What is complementary position, navigation and timing (PNT), and what is OxTS’ position on complementary PNT technologies?
OxTS manufacture Inertial Navigation Systems (INS). Our products are used globally by automotive test engineers and surveyors to provide them with highly accurate inertial measurements. These include centimetre-level position accuracy and vehicle heading, pitch and roll measurements.
On-board GNSS receivers provide users with accurate position data, whereas MEMS IMU sensors offer detailed heading, pitch and roll information. The measurements provide users with precise, reliable groundtruth information that they can use to inform decision making in many different projects and applications.
To get accurate position data, a GNSS receiver needs to take data feeds from at least four satellites. In open sky conditions this is relatively simple. However, not all testing and/or surveying takes place in an open sky environment. In an urban canyon, tall buildings may interfere with signal, or alternatively in the countryside, tree canopies may block the signal intermittently.
To help increase the amount of time spent with the most accurate position data possible, it is possible to use complementary technology.
Earlier this year, OxTS Senior Product Manager Pete Rylands took part in an interview by respected industry magazine GPSWorld. During the interview, Pete gave his thoughts on complementary PNT technology.
You can read his responses here:
1. There is much talk about the limitations of GNSS and the need to develop complementary sources of PNT. What are the most promising approaches and how does simulation technology help?
I’m going to preface this with a reference to my April edition article, where the technologies for successful autonomous solutions have a foundation. We spoke about where they are deployed and what for.
Global, open-road, complementary sources of PNT have a core need of allowing free movement anywhere, while maintaining accurate positioning. I think there are two approaches that are of particular interest.
The first is looking at other satellite systems (such as LEOs) 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 Camera, that can provide relative positioning (or absolute once you have a space mapped) using SLAM algorithms. While this may increase onboard hardware dependencies, it creates a localised 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 the infrastructure is located and a potentially more reliable source of PNT, especially when GNSS is not available when going indoors.
Ultra-wide band is definitely the up-and-coming technology here, but systems using WiFi, Cameras, Bluetooth and others are also 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 change configuration settings to improve visibility or positioning, simulation allows you to do this without needing the expense of going straight into the environment itself or configuring the actual vehicle under test.
2. 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 centimetre-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.
3. What kinds of complementary PNT are most useful in addressing specifically the challenges posed by jamming and spoofing and how does simulation help?
To try to avoid jamming and spoofing, we need to look at systems that cannot be impacted by, or have mitigations from, the impact of these actions.
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’ use of IMU technology, and visual aiding systems, such as LiDAR and Camera.
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.
Peter Rylands – Senior Product Manager, OxTS
For more information or to talk to us about how OxTS can help you achieve accurate position with complementary position, navigation and timing technology, contact us using the link below.
