All four are Global Navigation System Satellite (GNSS), in other words satellite positioning systems. They are used to find out its position on Earth from a reception terminal (a smartphone, a computer or other). Obviously, this type of service is particularly important at the present time, notably for aviation, maritime transport, but also for rescue and emergency services.
It is to no longer be dependent on the United States that several countries have set out to develop their own service. A way for Russia, China and the European Union to distance themselves from the pioneer of satellite location services, the American GPS.
To locate an individual, an airplane or a ship at sea, satellite positioning systems calculate the geographic position of the geometric intersection of several satellite signals. In other words, GNSS is based on the trilateration of the electromagnetic signals emitted by the satellites and their synchronization. Depending on the number of signals received - at least 4 are needed - the position is more or less precise.
Everyone has their "little" system
The first satellite positioning system project was launched in the United States in the early 1970s, but it was not until the mid-1990s that GPS (Global Positioning System) became fully operational. It is the result of military research and its use was reserved for the American army until 2000 when the GPS was opened to the public.
In parallel with the GPS, it is the Russian counterpart which was born. The Glonass project was launched in the 1980s, in the heart of the Cold War, and became operational in 1996. Its development encountered many problems, notably the lack of funding, which slowed down the project.
On the European side, the desire to develop its own GPS system was born at the dawn of the 2000s. However, it was not until 2016 that the project became operational.
Finally, the Chinese GPS project was launched in the mid-1980s. The first satellites were sent into orbit in 2000. It has been operational since 2003 and continues to be developed. Beidou should be fully operational this year.
Different capacities
Each of the systems is available in a public version and a “professional” version, used by professionals, notably the railways, emergency services, the army, etc. What sets them apart is the precision with which the system locates a device.
Inevitably, with a system implemented in the early 1990s, the American GPS presents an older technology than the newer systems, although it has been updated. In fact, the American public GPS offers a precise location at 4 to 5 meters and this can vary greatly depending on whether a good signal is received or not.
At the moment and even if it is not yet completely finished, it is Galileo which offers the greatest precision. It is a few centimeters. Obviously, this precision is only available for special services. For the general public, the accuracy of the location via Galileo is around a meter, in the best conditions.
As far as Glonass is concerned, its accuracy is today close to that of GPS. By way of comparison, in the early 2000s, the accuracy of the Glonass was around 30 meters. Many elements explained this margin of error, in particular the poor settings of the on-board atomic clocks.
Finally, Chinese GNSS offers an accuracy of less than 5 meters in Eurasia and +/- 10 meters in the rest of the world.
Numerous satellites
Beyond the modernity of satellites, the number of spacecraft sent into orbit also plays a huge role in the accuracy of the signal. The American pioneer only has 24 operational operational satellites and 4 reserve satellites which take over in the event of a malfunction of an operational device.
The Russian Global Navigation Satellite System (GNSS) has 26 orbiting satellites of which 24 are titular. With regard to Galileo, the objective is to place 30 satellites around the Earth, including 24 operational and 6 in reserve. Currently there are 26.
Finally, Beidou has 35. They are placed in 3 different orbits; geostationary, medium terrestrial and inclined geosynchronous.
Because yes, if the number of satellites plays on the signal, the orbit on which they are positioned also plays. Russian spacecraft are the closest to Earth and focus on Russia. American devices are in second position and Galileo satellites are the most distant from Earth.
A military vocation
As we said, the GPS was born for military use. This is also the case for Glonass and Beidou. Only Galileo is a public initiative, developed by the European Union.
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- Geolocation
- Galileo
- Russia
- Gps
- China
- United States
- EU
- Europe
- Satellite
- High-Tech