Satellite Navigation current status
Tuesday, January 15th, 2008The situation with the Global Navigation Satellite Systems is not easy to predict so for now just explaining the current situation may illuminate what could happen in the near future.
We currently have only free signals. This is sometimes lost on regular users, the two flying constellations GPS and GLONASS offer services that are essentially free. I say essentially because obviously you have to buy a receiver, but there is a huge range of GNSS receivers so the good news is that there is a receiver out there for everyone! In any case the signals any receiver uses to calculate position and to ‘navigate’ are completely free.
The only difference between services in GPS and GLONASS is ‘open’ or ‘restricted’, the latter is only available to authorised users which can buy athorised receivers (military users, etc) so they will not be discussed further. In any case both services are free as the signals emmitted from the satellites can be received by any GNSS receiver.
For the future we assume that Galileo (Europe) and Compass (China) will also fly satellite constellations to provide navigation services. All of these systems should be interoperable but so far only GPS and Galileo have done the difficult work of properly coordinating the signals so as to provide interoperability.
Such interoperability is difficult at the moment since GPS and GLONASS do not interoperate very well. Of course the systems were designed during the Cold War so interoperability was never considered, but the decision of GLONASS to continue using FDMA instead of CDMA as GPS and Galileo use means that GLONASS could be relegated. The complexity of including FDMA and CDMA technology in a receiver would not be cost effective for the mass market. For high accuracy applications, where more signals means increased accuracy, as soon as an option exists most high-end receivers will use only the CDMA systems.
Therefore I predict that multiple system receivers (GPS, GLONASS, Galileo, Compass) will be very limited. On the other hand if GLONASS and Compass agree to interoperability terms with GPS and Galileo more 4-system receivers will be available in the future, otherwise GPS+Galileo receivers will dominate the high-end market and GLONASS receivers will become even more difficult to find!
Of course I could be wrong, what do you think?