Other sources, such as lidar, can be used to aid navigation in the absence of GNSS signals. (Photo: OxTS)
We discussed complementary PNT with Peter Rylands, senior product manager at OxTS.
What are some of the most promising approaches to complementary PNT and how does simulation technology help?
There are two approaches of particular interest. The first is looking at LEO satellite systems that can provide supplementary and potentially more secure methods of navigation, with global coverage from a single system. But these will still suffer from some of the issues GNSS systems experience, namely, what happens when you can’t obtain a signal?
The second is the use of visual aiding through sensor fusion, such as lidar and cameras, that can provide relative positioning (or absolute positioning once you have a space mapped) using SLAM algorithms. While this may increase onboard hardware dependencies, it creates a localized navigation system that can be better protected from malicious actors.
In contrast, closed-loop systems can look to an infrastructure-based system, allowing free movement within the specific area in which the infrastructure is located and a potentially more reliable source of PNT, especially indoors, where GNSS is not available. Ultra-wideband is definitely the up-and-coming technology here, but systems using Wi-Fi, cameras, Bluetooth and others also are being used.
Simulation, as within many domains, allows users to test on a large scale with fewer barriers to entry than real-world testing and an ease in making iterative changes to find an optimal solution. Whether that is to benchmark performance in locations of interest or to change configuration settings to improve visibility or positioning, simulation allows you to do this without the expense of going straight into the environment itself or configuring the actual vehicle under test.
How does OxTS fit in that mix?
OxTS provides customers with the ability to navigate anywhere; whether for reference data in R&D, georeferencing for survey and mapping, or active navigation of autonomous solutions. To do this we provide an IMU-first offering that we then complement with other technologies. Traditionally, this is with GNSS, to form an INS that can provide centimeter-level accuracy. However, we are also aware of the vulnerabilities of GNSS. For us, this is when it becomes an unreliable source of PNT in denied areas, such as indoors, in urban canyons or under tree canopies.
Because of this, we are also investigating and developing complementary solutions that can enhance our offering for users who need confidence in their position even when GNSS is not available. Whether that is through sensor fusion, our Pozyx UWB solution for indoor navigation or other proprietary software and firmware capabilities.
What kinds of complementary PNT are most useful in addressing specifically the challenges posed by jamming and spoofing and how does simulation help?
We need to look at systems that cannot be impacted by, or have mitigations from, the impact of jamming and spoofing. Solutions that are independent of radio communications or satellite use are then valuable in providing this layer of protection. This is where we could look toward OxTS’s use of IMU technology and visual aiding systems. Simulation technologies would then allow you to run hardware-in-the-loop testing, where the primary GNSS solution can have simulated jamming and spoofing to understand the performance of your complementary and protected systems when GNSS cannot be trusted.
Editor-in-Chief Matteo Luccio sat down with experts from Spirent Federal Systems to discuss how simulation technology helps improve positioning, navigation and timing (PNT) and GNSS products and systems.
Data shows how successful baseline validation testing of Spirent’s inertial simulation model as compared to real world inertial system performance. Photo: Spirent Federal Systems
We discussed complementary PNT with Roger Hart, head of engineering and Jeff Martin, head of sales at Spirent Federal.
What are some of the most promising approaches to complementary PNT sources and how does simulation technology help?
Roger Hart: The vulnerabilities of GNSS have been recognized. Legacy GNSS are all operating on pretty much the same frequencies and power levels, so, they have some significant common vulnerabilities. There is great interest in finding ways to complement or even replace those capabilities.
Dead reckoning, magnetic and inertial systems have been around for a long time. There are emerging markets to make use of alternative radio frequencies for navigation. In some cases, we are piggybacking on communications signals and deriving PNT from them. In other cases, we are using new PNT signals. A couple that we’ve been focusing on are the alternative navigation systems.
They may be using different orbits, different frequencies, different encoding schemes that set them apart from the legacy GNSS systems, so that, used together, they provide greater resiliency and even stand alone when one or the other system may be affected by interference.
Not to be forgotten is inertial navigation. It’s been around for a long time and is still a standard of navigation. Together with GNSS, it makes it a terrific navigation system. It almost defines complementarity because where GPS is vulnerable inertial can fill in the gaps and where inertial drifts GPS does not. So, paired, they make a very strong system.
At Spirent, we’ve been working with customers to provide a variety of options for both those alternative navigation systems and inertial. Both are a very active field of development and we’re keeping abreast of that.
Jeff Martin: Some good points, Roger. This is something we’ve been engaged in for quite a long time. Since we provide test equipment to the community, it’s critical that we understand what they’re worried about, what the vulnerabilities are. It keeps things exciting, it keeps us on our toes and looking ahead to what’s coming.
What are some of the remaining challenges of integrating GNSS receivers with inertial sensors and, again, how does simulation technology help with that?
Hart: Inertial works by integrating sensor measurements that come in. Therefore, any errors that are present just accumulate over time and can corrupt your navigation solution. So, there’s a strong focus on updating error models and on translating them so that everyday users can use them and get real-life-type performance out of them.
There’s a tendency to think of integrating GPS-INS as putting everything together in one box. There are packages that do that. However, the push now is to go to more distributed systems that are integrated but not packaged in the same box. One example is the all-source positioning and navigation standard that is being developed by the Department of Defense. It will allow you to swap one sensor for another as long as they adhere to the standard. That information all goes back to a sensor fusion engine.
Martin: We have known GNSS simulators well for about four decades. We have been playing in the inertial sandbox for at least a couple of decades as well. This has given us the opportunity to build relationships with the with the key manufacturers and designers of inertial systems. Those relationships have been expanding well beyond inertial to many other sensors and systems that are now coming online. It’s been exciting.
Much work is going into using low Earth orbit satellites for PNT—whether piggybacking on the Iridium satellites or launching new ones. How does simulation help with that?
Hart: It certainly helps with the development of the receivers. The groups that are using these alternative RF and LEO or MEO systems need simulation as they develop the receivers. It gives you the ability to try things certainly before you launch them. At this conference there is considerable interest in making things reprogrammable. We have the NTS-3 satellite, which will be running experiments for different waveforms that can be generated. Even M-code is a step in the direction of giving more flexibility to the signal. It has a lot more flexible cryptography and signal generation than the legacy system with the C/A and P/Y codes.
Our simulation platforms are software based, so we can generate and receive data that can be useful for developing software-defined receivers. It gives you the opportunity to try different waveforms. We have already delivered a satellite-based alternative navigation system simulator. Now, we can build on that one to help the other Leo constellations as they come forward.
Martin: Roger put it well. This is where things get fun. People are concerned with PNT vulnerabilities, so we’re seeing these alternative navigation solutions coming forward. Spirent has done a good job over its nearly 40 years of existence of manufacturing and designing its own hardware and software. It has given us the opportunity to respond quickly. These things are coming fast. People need solutions quickly. We have some solutions already and the platform that we have created gives us the flexibility to develop more. We’re seeing more and more ideas come to fruition and people need to test them. So, this is where it gets fun. We’re excited.
Much work has gone into addressing the enduring challenge of urban canyons. How does simulation technology help?
Hart: Urban canyons are the worst nightmare for GNSS signals. If you’re surrounded by tall buildings, signals are blocked. You may have few or even no satellites in a direct line of sight and many multipath reflections. So, diminished and corrupted signals are available to you. Of course, the more GNSS satellites you have, the better chance you have of getting good signals. But complementing that are radar and vision systems. Those are the ones that will stand out, particularly the vision systems that can read the street signs, see where the curb is, look for parked cars. All those kinds of things will help fill in when you have poor GNSS coverage.
You can observe what’s going on in the environment and simulate it. You can also use our forecasting tool to look ahead.
Martin: This is where things get exciting, isn’t it? In these terrible environments where GNSS is contested—whether it’s an urban environment or one with intentional jamming—there is a lot we can do to help our industry. When this happens in real life, it’s bad news. But when you create that scary situation in the controlled environment of a laboratory, it is great. You can pick things apart and see where you need to improve. I get excited about it. It’s probably the geek in me. It gives us and our partners a lot to look forward to.
How does simulation technology help with sensor fusion?
Hart: It definitely helps you put all the pieces together. You can’t know how your system will work by individually testing each piece. System is the key word here. Simulation enables you to generate the signals and bring them together into a sensor fusion engine. You can test different algorithms. It’s certainly much cheaper and quicker than trying to build this into a product and then test it. Over the decades, simulation has proved itself as a very valuable way in both basic development and integrating the final product.
Martin: That system-wide fusion is where the magic happens.
It sounds like simulation technology—and Spirent Federal in particular—are very much at the center of a lot of the current developments and discussions about complementary PNT. Do you have any final comments?
Hart: As Jeff said, it’s an exciting time. There are many things going on—new technologies, new ways of communicating. It’s a busy time and a bit of a scramble sometimes to keep up with all the new things that are coming.
Martin: People look to Spirent to be their testing resource and it puts us right in the middle of it.
The U.S. Army considers virtual reality training as an important path ahead to prepare warfighters.
The U.S. Army awarded Bohemia Interactive Simulations (BISim) a major extension to demonstrate technologies for a cloud-enabled, virtual world training capability.
BISim is a global developer of advanced military training and simulation software.
The contract award helps meet the requirements of the Army’s Synthetic Training Environment (STE) initiative. STE aims to converge virtual, constructive and gaming training environments into a single unified architecture.
The ambitious STE project will enable simulation systems Army-wide to leverage a persistent virtual world for any imaginable training need, including support for multi-domain operations incorporating cyber and space.
Central to STE is a cloud-enabled One World Terrain (OWT) that will let warfighters conduct virtual training and complex simulations anywhere on a virtual representation of the Earth. OWT will leverage cloud technologies to deliver to the point of need, ensuring a common and high-fidelity whole-Earth terrain representation for a multitude of different simulation systems.
The Synthetic Training Environment will assess Soldiers in enhancing decision-making skills through an immersive environment. (Photo: U.S. Army)
“The U.S. Army’s vision for STE marks a monumental change in how they acquire, develop and deliver new simulation and virtual training technologies to soldiers,” said Pete Morrison, BISim’s co-CEO and chief product officer. “We’re honored to be selected to assist the Army in developing innovative solutions that will shape the future of how virtual training is used to enhance operational readiness.”
BISim has been developing its next generation of simulation technologies since 2014. The new technology suite includes a cutting-edge, military-specific whole-earth game engine, deterministic AI, an efficient geospatial terrain server and component-based development technology.
BISim technology underpins funded research and development for One World Terrain. Additionally, BISim recently demonstrated Reconfigurable Virtual Collective Trainer (RCVT) prototypes for STE. The latest OTA extension is a significant ramp up in the breadth and ambition of the technology being demonstrated.
BISim’s STE offering includes four core technologies uniquely suited to meeting future military simulation requirements (including U.S. Army requirements).
VBS Blue. A high-performance, whole-planet data ingestion and rendering engine with a very high level of procedural detail, designed to ingest any conceivable terrain data format as well as source data directly. VBS Blue will support networked (cloud) terrain paging and geo-specific insets as well as the latest graphics technologies. It provides photorealistic detail, and includes a massive vegetation library representing every region on Earth. The technology is highly applicable across all types of image generation and is optimized for many AR/VR applications.
STEWS. A geospatial data server that provides efficient networked access to the various data sources required for rendering applications. STEWS provides a curated database of terrain data layers that can be streamed into any STE-connected client application at run time (including non-BISim applications). Any application connected to STEWS can stream high fidelity terrain data in a performant manner. Both new and legacy terrain formats are supported through new STEWS plug-ins.
VBS Control. High fidelity, doctrinal and deterministic entity-level artificial intelligence that is uniquely suited to operation on whole-earth terrain. VBS Control runtime offers highly efficient real-time path planning that allows AI to move seamlessly through open, urban and interior spaces. The VBS Control Editor allows powerful new AI behaviors to be developed at both the individual entity level and at higher levels of command for land, sea and air assets.
Gears. A software development framework that defines a standard way for components to communicate through formal interfaces. Gears uses a component-based architecture to promote rapid development by building applications from self-contained systems and having them communicate via formally defined interfaces. This allows functionality to be reused and avoids the complexity of tightly coupled systems. See www.gears.studio for more information.
The Army also selected BISim for a five-year contract to support their Games for Training Program and BISim’s technology is being rolled out on CCTT (the U.S. Army’s largest ground simulator training program).
