Augmentation satellites constellations, a simulation on EGNOS and QZSS for Europe coverage

The European Geostationary Navigation Overlay Service (EGNOS) is a satellite based augmentation system and a joint program of the European Space Agency (ESA), the European Commission (EC) and Eurocontrol. EGNOS supplements the US GPS and probably in future the Russian GLONASS, improving the positioning performances in Europe. EGNOS consists of a network of ground stations and three geostationary satellites transmitting GPS-like signals, differential corrections and integrity information for ECAC region; EGNOS will achieve operational capability in the first half of 2008 and soon after it will start its services as a precursor to Galileo. The Quasi - Zenith Satellite System (QZSS) is a joint program of the Japan Aerospace Exploration Agency and a consortium of Japanese industries. It would be operative in 2009 and, used in addition to GPS will provide an improvement in the positioning accuracy over Japan. QZSS consists of several ground stations and three geosynchronous satellites, with identical Highly Elliptical Orbits (HEO) and coinciding 8-shaped ground traces. QZSS constellation is planned to have always at least one satellite positioned near zenith over Japan, so users can receive positioning signals without obstructions in urban and mountainous areas. So QZSS will be really useful to enhance GPS performance in areas highly urbanized, characterized by the so called "urban canyon", where a lot of GPS signals are blocked by buildings and they can't be used by GPS receivers, so there are often bad satellite observation geometries with no precise or even impossible positioning. Such a coverage improvement could be obtained in every place of earth changing the reference meridian of QZSS ground tracks. In this study a simulation software has been developed in MATLAB® environment in order to analyze the coverage of positioning constellations; it is analyzed the number of useful visible satellites and above all their distribution in the sky, evaluating the DOP parameters. So by the developed software the constellation, consisting of all GPS satellites and three geostationary EGNOS satellites, is analyzed to verify the coverage improvement in Europe. Then the quantitative and qualitative features (visibility and DOP parameters) of this constellation will be compared with GPS ones. Moreover by means of this simulation, the GPS satellites, and QZSS constellations translated on Europe, is also applied to check the coverage improvement. The analysis is made with different mask angles and by a 3D-model of an urban canyon.