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Pervasive Personal Navigation Bridges the GPS Gap October 2008
A soldier uses a global positioning system (GPS) unit to find a bombed-out building where enemy combatants are seeking shelter. He enters the building and descends to the lower level. Suddenly, his GPS can't access a signal in the confined space and cuts out. In this GPS-denied environment, the soldier, his commander, and squad members can't determine his position. GPS outages like this impede reconnaissance and increase vulnerability to attack. But body-worn sensors being developed by MITRE researchers offer a promising solution to this technology gap. Senior principal signal processing engineer Thom Bronez, with co-principal investigator Perry Hamlyn, is leading the research to develop miniature, light-weight sensors—cubes roughly the size of a quarter on each side—to enable personnel on foot to precisely track their own location and the location of fellow soldiers. In a combat environment, both safety and mission success rely on such situational awareness. The same is true for civilian search and rescue efforts. "We can use this technology to help soldiers, police, firefighters, and so on—who generally have only a radio and sometimes GPS—to more effectively do their jobs," says Bronez. "These are people who have their boots on the ground. They're getting shot at or rescuing someone from a burning building." The research team aims to make this innovative technology, known as Pervasive Personal Navigation (PPN), functional in a wearable form within the next 18 months. Going Where GPS Cannot While GPS is the current means of navigation, it's limited in accuracy and is blocked in many environments, such as natural and urban canyons, under heavy foliage, inside buildings, and underground. These are the very places where today's warfighters and first responders must go. When GPS is available, it's an insufficient tool for certain types of reconnaissance, such as mapping the interior of a building. "Let's say you walked 17 feet. Our objective system would say you walked 16.8 feet, a one-percent relative accuracy, whereas GPS might say you walked 27 feet, an accuracy of a few meters," explains Bronez. Commercially available dead-reckoning units (navigating with a magnetic compass, an accelerometer-based pedometer, and a barometric altimeter) achieve only about five to 10 percent accuracy in published results. Errors of this scale pose threats to the safety and security of the nation's armed services. "Clearly, a radically new approach offering much better accuracy is urgently needed." Providing novel foot-to-foot measurements, wearable sensors have the potential to provide up to 99 percent relative position accuracy (or one-percent error) during GPS loss. Integrating the system with available GPS enhances accuracy even further. Meeting a Real-Time Need MITRE's sponsors are well aware of the need for more powerful personal navigation technology. The U.S. Army Training and Doctrine Command identified "near real-time combat ID geo-spatial data" for soldiers in the field as an immediate need in 2006. The same year, the U.S. Office of Naval Research issued a Broad Agency Announcement for "navigation in a GPS-denied environment" to address this problem for Marines. In response, the Defense Advanced Research Projects Agency launched a portable Inertial Measurement Unit program, and the Department of Homeland Security started the Advanced 3D Locator program.
Bronez thought about how to solve this problem and help MITRE's sponsors better equip warfighters. He used his previous research on wireless relays for maintaining communications in difficult locations as a starting point. "I kept thinking, if you can help individuals talk with each other, can you do something else to help them figure out where they are relative to each other?" That first question led to a series of questions: Is there something that people can carry or wear that is small, doesn't weigh much, and goes easy on batteries, that will allow them to navigate their position? Bronez and Hamlyn want to develop innovative methods and equipment that personnel on foot can use for precise position determination and navigation. "MITRE does this research so we can truly understand the problem and help the government make a good acquisition decision," Bronez says. Shrinking to Fit Developing a useful PPN system requires much more than working sensors, however. For instance, there's the issue of size. Firefighters and soldiers are already weighed down with pounds of equipment and protective gear, "so you cannot develop something that requires a car battery as a power source," explains Bronez. "Having something wearable, light-weight, low-powered, and extremely accurate is essential." Minimal processing time is as important as portability. In contrast to signal processing on large ships or technology used by surveyors, warfighters and emergency responders need instant location information—they have neither the time nor the option to stop, look down, and figure out their position or the position of other squad members. To meet this need for instant position data, Bronez and his research team ultimately aim to display the information in a heads-up screen or via synthetic speech (for instance, "25 meters to exit point."). Wanted: Tough But Accurate Sensors "We've proven in lab experiments—and at technology demonstrations—that we can get one-millimeter-level raw accuracy out of some of the sensors. But error accumulates, and the system needs to be portable," says Bronez. "So there are many nuances and a lot of challenges to make this work." One of the challenges is that the sensors must be ruggedized (hardened) to withstand harsh environments and rough terrain. Unfortunately, rugged sensors are 100 times less sensitive. In their circuit design, Bronez and his team must determine what could be developed in a small package and still provide an accurate measurement even when ruggedized. Another challenge is time. First responders and warfighters need PPN technology now. Bronez and his team plan to test a portable data collection system in a real environment and to follow up with testing in conjunction with a sponsor. "We might even put it on the boots of a soldier and have him walk around," he says. "This will provide us with sensor data. We'll then analyze the navigation results, since that data won't be immediately available." But that's soon to change. In 2009, Bronez hopes to have a real-time, wearable prototype system ready—one that provides results instantaneously. "I'm excited about the possibility of bringing a capability to people that they don't have now. That's what really drives me." —by Karina H. Wright Related Information Articles and News
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