The Impact of Two Additional Civilian GPS Frequencies on Ambiguity Resolution Strategies

Shaowei Han, Chris Rizos

Abstract:	In Washington D.C., on 25 January 1999, Vice Presi-dent Al Gore announced that two new civil signals would be broadcast on future Block IIF GPS satel-lites. These new civilian signals, in combination with the L1 signal now available, will greatly en-hance the accuracy, reliability and robustness of ci-vilian GPS receivers, resulting in significantly im-proved system capabilities. This improved GPS performance will have a tremendous impact on navi-gation, positioning and timing services, but especially for high accuracy users engaged in surveying, geod-esy, atmospheric monitoring, etc., who make use of GPS carrier phase measurements. The mathematical process that converts ambiguous carrier phase meas-urements to unambiguous ranges of millimetre meas-urement precision, referred as Ambiguity Resolution (AR), is a critical requirement for high accuracy posi-tioning. AR techniques will be significantly impacted upon were two additional civilian frequencies to be-come available. In this paper, the AR strategies that take advantage of carrier phase measurements on the second and third signal frequencies will be discussed. The linear combination theory of carrier phase meas-urements will be extended, and following error analy-sis, several new combination measurements which have longer effective wavelength and less "noise" will be proposed. The new measurement combinations provide an opportunity to resolve double-differenced integer ambiguities using pseudo-range observations directly and with almost no baseline length constraints. Although the new signals are planned only for the Block IIF satellites, and the service will not be avail-able before 2005, the AR strategies described in this paper may be useful for planning purposes, particularly in regard to new applications that may be addressed by lower cost, multiple frequency GPS user technology in the early years of the 21st century.
Published in:	Proceedings of the 55th Annual Meeting of The Institute of Navigation (1999) June 27 - 30, 1999 Royal Sonesta Hotel Cambridge, MA
Pages:	315 - 321
Cite this article:	Han, Shaowei, Rizos, Chris, "The Impact of Two Additional Civilian GPS Frequencies on Ambiguity Resolution Strategies," Proceedings of the 55th Annual Meeting of The Institute of Navigation (1999), Cambridge, MA, June 1999, pp. 315-321.
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