One Meter Positioning on a Ship with PLGR

James R. Clynch

Abstract:	The errors in a real time PPS system are dominated by the broadcast ephemeris and clock errors and the local multipath errors. Ships are one of the worst cases for the latter. An experiment was carried out to isolate these errors and to test methods of utilizing reference station data to improve the positions. The experiment consisted of three GPS receivers on the ship on one antenna and an identical setup on land. Each site had two Precision Lightweight GPS Receivers (PLGRs) in PPS mode and an Ashtech Z12. The Ashtechs were used to provide a truth trajectory. The ship track came within 1.5 km of the reference site to help establish integers for a kinematic truth trajectory. An integer freed trajectory out to over 100 km was established. The ship was at sea for 3 days collecting one second data. This was followed by a day of data at dockside. The accuracy of the PLGR PPS positions were evaluated in several ways. In addition to the standalone solutions both at sea and land the use of the land solution errors to update the ship solution was investigated. To enhance the value of this technique, a new data logger/controller was written that could direct the PLGRs to specific tracking scenarios. Direct solutions of differential positions were computed using raw data. The statistics of the position errors as well as separation of the errors into various causes are presented.
Published in:	Proceedings of the 10th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1997) September 16 - 19, 1997 Kansas City, MO
Pages:	973 - 980
Cite this article:	Clynch, James R., "One Meter Positioning on a Ship with PLGR," Proceedings of the 10th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1997), Kansas City, MO, September 1997, pp. 973-980.
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