![Posted by a snivelling, miserable coward Anonymous Coward](/design_picker/fa16d26efb42e6ba1052f1d387470f643c5aa18d/graphics/icons/comment/anonymous_48.png)
its starting
To get crowded up there.
China will expand its home grown GPS rival Beidou by launching three global positioning satellites that it hopes will make it possible to have the service up and running in Asia Pacific by the end of the year. Beidou, which translates as “Big Dipper”, will be able to provide a high quality positioning, navigation and time …
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In the same manner as to how 'Beijing' is pronounced as 'Peking'.
<pedantry alert>
Beidou-1 has been in service since 2000 with 3 satellites, though it is classified as experimental.
Beidou-2, or Compass [BeiDou (Compass) Navigation Satellite System], is a new system, launched in 2011. This has 11 satellites in orbit now, with reported plans to extend this number to more than 70 to provide global coverage.
</pedantry alert>
GPS can be turned off a or a completely new coding system introduced any time that the USA DoD
feels like; with so much stuff depending on global navigational and time distribution it makes some
sense for other countries to have their own satnav.
However to me 4 systems (GPS, GLONASS, Beidou, Galileo) seems excessive.
If you have a GPS receiver that can simultaneously interpret the signals from more systems than the standard GPS then you are more likely to get an accurate fix due to the higher number of visible satellites.
However, it might affect processing time for the first fix as it calculates the geometries etc from different systems especially if you can't use AGPS.
Is it not a matter of them using conventional orbits, but having a fairly sparse constellation? Presumably any given point on the Earth's surface can see these satellites at one time or another, but only certain bits of the planet can actually guarantee sufficient coverage for a positioning system to work?
This makes more sense if the Beidou-1 satellites are involved too, given that they are in geostationary orbits.