A Novel Approach to Improving the Accuracy of Real-Time Ionospheric Delay Estimation Using GPS

Lao-Sheng Lin

Abstract:	When transmitted radio waves, such as the GPS signals, propagate through the ionosphere, they experience an extra time delay. The ionospheric delay can be eliminated (to the first order) through a linear combination of L1 and L2 observations made using measurements from dual-frequency GPS receivers. Taking advantage of this physical dispersive principle, it is possible to use one or more dual-frequency GPS receivers to determine a model of the ionospheric delays over a region of interest, and if implemented in real-time can support single-frequency GPS positioning and navigation applications. There are, however, several factors which may affect the accuracy of real-time ionospheric delay estimation using dual-frequency receivers. Two of the dominant effects are the subject of investigation here. One of them is the multipath effect on pseudo-range measurements, and the other is “failure” in the carrier phase observations, such as the occurrence of cycle slips. In order to improve the real-time ionospheric delay estimation accuracy and efficiency, a novel approach to overcoming these problems is presented here. The proposed approach involves two processes: (1) applying a “multipath template” procedure to mitigate the pseudo-range multipath, and (2) applying a statistical test to the state difference estimated from robust and conventional Kalman filters in order to detect (and repair) carrier phase failure. Test results confirm that the multipath effects on pseudo-ranges are effectively mitigated and that the carrier phase cycle slips are successfully detected and repaired.
Published in:	Proceedings of the 10th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1997) September 16 - 19, 1997 Kansas City, MO
Pages:	169 - 178
Cite this article:	Lin, Lao-Sheng, "A Novel Approach to Improving the Accuracy of Real-Time Ionospheric Delay Estimation Using GPS," Proceedings of the 10th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1997), Kansas City, MO, September 1997, pp. 169-178.
Full Paper:	ION Members/Non-Members: 1 Download Credit Sign In