Stochastic Assessment of the GPS Measurements for Precise Positioning

Jinling Wang

Abstract:	GPS measurements are commonly processed using the least-squares method. To obtain reliable least-squares estimates, the most critical task is to correctly specify mathematical and stochastic models used in data proc-essing. Mathematical modelling for GPS measurements is usually based on the so-called double differencing (DD) procedure, because it can cancel many systematic errors existing in GPS measurements, and the resultant DD measurements have a simplified mathematical model. In practice, however, stochastic modelling for GPS measurements is both a controversial topic and a difficult task to accomplish. In this paper, the importance of the stochastic model in GPS precise positioning is emphasised. Some aspects of mis-specification in the stochastic model for GPS meas-urements are analysed in detail. It is shown that the GPS measurements have a heteroscedastic, space- and time-correlated error structure, and that any mis-specification in the stochastic model may have a significant influence on ambiguity resolution and positioning results. After re-viewing the existing methods for the stochastic modeling of GPS measurements, a new method has been proposed, in which the aforementioned features of GPS errors are taken into account. Experimental results show that by us-ing the estimated stochastic models, reliability of the am-biguity resolution and baseline component estimates can be improved and the resulting accuracy of the baseline components becomes more realistic.
Published in:	Proceedings of the 11th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1998) September 15 - 18, 1998 Nashville, TN
Pages:	81 - 89
Cite this article:	Wang, Jinling, "Stochastic Assessment of the GPS Measurements for Precise Positioning," Proceedings of the 11th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1998), Nashville, TN, September 1998, pp. 81-89.
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