Performance Evaluation of Adjusted Spherical Harmonics Ionospheric Model Over Indian Region

Abstract

The ionosphere is perceived to be a predominant source of ranging error of Global Navigation Satellite System (GNSS) signals to degrade the positional accuracy. The suitable ionospheric model is necessary to improve the positional accuracy of GNSS and Satellite-Based Augmentation System (SBAS) users. In this paper, the regional ionospheric model (RIM) over the Indian region is implemented based on the adjusted spherical harmonics function (ASHF) model from dense GPS TEC stations over the Indian region. Also, the evaluation of the different ASHF order models conducted to identify the proper order of the ASHF model for Indian low latitude ionospheric calm and adverse space weather conditions. The results confirm that the 4 th order ASHF ionospheric model can identify the northern Equatorial Ionization Anomaly (EIA) TEC crest patterns over the Indian region. The comparison of the 4 th order ASHF ionospheric model carried out with dual and single frequency ionospheric models like as Klobuchar model, Centre for Orbit Determination in Europe (CODE) Klobuchar model, NeQuick G model, BeiDou System (BDS2) model and CODE Global Ionospheric Maps (GIM) models. The outcome of the results indicates that the 4 th Order ASHF ionospheric model would be potential for single and dual-frequency ionospheric models for GNSS and SBAS systems. INDEX TERMS Ionosphere, Total Electron Content (TEC), GPS Aided GEO Augmented Navigation(GAGAN), Adjusted Spherical Harmonics Function (ASHF).

A Bidirectional Deep-Learning Algorithm to Forecast Regional Ionospheric TEC Maps

“…Step 3: The VTEC maps over 64 ionospheric grid points (IGP) are estimated using the ASHF nowcasting TEC model [3]. The GPS TEC maps are generated with a temporal resolution of 1-hour step size.…”

“…The Indian low latitude GPS network of 26 GPS receivers as a part of the Geo Augmented Navigation (GAGAN) system is operational for civil aviation, navigation, and timing applications. Siva Krishna et al have implemented a regional Adjusted Spherical Harmonics Function (ASHF) based TEC model using 26 GPS TEC stations data over the Indian region [3]. The ASHF TEC model performed well to capture northern EIA features and ionospheric TEC variability for quiet and disturbed day conditions [3].…”

“…Siva Krishna et al have implemented a regional Adjusted Spherical Harmonics Function (ASHF) based TEC model using 26 GPS TEC stations data over the Indian region [3]. The ASHF TEC model performed well to capture northern EIA features and ionospheric TEC variability for quiet and disturbed day conditions [3]. These ionospheric TEC time series forecasting models are implemented at a specific location using time series and statistical methods [4,5,6].…”

Effect of Higher-Order Ionospheric Delay on Precise Orbit Determination of GRACE-FO Based on Satellite-Borne GPS Technique

“…Ionospheric delay is one of the main error terms in satellite-borne GPS POD technology. The variation of electron density distribution with time and space results in the complexity of ionospheric delay [10][11][12] . How to deal with ionospheric delay is an important factor to improve POD precision.…”