Where are we with satellite-based navigation and positioning systems?

摘要

In the last year we have seen a continuing build-up of momentum towards the eventual deployment of the European Galileo satellite-based navigation and positioning system. There have been a number of financial and political hurdles to overcome, and a number more will have to be tackled before the system becomes fully operational. Two test satellites are planned for launch in 2005 with the primary function of securing the frequencies to be used by Galileo. Although the frequencies themselves are decided, the actual signal structure on these various frequencies is still in the melting pot. We are getting closer to having a definition of these signals - at which point receiver design can really get moving.