The road to the signals Galileo has today as a baseline has been tedious and long, but has followed a logic from the start. From the very beginning, one of the main challenges that Galileo set for itself was to offer three wide band signals, satisfying the requirements of mass market and pushing the potential performance to its natural limits. The historical Agreement of 2004 between the US and the EC impacted the initially planned signals but has intensified the cooperation between Galileo and GPS. The final touch to the Galileo signal plan was achieved in 2006 when the Working Group on GPS and Galileo Compatibility and Interoperability finally agreed upon the great interest in a new modulation for the E1/L1 frequency, namely the Multiplex Binary Offset Carrier. Galileo has thus accomplished the original objective of providing three wide band signals for the civilian GNSS community.
This paper reviews the status of satellite navigation (as per 11 May 2020)—without claim for completeness—and discusses the various global navigation satellite systems, regional satellite navigation systems and satellite-based augmentation systems. Problems and challenges for delivering nowadays a safe and reliable navigation are discussed. New opportunities, perspectives and megatrends of satellite navigation are outlined. Some remarks are closing this paper emphasizing the great value of satellite navigation at present and in future.
Satellite Navigation has become a keystone for the development of Europe and its citizens. It is then essential to provide adequate educational programmes so to ensure a prepared workforce for the GNSS sector in Europe. In this context, ESA has launched a complete Satellite Navigation Educational program, called EDUNAV, aiming at providing upto-date GNSS based educational material and educational tools. The GNSS-Lab (gLAB) Educational Software Tool is part of this ESA EDUNAV initiative.
gLAB, developed under ESA Contract by the research group of Astronomy and Geomatics (gAGE) from the Universitat Politecnica de Catalunya (UPC), is an interactive educational multipurpose package to process and analyse GNSS data. gLAB performs precise modeling of GNSS observables (pseudorange and carrier phase) at the centimetre level, allowing both standalone GPS positioning and PPP. Every single error contributor may be assessed independently, which, in turn, provides a major educational benefit. gLAB is adapted to a variety of standard formats like RINEX-3.00, SP3, ANTEX and SINEX files, among others. Moreover, functionality is also included for GPS, Galileo and GLONASS, allowing performing some data analysis with real multi-constellation data.The gLAB software tool is quite flexible, able to run under Linux and Windows operating systems and is provided free of charge by ESA to universities and GNSS professionals.
Within the next future, the advent of Galileo, GPS modernization and of the GNSS augmentation systems, will lead to a rapid development of GNSS receiver technologies. It is expected that the improved accuracy performance will extend the use of satellite positioning and navigation to applications where present systems do not fulfill user integrity requirements and do not allow the receiver certification.In this scenario a central role is played by the integrity receiver capability. In fact a large part of users is carrying out applications in which an error in might represent an excessive risk, in particular when human lives are involved. For these applications, the system capability of protecting the user against system failure is of primary importance. The main example is given by aeronautical applications where at present the fulfillment of integrity requirements during approaches of type CAT I (and higher) has still to be reached.In this context, it is essential for the user to take advantage of Receiver Autonomous Integrity Monitoring (RAIM) techniques. In fact, although regional integrity is provided by space-based augmentation systems (SBAS) like EGNOS, WAAS and MSAS and global integrity will be transmitted by the European Galileo satellite navigation system in the near future, RAIM is the only technique able to monitor receiver local errors. Since it is located at the end of the integrity processing chain, its role is essential in the integrity determination process.It is also highlighted that present RAIM techniques have limitations, which in particular jeopardize the possibility to certificate satellite navigation receiver as sole or stand alone positioning platform in aeronautical applications. The main limitation is represented by the fact that all present RAIM techniques protect users only against one single failure affecting a particular satellite range measurement. Multiple failure events are usually assumed to have a very low probability of occurrence. But since in safety of life applications the continuity and availability requirements in terms of probability of missed detection are very strict, the multiple failure events need more attention and cannot be disregarded anymore by RAIM techniques.This paper presents an investigation on present RAIM technique and their performance with respect to multiple failures. Furthermore it presents a technique able to overcome the present integrity monitoring limitations and to protect the user receiver in case of multiple failures.
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