GNSS - Global Navigation Satellite System
GNSS (Global Navigation Satellite System)
GNSS is a service that enables high accuracy positioning with the help of satellite signals. Other criteria for GNSS signals are real time accuracy, continuity of signal and signal coverage as wide as possible.
Applications using GNSS signals are applied not only to road, rail, air and maritime transport but also in other areas such as telecommunications, geodesy, agriculture, mineral prospecting and mining or environmental Earth observation. Important is real time prediction of possible critical situations and natural disasters. Furthermore it is connected with civil security at all levels of a society.
The use of GNSS applications brings a strong impact for both economic and industrial development of every country. The market with these products and services is growing at an annual rate of 25%. It is expected that in 2020 will be operating for about 3 billion satellite navigation receivers. Satellite navigation is becoming an important part of everyday life, not just in cars and mobile phones, but also in energy distribution networks or time and banking services and many other fields.
The autonomous development of these systems in Europe will be guaranteed by the European Union's Galileo GNSS project.
(European Geostationary Navigation Overlay Service) is a European project that provides a form of differential correction signal for GPS. Corrections are provided for the territory of Europe and are important for eliminating errors, which are inevitably burdened with broadcast signals. Differential signal processing in GNSS receivers give more precision to positioning.
More about EGNOS you can find here
is planned as autonomous European Global Navigation Satellite System (GNSS), which should be similar to the U.S. Navstar GPS system and Russia's GLONASS. Construction is provided by the European Union (EU), represented by the European Commission (EC) and European Space Agency (ESA). Start the Galileo GNSS should be initially operational by the year 2010. According new plans it should be run till 2015th
More about Galileo you can find here
Global Positioning System (GPS) is at present the only one fully operating satellite navigation system. Users can measure their position, velocity and time, in passive, listen-only mode. GPS receivers collect signals from satellites in view.
Since the first satellite had been launched in 1978 the GPS begin indispensable in many segments like marine, terrestrial, or aeronautical applications. Furthermore, the ground control network also updates the satellite clock corrections and ephemerides as well as numerous other parameters essential to determining user position, velocity and time.
The basic satellite constellation consists of 24 satellites in low earth orbit that provide system ranging signals and navigation messages to ground segments. With this constellation, users with a clear view of the sky could have four satellites in view minimally. The user equipment receives signals from the satellite constellation and computes user PVT.
More info about GPS: www.gps.gov/
The Global Navigation Satellite System (GLONASS) satellite navigation system of the Russian Federation Governm ent. The system is analogy to the United States Global Positioning System (GPS) and both systems share the same principles in the data transmission and positioning methods. The first GLONASS satellites were launched into orbit in 1982. The original plans called for a completing the operational system by 1991. GLONASS was officially declared operational on September 24, 1993 by a decree of the President of the Russian Federation.The operational space segment of GLONASS consists of 21 satellites in 3 orbital planes, with 3 on-orbit spare ones. GLONASS is based on a constellation of active satellites which continuously transmit coded signals in two frequency bands, which can be received by users anywhere on the Earth's surface to identify their position and velocity in real time based on ranging measurements
More info about GLONASS:
Beidou Navigation Satellite System (Compass) is Chinese project of satellite navigation system. Compass is created as independent system and consists of two project generations, BeiDou 1 and BeiDou 2.
The first generation consists of 3 satellites and was known as BeiDou 1. It has been working since 2000. System provides services in China and adjacent countries. New project BeiDou 2 is still under construction and should be finished in 2020.
BeiDou 2 contains 35 satellites. Contrary to GPS or Compass, BeiDou uses satellites in geostationary orbit. The system uses 5 geostationary orbit satellites and 30 low orbit satellites. That will provide perfect signal all around the world. The accuracy of positioning will be 10 meters and will measure speed within range of 0,2m/s.
More info about BeiDou: http://www.beidou.gov.cn/
Indian Regional Navigational Satellite System is managed by Indian Space Research Organisation as a fully civilian system. It is under control of Indian government. India has got higt-tec experience from previous project Gagan therefore all parts are Indian origin. The project was launched in 2006 with the intention to compete the system in 2014. The system will consists totally of 7 satellites, 3 in geostationary orbit. The system is intended to provide positionong with accuracy better about 20 meters throughout India and within a region extending approximately 2,000 km around it.
More info about IRNSS: http://www.livemint.com/2007/09/05002237/India-to-build-a-constellation.html
Quasi-Zenith Satellite System is a proposed three-satellite regional time transfer system and enhancement for the Global Positioning System within Japan. QZSS is targeted at mobile applications to provide communication-based services and positioning information. QZSS provides accuracy measurement of location, velocity and time in cooperation with GPS. The system was launched in 2010 and is planned to be finished in 2013. The satellites would be placed in a periodic highly elliptical orbit. QZSS carry two types of space-borne atomic clocks: a hydrogen maser and a Rb atomic clock.
More info about QZSS: www.jaxa.jp/index_e.html