Global Navigation Satellite System Overview
GNSS stands for Global Navigation Satellite Systems. The Global Position System (NAVSTAR GPS) is the best known of these satellite navigation systems. Global Navigation Satellite System (GNSS) is the standard generic term for satellite navigation systems that provide autonomous geo-spatial positioning with global coverage. A GNSS allows small electronic receivers to determine their location (longitude, latitude, and height) to within a few metres using the signals as transmitted by the GNSS satellites. In the same process the receivers also calculate the precise time of the signal reception and as such GNSS receivers can be used as highly accurate clocks.
Currently, the United States NAVSTAR Global Positioning System
(GPS) is the only fully operational GNSS. The Russian GLONASS is a GNSS
in the process of being restored to full operation. The European
Union's Galileo positioning system is a next generation GNSS in the
initial deployment phase. China has indicated it may expand its
regional Beidou (also called COMPASS) navigation system into a global
system. India's IRNSS, is also a next generation GNSS. However, its
status and future is unclear as India seems to have entered into a
close cooperation with the Russions on the GLONASS system.
In 1978 the United States launched its first satellites of the Navstar Global Position System, more commonly know as GPS. Today, GPS is the primary satellite navigation system world wide for determining position and time information. Since the very beginning of GPS there has been a large interest in developing technologies to exploit the system. Furhtermore, the scientific, commercial, and even private use of satellite-based navigation and timing information has grown enormously. The applications of satellite based positioning and timing are manyfold. They included maritime and aircraft navigation, fleet management, private car navigation, communications system time synchronization, and also high-accuracy (few mm level) geo-surveying.
GPS is very popular and its accuracy can support a large number of navigation and timing applications. However, it is generally recognized that the GPS system lacks the accuracy, integrity, and availability to satisfy the more critical transport and safety related applications. This has led to the development of techniques to augment the basic GPS service. Furthermore, there are significant concerns regarding the fact that GPS is a military service and that it is controlled by one single country. These concerns, coupled with concerns regarding the long-term and uninterruped availability of the system and possible reduced capabilities of the system in case of national and/or military security interest, have led to the study and development of augmentation systems but also of completely new global navigation satellite systems.
To secure the availability of satellite navigation systems it will be important to have a system under civil and international ownership and control. However, since international collaboration is not that simple these considerations have led to the paralel development of different satellite navigation systems. Besides the GPS system the Russians started very early with their own system, GLONASS, which is also military. Europe has, finally in 2003, decided to build its own civil global navigation satellite system which will be called Galileo. In the last couple of years the Chinese have very rapidly started the development of their system called Beidou, also referred to as Compass. Also other countries are looking into building their own GNSS infrastructure, e.g., Japan and India.
PosiTim GNSS Overview
At PosiTim we have excellent expertise in GNSS which
we currently use to provide the information contained on these pages.
In the near future we also hope to be able to do some GNSS
On our PosiTim GNSS Overview pages we give a general overview of the principles of how GNSS systems work. On the Navigation Systems pages we give an overview of the currently existing and planned GNSS satellite systems like, GPS, GLONASS, Galileo, and Beidou/Compass. On the Augmentations pages we discuss systems which enhance the performance of the GNSS systems, like WAAS, EGNOS, MSAS, but also including real time, and near-real-time, differential GNSS services. The Applications pages give an overview of applications and services in which GNSS plays a central role. The BLOG provides access to our GNSS web log on which you will find more information regarding the GNSS systems discussed on these pages.
Note that we are currently
building up our GNSS web pages. So not all links are "active" yet. In
case any of the links has brought you (back) to this page the page you
wanted to look at does not yet excist. We appologise for that! We hope
to have our pages ready as soon as humanly posible.