The Wide Area Augmentation System (WAAS) Signal Specification

A. J. Van Dierendonck, Per Enge

Abstract:	The RTCA, Inc. Special Committce SC-159 has been tasked with defining the Minimum Operational Perform- ance Standards (MOPS) for Aviation Navigation Equip- ment Using GPS Augmented with Other Sys- tems/Equipment. One of these augmentations is that of the Wide Area Augmentation System (WAAS). The WAAS augments GPS with geostationary satellites (GEOs) that broadcast GPS signal integrity information and wide area differential corrections, derived in a ground network. The GEOs broadcast this information on GPS-like signals that can also be used as additional ranging sources, further augmenting the GPS constella- tion. Working Group #2 of SC-159 has been tasked with gen- erating a MOPS using the WAAS as the augmentation to GPS. This MOPS is different from those being generated by the other working groups in that it includes perform- ance standards for the precision landing phase-of-flight. One of the purposes of the WAAS is to provide differen- tial corrections to meet Category I precision landing ac- curacy requirements. A major task of the Working Group has been the generation of the WAAS Signal Specification, which includes the definition of the GE0 signal structure, the data format and the data contents. This task is completed and the specification has been, for the most part, adopted by the FAA. The FAA is using a version of the specification for their procurement of the WAAS. This signal specification has evolved over the last three years. This paper is a presentation of the WAAS signal struc- ture, the data format, the data contents along with the rationale for its development. Differences, although only recommended differences, with the FAA’s version will be noted.
Published in:	Proceedings of the 7th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1994) September 20 - 23, 1994 Salt Palace Convention Center Salt Lake City, UT
Pages:	985 - 994
Cite this article:	Van Dierendonck, A. J., Enge, Per, "The Wide Area Augmentation System (WAAS) Signal Specification," Proceedings of the 7th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1994), Salt Lake City, UT, September 1994, pp. 985-994.
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