The advent of the Global Navigation Satellite System (GNSS) is having a profound impact on surveying, mapping, and navigation. Nowhere is this more evident than in civil aviation. In addition to the capability for cost effective precise positioning and navigation, there is now the possibility to conceive systems based on this technology that for the first time can provide automatic dependent surveillance (ADS), cockpit display of traffic information (CDTI), and collision avoidance (CA) functions at, and incremental cost to, the aircraft operator relative to the cost of a GNSS navigation capability alone. To accomplish the precise navigation and other functions a complementary data link is needed. Preferably this data link should enable the needed functionality, without the need for the government to create an extensive ground infrastructure or mandate artificially expensive airborne equipage. Instead, aircraft equipage should be driven by the system’s ability to deliver the desired user benefits with cost effective flexible avionics systems. This article specifically addresses a concept to accomplish these desired aviation functions, referred to here as the GNSS augmentation data link. © 1994 John Wiley & Sons, Inc.