The GIVE Ionospheric Delay Correction Approach to Improve Positional Accuracy of NavIC/IRNSS Single-Frequency Receiver

The Navigation with Indian Constellation (NavIC)/Indian Regional Navigation Satellite System (IRNSS) is an independent navigation system developed for the Indian subcontinent by the Indian Space Research Organisation (ISRO). The positional accuracy of this system is mainly affected by the ionosphere of the low-latitude equatorial Indian subcontinent, as large ionospheric gradients and intense irregularities are present in it. The objective of this study is to improve the positional accuracy of NavIC/IRNSS systems by applying ionospheric correction using the most suitable single-frequency model. The data to be analysed were collected from the NavIC/IRNSS receiver provided by the Space Applications Centre, ISRO. A comparative analysis between the dual-frequency model and single-frequency model (e.g. GIVE model, coefficient-based model) was performed on the data from the NavIC/IRNSS receiver. Different ionospheric models were applied to compute ionospheric delay (ionodelay) on a quiet day (3 < K_P < 5). Our result shows that both the single-frequency Grid Ionosphere Vertical Error (GIVE) model and dual frequency model outperform remarkably compared to the traditional coefficient-based model. The GIVE model was also analysed on FAR categorized satellites for different stormy days of different months. It was observed that during stormy days also, the 3D position computed by applying the GIVE model was nearly the same as the dual-frequency model.