While GPS technology plays an important role in modern navigation, it's not perfect. Although GPS might perform well enough consumer usage, signal jamming or other disruptions present serious threats to military operations.
Enter assured positioning, navigation, and timing (A-PNT), new technology that enhances traditional GPS timing. Assured PNT uses additional sources to augment GPS and prevent vulnerabilities. Its goal is to ensure that accurate positioning, navigation, and timing (PNT) is always available.
In this blog, we'll review GPS, its flaws, and other PNT systems (like the GNSS) and give you an overview of how assured PNT technology uses other systems to improve effectiveness.
What Is GPS?
The Global Positioning System (GPS) is a form of PNT technology. While the origins of GPS can be traced back to the 1950s, it wasn’t until the Persian Gulf War in 1991 that it made its first real battlefield debut, and it played a significant role in bringing about the rapid US victory.
GPS allows military forces to accurately pinpoint their location and plan their movements. The most important thing a soldier must maintain on the battlefield is situational awareness: being able to identify and understand what is happening around them and how it pertains to the mission. Over the past few decades, GPS has become an integral tool for helping US forces stay aware of their surroundings.
Over time, GPS technology has been adopted for commercial purposes and is now widely used by consumers for personal navigation. It also plays a vital role in aerospace and commercial aviation.
3 Problems with GPS Timing
As powerful as GPS timing is, there are three main problems associated with depending on it:
- Unreliability: GPS coverage isn’t always available and the signals can also be jammed.
- Accuracy: The accuracy of GPS signals can be problematic when dealing with vertical locations and varied elevation, a significant problem for unmanned aerial vehicles (UAVs).
- Over-reliance: The Department of Defense has been concerned about over-reliance on one form of technology. If GPS guidance becomes unavailable, soldiers and drones in the battlefield could be unable to navigate. If that awareness is lost, even for a minute, the consequences can be disastrous. GPS also plays an important role in targeting and guidance systems for missiles. As such, GPS has become both a strength and a vulnerability.
To overcome these problems, assured PNT (A-PNT) systems are being developed that can enhance the effectiveness of existing GPS and take advantage of alternatives to conventional GPS. A-PNT
Other PNT Systems: GPSS & GNSS
The term GPS applies primarily to the satellite navigation system developed by the United States. There are other PNT systems set up by other governments around the world, as well as a number of emerging technologies which will change the way PNT systems will operate in the future. Together, these systems are referred to as the Global PNT System of Systems, or GPSS.
The bedrock component of the GPSS is the Global Navigation Satellite System (GNSS). This term encompasses the four space-based navigation systems built by major governments for military purposes, which were later applied to civilian and commercial uses.
The GNSS includes GPS (United States), GLONASS (Russia), Beiduo (China), and Galileo (European Union). Regional PNTs, such as the Indian Regional Navigation Satellite System (IRNSS), may eventually be incorporated into the GNSS.
While GPS was the first, the United States certainly has no monopoly on advanced PNT solutions. But for security purposes, the US military could never depend on foreign PNT systems to upgrade its capabilities. As more and more nations develop their own navigation systems, different technologies are being developed to help the US military and others maintain a competitive advantage in PNT.
Augmenting the Existing System with GPS III
GPS III is a next-gen form of GPS being developed by the US Airforce and Lockheed-Martin. The system is based on new GPS Block III satellites, which include sophisticated anti-jamming features and allows accuracy up to 3x greater than that of GPS satellites currently in use. The first satellites for GPS III was launched in 2018.
3 Powerful Ways Assured PNT Improves Effectiveness
While GPS III and older GPS timing systems will continue to form the foundation of the GPSS for many years to come, newer technologies and separate terrestrial systems are being developed to augment the effectiveness of existing PNT systems.
1. Terrestrial PNT Systems: GBAS & GBPS
Ground-based augmentation systems (GBAS) are surface-based systems that enhance the abilities of space-based PNT over specific local geographical areas. At present, GBAS is used primarily in civilian air traffic applications and plays an important role in precision approach operations, such as airplane landings.
Ground-based PNT systems (GBPS) also play a key role in enhancing and strengthening PNT capabilities. GBPS are separate from the GNSS network, but they are time and geo-referenced to GNSS, and boost the overall accuracy and effectiveness of satellite PNT networks.
Terrestrial PNT systems do offer some advantages that space-based GPS doesn’t have. The RF spectrum is filled with signals intended for other purposes (mobile phone service, Wi-Fi, etc.) and these signals can be harnessed and repurposed for navigation uses. These signals are lower frequency and more difficult to jam than GPS signals. By using them for navigation, these ground-based systems can also act as an effective redundant PNT system, providing backup for areas where GPS signals are unavailable.
2. Hybrid & Autonomous PNT Systems (HAPS)
Hybrid and autonomous PNT systems (HAPS) offer a variety of ways to improve capabilities. Using other signals, as we just discussed above, is a good example of a hybrid PNT. Re-tasking cellular and other networks to cover gaps in GPS is just one of the many alternate-frequency PNT methods that can be developed to produce more accurate and consistent coverage.
The ultimate goal at some point in the future is to have completely autonomous PNT systems within devices or vehicles. These autonomous systems wouldn’t require positioning and timing from external sources, but would still offer PNT at the same or higher quality than existing systems.
While autonomous systems are many years away, newer technology like chip-scale atomic clocks (CSACS) and micro-electro-mechanical systems internal measurement units (MEMS-IMU) offer glimpses at how this might one day come to fruition. Feature mapping and visualization technology would also make this happen, but this would require a huge feature and terrain database built right into the PNT device, and would have to be regularly updated with real-time information.
3. GPS Disciplined Oscillators (GPSDO)
Precision timing is an important function of PNT systems. Critical infrastructure systems (like electrical grids, communication networks, and financial institutions) use GPS for synchronization, making them particularly vulnerable to GPS signal disruptions.
Using a GPS disciplined oscillator (GPSDO) and other assured PNT products provides resilient timing data and protects against signal jamming.
What's Next for Assured PNT?
Autonomous PNT may be a distant dream for now, but until then, GPS III, GBAS, and terrestrial hybrid systems offer promising alternatives to traditional GPS timing for enhancing situational awareness and achieving mission success.
At Bliley, we're proud to provide some of the most innovative GPS disciplined oscillator (GPSDO) technology for assured PNT solutions. As PNT technology continues to evolve and improve, we’ll continue to be on the cutting edge of RF and timing technology.