The Wide Area Augmentation System (WAAS) is a safety-critical system. It enables the Global Positioning System (GPS) to meet air navigation performance requirements for enroute, terminal, non-precision approach and precision approach phases of flight.

WAAS expands the number of satellite ranging signals to significantly increase GPS navigation system availability. It monitors GPS performance and provides timely warnings to users when unsafe conditions exist to improve integrity. It also substantially increases the accuracy of the GPS and enables precision RNP RNAV operations.

WAAS was officially commissioned by the FAA for public aviation use on July 10, 2003. It enables WAAS enhanced navigation services and procedures that include LNAV, LNAV/VNAV, and LPV (APV-I) approaches with vertical guidance. In addition, WAAS has been running 24 hours a day, seven days a week since early 2000, providing high integrity navigation signals for non-aviation users such as boaters, precision agriculture, crop dusters, surveyors, vehicle dispatchers and location services, cell phone 911 emergency services, hikers, and other personal recreation uses.