GNSS / GPS — Global Navigation Satellite System

What GNSS Is

GNSS is an umbrella term for constellations of satellites that broadcast timing and positioning signals, allowing a receiver on an aircraft to calculate its position, altitude, and time by measuring signals from multiple satellites simultaneously. GPS, developed and operated by the United States, was the first such system to reach global operational use and remains the most widely referenced, but it is only one of several GNSS constellations in service.

Other Constellations

Modern avionics receivers are often able to use signals from more than one of these constellations to improve accuracy and availability.

Augmentation Systems

Because raw satellite signals alone may not meet the accuracy and integrity needed for some phases of flight, aviation uses augmentation systems that improve or verify GNSS position:

Use in Aviation

GNSS underpins much of modern area navigation (RNAV) and required navigation performance (RNP) operations, allowing aircraft to fly precise routes and approaches that are not tied to the location of ground-based navigation aids such as VOR stations. It also supports satellite-based approach procedures that can provide vertical guidance similar to an ILS at airports without ground-based precision approach equipment, and it provides the position source used by systems such as ADS-B to broadcast an aircraft's location.

Regulatory Framework

International standards for GNSS use in civil aviation are set out in ICAO Annex 10, Volume I (Radio Navigation Aids), which defines the performance and integrity requirements that satellite navigation systems and their augmentations must meet to be used for specific types of air navigation operations.

Why It Matters

GNSS has reduced aviation's dependence on ground-based navigation infrastructure, enabled more direct and fuel-efficient routings, and made precision approach guidance available at many airports that previously lacked it.