The Galileo High Accuracy Service: Assessment of the Quality of Corrections and Preliminary PPP Performance

The Galileo High Accuracy Service (HAS) offers free corrections for PPP through the E6b signal and the internet. Presently, HAS aims to deliver 95% horizontal and vertical accuracy within 20 cm and 40 cm. To evaluate the accuracy of the current HAS corrections, they have been received, decoded, and used in a PPP positioning. The corrections have been received during two sessions. The first one, in November 2022, served to validate our decoder with a comparison with identical data recorded by the Galileo High Accuracy Reference Algorithm and User Terminal (HAUT). Our decoder was fully validated. The second session, 45 days in April and May 2023, aimed to assess the availability and accuracy of the HAS corrections for a longer time with the service officially available. With the HAS corrections added to the navigation messages, the orbit error decreased up to 41% for Galileo and 79% for GPS. The clock error was lower with HAS too. For example, for Galileo, it has been reduced by 57%. The code biases have been evaluated as well, and their accuracy is at a sub-nanosecond level. Once the quality of the products has been attested, the HAS corrections accuracy was validated through a PPP positioning. The use of two networks, with 4 stations each, has demonstrated the limitations of the HAS coverage. Indeed, in Europe, with GPS and Galileo processing, the obtained 95% horizontal and vertical accuracies are 10.2 cm and 30.7 cm, which is aligned with the targeted performance of HAS. But, as stated in the Service Definition Document, the HAS corrections are not as good in the Pacific area, and the achieved 95% horizontal accuracy is 19.6 cm and the 95% vertical accuracy is 44.4 cm, which is higher than the target.