Aircraft throughout Europe are guided by EUROCONTROL, which will have access to ADS-B data through Aireon. Here, a plane lands at Schiphol Airport in The Netherlands. (Photo: Sjo/iStock Unreleased/Getty Images Plus)
Aireon and EUROCONTROL have signed a 10-year agreement to integrate space-based ADS-B data into their air traffic management processes across EUROCONTROL’S 41 Member States and two Comprehensive Agreement (CA) States.
The space-based automatic dependent surveillance-broadcast (ADS-B) data will enhance aircraft management capabilities, contributing to improve predictability, capacity, environmental impact supporting sustainable growth throughout the European region.
It will also support other applications, such as crisis management, contingency management, environmental monitoring, performance monitoring and expanded datasets for post-analysis, traffic statistics and safety-related assessments.
Spanning 43 countries from Turkey to Ireland, Finland to Portugal, EUROCONTROL’s aircraft management states encompass over 11.5 million square kilometers of terrestrial airspace, as well as part of the airspace over the North Atlantic, Mediterranean and Baltic.
Aireon data will be integrated into the EUROCONTROL’s enhanced tactical flow management system (ETFMS), which provides data to European aviation stakeholders, regardless of operational borders, in real time.
Space-based ADS-B data will enrich ETFMS’s complex traffic demand and slot allocation calculations, which currently rely on ground-based surveillance data and flight plan processing systems. As a result, Aireon’s data will support Europe’s primary flow management system to be more accurate in its trajectory predictions and unlock an otherwise unavailable operational capacity.
“With Aireon’s high-integrity, high-quality data, the EUROCONTROL network manager will have the ability to work with information from beyond the European airspace,” said Eamonn Brennan, director general, EUROCONTROL. “Full integration of Aireon space-based ADS-B data will allow us to be more accurate in our trajectory predictions and ensure higher levels of safety, predictability and efficiency in our flow management operations. This partnership is the latest development in our effort to ensure European airspace is one of the most dynamic and efficient in the world.”
EUROCONTROL. Having been nominated as the Network Manager by the European Commission until the end of 2029, EUROCONTROL is driving a coordinated and technologically advanced approach to the challenges faced by the European air traffic network.
Helping address the improvements that are needed in operations, cybersecurity, service provision, crisis management, airspace design, utilization and more, EUROCONTROL provides support and expertise to air navigation service providers (ANSPs), airlines, airports and military partners in the region to help make European aviation, safe, synchronized, efficient and environmentally friendly.
Aerion. In 2019, the European Aviation Safety Agency (EASA) certified Aireon as the first provider of aircraft surveillance-as-a-service. Additionally, Aireon has the only global, single-source dataset available to the industry.
For EUROCONTROL, this means that once the service is integrated into its systems, it will have unprecedented visibility into the full picture of aircraft arriving, departing and crossing over Europe over an area of six flight hours and 3,000 nautical miles around EUROCONTROL Member States.
“EUROCONTROL is a leader in air traffic flow management. They are the first customer to use Aireon data well beyond their own area of responsibility. This will enable them to maximize the effectiveness of their processes and procedures by including long-range arrivals and neighboring States into their capacity and demand measures,” said Don Thoma, CEO, Aireon. “EUROCONTROL recognizes the global value in connecting ANSPs through a common, high-fidelity, global data source that provides situational awareness of actual aircraft position information. We look forward to the benefits all EUROCONTROL customers will see in the near, medium and long-term.”
Aireon’s data will also be integrated in EUROCONTROL’s new system called iNM, which will implement incremental updates to all of EUROCONTROL’s operational systems and digital infrastructure in the course of this decade.
Carlson Machine Control has introduced the Vsx7 multi-frequency position and heading receiver. The Vsx7 is a multi-GNSS receiver designed specifically for machine control and can be installed on excavators, drills, pile drivers and more.
Paired with the Carlson A45 antennas, the Vsx7 features high-precision positioning in Athena RTK, Atlas L-band and SBAS and heading accuracy of up to .01 degrees. The whole Vsx7 system is designed to operate in harsh conditions from -40 degrees Fahrenheit to 158 degrees Fahrenheit. It can be mounted either by bolts or with magnets depending on the application and external environment.
The Vsx7 is primarily used in the mining and construction industries but can be adopted into similar industries with its companion software, Carlson Grade. Field data can be collected and viewed in real-time both at the machine with either, the MC8 or MC10 control box as well as in the office with Carlson Command.
“Our customers are able to operate day after day with complete confidence in their machine guidance,” says Tim Jones, director of Machine Control. “The Vsx7 is a perfect form factor for our customers and to Carlson Grade and Carlson Command as a ruggedized GNSS receiver.”
Carlson Grade is a machine guidance software solution that can be adapted to any heavy machine for grading, excavating, mining, shoveling, drilling, pile driving and landfill operation. Carlson Grade provides real-time field reporting and allows operators to view where they are in the project and at all times.
Carlson Command is a site management software solution that provides multiple viewing options of multiple and single machines in real-time. Command allows machine positions to be viewed as well as cut/fill and elevation. Managers can also remote into machines and transmit messages directly to an operator.
Stan servicing vehicles at the Lyon Airport. (Photo: Stanley Robotics)
Stan incorporates the Trimble BX992 dual-antenna enclosure for accurate, available and reliable localization
The Stanley Robotics team has called on Trimble to equip Stan, its autonomous parking and valet robot, with accurate localization.
To achieve centimeter-level localization, Stanley Robotics needed to combine perception algorithms and intelligent management software with reliable GNSS technology.
“The robot must move fast to handle high traffic flow and precisely to park cars as densely as possible,” said Anthony Troublé, robot team manager at Stanley Robotics. The team selected the Trimble BX992 dual-antenna enclosure and two Trimble AV59 GNSS antennas.
The BX992 is installed inside the robot and the two antennas are mounted on the robot’s head with maximum separation between them. For the robot to attain centimeter-level localization, a Trimble BX992 base and a Trimble Zephyr antenna are installed at the drop-off cabins where customers leave their cars until robots move them to a more permanent location.
The Trimble BX992 base broadcasts real-time kinematic (RTK) corrections over a Wi-Fi link to the robots.
What Stan Does
Photo: Stanley Robotics
With the Stan robotic valet, passengers no longer waste time looking for a free space or trying to locate their vehicle, according to Stan’s creators. After booking their parking space in just a few clicks on the Lyon Airport website, passengers drop off their vehicle in dedicated cabins and make their way to the terminals using the shuttle bus located just a few steps away.
The robot takes care of the car, parking it in the secure car park. When they return, passengers pick up their vehicle, which is waiting for them in one of the cabins.
“The service offers security, simplicity and time savings. With this new technology, parking becomes a no-fuss experience that takes only a few minutes of passengers’ time, leaving them free to travel in a relaxed state of mind,” Stanley Robotics said in a press release.
The system also constitutes a new way of arranging vehicles in a car park and makes excellent use of space since cars can be parked in dense blocks.
In addition, the robot uses two lidar scanners and four cameras. Stan relies on lidar-based simultaneous localization and mapping (SLAM) techniques to locate the robot and build a map. The lidar-based SLAM system is always running and is fused with the GNSS localization and odometry.
“The lidar is mostly critical in the cabins where the GNSS availability and reliability is not sufficient,” Troublé said. “The full integration with our localization system, especially the transition from indoor-to-outdoor when the robot enters a cabin was a challenge. We have tuned and improved our localization fusion algorithm to get the best out of each component and deliver a consistent confidence index.”
Stan is equipped with three levels of safety to ensure operational effectiveness.
First, Stanley Robotics continuously monitors the accuracy, availability and consistency of the RTK GNSS, SLAM and odometry localization signals. “If these signals are too inconsistent or if the overall confidence is too low, the robots are stopped and a site supervisor is alerted,” Troublé said.
Further, the site is monitored through lidars and cameras on the robot to prevent any collision with obstacles.
Finally, a trained Stan maintenance worker is assigned to every parking lot. These individuals wear a safety badge. Every robot is equipped with a safe-stop feature that will trigger if the operator gets within a defined proximity to the robot.
The first outdoor car park managed by robots opened to the public in 2018 at Lyon Saint-Exupéry airport. Since testing started in 2017, four Stan robots are now fully operational in the Lyon Saint-Exupéry airport car park, which can accommodate up to 500 vehicles.
Stanley Robotics announced in January 2019 that they will open 2,000 spaces at Lyon in the summer of 2020. The airport is looking to eventually expand this system to up to 6,000 spaces in total.
In 2019, Stanley Robotics signed a contract with Gatwick Airports, the first U.K. airport to use robots that valet park passengers’ cars. The Stanley Robotics team is gearing up to begin work at another airport to be announced soon.
The Institute of Navigation (ION) has published its Global Navigation Satellite Systems (GNSS) Software Defined Radio Metadata Standard document.
According to ION, The standard is the product of a three-year long effort of the ION GNSS SDR Standard Working Group and defines parameters and schema to express the contents of SDR sample data files. The standard promotes the interoperability of GNSS SDR data collection systems and processors, ION added.
“In recent years there has been a proliferation of software defined radio data collection systems and processing platforms designed for Global Navigation Satellite System receiver applications or those that support GNSS bands,” ION said in a press release. “For post-processing, correctly interpreting the GNSS SDR sampled datasets produced or consumed by these systems has historically been a cumbersome and error-prone process. This is because these systems necessarily produce datasets of various formats, the subtleties of which are often lost in translation when communicating between the producer and consumer of these datasets. This specification standardizes the metadata associated with GNSS SDR sampled data files and the layout of the binary sample files.”
Robotic Research LLC, a leading provider of autonomy and robotic technologies, will begin testing fully autonomous low-speed shuttles that are totally unmanned in the second quarter of this year.
Current commercial applications of low-speed shuttles use onboard safety attendants to monitor the safety inside and outside the vehicle. Robotic Research plans to start testing without onboard attendants.
The first step is to have the attendants in fixed on-site locations, with the future goal to move attendants to an offsite safety monitoring facility.
“Through our work with the U.S. government over the past four years, we have already demonstrated that fully autonomous trucks are a reality. We are committed to making our shuttle and bus manufacturing partners successful by accelerating state-of-the-art technologies for unmanned vehicles ahead of regulatory agencies’ progress,” said Alberto Lacaze, president of Robotic Research.
“The level of safety certification and redundancy necessary to drive fully autonomous vehicles is a significant undertaking that needs to be designed from the top down. Just adding more ADAS is not a reasonable or cost-effective pathway to full autonomy,” Lacaze said. “The advancements driven by the Robotic Research team will provide a product that significantly reduces the cost of operation and therefore improves market size.”
Current local, state and federal regulations for most commercial shuttle operations require the safety attendant to be inside the cab of the vehicle. However, many transit operators are seeking to change these regulations to allow remote attendants to oversee system safety operations. The change is integral to the viability of low-speed shuttles, which are an innovative solution to the first/last mile problem, which is the distance between a traveler’s origin or destination, and a transit station or stop.
Robotic Research has been developing and testing unmanned, autonomous operations for a wide range of vehicles for nearly a decade. The company currently provides autonomy kits that fully automate logistics convoy trucks for the U.S. government and several of its allied nation partners. Nearly 100 trucks have already been delivered. The tests for these vehicles have included operations with no safety attendants on board, with a single operator monitoring three unmanned vehicles.
Robotic Research’s AutoDrive autonomy kit is platform agnostic and can be retrofitted to vehicles of all sizes, from small, portable robots to large trucks and buses. The system provides autonomous functionality on surfaces ranging from urban-improved roads to off-road terrain, all while the vehicle is collecting and analyzing data to better enhance the future of autonomous vehicles and transportation.
Robotic Research’s technology provides automation to one of the largest international shuttle providers as well as to the largest U.S. manufacturer of commercial buses. The company’s AutoDrive kit also supports various autonomy programs in commercial and government sectors and is currently operating in communities and cities around the globe, including 30 states and four continents.
The Snoopy CL-360 lidar scanner. (Photo: Lidar USA)
The Optech CL-360 has joined the ranks of Lidar USA Snoopy systems.
The Snoopy CL-360 has been meticulously designed for integration on backpack, vehicle and UAV applications. Weighing 5 kilograms fully assembled, the Snoopy CL-360 is capable of delivering highly accurate results, up to +/-0.01 feet on paved surfaces from a vehicle.
The system has a scan line rate of 250 Hz with a 500-kHz data rate, giving a uniform result along and across track. The systems are easily configurable with multiple scanners (similar to internet of things applications) to avoid occlusions.
“We are pleased to again partner with LidarUSA in their innovative approach to UAV integration with the addition of our CL-360 to their product portfolio. Featuring true 360-degree scanning without blind spots, CL-360 integrated by LidarUSA will provide an exciting addition to the UAV marketplace,” said Optech Executive Vice President and General Manager Michel Stanier.
Users can also benefit from a UAV deployment, achieving scans with usable data as much as 60 degrees off nadir (widths of more than 1,100 feet while scanning at the 400-foot ceiling). The small beam size of 0.3 mrad allows the CL-series to reliably collect ground points (such as on or near the dirt through vegetation) while also providing better detection of fine linear features such as power lines and railroad tracks.
The integration of the CL-360 into the Snoopy series of systems from Lidar USA is expected to be a huge plus to the mapping community in 2020, according to Lidar USA. Users can expect to see the benefit of decreased field-collection effort and increased product quality resulting in a growing and profitable business.
“As more technologies embrace lidar collection to reduce their field time, we expect to see the CL-series become the ‘go to’ solution for many of them,” said Jeff Fagerman of Lidar USA. “The CL-series provides the accuracy and point density often necessary to meet the client’s every growing demands for more, more, more. By designing the system for car and UAV, as well as multiple configurations (two or more systems running together), our users will greatly benefit where they feel it most — the bank.”
The new version of all-in-one MultiStation addresses a wide range of needs. (Photo: Leica Geosystems)
The new Nova MS60 MultiStation combines upgraded, faster 3D laser-scanning capabilities, GNSS connectivity and digital imaging with a high-end total station. According to Leica Geosystems, part of Hexagon, the multi-station brings sensor fusion to the “next level.”
The MS60 features several laser scanning updates, including an fast scanning speed of up to 30,000 points per second, optimized scan area definitions, adapted scan managements, and an improved scanning path for zenith scans.
It is also equipped with the unique AutoHeight feature, enabling users to save time by automatically measuring the instrument’s height with a simple button press. Measurement professionals can make decisions directly in the field, performing point-cloud analysis such as flatness analysis and as-built checks in the Inspect Surface app of the MS60.
“Scan data combined with traditionally measured points, whether it’s from the total stations or the GPS receivers, is one of those immediate deliverables that help our clients see what we’re doing. With the scan data of the Leica Nova MS60 MultiStation, we can graphically show — the same day it is collecting — the locations in the field to any person,” said Donald Smith, senior land surveyor and principal at BL Companies. “When you deliver on time and provide customers with a deliverable they can see, you’ve just got yourself a recurring client.”
The MS60 speeds up workflows by combining technologies in this all-in-one instrument. The MultiStation total station offers advanced imaging, scanning capabilities and GNSS connectivity. With Leica Captivate field software, all measurement and scanning data can be visualized in 3D for quality and completeness checks.
MS60 users can seamlessly transfer all data into Leica Infinity software to manage, process, analyze and perform a quality check. The MultiStation helps users deliver projects on time, save money and have high flexibility in the field.
“The MS60 merges data in a multi-level process — total station measurements are complemented by 3D point clouds, which are automatically registered and coloured by the image information. All data perfectly fits within the same coordinate system, globally referenced by GNSS measurements or by measuring known points,” said Falko Henning, senior product manager at Leica Geosystems.
“Unlike other measurement devices, the MS60 offers familiar total station capabilities and scanning functionality to fulfil job requirements on site.” Henning said. “The operator can use the red laser pointer to perform reflectorless measurements for direct remedial work on-site or stakeout points and use the field controller even while a scan is performed.”
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.”
