What is assured PNT?

Whether on land, sea, or in the air, you need to trust that your global navigation satellite systems (GNSS) positioning system will deliver, keeping you safe and headed in the right direction. That is where assured positioning, navigation, and timing (PNT) comes in. So, what is assured PNT?

Assured PNT is a goal toward trusted precision that requires a layered approach to positioning solutions paired with sensor fusion. New challenges to PNT—including jamming, spoofing, and even size, weight, and power limitations—are always evolving, which requires constant innovation to deliver assured PNT. While the goal posts of achieving assured PNT may change as new threats emerge, a multilayered approach with built-in redundancies helps ensure GNSS reliably performs.

Multilayered defence for assured PNT

Impacts on GNSS accuracy can come from both natural and intentional sources. When satellite signals arrive at the antenna of a GNSS positioning system, they are typically very weak. This makes them susceptible to atmospheric fluctuations, interference from other signals transmitted on that same frequency, obstructions from trees and buildings, topography, and even weather. These situations make it difficult for a GNSS receiver to calculate an exact position. The best way to ensure assured PNT is through a multilayered and robust positioning solution.

A multilayered approach to assured PNT requires trust and innovation in today's technologies. There’s no one silver bullet that will solve an interference challenge; instead, it’s the combination of multi-constellation and multi-frequency receivers and antennas, and sensor fusion with inertial measurement systems, vision navigation equipment, external position, velocity, and attitude sensors, resiliency and situational awareness firmware, and other technologies that can enable assured PNT.

The building blocks of assured PNT

To counteract these impacts on assured PNT, let's take a high-level look at what goes into ensuring your GNSS positioning systems are robust, reliable, and accurate.

Antennas

Antenna selection is a vital hardware decision in assured PNT, both in terms of installation and the reception of frequencies. A GNSS antenna is a device designed to receive and amplify the radio signals transmitted on specific frequencies by GNSS satellites and convert them to an electronic signal for use by a GNSS receiver. An antenna must match the receiver’s capabilities, specifications, and meet size, weight, environmental, and mechanical specifications for the intended application. When choosing an antenna for assured PNT, some factors to consider include multi-constellation, multi-frequency (MCMF) signal reception, antenna gain, element gain, antenna beamwidth and gain roll-off, phase centre stability, and application. Learn more about these considerations in our An Introduction to GNSS primer.

Receivers

The foundation of assured PNT is the receiver. Like the name indicates, receivers are devices that receive signals transmitted from GNSS satellites and process those signals to determine the user’s position, velocity, and precise time. The powerful processor within the MCMF receiver leverages complex algorithms for a resilient and precise position, including sensor fusion capabilities with additional sensors. An assured PNT solution includes a receiver that can handle multiple frequencies from multiple constellations to optimise the resolution of errors inherent in transmitted satellite signals. When an MCMF receiver utilises signals from various constellations, it establishes a level of redundancy against signal blockages.

Correction services

GNSS signals have inherent errors that limit the accuracy of positioning. These errors can be caused by the satellite clock, orbital drift, and atmospheric delays. GNSS corrections mitigate these errors, ensuring the receiver can output real-time, highly precise positioning, velocity, attitude, and timing. These errors can be corrected in many ways, with real-time kinematics (RTK) and precise point positioning (PPP) being the leading methods.

Inertial sensors, vision navigation, and ranging systems

Sensors like inertial navigation systems (INS), cameras, RADAR, LiDAR, and more provide an orientation in the world. These measurements can be used to resolve potential errors in a GNSS solution and to bridge a gap during a satellite signal interruption. When these sensors provide measurements to a powerful GNSS receiver, algorithms can be deeply or tightly coupled to enhance accuracy and resiliency. Using any external position, velocity, and attitude input, sensor fusion empowers the system to better withstand interference, resolve errors more quickly, and reacquire satellite signals after an interruption. Learn more about the benefits of GNSS+INS integration.

Anti-jamming and anti-spoofing solutions

A critical challenge faced by those relying on assured PNT is intentional GNSS signal interference. Disruptions to GNSS signals can result in the loss of PNT. Jamming refers to the intentional transmission of radio signals on the same frequency as GNSS signals to disrupt or overpower the signals. Spoofing involves creating fake GNSS signals designed to deceive a receiver and cause it to provide false position information. Our white paper provides a foundation for understanding the differences between jamming and spoofing.

Anti-jamming and anti-spoofing solutions can provide a level of situational awareness to understand the interference threat better, in addition to mitigating interference. Whether in the form of hardware or firmware, anti-jamming and anti-spoofing technologies can build a solution’s defence that, when combined with other PNT sources like GNSS+INS, corrections, and MCMF receivers and antennas, continues to provide robust and assured PNT. Learn how Hexagon | NovAtel’s GNSS Anti-Jam Technology (GAJT) antenna systems and GNSS Resilience and Integrity Technology (GRIT) firmware expand situational awareness and provide interference mitigation tools across applications and environments.

Advances in assured PNT are all about location, location, location

A more resilient and robust assured PNT is closer than you think. Low earth orbit (LEO) satellites are among the viable options we are exploring that can complement GNSS, adding resiliency, security, and precision to PNT. NovAtel has worked with Xona Space Systems and Spirent to advance LEO PNT, tracking a simulated PULSAR signal with the OEM7 receiver. You can read more about these exciting developments in Velocity magazine.

Assured PNT has become more critical than ever as incidents of atmospheric impacts and interference threats rise, and the development of autonomous technologies continues to grow and evolve. Understanding that your assured PNT solution requires a multilayered approach ensures you have a robust system with built-in redundancies. Working with a partner like NovAtel that understands the building blocks to assured PNT is the best way to develop a GNSS solution you can trust.