Enhancing Global PPP Service Reliability with Hemisphere Atlas® and Galileo HAS: A Dual Redundant Approach

Abstract

Precise Point Positioning (PPP) is a technique that provides high global accuracy without the need for nearby reference stations. The approach, at minimum, requires GNSS satellite orbit and clock errors generated from globally distributed reference stations to achieve high accuracy. End users can then utilize either an ionosphere-free linear combination to eliminate the first order of ionosphere delays or an undifferenced and uncombined model to estimate ionosphere delays. Hemisphere Atlas is an innovative global L-band service from Hemisphere GNSS, which has global coverage. The Galileo High Accuracy service (HAS) is a free service provided by the European Union with Interface Control Document (ICD) published in May 2022. The HAS will have two service levels: Service Level 1 with global coverage orbits, clocks, and code biases, and Service Level 2 with regional coverage of atmospheric corrections. Initial assessments of Service Level 1 have already shown that it meets expectations around the world. Atlas H10 has a 95% accuracy of 8cm, and Galileo HAS achieves a 95% accuracy of 20cm. Therefore, Galileo HAS can be an excellent backup to Atlas in case of service outage or severe interference on the L-Band frequency of Atlas. In this article, Atlas and HAS global performance will first be introduced. Next, we will present their actual performance metrics from five different locations spanning five continents, and subsequently provide insights into the switching logic. Lastly, a patent-pending dual redundant service using Hemisphere Atlas and Galileo HAS will be introduced, with higher priority given to Atlas.