Testing of a Multi-Reference GPS Station Network for Precise 3D Positioning in the St. Lawrence Seaway

Luiz Paulo Fortes, Gérard Lachapelle, M. Elizabeth Cannon, Guy Marceau, Sam Ryan, Sun Wee, John Raquet

Abstract:	The St. Lawrence Seaway is a constricted, shallow navigable waterway where three-dimensional positioning at the cm-accuracy level would be desirable for maintenance tasks such as hydrographic mapping after spring ice break-up and 3D navigation at the cm-level to increase capacity. Differential GPS has the capability to provide cm-level 3D ship trajectories as long as the carrier phase ambiguities are resolved on-the-fly (OTF) to integer values. Existing methods are based on the use of a single fixed reference station located in the vicinity of the moving platform. The maximum distance allowed between the reference station and the ship is generally limited to about 10-30 km due to atmospheric and orbital errors. The number of reference stations can be increased to extend the coverage, however, the installation and maintenance of such stations and their data transmission links is operationally complex and expensive. The optimal use of existing stations established for other purposes is therefore of utmost importance to maximize cost effectiveness. In the St. Lawrence River, several marine radiobeacons equipped with high quality dual-frequency receivers cover a critical portion of the waterway. A novel method, which uses all available reference stations to generate regional code and carrier phase corrections in an optimal manner, is tested herein. One of the major advantages of this method is to increase the coverage under which successful OTF integer ambiguity resolution is possible. In order to test the feasibility of this method, code and carrier phase data were acquired on the radiobeacons as well as on a hydrographic surveying vessel in November, 1998. Another data collection was carried out in August, 1999, in order to verify the performance under different network geometric conditions. Results and analysis using the regional code and carrier phase corrections are presented and compared to the single reference receiver approach to demonstrate the improvements achieved by this method.
Published in:	Proceedings of the 12th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1999) September 14 - 17, 1999 Nashville, TN
Pages:	1259 - 1270
Cite this article:	Fortes, Luiz Paulo, Lachapelle, Gérard, Cannon, M. Elizabeth, Marceau, Guy, Ryan, Sam, Wee, Sun, Raquet, John, "Testing of a Multi-Reference GPS Station Network for Precise 3D Positioning in the St. Lawrence Seaway," Proceedings of the 12th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1999), Nashville, TN, September 1999, pp. 1259-1270.
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