The Design and Performance of GPS Phase II User Equipment Navigation Software

G. Krishnamurti, S. A. Harshbarger, T. N. Smith

Abstract:	This paper describes the design of Navigation Software implemented for the family of GPS l:Jser Equipment developed by Rockwell-Collins for the USAF NAVSTAR GPS Phase liB Program. The family consists of one channel, two channel and five channel sets. The goal of the software design was to maximize commonality of software functions across the entire family while minimizing the modifications required for new applications. The one channel set is specifically targeted to the manpack/vehicular application, while the two and five channel sets are generic sets adaptable to many applications. Adaptation to a particular host vehicle requires modification of only an outer layer of software modules, leaving the core software - including the navigation function intact. The one channel navigation function centers around an 8-state Kalman filter processing measurements from one satellite every second. The navigation function of the two and five channel sets is common to both families at the object code level and centers around a 12-state Kalman filter. This filter runs at 1Hz in one of three basic modes, in conjunction with high iteration rate processing of host vehicle sensor data that enables the maintenance of a navigation solution close to real time. This solution is used to aid satellite signal acquisition and tracking and may be used by host vehicle subsystems. This paper also discusses certain special features such as adaptive process noise, under-determined operation, and handling of INS resets. It concludes with a sample of performance data from in-plant and field tests.
Published in:	Proceedings of the 1985 National Technical Meeting of The Institute of Navigation January 15 - 17, 1985 San Diego, CA
Pages:	101 - 109
Cite this article:	Krishnamurti, G., Harshbarger, S. A., Smith, T. N., "The Design and Performance of GPS Phase II User Equipment Navigation Software," Proceedings of the 1985 National Technical Meeting of The Institute of Navigation, San Diego, CA, January 1985, pp. 101-109.
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