How Long Must We Wait? Duration of GPS Observations for Long GPS Baselines

Gerald J. Creager and Robert C. Maggio

Abstract:	Objective: Observation time in long-baseline Global Positioning System (GPS) surveying has required campaigns of several weeks to adequately resolve a position, using traditional GPS long-baseline methods. Similarly, conventional GPS surveying requires considerably less time but may involve more receivers. The objective of this work was to establish the duration of observation necessary to achieve sub-decimeter positioning accuracy using long baseline techniques, with control data taken from concurrent observations made by the National Geodetic Survey’s (NGS) Continuously Operating Reference Stations (CORS). Results: Observation times as short as 2 hours were sufficient to fix the position of the Point Of Interest within a 0.04 m spherical probability of error. Results for 4-hour observations were more pronounced. Individual axis errors were determined to be 0.066 m (X), 0.38 m (Y) and 0.029 m (Z) for 2-hour observations. X error decreased as observation length increased, while Y and Z error were not statistically different. Conclusions: 1. Observation time may be decreased to approximately 6 hours for geodetic survey control positioning using appropriate long baseline technique and software tools. 2. Use of precise ephemeris is required for adequate solutions. 3. Use of well-established fiduciary control sites produces the best results. 4. Multiple observations are useful in establishing statistical significance of the resulting position, but the data suggest that a single, short observation with appropriate processing will yield a satisfactory result.
Published in:	Proceedings of the 54th Annual Meeting of The Institute of Navigation (1998) June 1 - 3, 1998 The Adams Mark Hotel Denver, CO
Pages:	467 - 475
Cite this article:	Creager, Gerald J., Maggio, Robert C., "How Long Must We Wait? Duration of GPS Observations for Long GPS Baselines," Proceedings of the 54th Annual Meeting of The Institute of Navigation (1998), Denver, CO, June 1998, pp. 467-475.
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