The term Airborne Based Augmentation System (ABAS) covers both AAIM (Aircraft Autonomous Integrity Monitoring), and RAIM (Receiver Autonomous Integrity Monitoring).

AAIM is a method of monitoring the integrity of the GNSS position data, using information from on board sensors such as barometric altitude data, IRS position data and potentially even conventional nav-aid autotuning (VOR, DME position data). This can allow our aircraft to notice any suspicious GNSS position data and notify the pilots that it may not be correct.

RAIM is a system which uses extra GNSS satellites to effectively verify the working order of the usual 4 required for a 3D position fix. 1 extra satellite (5 in total) can give the ability to notice when a fault occurs (Fault Detection). 2 extra satellites (6 in total) gives the ability to detect and identify which satellite is faulty (Fault Detection and Exclusion).