Indoor Localization Using Pedestrian Dead Reckoning Updated with RFID-Based Fiducials Samuel House Student Member, IEEE, Sean Connell, Ian Milligan, Daniel Austin Member, IEEE, Tamara L. Hayes Member, IEEE, and Patrick Chiang Member, IEEE, Abstract— We describe a low-cost wearable system that tracks the location of individuals indoors using commonly available inertial navigation sensors fused with radio fre- quency identification (RFID) tags placed around the smart environment. While conventional pedestrian dead reckoning (PDR) calculated with an inertial measurement unit (IMU) is susceptible to sensor drift inaccuracies, the proposed wearable prototype fuses the drift-sensitive IMU with a RFID tag reader. Passive RFID tags placed throughout the smart-building then act as fiducial markers that update the physical locations of each user, thereby correcting positional errors and sensor inaccuracy. Experimental measurements taken for a 55 m x 20 m 2D floor space indicate an over 1200% improvement in average error rate of the proposed RFID-fused system over dead reckoning alone. I. I NTRODUCTION There currently exist a wide variety of solutions to the indoor localization and tracking problem. Current solutions include computer vision camera systems [1], ultrasound [2] or passive infrared sensors (PIR) [3], wireless sensor networks (WSN) [4], and ultra-wideband (UWB) RF prop- agation [5]. Each of these has significant drawbacks, such as privacy concerns, multi-user error, poor resolution, and complex installation, respectively. One common solution for tracking the physical location of individuals is the use of personal dead reckoning (PDR). Unfortunately, unaided PDR exhibits significant sensor drift limitations [6], preventing it from being used effectively over any reasonable time period. Conventionally, multiple solutions can be combined in order to achieve better overall results. In this work, we combine PDR with passive RFID updating to provide additional fiducial information, resulting in significantly improved lo- calization accuracy. 1) Application of Indoor Localization to Medicine: The ability to track the locations of multiple individuals in an indoor environment has many relevant applications in medicine. For example, locating patients in their homes is important for providing context-aware services such as medication reminders [7]. Long term location, activity, and behavioral tracking of elderly patients at home enables them to live independently in their homes for a longer duration. Samuel House (e-mail: houses@engr.orst.edu), Sean Connell (e-mail: seanrobertconnell@gmail.com), Ian Milligan (e-mail: ianmllgn@gmail.com), and Patrick Chiang (e-mail: pchi- ang@eecs.oregonstate.edu) are with the School of Electrical Engineering and Computer Sciences, Oregon State University, Corvallis, OR, USA Daniel Austin (e-mail: austidan@bme.ogi.edu) and Tamara L. Hayes (e-mail: hayest@bme.ogi.edu) are with the Department of Biomedical Engineering, Oregon Health & Science University, Portland, OR, USA Fig. 1: Equipped prototype device adjacent to a passive RFID tag used as a fiducial waypoint. Aging in place is accomplished by allowing physicians to easily check on a patient’s physical activity levels [8] and evaluate patterns of early cognitive decline [9], [10]. Demen- tia patients at risk for wandering could have their location updated to care-givers, alerting as soon as the patients have left a pre-defined area. The precise location tracking of doctors, staff, and equipment within a medical complex could also be beneficial for time-critical emergencies that require immediate attention. 2) Personal Dead Reckoning: Dead reckoning devices operate by starting with a known position of the tracking device and then measuring inertial changes on the device, made possible using an inertial measurement unit (IMU). The IMU typically consists of at least a three-axis accelerometer as well as a three-axis gyroscope. In certain systems an IMU will also include a three-axis magnetometer to detect the 978-1-4244-4122-8/11/$26.00 ©2011 IEEE 7598 33rd Annual International Conference of the IEEE EMBS Boston, Massachusetts USA, August 30 - September 3, 2011