Galileo High Accuracy Service Reference User Algorithm Formulation and Verification

The Galileo High Accuracy Service (HAS) is an open access service broadcasting Precise Point Positioning (PPP) corrections through the data component (E6-B) of the Galileo E6-B/C signal and by the internet. The implementation of the Galileo HAS will be staggered in two main phases, indicated as Phase 1 and Phase 2. In Phase 1 (also referred to as Initial Service) precise orbit and clock corrections for Galileo I/NAV and GPS LNAV navigation messages and satellite biases are being transmitted. Phase 2 will provide the HAS Full Service where, in addition to the above corrections, atmospheric corrections, authentication and other features will also be broadcast. On the 24th of January 2023, Galileo started to offer the Galileo HAS Initial Service, an anticipation of further fundamental technological advancements in Galileo's signals and infrastructures. HAS extends not only the consolidated Open Service (OS) capabilities by providing more precise Global Navigation Satellite Systems (GNSSs) satellite orbits, clock errors and biases but also the perimeter of the system support, providing reference algorithms, guidelines, and standards to be implemented by the users to achieve the service goals. The scope of this contribution is to introduce the HAS-User Reference Algorithm (HAS-UA), to be published in its full entirety soon, and provide a general description of it, including the main algorithm assumptions, and to provide the results of an extended verification campaign.