Satellite navigation
Satnav systems operate independently of any telephonic or internet reception, though these technologies can enhance the usefulness of the positioning information generated.
A team, led by Harold L Jury of Pan Am Aerospace Division in Florida from 1970 to 1973, found solutions and/or corrections for many error sources.
[citation needed] Using real-time data and recursive estimation, the systematic and residual errors were narrowed down to accuracy sufficient for navigation.
Originally, the US Naval Observatory (USNO) continuously observed the precise orbits of these satellites.
The orbital ephemeris is transmitted in a data message that is superimposed on a code that serves as a timing reference.
The basic computation thus attempts to find the shortest directed line tangent to four oblate spherical shells centred on four satellites.
Satellite navigation receivers reduce errors by using combinations of signals from multiple satellites and multiple correlators, and then using techniques such as Kalman filtering to combine the noisy, partial, and constantly changing data into a single estimate for position, time, and velocity.
Satellite navigation also allows forces to be directed and to locate themselves more easily, reducing the fog of war.
The range of application of satellite navigation in the future is enormous, including both the public and private sectors across numerous market segments such as science, transport, agriculture, insurance, energy, etc.
Operational since 1978 and globally available since 1994, GPS is the world's most utilized satellite navigation system.
First launch year: 1982 The formerly Soviet, and now Russian, Global'naya Navigatsionnaya Sputnikovaya Sistema, (GLObal NAvigation Satellite System or GLONASS), is a space-based satellite navigation system that provides a civilian radionavigation-satellite service and is also used by the Russian Aerospace Defence Forces.
First launch year: 2000 BeiDou started as the now-decommissioned Beidou-1, an Asia-Pacific local network on the geostationary orbits.
[16] At an estimated cost of €10 billion,[17] the system of 30 MEO satellites was originally scheduled to be operational in 2010.
The receivers will be able to combine the signals from both Galileo and GPS satellites to greatly increase the accuracy.
It is intended to provide an all-weather absolute position accuracy of better than 7.6 metres (25 ft) throughout India and within a region extending approximately 1,500 km (930 mi) around it.
[29] The first two generations of China's BeiDou navigation system were designed to provide regional coverage.
Currently, it supplements GPS by reporting on the reliability and accuracy of their positioning data and sending out corrections.
27 operational + 3 spares Currently: 26 in orbit24 operational 2 inactive6 to be launched[35] Using multiple GNSS systems for user positioning increases the number of visible satellites, improves precise point positioning (PPP) and shortens the average convergence time.
[3] Doppler Orbitography and Radio-positioning Integrated by Satellite (DORIS) is a French precision navigation system.
Unlike other GNSS systems, it is based on static emitting stations around the world, the receivers being on satellites, in order to precisely determine their orbital position.
The coordinates are sent back to the transceiver unit where they can be read using AT commands or a graphical user interface.
[47] RNSS is regarded as a safety-of-life service and an essential part of navigation which must be protected from interferences.
Aeronautical radionavigation-satellite (ARNSS) is – according to Article 1.47 of the International Telecommunication Union's (ITU) Radio Regulations (RR)[48] – defined as «A radionavigation service in which earth stations are located on board aircraft.» Maritime radionavigation-satellite service (MRNSS) is – according to Article 1.45 of the International Telecommunication Union's (ITU) Radio Regulations (RR)[49] – defined as «A radionavigation-satellite service in which earth stations are located on board ships.» ITU Radio Regulations (article 1) classifies radiocommunication services as: The allocation of radio frequencies is provided according to Article 5 of the ITU Radio Regulations (edition 2012).
