NeQuick: In-Depth Analysis and New Developments

An empirical model called NeQuick has been selected for the modelling and correction of the ionospheric delay contribution in GALILEO single frequency receivers. The current baseline version of NeQuick for GALILEO is the one available in the International Telecommunication Union – Radiocommunication Sector (ITU-R) since 2001. From that time, several improvements have been proposed leading to the need of a better understanding and comparison of these different versions and an analysis of the weaknesses. Better results have been obtained by means of simpler ionosonde and profile parameters calculations, different topside formulation and new data files.
The interest of a newer version of NeQuick including the above-mentioned modifications is highlighted as its error behaviour towards latitude shows a better agreement with reality. Those modifications should be coupled to a less simplistic topside formulation involving several layers with appropriate transitions such as the proposal introduced in this paper. The need of a different treatment regarding the daily effective use of the model for GALILEO single frequency algorithm compared to a physical use (that uses monthly median underlying data) is addressed.
For the analysis and comparison of the different variants of the model, a software tool with a Graphical User Interface was developed. Preliminary comparisons for the physical use between different versions and also between modelled and measured data are presented. Such comparisons should be extended in the future for the effective use of the model.
Finally, the structure and analysis of the mentioned issues and the results of the different comparisons are shown. Also solutions or potential paths to investigate solutions are proposed.