Global Navigation Satellite System (GNSS) refers to a constellation of satellites providing signals from space that transmit positioning and timing data to GNSS receivers. The receivers then use this data to determine position, altitude, time, and velocity. This performance can be improved by regional satellite-based augmentation systems (SBAS).

SBAS improves the accuracy and reliability of GPS information by correcting signal measurement errors and by providing information about the integrity of its signals.  SBAS is essential for applications where accuracy and integrity are critical. SBAS is a key enabler of Performance Based Navigation (PBN) usage for Automatic Dependent Surveillance-Broadcast (ADS-B) and Localizer Performance with Vertical Guidance (LPV).