The GPS Accuracy Improvement Initiative

Stephen Malys, Margaret Larezos, Steven Gottschalk, Shawn Mobbs, Bryant Winn, William Feess, Michael Menn, Everett Swift, Michael Merrigan, William Mathon

Abstract:	The accuracy of the GPS Precise Positioning Service (PPS) has been well-characterized and routinely monitored by several DoD organizations since 1989 when the first Block II vehicles were launched. The measured 'Signal In Space' PPS performance levels have consistently been much better than the corresponding PPS 'specifications'. The annual GPS Performance Analysis Working Group (PAWG), sponsored by the 2nd Space Operations Squadron, has been a key forum within the DoD to share information and analysis regarding PPS accuracy and integrity issues. This forum has yielded significant advancements in the understanding of the error budget for PPS users and the performance of the Operational Control Segment (OCS). With this understanding, several opportunities for GPS improvement emerged which did not involve costly, long-term satellite modifications. In particular, several OCS improvements, collectively known as the GPS Accuracy Improvement Initiative (AII) obtained funding support within the DoD and are now in the process of being incorporated into the OCS. These improvements will be defined and described. Empirical test results will be presented which demonstrate the expected OCS performance levels once these OCS improvements are implemented. Note that these PPS accuracy improvements are being achieved without any system 'augmentations' or receiver modifications. Moreover, if/when Selective Availability is deactivated, these accuracy improvements will benefit many Standard Positioning Service (SPS) users as well.
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:	375 - 384
Cite this article:	Malys, Stephen, Larezos, Margaret, Gottschalk, Steven, Mobbs, Shawn, Winn, Bryant, Feess, William, Menn, Michael, Swift, Everett, Merrigan, Michael, Mathon, William, "The GPS Accuracy Improvement Initiative," 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. 375-384.
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