What will the Global Positioning System (GPS) look like in 10 years? This article discusses improvements to the overall GPS planned over the next decade and examines their impact on system performance for several applications. The Presidential Decision Directive (PDD) released in March 1996 states that selective availability (SA) will be turned off within 10 years. Efforts have been ongoing during the past year to place a second civilian frequency on the Block IIF satellites. In addition, a program known as the GPS Modernization Effort, or GPS-III, is underway to identify future enhancements to GPS. Finally, the Air Force is in the process of upgrading the Control Segment, which ...