The Benefits of Multi-constellation GNSS Augmentations

The future of the GNSS presents a variety of satellite navigation systems, starting from global GNSS systems as GPS / GLONASS / GALILEO, continuing with regional augmentations as SBAS and finishing with other local of systems such as GBAS which provide also navigation capabilities. It seems clear that many of those systems, if not all, will have to live together. The current paper provides a potential solution to the future GNSS word by presenting a multi-constellation concept which includes some of those navigation systems into a single concept taking profit of the advantages of the particular navigation systems and providing enhanced functionalities to the user needs. It will be shown that the multi-constellation system concept proposed integrates the global navigation satellite systems (GPS, GLONASS, GALILEO) in one common interface to make the user profit from enhanced capabilities. The objectives of the paper are to show the validity and benefits of such a multi-constellation concept and to analyze one of the preferred approaches for its incorporation, namely, by using the current Space Based Augmentation Systems (SBAS) infrastructure. SBAS systems allow the incorporation of all GNSS systems into a single interface already qualified and understandable to the user. They also provide a common integrity service provision for the various GNSS with different global integrity concepts. Current systems like EGNOS, WAAS or MSAS are clear precursors of the multi-constellation augmentation systems. The paper will analyze the benefits of the multi-constellation systems with respect to stand-alone GNSS systems in the first place and then the benefits of the SBAS approach for the implementation of the concept, with special attention to the net benefits at user level, namely: Improved performances, which may lead to enhanced service levels. Possibility of sole means Safety of Life navigation, since redundancy is implicit in the concept. As a practical example of the benefits of using the concept, a comparison of the current SBAS performances when augmenting the GPS constellation and the GPS and GLONASS constellations will be shown. The performances will be analyzed at user level (position solution performance in terms of Protection levels vs. Navigation Solution errors). Finally, it will be shown how the EGNOS system is already prepared for the introduction of the multi-constellation concept since the design already envisaged the augmentation of the GPS and GLONASS systems.