GPS Tracking Technology

From the UK's GPSTraining (www.gpstraining.co.uk) email update:

"Did you know that the U.S. government is placing a high priority on developing a more reliable real-time position tracking technology whose signals won’t disappear in blind spots

and can’t be jammed after finding that GPS can be unreliable in certain situations?  DARPA an agency of the US Department of Defence recently said it was researching “radically” new technologies to deliver more advanced position- and navigation-tracking systems that are more reliable and accurate than the current GPS System.  Don’t expect developments any time soon but remember that it was the US military that developed the GPS System; our guess is that this is a serious project."