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European Satellite Navigation System



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Europe's contribution to GNSS

GNSS Supervisory Authority

A myriad of possibilities
The programme
Programme phases, Technical features
Different actors in the programme
International co-operation
GALILEO - a global system
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|GALILEO as a major technological, economic and political challenge

|A system that both competes with and complements the American GPS system

|The future of GNSS: GALILEO + GPS

|Unquestionable economic viability

|European GNSS: A two-step approach

The future of GNSS: Galileo + GPS

The vast majority of satellite navigation applications are currently based on GPS performances, and great technological effort is spent to integrate satellite-derived information with a number of other techniques, in order to reach better positioning precision with improved reliability.

This scenario will significantly change in the short-term future. First, EGNOS, the European regional augmentation of GPS, will start to provide its services. Then, the global satellite navigation system (GNSS) infrastructure will double with the advent of GALILEO. The availability of two or more constellations, more than doubling the total number of available satellites in the sky, will enhance the quality of the services, increasing the number of potential users and applications.

GALILEO specific characteristics will bring themselves significant enhancements. Firstly, for urban areas or indoor applications, the design of the GALILEO signals will improve the availability of service (broadcast of dataless ranging channels, in addition to the classical pseudo random ranging codes). Secondly, the high-end professional market will also benefit from GALILEO signals characteristics. Three carriers phase measurements will be essential for the development of specific "TCAR" algorithms, leading to centimetre accuracy over large regions.

The following figures show a simulation of the improvement in positioning accuracy (over 95% of time) brought by the use of EGNOS and GALILEO.

Figure 1: Mean horizontal positioning accuracy (95%) achieved through the GPS constellation alone (in m) (1)

GNSS performance simulation: GPS alone; İESA

Figure 2:  Mean horizontal positioning accuracy (95%) achieved through the GPS constellation augmented by EGNOS (in m) (1)

GNSS performance simulation: GPS + EGNOS; İESA

Figure 3:  Mean horizontal positioning accuracy (95%) achieved through the use of GPS, EGNOS and GALILEO (in m) (2)

GNSS performance simulation: GPS + EGNOS, Galileo; İESA

(1) Simulated GPS performance is based on empiric performance parameters reported in "GPS Standard Positioning Service Performance Standard", Oct. 2001. Results include atmospheric and local effects.
(2) For this simulation the ranging performance of modernized GPS was assumed to be equal to GALILEO. Results include atmospheric and local effects.

last update: 10-02-2009