In today’s digital age, GPS (Global Positioning System) has become an integral part of our daily lives, guiding us through city streets, tracking packages, and even directing drones. But have you ever wondered about its vulnerabilities and how we might overcome them? GPS denied navigation.
The Fragility of GPS
While GPS is nothing short of revolutionary in terms of accuracy, ubiquity, and cost, it’s not without its flaws. It relies on direct line-of-sight to at least 4 satellites to get precise position on earth. GPS is one of the satellite-based radio navigation systems owned by the US, the European Union has Galileo, Russians have GLONASS and the Chinese have BaiDou. Although GPS works well outdoors in open skies, it doesn’t work well indoors or underwater. Another limitation stems from these systems being an RF (Radio Frequency) technology. This means that it’s susceptible to a range of vulnerabilities, particularly in conflict zones where it can be jammed or spoofed. Even as civilians, we’re already experiencing GPS outages which are creating dangerous situations in air control and interfering with fleet management and asset tracking.
Both commercial and military sectors heavily rely on GPS for positioning and navigation. However, this reliance can be a potential Achilles’ heel. GPS, in its standalone form, is fragile and vulnerable. A stronger and more resilient positioning and navigation methodology is critical.
The Impact on Warfighters
There’s absolutely no question that electronic warfare targeting Positioning Navigation and Timing (PNT) will play a major role in present and future conflicts. The recent events in Ukraine, where drones were lost to electronic warfare systems, underscore the vulnerabilities in our current systems. A war fighter’s missions will undoubtedly take them into terrain where blockage results in loss of signal. Even M-Code Military GPS is anticipated to experience blackout in building basements, underground tunnels or underwater. Alternate Positioning and Navigation technologies that don’t rely on GPS are needed to bridge such blackouts.
All tactical assets must have access to reliable, accurate PNT, including the dismounted Warfighter and small platform drones and vehicles that require small, low-power solutions. The Warfighter’s load can add up to more than 68 pounds and in a combat mission, that weight can be as much as 120 pounds. Any A-PNT solution for the dismounted soldier needs to be small Size, Weight and Power (low SWaP) to not add additional weight to the soldier.
Civilian Scenarios: GPS’s Limitations
It’s not just the military that faces challenges with GPS. Even in everyday civilian life, GPS has its limitations. Indoor environments, for instance, present a challenge for GPS signals. Buildings, urban canyons, and dense forests can occlude or distort GPS signals, leading to inaccuracies.
Moreover, critical infrastructure like airports is heavily reliant on GPS. Imagine the potential chaos and danger if a major airport lost its GPS signal, as Denver International Airport did for over 33 hours.
A Glimpse into Alternative Positioning and Navigation
Alternative Positioning and Navigation (APN) refers to methods and systems used to determine position and guide movement without relying on traditional Global Positioning System (GPS) signals. This becomes essential in environments where GPS signals are weak, jammed, or non-existent. Here are some common APN systems:
- Magnetometers: Measure Earth’s magnetic field to determine orientation.
- Acoustic Systems: Underwater navigation systems such as sonar that use sound waves.
- Dead Reckoning: Estimates position based on known starting position, time, speed, and course.
- inertial Navigation Systems (INS): Uses accelerometers and gyroscopes to estimate position, velocity, and orientation based on motion sensors.
The key is to combine multiple sensors and data sources (sensor fusion) to provide reliable and accurate positioning and navigation, especially in challenging environments where GPS might be unreliable or unavailable.
Radio beacons for positioning:
Ultra-wideband, low-energy Bluetooth beacons and Wi-Fi radio signals are being used to enable indoor position tracking. Precision position can be determined using RF signal strengths from beacons deployed in known locations. The denser the network of beacons, the more accurate the position, but creating a dense network of beacons will require more infrastructure setup and maintenance of the network over time. Although Google and Apple with their Android and iOS devices have been able to crowd source Wi-Fi and create Wi-Fi fingerprints for a great number of indoor venues, currently it would still not provide ubiquitous, accurate positioning indoors because the Wi-Fi signals are not always available and Wi-Fi device IDs can change from what is available in the data base.
Relying on Wi-Fi for location can provide a general indoor location of about 5m-20m depending on how close one is to the Wi-Fi access point, the number of people or objects present etc. Bluetooth beacons are small and require little power, hence small battery-operated beacons can be deployed easily. But Bluetooth is a short-range RF technology and to get precise location, one may need to deploy a beacon every 5 meters.
A hybrid solution where MEMS sensors (namely sensor fusion of gyroscopes, accelerometers and magnetic sensors) are used in conjunction with radio-based location technologies would provide more accurate location and would reduce the number of beacons deployed for location tracking. For motion MEMS sensors to be effective in this hybrid solution, minimizing the position error derived from the motion MEMS sensors will be key to the hybrid solution. Sophisticated sensor fusion algorithms are required to combine data from multiple sensors in order to accurately track motion, calculate accurate heading and determine orientation.
Dead Reckoning:
Unlike indoor navigation for pedestrians, on the battlefield and when GPS is jammed or spoofed, radio beacons such as Ultra-Wideband, Bluetooth or Wi-Fi cannot be used to provide location for the Warfighter. Dead reckoning using MEMS sensors seems to be the ideal, self-contained, small, low-power method for positioning and navigation.
Dead Reckoning methods use only inertial sensors (gyroscopes, accelerometers and magnetometers), to calculate one’s current position based on their movement from a known location. As discussed in the hybrid solution above, achieving high accuracy with only motion sensors, especially with low SWaP-C (Size, Weight, Power and Cost) sensors such as MEMS sensors remains a challenge.
AI/ML (Artificial Intelligence and Machine Learning) used with an adaptive filtering algorithm would be one way to tackle this challenge. One such solution is PNI’s FORT (Field Ops Remote Tracker) which is self-contained and relies only on magnetic, inertial, and pressure sensors in conjunction with its unique AI/ML algorithms to compute position by learning the human body kinetics to determine distance and direction of travel. Additionally, FORT’s accuracy and performance is greatly enhanced by a separate set of AI/ML models that correct for traditional sensor error sources, such as gyro bias drift, ambient magnetic anomalies and age-related performance degradations, all of which combine to make FORT’s performance stand head and shoulders above traditional approaches where a simple stride length and limited body movement detection is employed.
Figure-2 represents an example of gyroscope, accelerometer and magnetometer readings during walking.
Figure-3 is a block diagram of how the FORT processes these signals using AI/ML and Kalman filters to derive position when GPS is denied.
The Future of Navigation
While GPS has revolutionized how we navigate, it’s essential to acknowledge its vulnerabilities and develop alternatives. Whether it’s the challenges faced by Warfighters on the modern battlefield or the civilian need for accurate indoor positioning, innovative solutions like FORT represent the future of navigation.
In an ever-evolving digital landscape, one thing is clear: the quest for accurate, resilient, and efficient navigation is far from over. It’s an exciting field, and the future promises even more groundbreaking innovations.
