Visibility and Geometry of Combined Constellations GPS and Galileo

Jacek Januszewski

Abstract:	As nowadays (November 2006) the American GPS system is fully operational and European Galileo will be operational most likely in 2010, the slogan GPS and Galileo will be actual in near future. Therefore as the observer’s position will be obtained from both systems, the advantages and disadvantages of different combined constellations of these systems must be taken into account. The distributions (in per cent) of the numbers of satellites visible by the observer at different latitudes situated in open areas for different masking elevation angles (Hmin) for two the most probable combined constellations GPS and Galileo systems (Const I - 29 GPS satellites + 27 Galileo satellites, Const II - 29 GPS + 30 Galileo) are presented in this paper. In addition to it the detailed distributions for the observer at latitudes 50-60O (latitude latitudes and different Hmin, alternatively for GPS system & Galileo system in open & restricted areas, were presented by the author in [1], [2], respectively, in the European Navigation Conference in Graz 2003 [3], in Rotterdam 2004 [4] and in Munchen 2005 [6] and in ION The National Technical Meeting 2005 in San Diego [5]. In these simulations the calculations were made for GPS constellations and different Galileo constellations separately in order to compare both systems. These calculations were made for so-called baseline constellations; for GPS there were 4 or 5 satellites in one of Poland) for other constellations & elevation angles are demonstrated. For the first constellation the difference between the number of GPS satellites visible by the observer above horizon (Hmin = 0O) at latitudes 50-60O and the number of Galileo satellites visible by the same observer at the same time can be equal each number between plus 6 and minus 7. For the second constellation and Hmin = 25O this difference can be equal each number between plus 5 and minus 5. For Const I & Hmin = 0O and for Const II & Hmin = 25O the total number of GPS and Galileo satellites visible by the observer changes between 16 & 29 and between 6 & 19, respectively. These facts must be taken into account in the production and the determination of the number of channels of GPS–Galileo integrated receivers. All calculations, based on reference ellipsoid WGS–84, were made by using author's simulating program.
Published in:	Proceedings of the 2007 National Technical Meeting of The Institute of Navigation January 22 - 24, 2007 The Catamaran Resort Hotel San Diego, CA
Pages:	252 - 262
Cite this article:	Januszewski, Jacek, "Visibility and Geometry of Combined Constellations GPS and Galileo," Proceedings of the 2007 National Technical Meeting of The Institute of Navigation, San Diego, CA, January 2007, pp. 252-262.
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