Combined GPS-Galileo positioning for Location Based Services in urban environment

Position determination is one of the key-elements of Location Based Services (LBS). One popular approach to positioning for LBS is using a Global Navigation Satellite System (GNSS). With such a system, three-dimensional positioning is available anywhere on, and above the Earth, in principle without any local or regional infrastructure. On the other hand, as satellite based radio positioning relies on relatively weak signals, indoor positioning is a hard job, in particular without any aids. Also urban environment can pose a serious challenge to satellite based radio positioning. In this contribution, the availability of today’s GPS positioning is analyzed using a three-dimensional model of the town of Delft in the Netherlands. This contribution starts with a demonstration of the range of position accuracy using today’s Global Positioning System (GPS). Different modes of kinematic and real-time positioning will be shown using a trial with a boat on the Schie-canal between Delft and Rotterdam. Standard GPS single point positioning with a simple handheld receiver offers 5-10 meter accuracy. With corrective information received from a geostationary satellite, the European Geostationary Navigation Overlay Service (EGNOS) comes down to the 1-meter level. Global Differential GPS, with a dual-frequency user receiver, reaches decimeter level accuracy, but currently only after a considerable initialization period. Although accuracy is one of the main issues regarding GNSS, it is clear that availability is another point of concern with the LBS context. If you cannot rely on your positioning device all the time, the usage of the service will be limited. Therefore it is of great importance that within five years from now, the European Galileo system is expected to get into orbit, next to the US GPS. Doubling the satellite constellation is expected to be beneficial to position availability. The impact of the advent of Galileo on this aspect is analyzed as well, using the same urban environment.