Twin IMU-HSGPS Integration for Pedestrian Navigation

Jared B. Bancroft, Gérard Lachapelle, M. Elizabeth Cannon, Mark G. Petovello

Abstract:	Pedestrian navigation includes locating individuals of interest, including citizens, police officers, fire fighters, search and rescue personnel, and cell phone users. GPS can typically provide users with this ability. In signal degraded areas such as in the indoors, underground parkades and urban canyons, GPS must be integrated with additional sensors to provide availability to users with a reasonable amount of accuracy. Fusing GPS with one inertial unit is a common integration strategy. Because pedestrian navigation systems are typically low cost, MEMS inertial units are used. To mitigate the large errors of these inertial units, they are placed on the foot facilitating zero velocity updates when the foot is at rest during the stance phase of the gait cycle. This paper discusses a Kalman filter that incorporates two inertial units. The twin filter contains two 27 state filters, with each block filter providing the position, velocity, attitude, and error states of a single IMU. With knowledge of the human gait cycle, relative updates between the positions of the IMUs are incorporated to further improve the accuracy of the system. The relative update can either use the distance between the feet (IMUs), or the three vector components. The filter’s performance is shown through data collected under trees, in bushes and indoor where multipath errors are extreme. The improvement when using a second IMU filter is shown relative to the single IMU case. When using the relative distance updates there is a 58 to 71% improvement when indoor with comparable performance outdoor, where the GPS only solution is sufficient. The correlation between each IMUs error states is also analyzed to show there are no significant correlations generated from the relative updates.
Published in:	Proceedings of the 21st International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2008) September 16 - 19, 2008 Savannah International Convention Center Savannah, GA
Pages:	1377 - 1387
Cite this article:	Bancroft, Jared B., Lachapelle, Gérard, Cannon, M. Elizabeth, Petovello, Mark G., "Twin IMU-HSGPS Integration for Pedestrian Navigation," Proceedings of the 21st International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2008), Savannah, GA, September 2008, pp. 1377-1387.
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