Improved Accuracy Estimation of Differential GPS: Theory and Results

Ahmed El-Rabbany and Alfred Kleusberg

Abstract:	High accuracy GPS differential positioning requires complete modelling of the GPS measurement errors. Generally, in GPS positioning, the mathematical model does not describe the observations perfectly. The remaining residual error components, if neglected, can lead to incorrect identification of the ambiguity parameters, particularly for medium and long baselines. Additionally, an overestimation of the accuracy of the resulting positions can be expected. One way of accounting for this remaining errors is to model them stochastically through the modification of the observations’ covariance matrix, using an empirical exponential model. Although this way yields a more realistic and fully populated covariance matrix, the inverse of this matrix is block diagonal. As a result, it can be implemented in either static or kinematic software without any large additional computational burden. In this paper, a modified least squares adjustment, including stochastic modelling of the remaining unmodelled errors, is developed. The results of this approach are compared with a commercially available software package.
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:	1303 - 1311
Cite this article:	El-Rabbany, Ahmed, Kleusberg, Alfred, "Improved Accuracy Estimation of Differential GPS: Theory and Results," 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. 1303-1311.
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