Comparison of WAAS and GALHAS Reference Frames
WAAS[1] and Galileo High Accuracy Service (GALHAS)[2] use different terrestrial reference frames, but the frames are closely aligned. Both are Earth-centered, Earth-fixed reference systems that are maintained in alignment with the International Terrestrial Reference Frame (ITRF).
WAAS augments GPS and provides positions in the WGS84 reference frame used by GPS.[3] The current realization, WGS84 (G2296), is aligned with ITRF2020 at its reference epoch.
GALHAS uses the Galileo Terrestrial Reference Frame (GTRF). GTRF is an independent Galileo reference-frame realization established and maintained using the Galileo ground infrastructure. It is aligned with the applicable ITRF realization to ensure consistency with other global geodetic reference frames.
Although WAAS and GALHAS used different reference-frame realizations, the frames are closely aligned, and coordinate differences are less than 3 cm globally.[4}
References
Federal Aviation Administration, Satellite Navigation - Wide Area Augmentation System (WAAS)
European Union Agency for the Space Programme, Galileo High Accuracy Service (HAS)
Federal Aviation Administration, Satellite Navigation - GPS - How It Works