Session Versus Single-Baseline GPS Processing

Michael R. Craymer and Norman Beck

Abstract:	Many software packages used for static GPS surveying are based only on baseline processing, where the mathematical correlations between simultaneously observed baselines are neglected. Moreover, all possible baselines, including socalled “trivial” baselines that are linear combinations of others, am often combined together in a 3D adjustment. To date there have been no known conclusive tests that permit an objective evaluation of the effect of ignoring these correlations and including trivial baselines. Realizing that many GPS users will have access to only baseline procming software, we investigate processing strategies that could be used to provide results equivalent to session processing. In principle, session solutions which account for all mathematical correlations are preferable since they also allow for orbit improvement, spatial modeling of atmospheric effects and enable easier ambiguity resolution. On the other hand, baseline processing with ail trivial baselines significantly distorts the formal accuracies by artificiaby increasing the redundancy in the model, resulting in overly optimistic covariance matrices. It is shown that using all possible baseline solutions (with the covariance matrix scaled by n/2, where n is the number of simultaneously observing receivers) is mathematically equivalent to session processing with all correlations only under certain conditions. This equivalence is verified empirically using simulated and real data However, the conditions under which this equivalence holds are difficult to achieve in practice.
Published in:	Proceedings of the 5th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1992) September 16 - 18, 1992 Albuquerque, NM
Pages:	995 - 1004
Cite this article:	Craymer, Michael R., Beck, Norman, "Session Versus Single-Baseline GPS Processing," Proceedings of the 5th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1992), Albuquerque, NM, September 1992, pp. 995-1004.
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