On Feb. 12, President Donald Trump signed an Executive Order establishing a comprehensive national policy to promote the responsible use of positioning, navigation and timing (PNT) services by the federal government.
The order directs federal agencies to take steps to reduce disruption of critical infrastructure that relies on PNT, including GPS. It also directs critical infrastructure owners and operators to strengthen their systems’ resilience.
Markets affected include including the electrical power grid, communications infrastructure and mobile devices, all modes of transportation, precision agriculture, weather forecasting and emergency response.
The federal government will engage both the public and private sectors to identify and promote responsible use of PNT services, with the goal of ensuring that “critical infrastructure can withstand disruption or manipulation of PNT services.”
“Because of the widespread adoption of PNT services, the disruption or manipulation of these services has the potential to adversely affect the national and economic security of the United States,” the order states. “To strengthen national resilience, the Federal Government must foster the responsible use of PNT services by critical infrastructure owners and operators,” the order reads.
PNT Profiles
The Commerce Department is tasked with developing PNT profiles, due a year from today, for PNT-dependent systems, networks and assets. The profiles will be developed through consultation with the private sector.
The profiles will also:
identify appropriate PNT services;
detect the disruption and manipulation of PNT services; and
manage the associated risks to the systems, networks and assets dependent on PNT services.
The profiles will be reviewed and updated every two years.
Reaction to the Order
Reacting to the Executive Order on PNT, J. David Grossman, executive director of the GPS Innovation Alliance (GPSIA), stated:
“The GPS Innovation Alliance (GPSIA) welcomes today’s Executive Order recognizing the critical economic and societal benefits of GPS and other Global Navigation Satellite Systems (GNSS). Resiliency is among the core attributes that have made GPS the gold standard for delivering positioning, navigation, and timing (PNT) functions to our military as well as a wide range of other sectors, including transportation, agriculture, electricity, and finance. Today’s Executive Order represents a crucial next step in ongoing efforts to maintain the security, robustness, and redundancy of PNT capabilities, including GPS, that millions of Americans rely on every day. GPSIA looks forward to working with key government stakeholders to support the implementation of this effort.”
The Department of Transportation stated,
“Our challenge is to enable increased resilience across our transportation systems and ensure the traveling public and freight transporters experience an increased level of safety and efficiency without the possibility of interference caused by loss or manipulation of PNT.
Department of Homeland Security Acting Secretary Chad F. Wolf said,
“From mobile phone applications to automobile navigation, our digital, interconnected society is dependent every day on PNT services.That is why it’s critically important that PNT services remain properly functioning as a major component of the nation’s critical infrastructure. By adopting responsible use of PNT services, the federal government and owners and operators of critical infrastructure can contribute meaningfully to national resilience and ensure the continuous, uninterrupted delivery of services to the nation.”
The new line of Sarbe search and rescue beacons. (Photo: Orolia)
Orolia is introducing the Sarbe Evo line at the Singapore Air Show, taking place Feb. 11-16 at the Changi Exhibition Centre. The line is being exhibited at Orolia’s Booth G10.
The search-and-rescue (SAR) beacon range has been improved to deliver upgraded operational capabilities, to meet the latest Cospas-Sarsat testability and maintenance requirements.
Part of Orolia since 2011, the Sarbe brand is a worldwide market leader for military (tri-forces) Personal Locator Beacons and Emergency Locator Transmitters. Sarbe beacons have been at the forefront of innovation in life saving Locator Beacons and critical communications for over fifty years.
Sarbe equipment is often integrated into air crew clothing such as Air Crew Life Preservers, ejection seats and survival packs, and can be optionally equipped with remote antennas and automatic activation.
The Sarbe Evo line offers new operational improvements in order to meet revised Cospas-Sarsat requirements in operating lifetime, location accuracy, voice signals management, integrated protocols, testability and maintenance.
Orolia’s development of the Sarbe Evo line has focused on the following key elements to improve customer safety:
Upgraded battery management with use-monitoring
Exceeds Cospas-Sarsat endurance requirements
Built-in-test further enhanced
More robust and frequent GPS/GNSS position acquisition with GPS, Galileo and GLONASS satellite constellations
Audio system improvement for greater clarity under all operating conditions
Introduction of the National Location Protocol
Rugged and reliability improvement (qualified to MIL-STD-810G standards) to support complex rescue missions in harsh environments
For both commercial and military needs in SAR operations, Orolia’s main goal remains the provision of highly accurate location data, and real-time voice and data communication to SAR operators through robust line of sight transmission.
A key feature of a new high-accuracy GNSS correction service
Innovation Insights with Richard Langley
INTEGER VITAE SCELERISQUE PURUS. So wrote the Roman poet Horace at the beginning of one of his odes — one which, incidentally, was sung by college choirs at one time. It is usually translated as “upright of life and free from wickedness” and is just about the only common Latin quotation in which we find the word “integer.”
Besides upright, the word can be translated as unimpaired, perfect or whole. It is this latter meaning that the English mathematician Thomas Digges appropriated to describe whole numbers. The modern mathematics definition of the set of integers includes the additive inverses of the whole numbers plus zero. We have to worry about the integer nature of carrier-phase ambiguities when trying to achieve high-precision GNSS positioning but that is a story for another day.
The Latin word integer is the root of the English word integrity. In everyday speech, integrity means the quality of being honest or trustworthy (and having strong moral principles). But it is also used to describe something that is unimpaired or uncorrupted, especially in regard to electronic data such as that provided by a navigation system.
As I wrote in an Innovation column back in 1999, “The performance of any navigation system is characterized by its accuracy, availability, continuity, and integrity. From a safety point of view, integrity is arguably the most important factor. Without some assurance of a system’s integrity, we have no way of knowing whether the information we receive is correct: How are we to know whether a navigation system is actually achieving its advertised accuracy and not misleading us with faulty information?” Navigation systems that provide safety-of-life services must ensure a very high level of integrity. For example, the Wide Area Augmentation System (WAAS) continuously assesses the integrity of GPS satellite signals as well as its own corrections, warning WAAS users when a failure is encountered within about 6 seconds of failure. This helps to ensure that aircraft do not use misleading data that could potentially create hazards.
And now, high-precision GNSS positioning technology using real-time augmentation is being adopted for autonomous applications in the automotive, rail, aviation and marine industries. These applications need high integrity in their position determinations in addition to high accuracy. As with the pioneering non-autonomous aviation use, augmentation services for the new market will need to monitor many aspects of their service to ensure a high level of integrity including the high-end data processing algorithms, real-time data transmission, end-to-end encryption, and functional safety assurance. This will be a challenging task that will require a multi-disciplinary approach, deep understanding of GNSS error modeling and risk assessment.
In this month’s column, we look at the design, construction, operation and performance of the first safety-critical, high-accuracy augmentation service created specifically for autonomous applications.
In addition to the need for high accuracy, the adoption of high-precision GNSS positioning technology for autonomous applications in the automotive, rail, aviation and marine industries has brought with it the need for high integrity and reliability. GNSS integrity concepts had their beginning in safety-critical applications in the aviation and marine industries, which have used GNSS to provide absolute position for precision runway approach, enroute navigation, port approaches, open sea and coastal waterway navigation.
For precision GNSS users (those using precision or high-end equipment) in the surveying, construction and agriculture industries, the focus has primarily been on accuracy. Over the past decade, real-time networks have been developed to offer sub-2-centimeter performance to end users. Although some integrity information has been provided, it has often been in the form of disturbance indices that network operators can use to inform users of suspected down time or periods of poor performance. But the information lacks a functional safety component. Additionally, this information has not typically been integrated in real time into position engines to aid in the generation of reliable integrity parameters for the end users.
Although GNSS does have limitations, particularly in urban environments, GNSS equipment is one of the few sensor types available to system integrators that can provide absolute position in autonomous applications.
This realization — combined with the further miniaturization, lower power consumption and expansion of inexpensive multi-frequency, multi-constellation GNSS chips capable of real-time-kinematic- (RTK-) style processing — has made the adoption of GNSS for mass-market applications very appealing.
Most mass-market applications don’t have the same accuracy requirements that drive the professional high-precision market. TABLE 1 summarizes applications that can benefit from a high-precision GNSS correction service. In most cases, decimeter-to-meter-level accuracy is typically acceptable. Reliability becomes more critical for these applications.
Table 1. Applications that can benefit from a high-precision GNSS service with integrity. (Data: Sapcorda)
The integrity demand, which we define as the degree of difficulty an application poses to the integrity monitoring system, is based on the required accuracy, availability, failure rate and continuity requirements of the application. Applications with a high integrity demand pose the most difficult challenges.
With the spread of autonomous applications in various areas, the likelihood of liability and legal cases being decided based on PVT data provided by the systems is high. This eventuality brings with it a need for a non-proprietary open standard for ensuring consistent implementation of the integrity information and functional safety along with the separation of end-user and provider responsibility. In this article, we describe the requirements and concepts for a high-precision GNSS correction system with high integrity.
SYSTEM OVERVIEW
Our Sapcorda correction service provides high-precision GNSS correction data on a continental scale. Its core component is an underlying tracking network of reference stations used to generate the precise corrections. The reference stations operate in real time and continuously transmit their data to the data control center. The data control center processes the data, computing orbit, clock, instrumental bias and atmosphere corrections and integrity information, and then encrypting the data before broadcasting it to the end user (see FIGURE 1).
The corrections are broadcast in the Safe Position Augmentation for Real Time Navigation (SPARTN) format developed by a consortium of GNSS manufacturers and service providers, via two communication channels, L-band and the internet. The data is then received by the end users who must decrypt it before it is used in processing. The SPARTN correction format consists of a set of messages that broadcast the GNSS corrections in a state-space representation. With our network, Sapcorda can offer a high-accuracy positioning service with fast convergence. An example of positioning performance for a monitoring station in Sapcorda’s European network coverage area is shown in FIGURE 2. The typical accuracy level is close to that of traditional network RTK services.
FIGURE 2. Horizontal position performance for a monitoring site in Europe using Sapcorda’s high-precision service. (Image: Sapcorda)
The system provides coverage for both North America and Europe as shown in FIGURE 3. Unlike traditional local or regional network RTK systems, Sapcorda’s network provides seamless coverage on the continental scale and operates in broadcast-only mode.
The integrity of a system can be described as the trustworthiness of the positions generated by the position engine. Trustworthiness is defined by the protection level associated with a given solution. Many of the concepts related to GNSS integrity originated from the development of the Wide Area Augmentation System (WAAS). The integrity concept was formalized by the Stanford Integrity Diagram, which outlines the key concepts related to integrity. TABLE 2 defines the terminology surrounding the integrity concept.
Table 2. Integrity terms. (Data Sapcorda)
The integrity risk is the probability that a user will experience a position error larger than the alert limit without an alarm being triggered. When this occurs, the user is in a potentially dangerous situation as the system is providing dangerously misleading information to the user, who is unaware.
The protection levels are computed based on the expected behavior of the error sources encountered in a GNSS positioning system. If the protection level is less than the system’s alert limit, then the system is operating within its normal bounds. If the error sources are not properly monitored or quantified, protection levels become optimistic. This occurs when the true position error, which is typically unknown, exceeds the protection level supplied by the system. When this situation occurs, it is labeled hazardously misleading information (HMI) because the system may believe that its position is more accurate than it truthfully is. If the true position error remains less than the alert limit, then this is classified as misleading information. As the true position is not beyond the alert limit, the operator/system can continue to rely on this information without being in a potentially dangerous scenario.
To define the true integrity risk of the system, it is necessary to understand its error sources, threat models, frequency of occurrences and potential failure modes. Many threats could render a correction service unavailable, including hardware failures, data outages or software bugs, atmospheric anomalies and satellite failures. The following section describes these threats along with the capabilities used for monitoring them.
Error Sources. The primary error sources in high-precision GNSS positioning are described in TABLE 3.
Table 3. GNSS network error sources, their magnitude and mitigation approach. (Data Sapcorda)
Although not mentioned in this table, additional error sources include site displacement effects such as solid earth tides, ocean tide loading and polar tides; carrier-phase wind-up at both the receiver and satellite; and satellite and receiver antenna phase-center variations and relativistic delays. These effects must be consistently modeled at both the server and the end-user for centimeter-level positioning.
Based on the error sources described in Table 3, it is necessary to convert this information into a format that can be used by the position engine to derive protection levels for each solution. How the final protection level is derived by a position engine is not within the scope of this article. For this, several approaches can be used including carrier-phase-based receiver autonomous integrity monitoring (CRAIM), solution separation and others.
The following equation can be used to describe the overall error contribution for each measurement:
where
is the total uncertainty for satellite i
is the uncertainty of the ionosphere model
is the uncertainty of the troposphere model
is the uncertainty of the combined orbit, clock and bias (ephemeris) corrections
is the uncertainty of the measurements in the given environment
The terms , and are derived from the real-time reference network operator while the term must be computed by the end-user receiver. This final term is perhaps the most difficult to determine, particularly for kinematic environments, as the value is highly dependent on antenna quality, multipath and measurement quality.
PERFORMANCE AND RESULTS
We processed 24 hours of data at three stations covered by Sapcorda’s European network and within the red circle shown in FIGURE 5.
FIGURE 5. Location of stationary testing carried out within Sapcorda’s European network. (Image: Sapcorda)
The test stations were situated in an open-sky environment with high-quality geodetic antennas and receivers. The position results and protection levels were derived from Sapcorda’s own position engine.
FIGURE 6. Integrity plots for the horizontal error and protection levels for three stations within Sapcorda’s European network coverage area.(Image: Sapcorda)
FIGURE 6 shows the horizontal component integrity plots for the three stations. The protection levels are computed for the five-sigma level. In all three examples, the protection level can properly bound the horizontal position error. In terms of the measured accuracy, the typical performance observed at the three stations is between 3 and 7 centimeters for the 95th percentile.
In addition to the stationary testing, two kinematic trials were carried out in cooperation with a system integrator. The integrator setup consisted of a commercial RTK receiver and position engine being fed with SPARTN corrections. The equipment was mounted onto the vehicle used for the tests. Both tests were carried out in an urban environment, which introduced measurement outages due to trees, overpasses and urban canyons. FIGURE 7 shows the area in which the kinematic trails were carried out, as well as some of the urban conditions with which the system had to contend.
FIGURE 7. Location of kinematic trials using Sapcorda’s North American correction service and examples of the environment encountered during the testing. (Image: Sapcorda)
FIGURES 8 and 9 show the position performance and integrity plots for the two kinematic trial scenarios. The reference trajectory was computed using a short baseline post-processed kinematic solution computed with a third- party application. The typical accuracy of the Sapcorda-enabled solution was on the order of 2 to 4 centimeters, while the maximum error was 10 centimeters. In both cases, the protection levels were able to properly bound the horizontal position error. Figure 8 shows an area of increased position error, which occurs around the 22.6- to 22.7-hour mark of the day. This period coincides with the image in the bottom right of Figure 7, where the vehicle passes into a difficult environment with overhead trees and walkways, as well as significant shading from a tall building. Even in this type of environment, the protection levels were able to properly bound the horizontal position error.
FIGURE 8a. Horizontal position performance for kinematic trial #1. The red line indicates the 1-sigma error of the position engine. (Image: Sapcorda)FIGURE 8b. Horizontal position performance for kinematic trial #1: The 5-sigma integrity diagram. (Image: Sapcorda)FIGURE 8b. Horizontal position performance for kinematic trial #1: The 5-sigma integrity diagram. (Image: Sapcorda)FIGURE 9b. Horizontal position performance for kinematic trial #2: The 5-sigma integrity diagram. (Image: Sapcorda)
In addition to the position performance, re-initialization time plays a critical role for precise positioning systems operating in difficult environments. Due to the regular outage and signal blockages, which occur in urban environments, the re-initialization time is critical to providing high availability. Traditional precise point positioning (PPP) systems, even those that perform ambiguity resolution, can take anywhere from 5 to 20 minutes to re-initialize and achieve an acceptable accuracy level (typically 10 centimeters) after a complete outage. Researchers in both academia and industry have developed several methods to reduce this time by “bridging the gap” after outages.
However, these approaches rely on assumptions about either the vehicle trajectory or the stability of the ionosphere before and after outages. The impact of these assumptions on overall integrity have not been adequately studied. Systems that rely on inertial measurement units (IMUs) to constrain the position after an outage introduce a dependency between what should be two independent sensors in the overall system.
FIGURE 10 shows the re-initialization time of the integrator’s position engine when using Sapcorda’s correction service. In this case, the re-initialization time is computed as the time it takes to return to RTK-ambiguity-fixed mode as indicated in the position engine output after an outage. Results based on comparisons against short-baseline RTK positioning showed typical accuracies below 10 centimeters upon re-initialization. In this definition, the time of the outage is included in the overall re-initialization time. In nearly all of the 42 occurrences, the time to re-initialize is less than 10 seconds. This is sufficient to allow an IMU to provide position updates during the GNSS outage.
FIGURE 10. Re-initialization time of the integrator’s position engine enabled by Sapcorda’s correction service. (Image: Sapcorda)
SYSTEM DESIGN CONSIDERATIONS
In addition to understanding GNSS error sources and performance, it is also important to consider the integrity of the entire system. This includes software development processes, hardware selection, data communication standards and security.
Software Design
Aspects needing to be addressed include:
Software Coding Standards. As software is used more and more in safety-critical scenarios, standards have been developed to minimize common errors and failures. Some standards relevant for safety-critical applications development include International Organization for Standardization (ISO) standard 26262 and Motor Industry Software Reliability Association (MISRA) C/C++ coding standards. Many of these standards can be automated via the static analysis tools described below.
Functional Safety. The objective of this analysis is to understand the possible failure modes of a system, how likely they are to occur, and how to mitigate their risk. Several methods can be applied for functional safety analysis. One such approach is failure mode effect analysis (FMEA). In general, functional safety analysis is a complex task requiring a wide range of experience and expertise. Understanding how design or feature choices impact overall failure modes is also critical for simplifying the number of cases and overall system complexity.
Test Coverage. Unit tests provide the fundamental verification that a function can perform its expected task. Coverage analysis tools provide insight into which sections, paths and combinations are being tested. Various metrics are possible, including:
statement coverage: measures the number of executable lines of code that are evaluated
branch coverage: measures which code paths are being evaluated (for example, if statements, both true and false must be covered)
modified condition/decision coverage (MC/DC): in addition to checking all branches, all combinations of branches must be considered.
The degree of effort to meet target coverage metrics greatly varies based on the type of metric chosen.
Code Quality Metrics. Code quality metrics attempt to reduce the complexity of functions and methods in the software. Code quality metrics may include:
cyclomatic complexity scores
establishing the maximum number of control statements within a function
establishing the maximum number of lines or methods called within a single function.
Static Analysis. Static code analysis provides an examination of source code prior to execution. It can detect common implementation issues such as divide-by-zero errors, bounds overrun, poorly defined loops or control statements, among others. Most commercial products provide support for MISRA C/C++ guidelines and other best practices for safety-critical applications.
Automated Testing. Test automation is critical for monitoring performance changes and ensuring high-quality code changes. Critical scenarios such as leap-second changes, week rollovers and ephemeris failures can be logged and then used as part of the automated test plan. And, as bugs emerge, adding additional test scenarios for these is also beneficial.
Data Communication Protocol
One must also consider several aspects related to the transmission of the correction service to users.
Open Source. A standardization of an open-source data communication protocol for mass-market applications allows for a receiving system to employ multiple corrections from more than a single specific provider without requiring independent functional safety requirements. This can provide a much higher level of redundancy than is possible when depending on only a single service provider.
Integrity and Functional Safety. To properly quantify the protection level, it is necessary to provide quality information about the corrections being provided by the service. Employing “do not use” flags ensures users drop satellites that may be unhealthy or performing poorly. General system status messages identifying the cause of a failure are also critical for proper separation of issues between server and recipient.
Encryption and Anti-Spoofing. As the use of GNSS expands, the threat of spoofing has become more significant. Data message encryption must be robust and resilient to protect the user of the data against external threats.
Self-Contained and Repeatable. Replication of events is important for safety-critical applications. A message format used for such applications should be self-contained and not rely on any external sources for factors such as initialization or the expansion of data. This may include the expansion of time-tagged data, or limiting the expansion of ephemeris to a specific Issue of Data Ephemeris (IODE).
SUMMARY
High-precision GNSS correction services for applications requiring both accuracy and integrity will continue to grow. To meet these demands, GNSS correction services that previously focused on accuracy as their primary goal must begin to work toward providing adequate integrity information to provide reliable positions and protection levels. This requires a multidisciplinary approach to achieve an in-depth understanding of GNSS error sources, integrity concepts and functional safety.
End users will benefit from the clear separation of the server and recipient responsibilities and through an open communication standard that facilitates the use of multiple correction service providers and is developed with safety and integrity at its core.
The adoption of formal safety practices, including software development strategies to reduce risk and mitigate errors, is also critical in achieving a reliable and safe high-precision correction service.
ACKNOWLEDGMENT
This article is based on the paper “Integrity for High Accuracy GNSS Correction Services” presented at ION ITM 2019, the 2019 International Technical Meeting of The Institute of Navigation, Reston, Virginia, Jan. 28–31, 2019.
LANDON URQUHART is the R&D engineering manager for Sapcorda Services Inc., with offices in Berlin and Hanover, Germany, and Scottsdale, Arizona, USA. He obtained his M.Sc.E. from the Department of Geodesy and Geomatics Engineering at the University of New Brunswick (UNB), Fredericton, Canada. His research interests are GNSS correction services for mass-market applications.
RODRIGO LEANDRO is the chief technology officer at Sapcorda Services in Scottsdale. He holds a Ph.D. in spatial geodesy from UNB. Dr. Leandro has been active in GNSS R&D for more than 15 years and has served in engineering leadership roles in various companies in the GNSS industry.
PAOLA GONZALEZ is a product engineer at Sapcorda Services and is based in Hanover. She completed her B.Sc. in geodesy at Zulia University in Maracaibo, Venezuela, and her master’s degree in geomatics at Karlsruhe University of Applied Sciences in Karlsruhe, Germany. In the past few years, she has been working in the GNSS industry, focusing mostly on performance analysis, evaluation and verification of different equipment, software and services.
FURTHER READING
• Authors’ Conference Paper
“Integrity for High Accuracy GNSS Correction Services” by L. Urquhart, R. Leandro and P. Gonzalez in Proceedings of ITM 2019, the 2019 International Technical Meeting of The Institute of Navigation, Reston, Virginia, Jan. 28–31, 2019, pp. 543–553, https://doi.org/10.33012/2019.16709.
• GNSS Integrity
“GNSS Position Integrity in Urban Environments: A Review of Literature” by N. Zhu, J. Marais, D. Betaille and M. Berbineau in IEEE Transactions on Intelligent Transportation Systems, Vol. 19, No. 9, September 2018, pp. 2762–2778, doi: 10.1109/TITS.2017.2766768.
“Carrier Phase-based Integrity Monitoring for High-accuracy Positioning” by S. Feng, W. Ochieng, T. Moore, C. Hill and C. Hide in GPS Solutions, Vol. 13, No. 1, January 2009, pp. 13–22, doi: 10.1007/s10291-008-0093-0.
“New Tools for Network RTK Integrity Monitoring” by X. Chen, H. Landau and U. Vollath in Proceedings of ION GPS/GNSS 2003, the 16th International Technical Meeting of the Satellite Division of The Institute of Navigation, Portland, Oregon, Sept. 9–12, 2003, pp. 1355–1360.
“The Integrity of GPS” by R.B. Langley in GPS World, Vol. 10, No. 3, March 1999, pp. 60–63.
• Satellite-Based Augmentation Systems
“Satellite Based Augmentation Systems” by T. Walter, Chapter 12 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.
Minimum Operational Performance Standards for Global Positioning/Satellite-Based Augmentation System Airborne Equipment, RTCA/DO-229E, prepared by SC-159, RTCA Inc., Washington, D.C., Dec. 15, 2016.
“The Stanford – ESA Integrity Diagram: A New Tool for The User Domain SBAS Integrity Assessment” by M. Tossaint, J. Samson, F. Toran, J. Ventura-Traveset, M. Hernandez-Pajares, J.M. Juan, J. Sanz and P. Ramos-Bosch in Navigation, Journal of The Institute of Navigation, Vol. 54, No. 2, Summer 2007, pp. 153–162.
“Validation of the WAAS MOPS Integrity Equation” by T. Walter, A. Hansen and P. Enge in Proceedings of the 55th Annual Meeting, The Institute of Navigation, Cambridge, Massachusetts, June 28–30, 1999, pp. 217–226.
“WAAS MOPS: Practical Examples” by T. Walter in Proceedings of NTM 1999, the 1999 National Technical Meeting of The Institute of Navigation, San Diego, California, Jan. 25–27, 1999, pp. 283–293.
• Jamming and Spoofing
“Interference” by T. Humphreys, Chapter 16 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.
• Ionospheric Threats
“Ionospheric Impact on GNSS Signals” by N. Jakowski, C. Mayer, V. Wilken and M.M. Hoque in Física de la Tierra, Vol. 20, 2008, pp. 11–25.
“Ionospheric Disturbance Indices for RTK and Network RTK Positioning” by L. Wanniger in Proceedings of ION GNSS 2004, the 17th International Technical Meeting of the Satellite Division of The Institute of Navigation, Long Beach, California, Sept. 21–24, 2004, pp. 2489–2854.
The MQ-9 Reaper drone. (Photo: U.S. Air Force/Paul Ridgeway)
A small aircraft’s encounter with a likely military drone near Edwards Air Force Base resulted in navigation failure, according to a report filed with NASA’s Aviation Safety Reporting System.
In October 2019, a single engine Piper P-46 Malibu was flying at 24,000 feet 36 miles north of Los Angeles en route San Diego.
Defense drone overhead
The pilot reported, “I saw a DOD drone (inverted V tail) pass overhead approximately 1,000 [feet] above. At the same time, my PFD [primary flight display] indicated that I had a large magnetic variation error, and in turn … indicated that I was now flying to a new way point (TCH VOR) located in Utah, well off my flight plan.”
Later, the navigation system indicated that the aircraft was on its way to a spot in Montana.
Interestingly, the flight plan displayed by another cockpit instrument, the Multi-Function Display, was not affected.
The aircraft had been operating under an Instrument Flight Plan. Federal Aviation Administration rules for light aircraft allow such operation with GPS as the sole navigation sensor.
With the primary flight display not operating properly, the aircraft was no longer able to fly a safe instrument approach to landing. Fortunately, the weather was such that it could proceed and land using Visual Flight Rules.
In the pilot’s words, “Had it not been a VMC [visual meteorological conditions] day allowing me to fly a visual approach, I would have had to [advise Air Traffic Control] – and find a way to land without any reliable approach capability.”
A combination of factors
The general consensus among experts is that this incident was inadvertent and likely arose from a combination of factors. Most significant were that the drone flew above the light aircraft, temporarily blocking some GPS signals, and emitting electromagnetic radiation from one or more of its on-board systems.
It is not possible to say what those systems and radiation may have been. It is unlikely they were intended to interfere with GPS reception, as that would pose serious safety-of-flight concerns in the nearby congested Los Angeles airspace.
GPS signals are infamously easy to disrupt, though. It is probable that the close proximity of the drone resulted in some radiation from its systems “spilling over” into GPS frequencies and causing the problem.
Of greater concern is that the light aircraft’s systems did not quickly reset and recover once the drone had moved off and the interference ceased. Had the aircraft been flying in the clouds or bad weather, the loss of its only radionavigation source could have been quite serious.
While not clear from the report, it is likely that the navigation system only recovered after a complete shutdown and restart. From the report in the NASA database:
“The system has since been checked and is operating correctly, but it seems pretty clear this was some type of interference / jamming arising from the DOD drone. Clearly, this is a significant risk to all aircraft, and because if [sic] occurred within the LA airspace it is a serious threat to safe flights.”
The need to address interference
Shortly before this incident, the International Civil Aviation Organization identified addressing interference with satellite navigation system signals an “urgent priority.” This was in response to concerns from several member countries and organizations citing safety of flight issues. One example cited was the near loss of a passenger aircraft flying in the mountains during a period of GPS disruption.
The October 2019 report of interference from the drone is number ACN 1696794 in the NASA Aviation Safety Reporting System. It can be accessed by searching here.
ADVA has launched a centralized GNSS monitoring and assurance tool that uses artificial intelligence (AI) and machine learning (ML) for comprehensive predictive maintenance.
The new customer-owned tool enables users to collect and analyze huge amounts of information from across the network to remotely identify issues and protect networks from GNSS vulnerabilities, including jamming and spoofing attacks.
It also helps to identify GNSS obstruction issues, detect blind/poor spots that appear over time, and enable optimal antenna positioning.
Built into ADVA’s Ensemble Controller network management suite with Sync Director, the solution enables customers to detect potential problems in advance, maintain the highest quality of network synchronization and significantly reduce opex. By complementing today’s limited distributed approach to GNSS assurance with a centralized-global system, it offers a major boost to critical infrastructure dependent on satellite-based timing.
“What we’re offering is a way for network operators to see the bigger GNSS picture. Using AI and ML to analyze the entire synchronization network, our centralized GNSS monitoring and assurance solution will be key in the fight against GNSS cyber issues, such as jamming and spoofing attacks,” said Gil Biran, general manager, Oscilloquartz, ADVA.
“This new technology provides the power to proactively tackle issues that jeopardize vital services,” Biran said. “Harnessing the capabilities of our synchronization devices to identify spoofing problems, it intelligently mines a wealth of data and gives network operators the precise info they need in a highly accessible way. By using long-term heat maps and enormous amounts of data from a wide range of GNSS receiver sources, our solution identifies patterns and preempts issues. It alerts maintenance teams to obstructions or jamming conditions so that countermeasures can be put in place well before services are affected.”
As part of the network infrastructure, ADVA’s centralized GNSS assurance and monitoring solution enables a network-wide view of GNSS receiver health. Requiring no additional hardware or site visits, it remotely delivers detailed analysis, automatically detecting abnormal patterns with a patent-pending algorithm.
Utilizing AI and ML, it alerts maintenance teams to potential GNSS service degradation and safeguards against spoofed signals. Network operators receive updates through a user-friendly GUI as well as regular reports tailored to individual criteria.
As a component of ADVA’s comprehensive Ensemble Controller suite, the new technology makes synchronization monitoring and assurance an integral part of overall network management and control. For network operators, having a single system to track inventory simplifies operations and helps bolster network security.
“GNSS is the fundamental source of network time, phase and frequency generation across so many of today’s industries. From IT to telecommunications, from energy to finance, the reliability of satellite-based timing is crucial and the cost of interference is huge. This latest launch is a key part of our ongoing mission to remove the risk of GNSS vulnerabilities,” said Nir Laufer, senior director, product line management, Oscilloquartz, ADVA.
“The new solution joins our multi-band, multi-constellation GNSS receiver technology — which overcomes ionospheric delay variation — as well as our range of grandmaster clocks with network-based timing and outstanding holdover capabilities,” Laufer said. “Combined with our highly stable cesium clock technology, these create our ePRTC solutions for ultimate GNSS backup. With our comprehensive portfolio, all industry verticals are guaranteed accurate, cost-effective and highly resilient timing.”
The design improves capabilities over the 70% digital payload used for GPS III space vehicles 1-10
L3Harris Technologies passed the critical design review (CDR) phase in development of a fully digital navigation payload for the U.S. Air Force’s GPS III Follow-On satellites.
CDR is a major milestone demonstrating the new payload’s design — specifically the fully digital Mission Data Unit (MDU) — is mature enough to proceed to final development, test and delivery.
The new MDU is the heart of the navigation payload and will provide more powerful signals and ensure flawless atomic clock operations. It will also provide improved capabilities over L3Harris’ 70% digital MDU used for GPS III space vehicles 1-10 (GPS III SV 1-10).
“The digital payload is flexible enough to adapt to advances in GPS technology and future warfighter mission needs,” said Ed Zoiss, president, Space and Airborne Systems, L3Harris. “Proceeding to the next stage in the GPS IIIF navigation payload development process moves the program closer to supporting evolving Air Force mission requirements.”
In September 2018, the Air Force selected GPS III prime contractor Lockheed Martin to build up to 22 GPS IIIF satellites, which add even more capabilities and technology to the new GPS III satellites — including the new fully digital navigation payload. GPS IIIF SV11 and 12 are currently under contract.
L3Harris is in a production cadence, having delivered to Lockheed Martin in July the eighth of 10 navigation payloads for the first 10 GPS III satellites.
GPS III SV 01 and 02 launched in December 2018 and August 2019 respectively, and are performing well on orbit. GPS III SV03 is expected to launch in April.
The remaining payloads are in various stages of integration with the satellites in Lockheed’s Colorado facility. L3Harris has provided navigation technology for every U.S. GPS satellite ever launched.
CP Aeronautics offers American-built combat-proven unmanned aerial systems for defense, homeland security and civil applications
CP Technologies has launched a new division, CP Aeronautics, to provide integrated turn-key solutions based on unmanned aerial systems (UAS) platforms, payloads, data links, ground control stations (GCS) and communications for defense and civil applications.
Designed as leading-edge UAS-based solutions, CP Aeronautics’ systems offer operationally proven solutions for intelligence, surveillance and reconnaissance (ISR) systems requirements. CP Aeronautics’ broad product portfolio has demonstrated excellent performance and operability in demanding environments, the company stated in a press release. Backed by continuous research and development, these systems are built on three decades of technological and operational experience.
“Through our in-house capability as a UAS manufacturer and integrator with specialist subsidiaries and technology partners, we offer a complete range of subsystems including air vehicles, inertial navigation and avionics, electro-optical payloads (EO), communications, propulsion systems, launch and retrieval systems, command and control units,” said Brad Pilsl, vice president of business development at CP Aeronautics. “We also offer high-end training solutions for our partners and customers.”
CP Aeronautics will support government and commercial customers with the entire infrastructure necessary for development, production, integration, flight-testing, certification and operational support of UAS throughout their service.
The combat-proven operational systems include:
Orbiter 2 Small-UAS (SUAS)
Orbiter 3 Small Tactical UAS (STUAS)
Orbiter 4 Small Tactical UAS (STUAS)
Aerostar Tactical UAS (TUAS)
Dominator XP (MALE UAS)
Pegasus 120 high-performance multi-mission vertical takeoff and landing (VTOL) UAS
SBG Systems has opened a new subsidiary in Singapore. Located in the center of the city, this new office brings sales and technical support to the Asian region.
SBG Systems is a leading supplier of MEMS-based inertial measurement units (IMU) and inertial navigation systems (INS) for land, air and marine applications. The company has been developing its sales distribution channels in Asia for many years and has decided to bring sales and technical support closer to its clients and distributors by establishing a subsidiary in Singapore.
“We wanted to get closer to our customers and distributors in the region,” said Thibault Bonnevie, SBG Systems’ CEO. “By getting geographically closer, we wish to build closer relations with our esteemed customers and distributors and provide them with the highest quality service they deserve.”
The Singapore office will provide support to new and existing clients in the region with demonstrations, training and technical support.
The nation’s third next-generation GPS III satellite — and the first delivered by Lockheed Martin to the new U.S. Space Force — has arrived in Florida for an expected April launch.
On Feb. 5, the third Lockheed Martin-built GPS III space vehicle (GPS III SV03) was shipped to Cape Canaveral from the company’s GPS III Processing Facility near Denver aboard a massive Air Force C-17 aircraft traveling from Buckley Air Force Base, Colorado.
GPS III SV03 — nicknamed “Columbus” — is the latest of up to 32 next-generation GPS III/GPS III Follow-On (GPS IIIF) satellites Lockheed Martin has designed and is building to help the Space Force modernize GPS with new technology and capabilities.
On Jan. 13, 2020, GPS III SV01 (“Vespucci”) was set healthy and active by the 2nd Space Operations Squadron (2 SOPS) at Schriever Air Force Base, in Colorado. 2 SOPS is now using the GPS III Contingency Operations (COps)-upgraded OCS ground control system to operate both the new GPS III and previously launched GPS satellites.
GPS III SV02 (“Magellan”), launched on Aug. 22, 2019, has completed its on-orbit testing and is currently awaiting its turn for integration into the constellation.
On Jan. 21, 2020, the Space Force called up GPS III SV04 for a launch later this summer. GPS III SV05-09 are now in various stages of assembly and test at Lockheed Martin’s commercial-like large satellite production line for GPS III satellites near Denver.
The company is expected to soon complete its critical design review with the Space Force to begin production on the first two GPS IIIF satellites under contract.
GPS III Advantages
GPS III is the most powerful and resilient GPS satellite ever put on orbit. Developed with an entirely new design for U.S. and allied forces, GPS III has three times greater accuracy and up to eight times improved anti-jamming capabilities over any previous GPS satellites in the constellation.
GPS III is also the first GPS satellite to broadcast the new L1C civil signal, which is shared by other international global navigation satellite systems, like Galileo, to improve future connectivity worldwide for commercial and civilian users.
“Every day, more than four billion civil, commercial and military users rely on the positioning, navigation and timing (PNT) services provided by 31 GPS satellites launched since 1997,” said Tonya Ladwig, Lockheed Martin’s program manager for GPS III. “We are excited to help the Space Force refresh the constellation to ensure U.S. and allied forces always have the best technology and that the U.S. Global Positioning System remains the gold standard for PNT.”
GPS III was designed to evolve with new technology and changing mission needs. The satellite’s evolutionary modular design will allow new GPS IIIF capabilities to start being added at the 11th satellite. These will include a fully digital navigation payload, a Regional Military Protection capability, an accuracy-enhancing Laser Retroreflector Array, and a Search & Rescue payload.
”It’s an exciting time across the GPS mission as we bring together the best of our space, ground, and operations systems to help the United States Space Force modernize this critical national capability,” commented Johnathon Caldwell, Lockheed Martin’s vice president for Navigation Systems.
Lockheed Martin’s GPS III team is led by the Production Corps, Medium Earth Orbit Division, at the Space Force’s Space and Missile Systems Center, Los Angeles Air Force Base.
2 SOPS, at Schriever Air Force Base, manages and operates the GPS constellation for both civil and military users.
Lockheed Martin shipped the U.S. Space Force’s third GPS III satellite to Cape Canaveral, Florida, ahead of its expected April launch. (Photo: Lockheed Martin)
On a test track in Sweden, a truck successfully merged between two cars driving alongside it in a fully automated maneuver. The live demonstration took place at the AstaZero test site near Borås, Sweden, on Nov. 21, 2019, showing automotive industry experts how well the automated merging solution performed.
The Fraunhofer Institute for Integrated Circuits IIS and project partners RISE, Scania, Waysure, Ceit-IK4, Baselabs and Commsignia are taking part in an EU-funded project PRoPART, which stands for Precise and Robust Positioning for Automated Road Transports.
Vehicles on the road already perform certain steps on behalf of the driver, such as parking. Together with its project partners, the Fraunhofer IIS has developed a precise and robust position determination system for use in autonomous trucks as part of PRoPART.
Autonomous driving is about interactions among vehicle systems, connecting vehicles and equipping them with precise and robust navigation solutions. The challenge is to ensure that different automated driving systems deliver precise and reliable positioning information.
Using GOOSE technology
With its GOOSE GNSS receivers, Fraunhofer IIS provides highly accurate and reliable positioning to the PRoPART project. The GOOSE can bridge signal interruptions for short periods of time, potentially obviating the need for the driver to intervene at all.
In conjunction with GNSS, developers are using a combination of sensors such as radar and cameras in the vehicle. Supplemented by reference stations along the route, the combination of GNSS and sensor data enables highly available position solutions up to the decimeter range.
“This is a key step on the road to autonomous driving,” explained group manager for precise GNSS receivers Matthias Overbeck, Fraunhofer IIS. “It’s about ensuring the merging maneuver is precise and avoiding accidents — something we can achieve only with highly accurate and reliable positioning technology.”
GOOSE platform. (Photo: Fraunhofer IIS)
Spoofing protection
These days, a variety of electronic systems for providing satellite navigation signals are available and are often used to generate fake positions for gaming apps on smartphones. Such systems could disrupt satellite receivers while remaining undetected.
GOOSE makes use of the Galileo Open Service Navigation Message Authentication (OS-NMA), which is not officially available until 2020. OS-NMA transmits encrypted keys on the Galileo satellite signals that make it extremely difficult to fake a position, thus ensuring that reliable positioning information can be provided to vehicles in the future.
Specifically, Booz Allen’s work will aid in the development and modernization of GPS systems through major programs such as Military GPS User Equipment (MGUE), GPS III and Next Generation Operational Control System (OCX).
The NIWC Pacific Positioning, Navigation, and Timing (PNT) Division is the Navy’s principal research and development center for navigation sensors and systems.
SMC is the center of technical excellence for developing, acquiring, fielding, and sustaining resilient and affordable military space systems.
With this contract, Booz Allen will continue to serve as a key mission partner for NIWC Pacific and SMC on the important endeavor of modernizing PNT systems for U.S. and Allied warfighters.
To execute this highly complex scope of work, Booz Allen will provide a range of essential services, including system definition, requirements synchronization, capability improvement, cybersecurity engineering, platform integration and testing, and acquisition program management.
“Booz Allen’s robust track record of work in both systems engineering and cybersecurity continues to inspire trust from our clients,” said Vice President Brian Zimmermann. “Our deep bench of leaders and technical experts reassures our clients that no project is too big or too complex. It’s our privilege to help the Navy and Air Force modernize GPS systems that are so vital to the security of our nation.”
Read more about Booz Allen’s work with PNT systems here.
Staff Sgt. Reag Wood of 1st Combined Arms Battalion, 5th Brigade, 1st Armored Division, illustrates how he uses an iphone to obtain a visual image of a mock with insurgent activity during a field training exercise at White Sands Missile Range, N.M. (Photo: U.S. Army/Lt. Col. Deanna Bague)
Professor Last was one of the first members of the foundation and had served on its International Advisory Council since its inception. He perished in the crash of a small plane he was piloting on the Nov. 25, 2019.
The foundation and three of its members have begun the drive with pledges totaling $24,000.
The fund will be administered in the United Kingdom and is envisioned to pay student expenses for attendance at navigation-related conferences and symposia.
Individuals and organizations wishing to contribute to the scholarship fund should contact the foundation at [email protected]. Donations can also be made through the foundation’s website.
