The system we know as GPS (Global Positioning System) is being modernised in a programme lasting until around 2015. This will mean that GPS derived raw positions will become increasingly more accurate and quicker to determine. Even so, it is no longer the only eye in the sky.
The European satellite navigation system Galileo will consist of 30 satellites and will provide a range of free and subscription services. The first operational Galileo satellites were launched in October 2011, with up to 14 more being launched over the next three or four years. The Russian GLONASS navigation system has been underfunded for many years but now looks to be becoming stronger in the coming years.
There are techniques available currently which will develop in the future that enable very fast acquisition (sub-second) of the GPS satellites after first power on through sending the receiver information about where to look for the satellites via a mobile phone (Assisted GPS or AGPS). It is also possible to obtain a position, quite inaccurate currently, indoors. High Sensitivity GPS works by detecting the very low strength GPS signals that permeate indoors – typically 20dB and 30dB lower.
If an inertial system is coupled with the GPS receiver, positioning is possible in places where the receiver cannot see the four satellites it needs (in tunnels, for example). Map-matching techniques, meanwhile, use the intelligence within digital maps to force a user's track onto the right road – this is useful in vehicle-tracking applications.