Users of the Global Positioning System (GPS) will be happy to hear that the
government's deliberate degradation of the public GPS signals (known as
Selective Availability or "SA") will be permanently turned off as of
midnight tonight.

This will radically improve the accuracy, stability, and repeatability of
GPS location and altitude information, plus enable receipt of extremely
accurate time signals (accurate to within 40 nanoseconds(!) of UTC).

   http://www.igeb.gov/

G.