerns have even included planned and announced military exercises that cause interference. Aviation industry groups have complained that the exercises disrupt and are too costly to their operations.
Safety of life has also been a concern.
In 2019 a commercial passenger aircraft was nearly lost to GPS interference in Sun Valley, Idaho. Flying a GPS-based approach through the mountains to the airport, low-level interference caused the aircraft to deviate from its course. In the words of the safety report filed with NASA, had a sharp-eyed radar controller hundreds of miles away not spotted the problem and intervened, “…that flight crew and the passengers would be dead, I have no doubt.”
This incident was cited by the International Air Transport Association (IATA) in a filing later that year urging international action. Along with other groups, it pressed the U.N.’s International Civil Aviation Organization (ICAO) concerning “An Urgent Need to Address Harmful Interferences with GNSS.” In 2020, ICAO issued a letter to all member states recommending action.
Similar concerns have been expressed by other international bodies as well.
In 2021 a EUROCONTROL seminar said that there had been a 2,000% increase in GNSS RFI incidents since 2018 as measured by voluntary incident reporting. Also, that 38.5% of European en-route traffic operated in regions regularly affected by interference.
The International Telecommunications Union, the U.N. body responsible for coordinating spectrum use, issued its own concern and warning in 2022. It cited more than 10,000 aviation-related incidents the previous year and, like ICAO, urged member states to take action to prevent such occurrences.
While interference with GNSS signals is unquestionably a concern for commercial aircraft, it is perhaps even more of a safety risk for smaller, general aviation users.
The only electronic navigation aids in many of these aircraft are consumer-grade GPS receivers. Since these are not certified by the FAA, they are only officially authorized for use to help pilots maintain “situational awareness” while they fly using visual reference with the ground. Interference with GNSS signals can cause disorientation and could result in aircraft becoming lost, running out of fuel, or straying into prohibited areas.
When the U.S. Air Force shot down a Chinese balloon flying at 60,000 ft (11.4 miles) on Feb. 4, the incident raised many questions about international security, international law, U.S.-China relations and technology. Among them, where is the end of a nation’s airspace — the portion of atmosphere it controls above its territory? Its horizontal boundary corresponds to that of its land border and territorial waters, which extend 12 miles out from its coastline. However, there is no international agreement on the vertical boundary.
The 1967 Outer Space Treaty — to which the United States is a party and which bans “appropriation” of outer space by any nation — omits a definition of “outer space” because none of the major powers wanted to limit their own freedom of action in space. At a United Nations meeting in Vienna in 2001, the U.S. delegation said, “Our position continues to be that defining or delimiting outer space is not necessary.”
The United Nations has historically accepted as the boundary of space the Kármán line, at an altitude of 62 miles above mean sea level. It roughly marks the altitude where traditional aircraft cannot effectively fly using lift generated by Earth’s atmosphere, because the air there is just too thin. The Fédération Aéronautique Internationale agrees with this definition.
Some countries have adopted a definition for their own legal purposes, usually based on either the Kármán line or on the altitude at which orbital flight is possible without utilizing atmospheric lift. As a courtesy, a state launching a space vehicle that will traverse another state’s territory during its sub-orbital flight will notify the overflight state.
The U.S. military and NASA on the other hand, define space to begin at 50 miles above Earth’s surface. “Pilots, mission specialists, and civilians who cross this boundary are officially deemed astronauts,” according to the U.S. Department of Commerce’s National Environmental Satellite Data and Information Service.
Escaping Earth’s atmosphere entirely is another story. It requires traveling at least 600 miles, to its outermost layer, where violent solar winds have greater sway than air. If that were the definition of space, however, the Space Shuttle (which orbited up to 200 miles up), the International Space Station (205 miles to 270 miles), active Earth observation satellites (280 miles to 500 miles), some of the National Oceanic and Atmospheric Administration’ s polar-orbiting satellites (540 miles) and most scientific satellites, including nearly all of NASA’s Earth Observing System fleet, would not be considered spacecraft! Lower orbits have significant air-drag, which requires frequent orbit re-boost maneuvers.
There’s no question that GPS satellites, orbiting at an altitude of about 12,550 miles, are in space. That is why they are acquired, sustained, and operated by the U.S. Space Force (USSF), established in December 2019 as the newest branch of the U.S. armed forces. Its mission is to organize, train and equip space forces to protect U.S. and allied interests in space and provide space capabilities to the joint force. As the USSF grows, we’ll hear more about it.
On Feb. 6, the United Nations Satellite Center (UNOSAT) announced via Twitter that it had activated emergency mapping services of Turkiye and northern Syria after the magnitude 7.8 earthquake hit earlier that day. The satellite images provide an overview of the damage, which can be used for humanitarian efforts and disaster relief, reported Space.com.
UNOSAT provides emergency mapping services, upon request, to provide satellite imagery analysis during emergencies and disasters. The maps show infrastructure that has been damaged during an emergency, which can then be used to provide relief by disaster response groups.
The impact of the earthquakes was significant and ranks in the red for economic losses and orange for fatalities, according to the U.S. Geological Survey (USGS). (Image: UNOSAT)
The earthquake caused massive destruction throughout Turkiye and Northern Syria, causing an estimated death toll of more than 19,000 as of Feb. 9. Several historical structures dating back thousands of years have also been severely damaged.
UNOSAT started in 2001 and is hosted by the European Organization for Nuclear Research. It does not operate its own satellites, but coordinates with United Nations member states to gather imagery from government agencies and privately owned satellites. United Nations offices, government agencies and relief organizations can request access to imagery collected by UNOSAT.
The USGS reports the earthquake resulted from strike-slip faulting at shallow depths. It appears to be associated with either the East Anatolia fault zone or the Dead Sea transform fault zone. (Image: UNOSAT)
All maps of Turkey and northern Syria from UNOSAT can be found here. A live interactive map can be found here.
ITU is the United Nations agency that deals with information and communications technology. Its remit includes coordinating spectrum use and satellite orbits.
ITU’s Radio Communications Bureau sponsors the World Radiocommunication Conference every three to four years. The issue of interference with GNSS signals was reported at the 2019 conference.
Since that time, according to this month’s circular, the group “has been informed of a significant number of cases of harmful interference to the radionavigation-satellite service…”
Despite concerns expressed by maritime and other interests, the circular focuses entirely on aviation interference. It says the reports it has received have been about “receivers onboard aircrafts and causing degradation or total loss of the service for passenger, cargo and humanitarian flights…” These have included “misleading information provided by RNSS [radionavigation satellite service] receivers to pilots.” An often cited example of this is a well-publicized 2019 incident in Sun Valley, Idaho. In that case a passenger aircraft nearly hit a mountain.
Describing interference with GNSS as a global and recurrent problem, the circular cites data collected by a major aircraft manufacturer. The company found “10,843 radio-frequency interference events … globally in 2021. The majority of these events occurred in the Middle East region, but several events were also detected in the European, North American and Asian regions.”
This year’s uptick in GNSS interference in Scandinavia, the Baltics, and around Ukraine since Russia’s February invasion of Ukraine is not mentioned. This is likely due, in part, to timing. ITU’s Radio Regulations Board met in March 2022 and directed the circular be issued.
Many within the positioning, navigation, and timing community have long asserted that interference with GNSS signals, whether deliberate or accidental, constitutes a violation of ITU rules and regulations. This month’s circular affirms this and cites several applicable provisions.
These include prohibitions on harmful interference with any authorized radio frequency transmission, requirements for users to transmit only in bands for which they have authorization, and for all to generally safeguard aviation operations.
The circular highlights provision 15.1 of ITU’s Radio Regulations as particularly applicable. It states:
“All stations are forbidden to carry out unnecessary transmissions, or the transmission of superfluous signals, or the transmission of false or misleading signals, or the transmission of signals without identification…”
As is the case with almost all international agreements, enforcement of ITU rules is the responsibility of its member states.
While most expect the advisory to have little immediate impact on reducing global interference with GNSS signals, it does help reinforce the issue as one of international concern.
According to a retired government official, “Member states that fail to comply with international rules to which they have agreed lose credibility and standing in the community of nations. Even when they have little credibility or standing to begin with, the behavior adds to their marginalization and life is just a little more difficult for them. This can, in the long run, nudge them toward being more responsible players.”
IMO is the United Nations body that coordinates and sets standards for international maritime operations and safety.
In a paper dated March 10, the service said that GNSS signals are “essential to safe and efficient navigation and an integral component of all maritime operations.” Interfering with them “jeopardizes the safety of life at sea.”
Deliberate disruptions in the eastern Mediterranean and the Black Sea, the paper says, affect vessels operating in international waters and engaged in innocent passage through territorial seas.
While nations typically have a right to do as they wish in their sovereign territory, they are also obliged to not have that intrude into other nations’ territory or international waters. This is also true for vessels passing through their waters but not calling at their ports, known as “innocent passage.”
The International Law of the Sea Treaty stipulates that, in the absence of some clear wrongdoing such as piracy, drug smuggling or discharging oil, vessels be allowed to pass through territorial seas unmolested by the coastal state.
The Coast Guard paper also points out that nations have other treaty obligations that prohibit this kind of activity. International Telecommunication Union Radio Regulations prohibits “All transmissions with false or misleading identification…”
Citing a March 2019 report in GPS World, the paper also documents that GNSS disruption is a global problem not confined to just one or two areas. A study by the German Aerospace Center (DLR) found interference during every phase of a vessel’s voyage between Europe and the Far East.
The Coast Guard paper was submitted for consideration at IMO’s Maritime Safety Committee that had been scheduled to meet on May 13, but has been postponed due to the COVID-19 emergency.
This planned consideration at IMO follows a resolution by the UN’s International Civil Aviation Organization (ICAO) in May 2019. In a paper entitled “An Urgent Need to Address Harmful Interferences to GNSS,” the International Federation of Air Traffic Controllers’ Association (IFATCA), the International Federation of Air Line Pilots’ Associations (IFALPA), and the International Air Transport Association (IATA) had introduced the issue.
This resulted in a resolution describing the eliminating interference as an urgent need.
About the same time the U.S .Coast Guard paper was due to be considered, IMO was to engage in the early stages of considering rules for autonomous vessels. Its Facilitation Committee was scheduled hold a “Regulatory scoping exercise for the use of Maritime Autonomous Surface Ships (MASS)” at a meeting the end of April. This meeting has also been postponed.
While not specifically mentioned, navigation issues will undoubtedly be part of the considerations when discussion of rules for autonomous shipping eventually takes place.
Public input to these international meetings is always sought in advance. For example, the U.S. State Department had announced a meeting for April 6 to receive public input on U.S. positions for the various issues to be discussed at the Facilitation Committee.
While we understand that this meeting will also be also be postponed, comments can be submitted to the points of contact listed in the Federal Register announcement as well as be raised during the eventual meeting.
Letter signed to advance role of geospatial knowledge infrastructure in global society and economy
Geospatial Media & Communications has signed a letter of cooperation with the United Nations Statistics Division (UNSD) to work together to advance the role of geospatial knowledge infrastructure in global society and economy.
Consistent with their respective mandates, the UNSD and Geospatial Media will collaborate to carry out activities related to their common objective of demonstrating the value of global geospatial knowledge, the data ecosystem, public-private partnerships, and their contribution towards building Geospatial Knowledge Infrastructure and the Global Development Agendas.
The agreement was signed by Stefan Schweinfest, director, UNSD, Department of Economic and Social Affairs, and Sanjay Kumar, CEO, Geospatial Media, in New York on Oct. 31.
“The United Nations 2030 Sustainable Development Agenda is ambitious and requires countries to have solid national information systems to successfully stir the process of implementation. It is a central task of my office, the United Nations Statistics Division, to support countries in building the necessary national information capacities, both in the area of statistics and geospatial information. For this challenging task we need the cooperation of the private sector through well established public-private partnerships. Geospatial Media & Communications is a unique partner in this respect, due to its global reach and its in-depth knowledge and understanding of country needs. I am, therefore, delighted to cooperate with them closely in the coming years,” said Mr. Schweinfest.
“Pursuing its vision to make a difference through geospatial knowledge in world economy nad society, Geospatial Media has been evangelizing geospatial industry globally for over two decades through research, advocacy, media and knowledge exchange platforms. It has contributed in the formation and strengthening of several institutions, including the Association of Geospatial Industries (AGI), World Geospatial Industry Council (WGIC), UNGGIM Private Sector Network and the National Think Tank on Geospatial Strategy for New India. Through this collaboration, our intent is to further our vision to showcase high level value of geospatial knowledge in global development agenda and facilitate alignment and evolution of geospatial stakeholders with emerging socio-economic development models in the fourth Industrial age,” said Mr. Sanjay Kumar.
The intended collaboration will focus on a number of common objectives at national, regional and global levels which will include:
Working together to create joint programs and projects to develop geospatial knowledge infrastructure, networks and human resource capacities;
Assessment of the prospective role of geospatial knowledge infrastructure in global society and economy;
Collaboratively developing broader methods, guidelines, architectures and policy frameworks for the adoption, utilisation and benefits of geospatial knowledge infrastructure;
Develop documents, training modules and other resources to assist National Geospatial Information Agencies in their transformation and modernization aspirations in alignment with the national to global vision of the Integrated Geospatial Information Framework;
Facilitate a collaborative knowledge exchange and engagement atmosphere between the commercial geospatial industry, national geospatial agencies, and the broader user industries and civil society, towards developing public-private partnership models for co-creating geospatial knowledge infrastructure and strengthening of industry and institutional capacities; and
Advocate, communicate and promote the value and utility of geospatial information and enabling technologies for sustainable development.
Letter signed to advance role of geospatial knowledge infrastructure in global society and economy
Geospatial Media & Communications has signed a letter of cooperation with the United Nations Statistics Division (UNSD) to work together to advance the role of geospatial knowledge infrastructure in global society and economy.
Consistent with their respective mandates, the UNSD and Geospatial Media will collaborate to carry out activities related to their common objective of demonstrating the value of global geospatial knowledge, the data ecosystem, public-private partnerships, and their contribution towards building Geospatial Knowledge Infrastructure and the Global Development Agendas.
The agreement was signed by Stefan Schweinfest, director, UNSD, Department of Economic and Social Affairs, and Sanjay Kumar, CEO, Geospatial Media, in New York on Oct. 31.
“The United Nations 2030 Sustainable Development Agenda is ambitious and requires countries to have solid national information systems to successfully stir the process of implementation. It is a central task of my office, the United Nations Statistics Division, to support countries in building the necessary national information capacities, both in the area of statistics and geospatial information. For this challenging task we need the cooperation of the private sector through well established public-private partnerships. Geospatial Media & Communications is a unique partner in this respect, due to its global reach and its in-depth knowledge and understanding of country needs. I am, therefore, delighted to cooperate with them closely in the coming years,” said Mr. Schweinfest.
“Pursuing its vision to make a difference through geospatial knowledge in world economy nad society, Geospatial Media has been evangelizing geospatial industry globally for over two decades through research, advocacy, media and knowledge exchange platforms. It has contributed in the formation and strengthening of several institutions, including the Association of Geospatial Industries (AGI), World Geospatial Industry Council (WGIC), UNGGIM Private Sector Network and the National Think Tank on Geospatial Strategy for New India. Through this collaboration, our intent is to further our vision to showcase high level value of geospatial knowledge in global development agenda and facilitate alignment and evolution of geospatial stakeholders with emerging socio-economic development models in the fourth Industrial age,” said Mr. Sanjay Kumar.
The intended collaboration will focus on a number of common objectives at national, regional and global levels which will include:
Working together to create joint programs and projects to develop geospatial knowledge infrastructure, networks and human resource capacities;
Assessment of the prospective role of geospatial knowledge infrastructure in global society and economy;
Collaboratively developing broader methods, guidelines, architectures and policy frameworks for the adoption, utilisation and benefits of geospatial knowledge infrastructure;
Develop documents, training modules and other resources to assist National Geospatial Information Agencies in their transformation and modernization aspirations in alignment with the national to global vision of the Integrated Geospatial Information Framework;
Facilitate a collaborative knowledge exchange and engagement atmosphere between the commercial geospatial industry, national geospatial agencies, and the broader user industries and civil society, towards developing public-private partnership models for co-creating geospatial knowledge infrastructure and strengthening of industry and institutional capacities; and
Advocate, communicate and promote the value and utility of geospatial information and enabling technologies for sustainable development.
Boundless is partnering with the United Nations (UN) to support the UN Open GIS Initiative, which aids UN operations around the world with open source geospatial software and services.
According to Boundless, using its technology, the UN can leverage a hybrid architecture approach and maintain interoperability with existing software systems to maximize the value of its open technology and open data in global peacekeeping and other UN operations.
The UN Open GIS Initiative aims to identify and develop open source geospatial software and services that meet the requirements of UN operations, taking full advantage of the expertise of mission partners including member states, technology contributing countries, international organizations, academia, non-governmental organizations and the private sector.
The scope of the initiative covers software development for the entire lifecycle of geospatial information at the enterprise level, from data collection, management and sharing to geospatial analysis and web and mobile applications. The initiative also focuses on the technology’s sustainability and eventual transfer from the UN to other potential user groups and developing countries.
“Boundless is honored to be a critical part of the UN Open GIS Initiative, and proud to see the real-world impact our open source software and technology is supporting for UN peacekeeping operations around the world,” said Anthony Calamito, chief geospatial officer at Boundless. “The ability to use Boundless in a hybrid architecture enables the organization to share freely with other UN operational partners and nations and interoperate with existing technologies already in use. It enables rapid innovation and prevents single vendor lock-in.”
The UN deployed Boundless’ technology after nearly two years of planning and development and a successful demonstration in a simulated UN field operational environment. In addition to providing technological support for the UN Open GIS Initiative, Boundless is also a sponsor of the OSGeo UN Committee Educational Challenge, a program focused on developing open geospatial educational material for the initiative.
As Galileo, BeiDou, the Quasi-Zenith Satellite System, the Indian Regional Navigation Satellite System, and a variety of satellite-based augmentation systems join GPS and GLONASS, we help celebrate the coming 25th anniversary of the IGS as a truly multi-GNSS service.
Editor’s note: Tables 1 and 3 in the print version of this article contain some incorrect values and missing designators. These errors have been corrected in the tables below.
INNOVATION INSIGHTS by Richard Langley
A QUARTER OF A CENTURY. That is how old the International GNSS Service (IGS) will be on Jan. 1, 2019. Conceived in the early 1990s as the International GPS Service for Geodynamics, the IGS continues to be the global standard bearer in providing receiver data, satellite orbit and clock products and other resources with the highest possible precision and accuracy. I remember the discussions that took place at international conferences about the need for such a service to provide the necessary data to advance our understanding of plate tectonics and other Earth-related phenomena. And this was well before GPS was officially declared fully operational in 1995. Remember, surveyors and geodesists were early adopters of GPS, making use of the technology even when only a partial GPS constellation was in place.
The initial ideas for the IGS were laid out in an article published in GPS World in February 1993 entitled “Geodynamics: Tracking Satellites to Monitor Global Change.” But the services provided by the IGS extended well beyond the needs of the geodynamics research community, and so its name was shortened to just the International GPS Service. When GLONASS data and products became available, the name was further changed to its current moniker.
One of the IGS’s notable achievements has been in advancing GNSS standards such as the Receiver-Independent Exchange format for receiver data and other information. The need for such a standard was clear even before the formation of the IGS, and it was documented in this column in the July 1994 issue of GPS World (“RINEX: The Receiver-Independent Exchange Format”). We continued to cover the evolution of the IGS over the years with, for example, the article “The International GNSS Service: Any Questions?” in the January 2007 issue of the magazine.
And now, as Galileo, BeiDou, the Quasi-Zenith Satellite System, the Indian Regional Navigation Satellite System, and a variety of satellite-based augmentation systems join GPS and GLONASS, we help celebrate the coming 25th anniversary of the IGS as a truly multi-GNSS service.
For going on 25 years, the International GNSS Service (IGS) has carried out its mission to advocate for, and provide, freely and openly available high-precision GNSS data, as well as derived operational data products, including satellite ephemerides, Earth rotation parameters, station coordinates and clock information. The IGS is a self-governed, voluntary federation of more than 300 contributing organizations from more than 100 countries around the world that collectively operate a global infrastructure of tracking stations, data centers and analysis centers to provide high-quality GNSS data products. The IGS products are provided openly for the benefit of all scientific, educational and commercial users.
The IGS was first approved by its parent organization, the International Association of Geodesy (IAG), at a scientific meeting in Beijing, China, in August 1993. A quarter of a century later, the IGS community gathers for a workshop in Wuhan, China, this November to blaze a path to multi-GNSS through global collaboration.
As a key component of the IAG’s global geodetic infrastructure, the IGS contributes to, extends and densifies the International Terrestrial Reference Frame (ITRF) of the International Earth Rotation and Reference Systems Service (IERS). The ITRF provides an accurate and consistent spatial frame for referencing positions at different times and in different locations around the world.
In addition, IGS products enable the use of GNSS technologies for scientific applications such as the monitoring of solid Earth deformations, monitoring of Earth rotation and variations in the liquid Earth, and for scientific satellite orbit determinations, precise timing, ionosphere monitoring and water vapor measurements.
IGS products are also considered critical by surveying, geomatics and geo-information users around the world, who rely on them on a daily basis to improve efficiency. Many applications that require reliable, accurate GNSS positioning in construction, agriculture, mining, exploration and transportation also benefit from the IGS.
Community Collaboration
At the heart of the IGS is a strong culture of sharing expertise, infrastructure and other resources for the purpose of encouraging global best practices for developing and delivering GNSS data and products all over the world. The collaborative nature of the IGS community leverages this diversity to integrate and make full use of all available GNSS technologies while promoting further innovation.
More than 15,000 geodetic community members, some of whom comprise the backbone of the worldwide geodetic community, ensure that new technologies and systems are integrated into operational IGS products. Responsive to this innovation, the IGS develops and publicly releases standards, guidelines and conventions for the collection and use of GNSS data and the aforementioned products.
The IGS strives to maintain an international federation with committed contributions from its members. Participation of individuals and organizations is often driven by user needs, a key characteristic of the inclusive culture within the IGS.
Structure of the IGS
The IGS consists of a central bureau, a global network of GNSS stations, data and analysis centers and a number of working groups all coordinated and overseen by a governing board.
Central Bureau. The IGS Central Bureau (CB) functions as the secretariat of the IGS, providing continuous management and technology to sustain the multifaceted efforts of the IGS in perpetuity. The CB responds to the directives and decisions of the IGS governing board. It coordinates the IGS tracking network and operates the CB information system, the principal information portal where the IGS web, FTP and mail services are hosted (www.igs.org). The CB also represents the outward face of IGS to a diverse global user community, as well as the general public. The CB office is hosted at the California Institute of Technology/Jet Propulsion Laboratory in Pasadena, California. It is funded principally by the U.S. National Aeronautics and Space Administration (NASA), which generously contributes significant resources to advance the IGS.
The IGS Network. The foundation of the IGS is a global network of more than 500 permanent and continuously operating stations of geodetic quality. These stations track signals from GPS, and increasingly also track signals from GLONASS, Galileo, BeiDou, the Quasi-Zenith Satellite System (QZSS), the Indian Regional Navigation Satellite System (IRNSS; also known as NavIC: Navigation with Indian Constellation), as well as space-based augmentation systems (SBAS).
FIGURE 1 shows the recent state of the IGS network, indicating which stations are GPS only, GPS+GLONASS and multi-GNSS. FIGURE 2 is a photo of the IGS station ARHT at McMurdo Station, Antarctica.
FIGURE 1 . The extent of the IGS network in 2017, showing the locations of stations monitoring just GPS, GPS and GLONASS, and GPS and GLONASS plus at least one other constellation. (Map: IGS)
FIGURE 2. The consistency of the final GPS satellite orbit solutions from individual IGS analysis centers over the past 25 years. Each line depicts the solution of one analysis center, as compared to the weighted mean. COD: Center for Orbit Determination in Europe, EMR: Natural Resources Canada (formerly Energy, Mines and Resources Canada), ESA: European Space Agency, GFZ: GeoForschungsZentrum (German Research Centre for Geosciences); GRG: Centre National d’Etudes Spatiales (Groupe de Recherche de Géodésie Spatiale); JPL: Jet Propulsion Laboratory; MIT: Massachusetts Institute of Technology; NGS: National Geodetic Survey; SIO: Scripps Institution of Oceanography; IGR: IGS rapid product. (Graph courtesy of T. Herring, MIT and M. Moore, Geoscience Australia)
The IGS is a critical component of the IAG’s Global Geodetic Observing System (GGOS), where it encourages and advocates for geometrical linkages of GNSS with other precise geodetic observing techniques, including satellite and lunar laser ranging, very long baseline interferometry and Doppler Orbitography and Radio Positioning Integrated by Satellite (DORIS). These linkages are fundamental to generating and accessing the ITRF.
Data and Analysis Centers. Lots of hard work and dedication from IGS contributing organizations goes into the fabrication of IGS products, which start at the tracking network, then are collected by data centers and sent to analysis centers. At these centers, the data are compared and combined by the analysis center coordinator, and finally made available as IGS products.
The IGS ensures high reliability by building redundancy into all of its components. In 1994, the IGS started with a network of about 40 stations; today, more than 500 receivers are included in the network. Critical to this activity are three categories of data center — operational, regional and global. At the ground level are operational data centers, which are in direct contact with IGS tracking sites and are responsible for such efforts as station monitoring and local archiving of GNSS tracking data. Operational data centers also validate, format, exchange and compress data. Regional data centers then collect tracking data from multiple operational data centers or stations, maintaining a local archive and providing online access to their data.
The six global data centers receive, retrieve, archive and provide online access to tracking data from operational and regional data centers. These global data centers are also responsible for archiving and backing up IGS data and products, and maintaining a balance of data holdings across the IGS network.
Analysis centers then receive and process tracking data from one or more data centers to generate IGS position, orbit and clock products. These products are produced in ultra-rapid, rapid, final and reprocessed versions for each analysis center.
FIGURE 3 shows the huge improvement in the precision and accuracy of the final orbit submissions from the analysis centers over the past 25 years.
Associate analysis centers produce specialized products, such as ionospheric information, tropospheric parameters or station coordinates and velocities for global and regional sub-networks. Regional and global network associate analysis centers complement this work as new capabilities and products emerge within the IGS.
FIGURE 3. The antenna of IGS station ARHT at McMurdo Station, Antarctica. (Photo: IGS)
Products from each analysis center are then combined into a single set of orbit and clock products by the analysis center coordinator, who monitors and assists the activities of analysis centers to ensure IGS standards for quality control, performance evaluation and analysis are successfully executed. The different analysis solutions ultimately verify the accuracy of IGS products, provide important redundancy in the case of errors in a particular solution, and average out modeling deficiencies of a particular software package.
TABLE 1 shows the quality of service characteristics of the various IGS GPS and GLONASS orbit and clock products. Similarly, TABLES 2, 3 and 4 show the characteristics of the tracking station coordinates, Earth rotation parameters and atmospheric parameters. See www.igs.org/products for further details.
TABLE 1. Quality of service characteristics for IGS orbit and clock products relating to GPS and GLONASS satellite orbits and satellite (sat.) and station (stn.) clocks as of 2017. (Data: IGS)
TABLE 2. Quality of service characteristics for tracking station positions and velocities. (Data: IGS)
TABLE 3. Quality of service characteristics for Earth rotation parameters: polar motion coordinates and rates of change and length-of-day (µas = microarcsecond). (Data: IGS)
TABLE 4. Quality of service characteristics for atmospheric parameters: tropospheric zenith path delay and gradients and global grids of total electron content. (Data: IGS)
Working Groups and Projects
The IGS technical working groups (WGs) focus on topics of particular interest to the IGS, and consider various aspects of product generation and monitoring. The current working groups of the IGS span topics from antennas to tide gauges.
Antenna Working Group. To increase the accuracy and consistency of IGS products the Antenna WG coordinates research on GNSS receiver and satellite antenna phase-center determination. The group manages official IGS receiver and satellite antenna files and their formats.
Bias and Calibration Working Group. Different GNSS observables are subject to different satellite biases, which can degrade the IGS products. The Bias and Calibration WG coordinates research in the field of GNSS bias retrieval and monitoring.
Clock Products Working Group. This group is responsible for aligning the combined IGS products to a highly precise timescale traceable to the world standard: Coordinated Universal Time (UTC). The IGS clock product coordinator forms the IGS timescales based on the clock solutions of IGS analysis centers, and IGS rapid and final products are aligned to these timescales.
Data Center Working Group. The Data Center WG works to improve the provision of data and products from the operational, regional and global data centers, and recommends new data centers to the IGS governing board.
Joint GNSS Monitoring and Assessment Working Group. This working group, in conjunction with a joint trial project with International Committee on GNSS’s (ICG) International GNSS Monitoring and Assessment (IGMA) Task Force, seeks to install, operate and further develop a GNSS Monitoring and Assessment Trial Project.
GNSS Performance Monitoring ICG-IGS Joint Trial Project. The quality of navigation signals enables numerous applications, including worldwide time and frequency transfer and GPS meteorology. This project of the IGMA task force, coordinated in partnership with the IGS, focuses on monitoring GNSS constellation status.
Ionosphere Working Group. This group produces global ionosphere maps of ionosphere vertical total electron content (TEC). A major task of the Ionosphere WG is to make available global ionosphere maps from the TEC maps produced independently by ionosphere associate analysis centers within the IGS.
FIGURE 4 shows an example TEC map recomputed from data collected on March 17, 2015. The large values of TEC in the ionosphere’s equatorial anomaly are plainly visible.
FIGURE 4. An example total electron content map recomputed from data collected on March 17, 2015. TECU: total electron content units. (Image: IGS)
Multi-GNSS Working Group. This group supports the Multi-GNSS Experiment (MGEX) Project by facilitating estimation of intersystem biases and comparing the performance of multi-GNSS equipment and processing software. The MGEX Project was established to track, collate and analyze all available GNSS signals including those from BeiDou, Galileo and QZSS in addition to GPS and GLONASS.
Reference Frame Working Group. This working group combines solutions from the IGS analysis centers to form the IGS station positions and velocity products, and Earth rotation parameters for inclusion in the IGS realization of ITRF. A new reference frame, called IGS14, was adopted on Jan. 29, 2017 (GPS Week 1934). At the same time, an updated set of satellite and ground antenna calibrations, igs14.atx, was implemented.
Real-Time Working Group. The Real-Time WG supports the development and integration of real-time technologies, standards and infrastructure to produce high-accuracy IGS products in real time. The group operates the IGS Real-Time Service (RTS) to support precise point positioning (PPP) at global scales, in real time.
RINEX Working Group. The RINEX-WG jointly manages the Receiver-Independent Exchange (RINEX) format with the Radio Technical Commission for Maritime Services Special Committee 104 (RTCM-SC104). RINEX has been widely adopted as an industry standard for archiving and exchanging GNSS observations, and newer versions support multiple GNSS constellations. Recently, the IGS governing board agreed to adopt the official RINEX V3.04 format, handling the ability for nine-character station ID and fixing the definition of GNSS reference time scales.
Space Vehicle Orbit Dynamics Working Group. This group brings together IGS groups working on orbit dynamics and attitude modeling of spacecraft. This work includes the development of force and attitude models for new GNSS constellations to fully exploit all new signals with the highest possible accuracy.
Troposphere Working Group. The Troposphere WG supports development of IGS troposphere products by combining troposphere solutions from individual analysis centers to improve the accuracy of PPP solutions. The goal of the Troposphere WG is to improve the accuracy and usability of GNSS-derived troposphere estimates.
Tide Gauge (TIGA) Working Group. When studying sea level changes, where the GPS height of the benchmark is used for defining an absolute sea-level datum, problems occur when correcting the time series for height changes of the benchmark. TIGA is a pilot study for establishing a service to analyze GPS data from stations at or near tide gauges in the IGS network to support accurate measurement of sea-level change across the globe.
A Multi-GNSS IGS Network
The development of a multi-GNSS sub-network within the greater IGS network, led by the MGEX Project, develops the IGS’s capability to operate with multiple GNSS constellations. It has 223 multi-GNSS-capable (GPS + GLONASS + at least one other constellation) stations. Also, the number of IGS stations capable of real-time data streaming in support of the IGS Real-Time Project has increased to 195.
MGEX was founded in 2012 to build a network of GNSS tracking stations, characterize the space segment and user equipment, develop theory and data-processing tools, and generate data products for emerging satellite systems. The stations within its network contain a diverse assortment of receiver and antenna equipment, which are recognized and characterized by the IGS in equipment description files. Other than GPS and GLONASS, no combination process has yet been implemented within IGS for precise orbit and clock products of the other, newer, constellations. Despite this, cross-comparison among analysis centers, as well as with satellite laser ranging, has been used to assess the precision or accuracy for various products.
The growing role of multi-GNSS within the IGS network was benchmarked by the transition of MGEX to official IGS project status in 2016. For the sake of consistency, and as a nod to its heritage, use of the acronym “MGEX” has been retained.
Making Strides in Real Time
Through the Real-Time Service (RTS), the IGS extends its capability to support applications requiring real-time access to IGS products. The RTS is a GNSS orbit and clock correction service that enables PPP and related applications, such as time synchronization and disaster monitoring, at worldwide scales. The RTS is based on the IGS global infrastructure of network stations, data centers and analysis centers that provide world-standard high-precision GNSS data products.
The RTS is currently offered as a GPS-only operational service, but GLONASS is initially being offered as an experimental product for the development and testing of applications. GLONASS will be included within the service when the IGS is confident that a sufficient number of analysis centers can ensure solution reliability and availability. Other GNSS constellations will be added as they become available.
Engagement with the United Nations
The IGS engages with diverse organizations, outside of the immediate precise GNSS community, that have an interest in geodetic applications of GNSS. Notably, the IGS has supported the development of the Global Geodetic Reference Frame resolution, roadmap and implementation plan within the United Nations Global Geospatial Information Management (GGIM) Committee of Experts.
The IGS also works with the United Nations Office for Outer Space Affairs (UNOOSA) International Committee on GNSS (ICG) to develop common understandings of the requirements for multiple system monitoring through the joint pilot project with the ICG’s IGMA subgroup. The IGS also co-chairs ICG Working Group D, which focuses on reference frames, timing and applications.
A Multi-GNSS Future
Though the accuracy of current IGS multi-GNSS products lags behind standard IGS products for GPS and GLONASS, multi-GNSS paves the way for complete exploitation of new signals and constellations in navigation, surveying, geodesy and remote sensing.
IGS also looks externally to other techniques through its participation in the IAG’s GGOS, which has illuminated how satellite laser ranging observations to GNSS satellites improves our understanding of observational errors and thus drives further improvement of IGS position, clock and orbit products.
As it enters its second quarter-century, the IGS is evolving into a truly multi-GNSS service. For 25 years, IGS data and products have been made openly available to all users for use without restriction, and continue to be offered free of cost or obligation. In turn, users are encouraged to participate within the IGS, or otherwise contribute to its advancement.
Acknowledgements
The authors gratefully acknowledge the contributions of the IGS governing board and associate members in the drafting of this article. Special thanks to Anna Riddell and Grant Hausler, who, along with Gary Johnston, have an extensive chapter on IGS in the Springer Handbook of Global Navigation Satellite Systems, published in 2017 by Springer (see Further Reading). This book chapter is the new recommended official citation for publications referencing IGS data, products and other resources.
Allison Craddock a member of the Geodynamics and Space Geodesy Group in the Tracking Systems and Applications Section at the NASA Jet Propulsion Laboratory in Pasadena, California. She is the director of the IGS Central Bureau, manager of external relations for the International Association of Geodesy’s Global Geodetic Observing System, and staff member of the NASA Space Geodesy Program.
Gary Johnston is the head of the National Positioning Infrastructure Branch at Geoscience Australia. Johnston is the chair of the IGS governing board and the co-chair of the Subcommittee on Geodesy under the United Nations Global Geospatial Information Management committee of experts.
FURTHER READING
GNSS Handbook Chapter on IGS
“The International GNSS Service” by G. Johnston, A. Riddell and G. Hausler, Chapter 33 in 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.
International GNSS Service Technical Report 2017 (IGS Annual Report), edited by A. Villiger and R. Dach, published by IGS Central Bureau and University of Bern, Bern Open Publishing, Bern, Switzerland, 2018, doi: 10.7892/boris.116377. Includes reports from analysis centers, data centers and working groups.
“The Multi-GNSS Experiment (MGEX) of the International GNSS Service (IGS) – Achievements, Prospects and Challenges by O. Montenbruck. P. Steigenberger, L. Prange, Z. Deng, Q. Zhao, F. Perosanz, I. Romero, C. Noll, A. Stürze, G. Weber, R. Schmid, K. MacLeod and S. Schaer in Advances in Space Research, Vol. 59, No. 7, April 1, 2017, pp. 1671–1697, doi: 10.1016/j.asr.2017.01.011.
“Data Formats” by O. Montenbruck and K. MacLeod, Annex A in 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.
Delegates from the UN’s International Committee Global Navigation Systems (UN ICG) at the entrance to ESA’s ESTEC Test Centre, used to test the last 22 Galileo satellites. (Photo: ESA)
The UN ICG group visited ESTEC on May 16 during a meeting in the Netherlands.
News from the European Space Agency (ESA)
Members of the United Nations (UN) technical group supporting global cooperation in satellite navigation toured ESA’s technical centre in the Netherlands to see key facilities used to develop Europe’s Galileo system.
Delegates from the UN’s International Committee on Global Navigation Systems (UN ICG) met in mid-May at the nearby Galileo Reference Centre, operated by the GSA, European Global Navigation Satellite Systems Agency.
ESA, one of the founding members of the ICG in 2005, invited them to visit the agency’s European Space Research and Technology Centre, ESA’s single largest establishment and home to its Navigation Directorate.
Javier Benedicto, ESA’s Galileo program manager was joined by Rodrigo Da Costa, GSA’s Head of Exploitation, in giving the visitors a hearty welcome. “I’m honored to work with the amazing team of engineers and managers responsible for developing the Galileo system,” Benedicto said. “The laboratory and testing facilities here are very much at the heart of Galileo development.”
ESA’s Receiver Testing Facility is the historic location of the first Galileo positioning fix in 2012. (Photo: ESA)
“I’m very happy to welcome members of the UN ICG group, doing a great job in bringing navigation satellite system operators together, to share achievements and challenges and encourage interoperability – our users love our systems working together.”
The tour began at ESA’s Receiver Testing Facility — historic location of the world’s very first Galileo positioning fix back in 2012 – equipped with a multitude of specialized satnav receivers for not only Galileo satellites but also the US GPS, Russian Glonass, Chinese BeiDou, India’s NAVIC and Japanese QZSS systems, together with augmentation systems such as Europe’s own European Geostationary Navigation Service, EGNOS. The signals from all these systems can also be recorded to very high fidelity for subsequent investigation or reuse.
Lab simulation systems can recreate all these outputs in combination to test receiver systems across a huge range of scenarios, such as amid interference induced by a solar storm, or to see how receivers cope while flying, or even in orbit.
Smartphone receivers can be assessed with simulated augmentation from cellular network stations, wifi mapping or inertial navigation, while simulating their user’s continuous motion. The flexibility the facility’s simulators offer also allows early testing of enhancements planned for next decade’s ‘Galileo Second Generation’ satellites.
“Our aim is to go closer to the market, and how they’re doing things because how current services are being exploited is very important for developing the next generation,” said Olivier Smeyers of ESA’s Commercial User Segment Section.
This table in ESA’s Galileo Payload Laboratory comprises a replica Galileo In-Orbit Validation satellite payload (other than its atomic clocks, which are housed separately nearby). Kept in cleanroom conditions at ESTEC in the Netherlands, it is employed for ground-based testing or anomaly investigation. (Photo: ESA)
Next came the Galileo Processing Centre, which provides ESA with continuous monitoring of Galileo services. It functions independently from the rest of the global Galileo infrastructure, to allow independent assessment of its performance, down to individual satellites and the onboard atomic clocks at the heart of the system — working closely with facilities such as the Galileo Time Validation Facility in Spain and the Galileo Control Centres in Germany and Italy.
The group was also shown ESA’s Time and Metrology Facility: an ensemble of six high-performance atomic clocks sufficiently stable to monitor the nanosecond-scale performance of Galileo System Time, and since 2012 maintaining their own timescale called UTC (ESTC), employed in turn to help set Coordinated Universal Time (UTC) — the world’s global time.
The cleanroom environment of the Galileo Payload Laboratory contains the same atomic clocks flown aboard Galileo satellites with the rest of its navigation payload, used to replicate any performance anomalies identified in orbit and make early tests of Galileo Second Generation design improvements.
“ESA is a very active member of UN ICG,” commented Rafael Lucas Rodriguez of ESA’s Galileo Services Engineering Unit and tour organizer. “We’re currently co-chairing an ICG working group on system performance enhancement and supporting the European Commission and GSA on all Galileo-related technical matters discussed at the committee.”
An aerial view of ESTEC. The Erasmus building is at front right. The T building (home to ESA’s Galileo team) is in the foreground.
