The U.S. Government provides two GPS augmentation systems. The Coast Guard operates the DGPS (Differential GPS) System for surface users. The FAA operates the Wide Area Augmentation System (WAAS) for the aviation users. Both are developed to international standards to promote seamless navigation around the world.

The DGPS System reached Full Operating Capability (FOC) on 15 March 1999. Specifics on DGPS, including status and technical background information are located at: http://www.navcen.uscg.gov/dgps/default.htm.

The (WAAS) is a critical component of the Federal Aviation Administration's strategic objective of a seamless satellite navigation system for civil aviation. On 11 July 2003, the FAA commissioned WAAS for instrument flight use. The Wide Area Augmentation System (WAAS) enhances the accuracy and reliability of the global positioning system (GPS) and transmits horizontal and vertical guidance capability. Real-time coverage a can be seen at: http://www.nstb.tc.faa.gov/vpl.html, with background information at: http://gps.faa.gov/FAQ/index.htm.

The FAA contracted with IBM Business Consulting Services to provide an independent analysis that estimates the benefits attributable to the Local Area Augmentation System (LAAS) beyond those provided by existing and planned navigation services. The results of this analysis will be used to support FAA, airlines and other industry stakeholders in their procurement and implementation decisions related to LAAS. A separate cost study is being conducted internally within the FAA.
Reports were delivered addressing “LAAS Safety and Social Benefits” in August 2004 and a “Benefits Analysis Report”, submitted in November 2004. The draft report is an update of the LAAS Efficiency, Safety, and Societal benefits. A description of the LAAS program is found at: http://gps.faa.gov/programs/index.htm.

An alternative to WAAS is GRAS (Ground-based Regional Augmentation System), which is being developed by AirServices Australia. The International Civil Aviation Organization (ICAO) is developing specifications for GRAS equipment. More information on the GRAS system can be found at the AirServices Australia Global Navigation Satellite Systems page.