Real-Time CDGPS Initialization for Land Vehicles Using a Single Pseudolite

Michael O’Connor, Thomas Bell, Gabriel Elkaim, and Bradford Parkinson

Abstract:	Real-time centimeter-level positioning using carrier phase differential GPS (CDGPS) has countless applications in land vehicles. Automobiles, aircraft on taxiways, construction equipment, and farm tractors are just a few types of the vehicles that could benefit from a reliable, accurate sensor producing high-bandwidth position measurements. Most CDGPS systems currently available are initialized using integer search techniques, techniques which have some fundamental limitations. A second initialization technique created for precision aircraft landing uses two or more GPS pseudo-satellite (“pseudolite”) transmitters for CDGPS initialization. In this work, the use of a single pseudolite for CDGPS initialization was explored in simulation and demonstrated experimentally on a farm tractor. Three aspects in particular were explored: the relationship between vehicle path geometry and navigation system accuracy, the mathematics of incorporating a ground constraint into the carrier phase equations, and the benefits and difficulties of using a dipole antenna to transmit the GPS signal to standard patch antennas.
Published in:	Proceedings of the 1997 National Technical Meeting of The Institute of Navigation January 14 - 16, 1997 Loews Santa Monica Hotel Santa Monica, CA
Pages:	717 - 724
Cite this article:	O’Connor, Michael, Bell, Thomas, Elkaim, Gabriel, Parkinson, Bradford, "Real-Time CDGPS Initialization for Land Vehicles Using a Single Pseudolite," Proceedings of the 1997 National Technical Meeting of The Institute of Navigation, Santa Monica, CA, January 1997, pp. 717-724.
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