Precise positioning techniques will continue to grow

Feb 2023 | No Comment

Solutions to deliver resilient PNT systems must be diverse, incorporating a mix of technologies

Andy Proctor

MA, CEng, FRIN, FIET Director RethinkPNT

As we know, the use of PNT information penetrates every sector, including military, aviation, transportation, agriculture, and many others. It is now well recognised that the years of increased reliance on the single source of satellite-based PNT systems, such as GPS, need to be reversed in terms of the technology mix used for PNT systems. Even though the deployment of new constellations and signals are making space-based systems more accurate and reliable.

There is and for the future will not be, one technology to fit all. Precise positioning techniques will continue to grow, such as Real Time Kinematic (RTK), Precise Point Positioning (PPP) and other High Accuracy Services (HAS) technologies. These are finding their niche in the autonomous sector for self-driving vehicles or positioning for commercial drone/unmanned air platform (UAP) services. New Low Earth Orbit derived PNT services will also target these areas as they grow. Customers and corporations in these areas are actively investing in technologies that give them a precise positioning advantage, such as the recent announcement of GM investing into Focal Point Positioning.

Other technologies on the up in the commercial domain are the development of low-power, low-cost PNT solutions for use in Internet of Things (IoT) applications. These solutions are designed to enable the precise positioning and timing of many devices, even in challenging environments where satellite signals may be weak or unavailable. Examples include the use of ultrawideband (UWB) technology and the continued miniaturisation and use of Micro Electro-Mechanical System (MEMS) Inertial Measurement Units (IMUs) for dead reckoning. We should not forget the innovation and advances in the timing community also, new distribution techniques for time such as wide-area time distribution over fibre and “networks as a clock” are starting to become reality.

The danger and opportunity in this diverse technology mix is that of resilience. Resilience refers to the ability of a system or network to continue functioning and providing critical services, even in the face of disruptions or failures. In the context of systems that use PNT information, such as our critical services, system resilience must and will grow to be an important consideration. We should also recognise that resilience is different from assurance as a “Resilient PNT system” is not the same as an “Assured PNT system”.

Solutions to deliver resilient PNT systems must be diverse, incorporating a mix of technologies and to achieve PNT System resilience we should stop thinking about it as a simple Boolean function (i.e., a system is not merely resilient or not resilient). No system is 100% resilient to all threats. Resilience is always a matter of degree, based on the risk profile of the end user application against the expected threats, and typically not measurable on a single ordinal scale of levels. In other words, it might not make sense to say that system A is more resilient than system B.

The trend I predict therefore is that a greater formality in requirements and systems engineering, and standards will be seen as the importance of PNT becomes more widely known. Basic questions that need to be asked for any PNT installation are:
• What critical PNT capabilities/ services must the system continue to provide despite threats?
• What types of threat can disrupt the delivery of these critical capabilities (i.e., what threats must the system be able to tolerate)? •
What are the types and levels of threat to what assets, that can cause harm?

In this way a commonly understood definition of resilient PNT systems can be determined “A resilient PNT system protects its critical capabilities (assets) from harm by using protective resilience techniques to passively resist or actively detect threats, respond to them, and recover from the harm they cause.”

Within the next few years, the importance of non-technology approaches with respect to resilience in all these new commercial domains will also rise. For example, establishing robust and well-coordinated communication and coordination systems can help to ensure that information about disruptions or failures is quickly disseminated and that appropriate actions are taken to mitigate their impact; the importance of skilled resources, training and education of engineers, customers and value chains, in particular about threats to PNT systems; the use of standards to properly facilitate PNT information exchange between the different PNT technologies and the higher level systems that they interface to; and having the right operational checks and balances in place such as processes, verification procedures and formalised testing.

In summary, building resilience into PNT systems is essential for ensuring the reliable and continuous operation of critical applications, meaning business and revenue critical as well as critical infrastructure. The growth areas mentioned here will be the driver behind implementing PNT system resilience as the industrial sectors will move faster than institutionally led endeavours. It will be achieved through a combination of technical approaches, such as the use of diverse technologies such as being championed by the European Space Agency navigation programme (NAVISP), and non-technical factors such as resources (skills, education), processes (verification, documentation), and threat/risk analysis.

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