Improvement of Indian-Regional Klobuchar Ionospheric Model Parameters for Single-Frequency GNSS Users

In general, global positioning system (GPS) ranging errors and positioning caused by the ionosphere can be corrected by the Klobuchar ionospheric model. GPS satellites broadcast the model coefficients to the single-frequency users based on the average solar flux and seasonal variations. In low-latitude regions, such as India and Brazil, correction of the ionospheric delay based on these coefficients is not accurate because of the large gradients and complex dynamic ionospheric behavior. The traditional employment of refining the ionospheric Klobuchar model parameters with single-shell approximation is inappropriate for the equatorial/low-latitude regions. In this letter, we propose a technique to determine the ionospheric delay by using the new Klobuchar parameters (coefficients) based on multishell-spherical harmonics function (MS-SHF) analysis. It has been reported that by using the MS-SHF model, the ionospheric delays can be modeled accurately in the low-latitude regions. Furthermore, the proposed model performance has been evaluated with the Denis Bouvet (2017) single-frequency ionospheric correction model. In the single-frequency usage, the proposed model can improve (62.69%/77.08%) during quiet/disturbed days. Preliminary results reveal that the refined Klobuchar model parameters impart enhanced ionospheric delay corrections to regional navigation satellite systems with single-frequency GPS receivers, such as the Indian Regional Navigation Satellite System.