Validity period of NeQuick (Galileo version) corrections: Trade-off between accuracy and computational load

PVT accuracy, in GNSS-based navigation, depends on various factors such as the quality of the measurements and the broadcast navigation data. GNSS broadcast signals (in L-band) are strongly influenced by the atmospheric layers. In particular ionospheric effects are the most important in open-sky. The ionosphere effect can be reduced using linear combination of dual frequencies measurements or differential methods. In single point positioning, the receivers have to apply a correction model to limit ionospheric effect. NeQuick-G is the emerging model developed for Galileo, it over-performs Klobuchar model, in the both measurement and position domains. These improvements are compensated by a higher computational load which is fundamental, for mass market devices. The main goal of this work is to identify a trade-off between accuracy and computational load; to this purpose NeQuick corrections are not computed every epoch, but only periodically. The effects of this approximation are assessed for several validity periods in position domain using GPS measurements. The coefficients necessary to use NeQuick-G model are extracted by Galileo navigation message. From the analysis emerges that an optimal threshold for the updating rate is about 15 minutes, this trade-off reduces the effort of the receiver without degrading PVT accuracy.