Pseudolite Navigation for Rotorcraft and Ground-Based Vehicles

Darin W. Brekke, Derek Wilson, Andrew Brown

Abstract:	Pseudolites are used in a variety of situations, both to augment GPS-based navigation and to navigate in the absence of satellite based systems. In general, at least four transmitters are placed in the field, where each transmitter knows its location either through GPS or by using a pre-surveyed location. Each transmitter creates a set of proprietary navigation messages, which are then modulated by C/A and P code spreading signals before being broadcast on a predetermined frequency. The Boeing Company has performed initial testing of a pseudolite system developed by the Center for Remote Sensing, Inc. (CRS). Testing of the system occurred at the Winslow-Lindbergh Regional Airport in Winslow, AZ between November 13 and 17, 2007. The pseudolite receiver was installed in a Boeing MD530F helicopter, while the pseudolite transmitters were operated from ground level at locations pre-surveyed using a Novatel DGPS system. During the test we used four pseudolite transmitters broadcasting at 915 MHz. The transmitter clocks were synchronized using GPS for ease of testing, but will be self-synchronizing in a future iteration. Throughout the course of the week, four flight tests and three ground vehicle tests were completed. We discuss the effect of outside interference, system geometry and transmitter blockage by the terrain on system performance as well as Kalman filter and kinematic data processing approaches. The test illustrated the well known near-far problem where pseudolites in the far field become difficult to track when the receiver is in close proximity to another transmitting pseudolite, due to the widely differing received signal powers. We present example conditions that were encountered and methods for improving the cross-correlation properties, subsequently reducing the effect.
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:	2583 - 2594
Cite this article:	Brekke, Darin W., Wilson, Derek, Brown, Andrew, "Pseudolite Navigation for Rotorcraft and Ground-Based Vehicles," Proceedings of the 21st International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2008), Savannah, GA, September 2008, pp. 2583-2594.
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