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GPS, GNSS and WAAS
GPS is the U.S. satellite constellation within the broader Global Navigation Satellite System (GNSS) concept. WAAS augments GPS for aviation by improving accuracy, integrity and availability across its service area, enabling approved en route, terminal and approach operations when the aircraft equipment and procedure support them.
VOR, DME and ILS
VOR provides radio-based course information; DME provides slant-range distance from a ground station; and ILS provides precision lateral and vertical guidance for an instrument approach. These conventional systems remain important to National Airspace System resilience even as satellite-based navigation expands.
RNAV and RNP
Area Navigation (RNAV) allows aircraft to fly desired paths within the capability and coverage of the navigation infrastructure and onboard equipment. Required Navigation Performance (RNP) is a form of performance-based navigation that includes onboard navigation-performance monitoring and alerting requirements.
Performance-Based Navigation and resilience
FAA Navigation Programs identifies Performance-Based Navigation (PBN) as the preferred navigation direction for the NAS while also sustaining conventional navigation systems such as DME, VOR and ILS as part of a resilient backup structure.