EGNOS Architecture

The goal of EGNOS (European Geostationary Navigation Overlay Service) is to augment the [GPS Introduction|GPS]] in order to improve the navigation performances in terms of accuracy and integrity (with the required levels of availability and continuity of service) over the European Civil Aviation Conference (ECAC) Region and to be expandable over neighbouring regions. These augmentations are obtained by providing a GPS-like Geostationary Ranging service (R-GEO), by broadcasting precise Wide Area Differential corrections to correct for GPS, GLONASS and GEO orbit and clock errors and also to correct the ionospheric delays affecting the signal paths to the users. The complex message broadcast by EGNOS GEOs also include Integrity data which allow to bound the remaining errors with a high level of confidence. EGNOS has deployed its Advanced Operational Capability (AOC) using two existing INMARSAT-III navigation transponders (AOR-E and IOR-W) plus a navigation transponder on board of Artemis satellite.