Characterizing the Effects of Ionospheric Divergence and Decorrelation on LAAS

Boris Pervan, Sam Pullen, John Andreacchi and Per Enge

Abstract:	In the Local Area Augmentation System (LAAS), as well as other local area DGPS systems which use single- frequency (L1) measurements only, differential ranging error due to the ionosphere is the result of two effects: the temporal divergence of the code and carrier and spatial decorrelation of delay. The effect of divergence is most significant when ground and air filter implementations are different; but even when filter implementations are identical, transient differential error can exist due to the different filter start times. The effect of spatial decorrelation is caused by variations in the delay between the ionospheric pierce points for the aircraft and the ground receiver. The effective separation between ground and aircraft antennas that defines pierce point separation is larger than the physical separation of the two antennas by an amount proportional to the filter time constant and the horizontal velocity of the aircraft. In this work, both ionospheric spatial decorrelation and divergence are analyzed with the goal of defining conditions for safe interoperability of ground and airborne systems.
Published in:	Proceedings of the 13th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2000) September 19 - 22, 2000 Salt Palace Convention Center Salt Lake City, UT
Pages:	653 - 661
Cite this article:	Pervan, Boris, Pullen, Sam, Andreacchi, John, Enge, Per, "Characterizing the Effects of Ionospheric Divergence and Decorrelation on LAAS," Proceedings of the 13th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2000), Salt Lake City, UT, September 2000, pp. 653-661.
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