Flight simulators range in price from free to tens of millions of dollars and in purpose from pure entertainment to serious business — such as learning to fly multi-million-dollar aircraft without crashing them in real life and getting anyone killed. Military and commercial pilots spend thousands of hours in simulators learning both routine operations and how to deal with emergency situations. They can become fully proficient through immersive training in these virtual environments. The U.S. Army, Air Force, Navy and Marines all use flight simulators to train pilots to fly in battle, recover in an emergency, and coordinate air support with ground operations. To do this, they use hardware and software developed both by military agencies and by commercial military contractors.
In high-end flight simulators, the trainee steps into a life-size replica of a cockpit, whereas others consist of several monitors that cover the trainee’s field of view, or, at the lowest end, everything is crammed onto a single monitor. All flight simulators, however, are designed to replicate as closely as possible the layout and controls of a real aircraft. (Ironically, the $120 Microsoft Flight Simulator Premium Deluxe Edition lets you fly 35 different planes, while flight simulators that cost tens of millions of dollars are limited to a few models because they have to physically replicate the cockpit layout, which varies from aircraft to aircraft. Some training centers invest in multiple simulators, while others privilege convenience over accuracy and use a single simulator model.)
Most professional flight simulators sit on top of either an electronically-controlled motion base or a hydraulic lift system that rotates the replica cockpit in three dimensions in reaction to both user input and simulated events. This provides trainees with haptic feedback, in other words, feedback they can feel. (Another example of a device that provides haptic feedback is a joystick with force feedback.)
Like when learning to sail offshore or to survive in the wilderness, a large component of any pilot training program is navigation. For flight simulators, this involves detailed aeronautical charts, huge amounts of Earth observation imagery including thousands of airports, and faithful replicas of several cockpit navigation instruments. While aviation programs provide standard training to ensure pilots can handle situations ranging from enemy fighters to bird strikes to engine failure, they may overlook the importance of duplicating actual cockpit instruments rather than relying on facsimile ones.
Simulating GNSS signals
This is where GNSS simulators come into play. They make it possible “to simulate the actual GPS signal required by the cockpit navigation instruments,” according to a case study by Orolia.
This approach, the company points out, offers advantages to both the trainees who use flight simulators and the engineers who develop them. For a trainee, “the advantage is that he is trained using the identical instruments as those in the actual airplane […] providing the same feedback as a real-world experience.” For an engineer developing a flight simulator, GNSS simulators make it possible to “design more effective flight simulation programs without compromising quality.”
Furthermore, “using real navigation instruments may […] reveal unexpected behavior from the instrument, which helps the pilot to be prepared for this possibility. If any conditions involving the plane dynamics are not properly handled by the navigation unit, the pilot can obtain actual feedback from real navigation instruments, which could differ from feedback provided by a facsimile instrument.”
Hardware-in-the-loop (HWIL) techniques enable Orolia to integrate its simulator in a flight simulator to reproduce the GPS/GNSS dynamics for the airplane in real time. “Because the pilot steers the aircraft in real time, the GPS simulator must also simulate GPS signals in real time, forming an HWIL integration,” the company said. “This integration enables the flight simulator to integrate the actual navigation unit to provide a very realistic environment for the trainee.”
Racelogic, another manufacturer of GNSS simulators, is launching a new RealTime LabSat that can connect to Microsoft Flight Simulator, including the new 2020 version. “This will create a live GNSS RF feed that accurately follows the trajectory in the simulator, enabling the testing of any GNSS device as though it were being flown on the aircraft,” said Julian Thomas, the company’s managing director. “To help make this a cost-effective solution, we have recently optimized our SatGen signal simulation software so that a real-time simulation such as this can be carried out on an entry-level PC with a full constellation of simulated satellites.”
The GNSS and flight simulation industries overlap even further. For example, Garmin, which manufactures consumer GPS receivers, makes the avionics used in some professional flight simulators.
Simulator demand on the rise
The utility of simulators is not limited to training human pilots and drivers. The demand for simulation is being sharply increased by the development of autonomous vehicles of every kind — from self-driving cars to unmanned aerial vehicles (UAV), from bathymetric vessels to urban air mobility (UAM) aircraft.
For example, manufacturers of self-driving cars need to simulate driving millions of miles, in all kinds of traffic and weather conditions, to perfect their vehicles’ algorithms. The result of all these simulations is better trained human and robotic pilots and drivers prepared for real situations, superior mission readiness, and maximum safety for both military and civilian operations on land, at sea and in the air.
Feature image: In a simulated G1000 NXi integrated flight deck for a King Air 350, a pilot refers to the Garmin Pilot app, used as a supplement during flight. (Photo: Garmin)
The number of GNSS constellations, satellites and signals is constantly growing. The threats to GNSS — from unintentional radio frequency interference (RFI), jamming, spoofing, multipath… and Federal Communications Commission rulings — are increasing, as are the public’s expectations of GNSS accuracy.
All these factors contribute to the need for ever more powerful and advanced simulators that can realistically simulate a wide range of optimal and suboptimal environments. That is why simulators are a rapidly growing sector of the GNSS industry.
At present, the main defense against jamming are continuous radiation pattern antennas (CRPA). Therefore, it is essential that simulators be able to accurately reproduce signals from CRPAs. They are even more useful when they can generate M-code (MNSA) signals, which not all simulators do.
Additionally, the development of autonomous vehicles requires engineers to simulate driving millions of miles, under a variety of environmental and traffic circumstances. To accomplish this in a reasonable amount of time requires them to run simulations faster than in real time, or run many simulations in parallel.
Finally, there is an increasing need to simulate alternative positioning, navigation and timing (PNT) signals being developed as supplements to and substitutes for GNSS signals in circumstances that make the latter unavailable or unreliable.
These are some of the challenges facing manufacturers of GNSS simulators. What follows are their brief descriptions of the approaches they are taking and the innovations they are introducing.
What is your most recent innovation?
Our latest simulator innovations contain wave-front generation signal technology, which allows you to generate GNSS and interference signals that represent the received signals for each antenna element in a phased array antenna manifold, usually referred to as a controlled radiation pattern antenna (CRPA). Our modular design approach enables users to simulate IMU data commensurate with the wave-front signals for a complete coherent GNSS/IMU simulation that is ideal for stimulating receivers that contain CRPA and IMU capabilities. Our simulators also contain proprietary synchronization technology that allows users to synchronize multiple systems to produce a “wave-front” of GNSS and IMU signals for multiple vehicles, or even an entire fleet.
Photo: CAST Navigation
What is your approach to jamming and spoofing?
CAST Navigations’ family of GNSS simulators are capable of realistically simulating a wide range of suboptimal conditions—such as jamming/spoofing, multipath, RF interference and satellite constellation perturbations—for virtually any commercial or military environment. Our interference signals or “jammers” can be located at any terrestrial location and can be static or dynamic in nature. A distinguishing feature of CAST Navigations’ simulation systems is that our interference signals are phase-controlled and coherent, allowing for proper phase transmission of each signal type for each receiving antenna element. You can also add an INS capability to any of our systems. These types of systems are perfect for testing GNSS and GNSS/INS types of navigation equipment.
What’s coming by 2023?
One of the key trends is the ability to generate M-code (MNSA) signals. Jamming and spoofing are becoming more prevalent, not just to the military but also to consumers. Every day, the military, as well as people like you and me, are starting to encounter more instances of interference that can deny GNSS equipment and even phones the ability to track some GNSS satellites or that transmit incorrect GNSS data, causing receivers to display incorrect position solutions. So, our focus is on products and capabilities that enable our customers to simulate those types of environments and help them to mitigate those kinds of events.
Orolia
Lisa Perdue Product Manager
What is your most recent innovation?
At Orolia we continue to evolve our innovative software-defined simulator approach. Our most recent innovation is our advanced spoofing option. We have taken our ability to define multiple jamming transmitters, each with their own trajectory and antenna pattern, and added the ability for the transmitters to send spoofing signals as well. By utilizing our capability to run multiple simulations on a single system, we give the user the ability to control every parameter of the generated spoofing constellation(s). The system automatically calculates the signal time of flight and the propagation loss, making this advanced capability powerful and easy to use.
What is your approach to jamming and spoofing?
Simulation of threat environments is a critical component of GNSS receiver testing. As awareness of the impact that jamming and spoofing can have on a GNSS-based system rises, so does the need to test. That is why we have implemented advanced jamming and spoofing options into our Skydel simulator’s core engine. Replication of degraded environments with threats ranging from one to hundreds is possible using the same hardware and software used for generating GNSS signals. No third-party hardware or software is required for complete testing against jamming and spoofing because we feel that this capability should be part of the core system, not an afterthought.
Photo: Orolia
What’s coming by 2023?
In the coming years, we expect to see more requirements for simulation of alternative positioning, navigation, and timing (PNT) signals. As governments and organizations continue to investigate alternate technologies, it will become necessary to simulate low Earth orbit (LEO) PNT, ground-based transmitters, and other signals being considered.
Another growing trend is the adoption of controlled reception pattern antennas (CRPAs) for their anti-jam capabilities. These anti-jam antenna systems can only be tested by specialized simulation systems, so we can imagine these simulation systems being commercialized for a broader market around 2023.
Racelogic
Julian Thomas Managing Director
What is your most recent innovation?
Recognizing the need of our customers to test their products with a simple solution that uses the latest GNSS signals, we have updated our SatGen software to create accurate simulations using all satellite data currently being transmitted across the various constellations. We have also optimized the performance of SatGen so that a standard desktop PC can be used to simulate these signals in real time. Also, the simulation can now be driven using an external NMEA stream, allowing full remote control of the trajectory.
What is your approach to jamming and spoofing?
The LabSat 3 Wideband records and replays all available GNSS signals in high fidelity, allowing jamming and spoofing signals to be reproduced accurately on the test bench.
Photo: Racelogic
What’s coming by 2023?
With so many employees now working from home due to COVID-19, the pressing concern for many companies developing GNSS technology is how to provide employees with suitable equipment that is required for them to carry out their jobs efficiently away from the office. Usually these employees would utilize the shared resources of a well-equipped office, with experts on hand to help, but working from home has made access to these devices challenging. Due to LabSat 3’s small size, low cost and ease of use, we have seen a significant increase in sales to companies furnishing their employees with a suitable method of testing their GNSS devices while working from home.
With the advent of a new breed of high-performance, low-cost GNSS receiver, many new applications are being developed in new and exciting sectors, utilizing a level of accuracy previously considered too expensive to be a commercial proposition. The number of GNSS engines will therefore increase rapidly in the marketplace, with a corresponding increase in demand for cost-effective signal simulation for test and development.
Rohde & Schwarz
Markus Irsigler Product Manager Signal Generators, Power Meters
What is your most recent innovation?
We further improved multi-frequency, multi-constellation simulation capabilities in our high-end segment. The GNSS high-end simulator R&S SMW200A provides signals for all GNSS frequency bands on a single RF output. A second internal RF path can be used for advanced interferer simulation, testing the receiver’s resilience to spoofing or to address dual-antenna scenarios. This keeps setups simple and compact. When more than two RF paths are required, two or more R&S SMW200A can be operated together in a master/slave configuration. Such setups are required for multi-antenna receiver test applications where the signals’ relative carrier phases are analyzed, like CRPA or attitude determination tests. Our new RF ports alignment software automates alignment of the GNSS signals and guarantees correct amplitude, time and phase relations at the RF inputs of the device under test. We also increased the maximum channel count to more than 600 channels to improve testing of multi-constellation, multi-frequency receivers against multipath, jamming and spoofing.
What is your approach to jamming and spoofing?
Besides our recent innovations, Rohde & Schwarz plans to provide new interference simulation capabilities within the GNSS simulator. This new feature will allow the user to replay recorded jammer signals as well as user-defined waveforms. The R&S Pulse Sequencer software helps with the definition of most complex interferer scenarios.
Photo: Rohde & Schwarz
What’s coming by 2023?
Developments in the field of advanced driver-assistance systems (ADAS) aiming for fully autonomous vehicles raise new challenges for reliable PNT solutions. Simulation of interference and jamming scenarios will hence become important in the automotive market. Antenna arrays have proven suitable to counteract RF interference (RFI) by incorporating spatial-processing techniques and might therefore find greater entry into the automotive market. Test solutions must address requirements for simulating all kinds of intentional and unintentional RFI for multi-constellation, multi-frequency and multi-antenna receivers. Apart from simulating GNSS and interference sources, test solutions for autonomous driving will require several other techniques and signals to be applied or simulated, such as RTK/PPP or outputs from other vehicle sensors to perform sensor fusion.
Spirent Federal Systems
Jeff Martin Vice President, Sales
What is your most recent innovation?
Launched in 2018, SimMNSA became the first MNSA simulator to achieve GPS Directorate security approval. The software enables users to simulate true MNSA M-code with real-time code and message generation, removing the constraints imposed by simulator data sets (SDS). SimMNSA v2.0 does even more. It is able to broadcast nominal M-code conditions and recreate SDS-defined events. It incorporates an advanced editor to edit military navigation (MNAV) content, allows users to craft and define scenarios, and much more.
What is your approach to jamming and spoofing?
Spirent offers numerous capabilities for emulating GNSS signals in the presence of interference and spoofing attacks. Our solutions provide accurate, repeatable and quantifiable signals, enabling customers to conduct accurate tests with trusted results. We can test against internally generated interference enabling multiple “fields” of jammers with various interference types; hundreds of interference signals using external IQ blended with simulator-generated GNSS, and Blue Force Electronic Attack jamming waveforms for testing MGUE devices operating in GPS-denied environments. Spoofing capabilities include signal, navigation data and cyber-level attacks via manipulation of up to 12 copies of each primary GNSS constellation, each fully editable; intuitive spoof attack generation via Spirent’s SimSAFE software option — which also allows live sky synchronization/spoofing, and more.
Photo: Spirent
What’s coming by 2023?
Threats to reliable and accurate GNSS navigation and timing are developing rapidly. Fortunately, innovative solutions for resilient PNT are in development and will continue to challenge the industry for years to come. The ability to simulate these threats and the mitigation techniques to overcome them is changing the landscape for the simulator industry. It’s more important than ever to have up-to-date test tools. Robust signals along with frequency and constellation diversity will continue to drive the market in addition to GNSS backup systems, or AltNav. The FCC has certainly presented the GNSS industry with an immense challenge.
Syntony GNSS
Sylvain Daubas Simulator Activity Manager
What is your most recent innovation?
Yesterday, GPS systems had to “work.” Today, they must work fine. This is the difference, and all equipment vendors have realized this. It is no longer acceptable to have 200 meters or more of error in an urban environment. Because of the extreme complexity of the electromagnetic situation in the GNSS spectrum, making a reliable and precise location system requires more and more powerful and advanced simulators. This is why the GNSS simulator market is booming.
Among the many new features implemented in Syntony’s GNSS simulator this year, two stand out.
First, 1000-Hz hardware-in-the-loop now allows an accurate simulation for high-dynamic receivers (up to more than 100 Gs!), with zero artifact and zero-effective latency. This is the ultimate in trajectory management.
Second, signal computing capacity has made a significant leap forward due to hardware and software optimizations. Constellator can now simultaneously generate up to 660 L1 C/A-equivalent signals. And this level of performance can be unlocked remotely, without a hardware update.
Photo: Syntony GNSS
What is your approach to jamming and spoofing?
Simulating a GNSS environment with a set of jamming or spoofing signal sources today is the standard. But what about a simulation of an extremely complex urban scene with 50 or 100 jamming/spoofing sources? The only reasonable solution to implement this would be a massive parallel software-defined radio (SDR)-based simulator solution. This is what Syntony can and will do, thanks to its full software GNSS simulator architecture, which can be distributed on a server farm.
What’s coming by 2023?
A revolution is arriving: the possibility of generating a full GNSS simulation including many hundreds of satellites and signals, in real time and in pure software. This is now possible, and Syntony has demonstrated it with the Constellator. This will change the simulation world. First of all, Moore’s law will bring significant improvements to this domain year after year. More importantly, new systems and services will be possible: massive parallel scenario simulation including jamming and spoofing, floating simulator licenses, software as a service, etc. In this trend, playback machines will be needed, and obviously a strong internet connection will be necessary to download hundreds of gigabytes of I/Q files overnight.
Feature image: Samuel King Jr./United States Air Force
1976: The first military GPS five-channel receiver built in one of several programs that studied the feasibility of GPS. The receiver weighed more than 270 pounds and had seats for two operators. (Photo: Rockwell Collins/Smithsonian)
Like the internet before it, GPS started as a niche technology and became a universally recognized one, though much misunderstood and often taken for granted. Both systems originated in the U.S. Department of Defense (DOD) to support military missions, and then exploded into mass-market civilian technologies. While the internet passed from military to civilian hands very early in its history, GPS is still operated by the U.S. Air Force, making it a unique experience for the DOD: a system for which it is responsible that has orders of magnitude more civilian applications and users than military ones.
GPS has transformed entire professions — most notably, surveying; created new industries — such as ride sharing; boosted innumerable fields of scientific research — from archaeology to zoology; facilitated many aspects of everyday life — such as finding retail outlets and getting there; and given an advantage to U.S. military forces. One application discussed 30 years ago that has not yet lived up to its promised return on investment is precision agriculture.
Challenges and debates that loomed large in the early days turned out to be growing pains —most notably, Selective Availability (SA). In 1990, Javad Ashjaee reflected the attitude of much of the GPS industry and user community when he said, “I can’t think of a word to say how bad it is.” Other debates have proven more persistent — such as the interference threat posed by LightSquared, reborn after bankruptcy as Ligado Networks.
GPS first drew considerable publicity in the wake of Desert Storm, when it became the subject of television features, newspaper reports, and special sections in the pages of recreational catalogs. “Ironically,” Brad Parkinson pointed out in September 1994 in GPS World, “civil companies [such as Garmin] developed most receivers used in Desert Storm, with no help from military sponsorship.” Later that decade, while most people were finally aware of GPS technology, it began disappearing deep into its applications and the systems that use it.
In September 1991 — three and a half years before U.S. Air Force Space Command declared the system’s full operational capability (FOC) on April 27, 1995 — in a speech to the International Civil Aviation Organization in Montreal former FAA Administrator James B. Busey said: “I want to emphasize that we fully support the eventual replacement of [GPS] by other systems — and we are certain that will happen.” That may still happen, in the distant future. However, what Busey did not foresee is that GPS became but an element, though a key one, in a much larger positioning, navigation and timing (PNT) system. This worldwide system includes three other GNSS and two regional ones, several publicly and privately operated augmentation services, and a wide range of complementary and alternative technologies. These include inertial navigation (which has advanced much in the past three decades) and RF signals of opportunity. It may soon include navigation signals from non-GNSS satellites, eLoran, enhanced distance measuring equipment, and Earth-fixed navigation using very low frequency.
I began my current career in geospatial technologies exactly 20 years ago, as this magazine’s managing editor, just a few months after the end of SA increased GPS’ accuracy by an order of magnitude, and equally expanded the number of its potential applications. Yet today, I still marvel at how pervasive this technology has become and how much further it will transform our lives.
I will end with a quote from an early GPS World columnist, Hale Montgomery, who wrote in October 1991, “GPS users show an insatiable appetite for ever more precise data. Give them a mile and they want an inch.”
Seeking back issues: I have the entire collection of GPS World’s print edition, except for the first issue, the 10 issues in the second year (1991), and the September through December 1993 issues. I would be thrilled to receive those missing issues, or facsimiles, from anybody who has them. Email [email protected].
Not just supporting players, alternative positioning, navigation and timing (PNT) systems strengthen, augment and — when needed — replace GNSS. We explore how companies are using alternative PNT, and talk with John Fischer of Orolia and Alexis Guinamard of SBG Systems about their companies’ latest developments.
Since the 1990s, GPS has provided the United States military with a substantial tactical edge. Civilian GPS applications are now deeply embedded in every aspect of our lives. The U.S. Department of Transportation recently reaffirmed that GPS’ positioning, navigation, and timing (PNT) services are critical to the safe and efficient use of the national transportation system, and a Feb. 12 presidential executive order declared that satellite-based PNT services “have become a largely invisible utility for technology and infrastructure.”
It has long been equally well known, however, that GPS is vulnerable to accidental and intentional interference (the latter known as jamming), spoofing, and degradation or denial of signals. Additionally, GPS satellites are increasingly vulnerable to damage or destruction by space debris or intentional attack. The executive order mentioned above declared it U.S. policy “to ensure that disruption or manipulation of PNT services does not undermine the reliable and efficient functioning of [the country’s] critical infrastructure.”
Protecting PNT requires not just strengthening GPS, but also developing alternative sources of PNT data and ways to integrate them into the myriad systems that currently rely on GPS.
The National Timing Resilience and Security Act of 2018 (passed by the U.S. Senate as part of that year’s Coast Guard authorization act), called for “a complement to and backup for” the GPS timing component “to ensure the availability of uncorrupted and non-degraded timing signals for military and civilian users in the event that GPS timing signals are corrupted, degraded, unreliable or otherwise unavailable.” It mandated the procurement of a wireless, terrestrial system that would provide wide-area coverage and be synchronized with UTC, resilient and extremely difficult to disrupt or degrade, able to penetrate underground and inside buildings, and capable of deployment to remote locations.
A report released on April 8 by the Department of Homeland Security (DHS), however, recommends “that responsibility for mitigating temporary GPS outages be the responsibility of the individual user and not the responsibility of the federal government.” It points out that research by one of DHS’ agencies “shows that users can mitigate short-term GPS disruptions (e.g., inability to read a GPS signal) with various strategies, ranging from using local backup capabilities to delaying operations until GPS is restored.” The report then focuses on “mitigation against long-term or permanent disruption or loss of GPS PNT capabilities.” It determines that the PNT functions in critical infrastructure “are so diverse that no single PNT system, including GPS, can fulfill all user requirements and applications” and notes that maximum resilience is found in diversity of solutions. Therefore, it recommends that the federal government “encourage adoption of multiple PNT sources [to expand] the availability of PNT services based on market drivers.”
In the interviews below, I discussed these challenges with John Fischer, vice president of Advanced R&D at Orolia, and Alexis Guinamard, chief technical officer of SBG Systems.
As part of the effort to combat the spread of COVID-19 in the United States, UAV company Draganfly has partnered with Australia’s Department of Defense (DOD), the University of South Australia (UniSA) and Vital Intelligence, a company that collects and analyzes healthcare data, to remotely detect and monitor people with infectious and respiratory conditions.
Draganfly’s UAVs will be fitted with a specialized sensor and computer vision system that can monitor people’s temperature, heart rate, and respiratory rate, as well as detect people sneezing and coughing in crowds. The collaboration, called The Vital Intelligence Project, utilizes technology developed with help from the DOD’s Science and Technology Group. Draganfly was selected as the exclusive integration partner on March 25, with an initial budget of up to $1.5 million to commercialize and deploy the technology.
The UAV uses u-blox LEA-M8S GNSS modules integrated into the company’s own interface printed circuit boards.
In late January, recalled Draganfly’s CEO Cameron Chell, the company began to consider what kinds of health data it could collect and analyze that could help public officials and private-sector managers flatten the pandemic’s curve. It then contacted Javaan Chahl, a UniSA researcher who had been a customer for 20 years, to discuss the use of UAVs for this mission.
The technology was originally designed to be deployed on helicopters in disaster relief operations, to measure the vital signs of survivors. It was then adapted to measure the health of wildlife populations, such as herds migrating or threatened by drought or fire, and in hospital neonatal wards to monitor the vital signs of newborns.
To provide core temperature readings as well as measurements of heart rate and respiratory rate, the technology uses RGB and thermal cameras, both fixed and mounted on UAVs. “The public sector and the private sector are both interested in this technology, but are approaching it very differently,” Chell said.
The system’s capabilities include detecting people who are coughing, not wearing masks, or clustering in violation of social-distancing rules. The objective is to provide population health information to public agencies to help them make better decisions by measuring the effectiveness of their COVID-19 policies in real time, rather than react to past information. The system, Chell stressed, does not record data on individuals but reports such figures as “84% of the people are socially distancing 24% of the time.”
“Based on what I see unfolding with the measurement and data industry as it relates to health technology,” Chell said, “six or eight months from now you are likely to see health measurement reports the same way that you see weather reports. Eventually, it will be broadcast to the consumer. That is our objective.” People, he predicts, will use these reports to make decisions about where and when to travel.
To obtain accurate core temperatures, Draganfly’s thermal sensor needs to be about 20 feet away from its subject, and uses software to zoom in on the tear ducts. To obtain heart and respiratory rates requires about 25 seconds of footage with at least a 4K camera, magnification to detect body micromovements, and machine vision to detect skin tone biometric measurements. The system also picks up movements — such as of the shoulders, lumbar area and upper torso — that indicate coughing, Chell points out. “The results certainly have been promising in terms of having real quantitative data,” he said.
The scenario is somewhat different in the private sector, which typically relies more on fixed-based cameras for entranceways — for example, to monitor workers entering a warehouse, a factory or a shipyard to guard against people who are infectious or have a respiratory disease. “We have seen several announcements by companies that they are using thermal cameras to do this,” Chell said. People pass through the company’s fixed system, which uses both thermal and RGB cameras, in less than three seconds, according to Chell, which is good for such facilities as parks, office buildings and convention centers. Private organizations can then ask people who exhibit certain symptoms to consent to a secondary screening in exchange for access.
Additionally, Draganfly will provide UAV services for disinfecting outdoor facilities.
Find out how more companies are helping fight COVID-19.
The John Deere StarFire 6000 RTK receiver operating in the field. (Photo: John Deere)
Precision agriculture — the practice of optimizing inputs of seed, water, and fertilizers while maximizing yields by mapping variations in soil characteristics and guiding machinery accordingly — began in the United States in the early 1980s and has been growing steadily. Key components include soil mapping based on sampling and remote sensing, proximal sensing of soils and crops, variable rate irrigation and variable rate spraying of fertilizers and herbicides, and automatic tractor navigation.
“GNSS-based guidance is probably the most highly adopted precision ag technology, followed by variable rate and section control,” said John Fulton, associate professor at The Ohio State University. “I suspect that somewhere around 40% of those GNSS receivers use RTK-level corrections — which provide sub-inch accuracy — and that number is increasing.”
Need for sub-inch accuracy
Water runs downhill, of course, which makes vertical accuracy critical for hydrology. “AgLeader builds a plow to put tile in soil to drain water,” said Bill Cran, AgLeader Technology’s GNSS product specialist. “It might only be 4 inches round; so, if we are off by 2 or 3 inches vertically, that affects where water can run.” To get the best vertical accuracy possible, he recommends farmers install a base station in the field where they are operating.
Sub-inch accuracy also enables farmers to determine where to plant each seed, rather than monitoring planters at the row level. “That may not be a requirement today, but it is certainly coming,” Cran said.
Market demand for RTK in agriculture is increasing, an important factor for drone guidance or machine control, said Gustavo Lopez, market access manager at Septentrio. “The robots are very close to the crops. When small robots are working in a corn field, the corn plants are causing multipath or shadowing GNSS signals,” Lopez said. “You need either a good RTK or GNSS-INS, because if you lose satellite lock you can still coast for a while with an IMU.”
Services and options
AgLeader’s displays have a built-in networked transport of RTCM via internet protocol (NTRIP) client that enables it to connect to NTRIP networks and CORS networks, as well as other free and subscription-based networks. “That allows us to get RTK from the internet for customers that want to go that route,” Cran said. Alternatively, the company offers NovAtel GPS receivers, including Satel- or Freewave-based RTK options with 400 MHz and 900 MHz radio options that can communicate with a similar base station. This spring, it will begin to offer NovAtel’s TerraStar-X service. “We are calling that ‘RTK from the sky,’” Cran said. “The expectation is sub-inch accuracy, with a convergence time of less than one minute. Many of our customers and dealers are very excited about that option.”
Septentrio’s GNSS modules for agriculture are used mostly in mapping drones, Lopez said. The modules mitigate interference and spoofing. “We have also been quite successful in robotics for agriculture,” Lopez said. Septentrio is working closely with the French agriculture robotics company Naïo Technologies, which integrates its robots with Septentrio’s smart antenna GNSS products, providing a full RTK solution as well as autonomy.
For areas without RTK networks, some farmers buy and install Septentrio base stations that provide corrections to their robots or UAVs. Septentrio provides agricultural mapping software for post-processing data gathered without RTK. Also on offer are L-band receivers — while not as accurate as a local RTK network and possibly with higher convergence time, the relative accuracy of L-band corrections is more than good enough for many ag robots, Lopez explained.
On the baseline
The vegetable weeding robot Dino — shown here operating in Yuma, Arizona — uses a Septentrio GNSS receiver. (Photo: Septentrio/Naio Technologies)
Most RTK users are on a short baseline — under 5 miles from the base station to the rover, according to Al Savage, manager of John Deere’s StarFire network. Medium baseline is about 5–8 miles, and long baseline is up to 12 miles. In 2015 John Deere released its Base Station Manager, which enables dealers to remotely upload firmware, upkeep the rover access list, and monitor their base stations.
As dealerships and their RTK networks merged and farms expanded, it became difficult for farmers to keep track of which base station to use. So, in 2019 John Deere released an Automatic Base Station Switching feature that links the RTK radio configuration to the field boundary in its Generation 4 display.
Also new: A John Deere StarFire receiver can continue to operate if it loses connection to a base station using the RTK Extend feature. The StarFire SF6000 rover receiver can continue operating with RTK-like accuracy for up to 14 days without connecting to an RTK base station, compared to only 14 minutes for a previous receiver, Savage explained. The increase “was very well received by customers, especially those operating in areas challenged by line of sight or trees and foliage on field boundaries.”
In South America, John Deere’s RTK Flex feature, “will automatically switch between RTK and SF3 during a time in the day when scintillation causes the greatest interference,” Savage said, enabling farmers “to continue working with similar accuracy when RTK is unavailable due to scintillation.”
Remaining obstacles to adoption
Despite’s RTK’s growing popularity, there are a few remaining obstacles to its adoption.
Cost. “Though the cost has been greatly reduced over the years, RTK is still more expensive than other correction signals out there,” Fulton said. Part of the cost is due to the hardware, Cran pointed out. “There are rover and base station radios, there are towers to put up. On the NTRIP side, there are cell modems to put in vehicles, and they require keeping a data plan active.” The agriculture market traditionally has been very cost-sensitive and conservative, Lopez said. “Farmers expect to implement very low-cost solutions. They want to know whether they will have an ROI (return on investment) on these solutions.”
Satellite services offer a cheaper alternative to RTK. TerraStar-X, for example, gets rid of the cell modem hardware and the requirement for base station hardware, Cran said. “At a lower accuracy level, there are other satellite-based TerraStar signals: TerraStar-C and TerraStar-C Pro, which get an accuracy maybe under 5 to 20 cm. Those are less-expensive alternatives that growers are using without making the leap to RTK.”
Lack of Internet Connectivity. While most RTK services, including NTRIP, require an internet connection, many rural areas have limited broadband and even cellular connections. Some areas lack support for RTK, Fulton said.
Lack of cross-platform compatibility. Farmers with a mixed fleet want to run a mix of receivers. “For example, John Deere and Trimble RTK do not work together,” Cran said. “It is still very manufacturer-specific. I cannot take a NovAtel receiver that is AgLeader branded and use it with a John Deere RTK network.” NTRIP partially enables cross-platform mixing and matching. “We’re excited about TerraStar-X, too, because, while it is specific to NovAtel receivers, it is not tied to any base station hardware,” Cran said. “So, a John Deere guy can put an AgLeader receiver on their vehicle and use TerraStar-X and still get that accuracy without being tied to the Deere RTK network.”
Liability. While safety is not nearly as big an issue as it is with autonomous vehicles on the roads, liability questions will soon loom. “If, for example, a robot destroys a whole plantation, someone must be liable,” Lopez pointed out. “Was it the robot? The GPS receiver? Other sensors? The farmer? What if there is a spoofing attack and the robot goes to a neighbor’s field?” Such challenges are slowing adoption. “That is where the reliability of the GNSS is becoming important,” he said.
The future
Soon, satellite-based internet connections could make RTK correction more widely available and give more growers the option of using NTRIP, though at a cost. WAAS, a free service of the U.S. government, is broadcast by satellites but does not achieve the accuracy level of RTK. “RTK is still a localized correction,” Fulton said. “We may see that shift to satellite, but it will more likely be an online or some other type of communication.
“Once farmers start using RTK, it is very unlikely that they will ever revert to another type of correction,” he added.“RTK is a very addictive correction service for folks.”
Savage concurs. “RTK is addictive because of its accuracy, efficiency and repeatability.” Ultimately, however, to achieve universal adoption, RTK solutions will need to work everywhere, with little intervention by the farmer.
