as a major technological, economic and political challenge
system that both competes with and complements the American GPS system
future of GNSS: GALILEO + GPS
GNSS: A two-step approach
The future of GNSS: Galileo +
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
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.
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.
following figures show a simulation of the improvement in positioning accuracy (over 95% of
time) brought by the
use of EGNOS and GALILEO.
1: Mean horizontal positioning accuracy (95%) achieved through the GPS
constellation alone (in m) (1)
2: Mean horizontal positioning accuracy (95%) achieved through the GPS
constellation augmented by EGNOS (in m) (1)
3: Mean horizontal positioning accuracy (95%) achieved through the use
of GPS, EGNOS and GALILEO (in m) (2)
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.