The EGNOS SBAS Message Format Explained

EGNOS
Title	The EGNOS SBAS Message Format Explained
Author(s)	Daniel Porras Sánchez & César Pisonero Berges, GMV S.A., Spain.
Level	Basic
Year of Publication	2006

Introduction

This article contains a brief summary of EGNOS signal structure as described in RTCA MOPS DO-229-C “Minimum Operational Performance Standards for Global Positioning System/Wide Area Augmentation System airborne equipment” (particularly in its Appendix A “Signal characteristics and format”) just to allow the reader to have a first contact with the specification of the SiS that is applicable for Satellite Based Augmentation Systems (SBAS), in particular for the European EGNOS. It is worthwhile to highlight that the SBAS SiS specification is also detailed in the ICAO SARPs “Standards and Recommended Practices”, Appendix B “Detailed technical specifications for the Global Navigation Satellite System (GNSS)”. These two standards are nearly aligned in what regards to the SBAS SiS specification but still some differences remain. In fact, some topics such as the augmentation of GLONASS constellation by EGNOS is covered by the ICAO SARPs but not by the MOPS (WAAS does not provides augmentation to GLONASS satellites) and hence both MOPS and SARPs will be referenced along the following paragraphs. For a more precise knowledge of EGNOS SiS specification the reading of the aforementioned annex of MOPS is recommended. The purpose of the material presented hereafter is just to summarise the contents of MOPS Appendix A in order to make easier the first touch with it for those readers that are not familiarised with aviation equipment standards.