"GPS-denied drones are used in various situations where standard drones have trouble functioning; think indoor environments, tight geological features like canyons, or even underground structures, caves, or dense vegetation."
With global GPS jamming and interference on the rise, the need for innovative strategies and technologies that help navigate GPS-denied environments is high. While it can be challenging to operate technology or human-based operations where GPS is unavailable, it is possible.
Some of the biggest challenges in developing solutions to navigate areas with little to no GPS connection are the number and variety of GPS-enabled devices.
Obviously, not every GPS device and receiver is the same, and considerations must be made regarding each device's size, weight, and function when developing applicable solutions for areas where GPS is unavailable.
Drones are of particular interest to the military, search and rescue teams, and remote explorers - mainly because they have proven useful in combat zones and rugged natural landscapes.
Drones can provide unmanned surveillance in high-risk areas, move quickly through spaces that would be difficult for humans to traverse, and they can even be equipped with weaponry to execute military objectives and support combat.
But the question is, can drones operate in areas where GPS is unavailable? The short answer is yes, although these differ from your average drones.
What Are GPS-Denied Drones?
Drones that can operate without using GPS signals for orientation, timing, and navigation are called ‘GPS-denied drones.’
GPS-denied drones are used in various situations where standard drones have trouble functioning; think indoor environments, tight geological features like canyons, or even underground structures, caves, and dense vegetation.
While the civilian demand for GPS-denied drones is on the rise, a more immediate need involves military operations, policing, remote exploration, and other scenarios in which humans might otherwise be put at risk.
Where Are GPS-Denied Drones Useful?
A drone that can operate without GPS is handy in countless scenarios. GPS-denied drones are most often used to avoid or reduce risk to humans in questionable scenarios, although they are also used for a variety of other reasons.
To expand on the safety and risk reduction issues, drones are also helpful in numerous scenarios because they can be equipped with various types of sensors and technologies that can help collect and analyze data.
For example, a drone equipped with LiDAR can sense cracks or breaks inside hazardous material tanks or similar infrastructure, potentially reducing operational costs, eliminating worker risk, and limiting service interruptions.
Below are more examples of situations where a GPS-denied drone might help reduce risk to humans, lower operational costs or liability, reduce the risk of data leaks, or simply offer a workaround to environments where GPS cannot function.
Combat Zones and Military Operations
Modern warfare is among the most valuable applications for GPS-denied drones. Human risk is high in any combat zone, and the technology used for military operations holds valuable data that are critical to mission success, human safety, and national security.
But how exactly do GPS-denied drones help navigate these landscapes and scenarios safely?
GPS jamming, RF interference, and other technology-based tactics have become commonplace in modern warfare, all of which can severely reduce the reliability of GPS-based technologies.
In a scenario where GPS jamming or other signal interference occurs, operating technologies that rely on GPS may be difficult, dangerous, or even impossible.
If GPS suddenly drops and the technology being used in a high-risk area stops working, it could limit mission success, put soldiers in danger, or allow military-grade equipment and technologies to fall into enemy hands.
In fact, with the right tactics, GPS-based drones can even be overpowered and tricked into navigating away from the original target or path - potentially to an enemy base or a location where others could retrieve the drone.
If military drones fall into enemy hands, the mission's historical data, technology, and objectives could all become enemy knowledge. However, if a drone operating without the use of GPS is used in the first place, the risk of data leaks is eliminated.
Search and Rescue Operations
Another highly applicable use case for GPS-denied drones is search and rescue operations.
According to DJI, a commercial drone technology company, more than 1,000 people in over 40 countries have been rescued with the support of DJI search and rescue drones—and that number is expected to increase as more adopt these technologies.
The company even has an interactive global map that highlights each rescue using the drones, which can be found HERE.
Image Source: DJI
One of the successful search and rescue missions found on the map involves a Michigan man who was hiking in the Angeles National Forest in Los Angeles, California. The man, who had been missing for several days, was found using a drone equipped with surveillance technology.
While this particular instance did not mention whether or not GPS was available in the area, it is the perfect example of how someone could be rescued with drone technology in areas without GPS reception.
Inspections
GPS-denied drones are highly valuable in numerous scenarios involving integrity and operational inspections. The industries with the biggest need for drone-supported inspections are those that involve a relatively high level of risk for human workers.
Maritime Inspections
The maritime industry relies on GPS-denied drones for ship and hull inspections, port and crane inspections, security and surveillance at docks and ports, search and rescue missions, and so much more.
Drones are so valuable for these scenarios because GPS is often unreliable inside a ship's metal hull and can even be semi-submerged when the ship is off-dock and out at sea.
Further, since most ships are massive and areas like engine rooms are deep into the ship's system, human inspections take a lot of time and can even be dangerous under certain conditions. Therefore, drones that can navigate a ship's infrastructure without GPS are highly valuable for the above reasons and more.
Mining Inspections
Mining operations are another example of how GPS-denied drones provide value and improve safety when there is some level of uncertainty. Since mining operations take place underground or deep into cave systems, GPS is almost always unavailable.
When mine operators want to survey, take samples, or collect data in an unexplored or potentially dangerous part of the mine, a GPS-denied drone can provide the necessary information without putting people or the operation at risk.
Critical Infrastructure Inspections
Critical infrastructure inspections are another valuable application for drones that work without GPS. Everything from dams to nuclear power plants to bridges and wind turbines can be effortlessly inspected from afar, even without reliable GPS.
Wind turbines are of particular interest due to their configuration. There is one rather famous photo of two mechanics caught at the top of a wind turbine when a fire broke out. The two men were stranded at the top with no way out, resulting in both of their untimely deaths.
If drones had been used for the inspections instead of humans, the two mechanics would likely still be alive today. While not all wind turbines are in areas without available GPS, there are many scenarios where this could be the case - mainly those turbines situated offshore in the ocean.
How Do GPS-Denied Drones Work?
Rather than using GPS signals for timing, stability, and navigation, GPS-denied drones rely on internal and external sensors for unmanned operations. While each GPS-denied drone may differ depending on the manufacturer, dimensions, and uses, there are some commonalities between most.
Cameras and Optical Sensors
Cameras and optical sensors send through basic imagery from the drone's perspective, which is used to track visual features in the surrounding environment. From there, the video is analyzed to estimate the drone’s movements relative to stationary objects, which can be highly effective in places with clear and distinct stationary landmarks.
LiDAR Sensors (Light Detection and Ranging)
LiDAR systems typically operate using pulsing lasers to measure the distance between the drone or device and surrounding objects. The collection of pulses creates a 3D image of the environment, which, once mapped, can be used to help navigate the drone and keep it oriented correctly in space.
Radar Sensors
Radar sensors detect objects in space and map the surrounding landscape accordingly, which, together with other aspects of the GPS-denied drone, help keep the drone balanced, oriented, and moving without colliding with anything in the local environment.
Ultrasonic Sensors
Ultrasonic sensors use sound waves to measure the distance between the drone and other objects. Once emitted from the sensors, the sound waves travel until they reach any object in the surrounding space. The estimated distance using sound waves is paired with other sensor data to calculate the actual distance and keep the drone from hitting objects, as well as maintaining altitude and orientation in the air.
Intertial Navigation Systems (INS)
Inertial Navigation Systems use accelerometers and gyroscopes to orient drones and track their movements through space. These data are integrated over time to estimate a drone’s position and velocity, as well as the device’s rotation, which can help navigate and orient a device in GPS-denied environments.
While these tools are helpful, they often result in errors when estimating position over extended periods, so it is important to use the data with other inputs derived from this list to ensure position and timing accuracy.
The Future of GPS-Denied Drones
It’s no secret that GPS-based technologies have drawbacks, many of which have become painfully clear over the past decade. Of course, we are mainly talking about GPS interference, which can come in the form of GPS jamming, RF interference, or spoofing.
Due to the influx of things like GNSS jamming and spoofing technologies, there is a big push throughout industries (aviation, maritime, and UAVs) to reduce the general reliance on GPS for operations.
According to the FAA, one of its future requirements will be the ability to navigate or operate technologies without the use of GPS. The FAA is already urging pilots to carefully monitor their performance equipment while under operation and to go under analog control rather than relying on GPS whenever GPS jamming or spoofing is suspected.
As tools and technologies like AI, ML, and sensor fusion continue to evolve, so will our ability to navigate GPS-denied environments. The good news is that while not all of the technologies and strategies used to navigate in places without GPS work as stand-alone solutions, they can be paired with other innovations and technologies to expand their impact.
With that said, we can all expect to see a rise in technologies that will far exceed our past limitations, pushing us toward a future that does not rely so heavily on GPS-based navigation.
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