The Navstar Satellite, one the 20 GPS Satellites in the constellation

The US govt has advised that the GPS satellite constellation that run GPS units across the world is close to its life expectancy and no replacement satellites have been launched.

The launch of the replacement satellites have been plagued by delays for the last 18 months, with the first replacement scheduled for November this year.

This has caused some concern, raising questions of the reliability of the GPS network as more businesses and individuals rely on GPS navigation on a day to day basis.

This in the face of increased competition from the European Union (Gallelieo) and China (Compass)