MEMS-based INS Tracking of Personnel in a GPS-denied Environment

The ability to track and locate personnel is an important requirement for security, intelligence, military, and firstresponder applications. GPS receivers provide location in many situations, but these require information in situations where reception is poor, such as in buildings, urban canyons, and tunnels. Inertial navigation systems (INS) can work in these environments, but traditional, accurate INS systems are bulky and power-hungry. Microelectromechanical systems (MEMS) rate-gyro and accelerometer sensors meet the size, weight, and cost requirements for navigation systems worn by pedestrians, but their inherent drift is large enough to discourage use for personnel tracking. While these systems may be insufficient in application or accuracy, new methods and algorithms are making MEMS sensors very accurate for people-tracking. G-TraxTM is a software approach patented by Acceleron Technologies, LLC that significantly improves the performance of MEMS-based INS for determining the location of ambulatory personnel. G-Trax operates by placing a sensor package on the shoe of a pedestrian and uses proprietary software to integrate the flight of the foot during each stride. By integrating each stride independently, G-Trax transforms a cumulative integral with a consistent bias into a series of short integrals with a random zero-mean bias. This process produces very detailed 3-dimensional paths from MEMS-INS, with vertical and horizontal drift rates on the order of 100 m per hour. This is a factor of 10 better than navigationgrade INS systems.