What is ARAIM or Advanced RAIM?

RAIM (Receiver Autonomous Integrity Monitoring) is a technology that is used to determine the integrity of the GPS signals that are being received at any given time. RAIM has been capable of supporting horizontal aircraft navigation using GPS for decades and has proven to be a very useful tool. Now, as more global navigation satellite systems (GNSS) become available, the potential for Advanced RAIM (ARAIM) to support vertical guidance for aircraft using multiple constellations has become an area of great interest. ARAIM employs redundant, dual-frequency measurements from multiple GNSS constellations, to support vertical aircraft guidance. Also, ARAIM supports LPV-200 worldwide with minimal ground infrastructure requirements, thus making it a potential candidate for both the integrity providers and receiver manufacturers for the provision of integrity for vertical guidance.

Why ARAIM?

Advanced RAIM extends RAIM to other constellations beyond GPS. It enables the use of other GNSS constellations to provide better levels of performance than RAIM with GPS alone. As, RAIM only supports lateral/horizontal navigation, Advanced RAIM (ARAIM) techniques were recommended to include vertical guidance. This inclusion provides better levels of performance of horizontal guidance than RAIM. Also, when sufficient satellites have dual-frequency (L1-L5) signals, ARAIM can enable aviation safety of life operations, including approaches with vertical guidance.

ARAIM has the potential to provide coverage to users that are outside SBAS coverage areas or in remote locations where ground-based augmentation systems (GBAS) are not available. Furthermore, the implementation of ARAIM requires almost no additional infrastructure; it relies solely on GNSS measurements, which are processed entirely at the user receiver. 

The increased number of satellites in view will certainly improve the user-satellite geometry, while the use of dual-frequency signals will allow the receivers to remove the first-order ionospheric delay, which is the major source of pseudorange error. These redundant dual-frequency pseudoranges will extend the use of satellite navigation to support worldwide vertical guidance of aviation users.

Click here to read more information on ARAIM in this published paper, entitled, New Advanced RAIM with Improved Availability for Detecting Constellation-wide Faults, Using Two Independent Constellations.