Optimal Rapid Static Positioning without Ambiguity Resolution

Lawrence R. Weill

Abstract:	The availability of 24-hour 3D GPS satellite coverage has made it possible to perform high-precision (centi- meter-level) static positioning at almost any time and any place on earth. Recent research has focused on how precise positioning can be achieved with a mini- mum amount of measurement time per position, lead- ing to the concept of “rapid-static” positioning, in which each position can be determined within minutes in- stead of appreciable portions of an hour. Historically, centimeter-level positioning has used car- rier-phase pseudoranges from a minimum of four sat- ellites to obtain a spatial lattice of possible precise positions. This requires additional information process- ing to resolve the position ambiguity. A major problem in rapid-static positioning is how to minimize the time required to collect the information needed for ambigu- ity resolution. Most current techniques treat the gen- eration of the lattice and the ambiguity resolution pro- cess as separate parts of the total solution. However, this results in a somewhat ad hoc approach of ques- tionable optimality. This paper shows that appropriate mathematical mod- eling of the high-accuracy positioning problem leads directly to a maximum likelihood solution or an opti- mum minimum mean-square error solution, neither of which requires ambiguity resolution. The approach is generic and can be applied regardless of the avail- able observables. This modeling assumes particular significance in view of the proposed encryption of the L2 P-code, which will reduce the effective signal-to- noise ratio of the L2 observables and stress the need for optimum processing in order to mimimize the time required for data collection. Results will be given for centimeter-level positioning using Ll and L2 phase information only, with suggestions for several other applications.
Published in:	Proceedings of the 6th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1993) September 22 - 24, 1993 Salt Palace Convention Center Salt Lake City, UT
Pages:	1069 - 1080
Cite this article:	Weill, Lawrence R., "Optimal Rapid Static Positioning without Ambiguity Resolution," Proceedings of the 6th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1993), Salt Lake City, UT, September 1993, pp. 1069-1080.
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