THALES Navigation's LRK., an improved RTK solution for long baselines: technique, applications and field results

Pascal Lutz and Rene Gounon

Abstract:	THALES Navigation (formerly DSNP) has developed the LRKÆÊ (Long Range Kinematic) technique, an innovative L1/L2 RTK method that surpasses the performance of standard RTK positioning in terms of accuracy, coverage and availability. The LRK technique is the dualfrequency evolution of THALES Navigation's KART technique, the first commercial solution offering OTF (On The Fly) kinematic performance on L1 GPS receivers. This paper first outlines the general technical principles and particularities of LRK. Subsequently, it presents the results obtained for standard baselines of 0 to 10km, configuration where most RTK techniques usually offer similar levels of performance. It then focuses on the remarkable results achieved for long baselines up to 40km. Most RTK techniques do not work for such distances where the spatial decorrelation of errors is a major difficulty. The LRK technique relies on advanced algorithms reducing the effects of decorrelation and thus increasing the operational range. A long range UHF data link between station and mobiles supports the technique in the field. The performance of the technique in terms of accuracy, availability and reliability is thoroughly examined in the paper. Eventually, we describe how the high quality standards offered by the LRK technique match the end user needs, through the detailed description of significant practical field applications of LRK around the world. It is first shown how the LRK technique currently contributes to the achievement of the large scale Yangtze River Estuary Project. This ambitious venture aims at developing the Yangtze regional economic assets and includes the deepening of the Shanghai harbor access, the construction of two 50km long dikes and the development of several intersections. The GPS infrastructure consists of two reference stations broadcasting DGPS signals. THALES Navigation GPS receivers equip the work vessels operating over typical ranges of approximately 20km. The use of LRK dynamic positioning results in important productivity gains for all project tasks. The second example illustrates the benefits of LRK on an extended bathymetric survey performed on the Saint- Lawrence River by the Canadian Coast Guard. This survey aims at controlling the navigability of the river on a 300km long channel. In this context, LRK proves to be a cost effective alternative to traditional tide gauges, as it offers possibilities and performance never reached before.
Published in:	Proceedings of the 14th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2001) September 11 - 14, 2001 Salt Palace Convention Center Salt Lake City, UT
Pages:	1027 - 1038
Cite this article:	Lutz, Pascal, Gounon, Rene, "THALES Navigation's LRK., an improved RTK solution for long baselines: technique, applications and field results," Proceedings of the 14th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2001), Salt Lake City, UT, September 2001, pp. 1027-1038.
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