Ingesting Ionospheric Characteristics for Regional Improvement of Galileo Single-Frequency Ionospheric Correction Algorithm
Abstract
As part of the Global Navigation Satellite System (GNSS), Galileo uses the NeQuick-G algorithm to provide ionospheric correction to single-frequency users. Within the framework of a research project, an improved Galileo single-frequency ionospheric correction approach has been proposed by incorporating regional ionospheric characteristics into the algorithm rather than relying solely on a global ionospheric model. The proposed algorithm that was designed to operate in long-term, short-term, and real-time mode has been evaluated over Cyprus and is going to be tested over a broader European region. The current study presents results from the real-time mode improvement of the algorithm over Nicosia, Cyprus. The real-time mode approach facilitates the local adjustment of Committee Consultative for Ionospheric Radiowave propagation (CCIR) files and the Az ionization level, which are crucial elements that control the ionospheric electron density profile in NeQuick-G. The Nicosia-specific CCIR maps are adjusted by using auto-scaled real time (every 5 min) foF2 and M(3000)F2 ionospheric characteristics from the Cyprus Ionosonde. The Az value is optimized using vertical total electron content (VTEC) measurements from a local GNSS receiver obtained from the previous day. This paper demonstrates the performance of this real-time improvement method, tested over Nicosia, Cyprus, using a retrospective dataset spanning 2014–2023. Results from the proposed real-time approach are in better agreement with the measured GNSS VTEC, compared to standard NeQuick-G operation, especially under high-solar-activity periods.