A New Ionospheric Model for Single Frequency GNSS User Applications Using Klobuchar Model Driven by Auto Regressive Moving Average (SAKARMA) Method Over Indian Region

I. Lakshmi Mallika,Gampala Sivavaraprasad,D. Venkata Ratnam,Saravana Raman

doi:10.1109/access.2020.2981365

Abstract

The single-frequency users of Global Navigation Satellite System (GNSS) require an effective mathematical model that mitigate the dominant errors due to ionospheric delays. Klobuchar model approximately reduces ionospheric effect up to 50% through its coefficients in the navigation message, which is not sufficient for the GNSS single frequency users at critical applications. Hence, a new model, for Single Frequency GNSS User Applications using Klobuchar model driven by Auto Regressive Moving Average Method (SAKARMA) is proposed to forecast and enhance the precision of ionospheric delay estimations for GNSS users. The hourly VTEC maps are obtained from the Assimilated Indian Regional Vertical Total Electron Content (AIRAVAT) by the process of data assimilation using the Kalman filter exclusively for the Indian region (longitude: 65°E to 100°E; latitude: 5°N to 40°N) using 26 GPS TEC stations over Indian region. The accuracy of the SAKARMA model is investigated using the AIRAVAT maps for various Indian geographic regions during both geomagnetic quiet and disturbed conditions of September month in 2016 year. Furthermore, in order to test SAKARMA model, a dual-frequency Navigation with Indian Constellation (NavIC) receiver located at the KL Education Foundation, Guntur, India (geographic: 16.37°N, 80.37°E; geomagnetic: 7.44°N, 153.75°E) is used to collect the observations during 2 - 12 September 2017. Furthermore, SAKARMA model is also validated with Klobuchar model, Klobuchar-style coefficients provided by the Center for Orbit Determination in Europe (CODE) (CODKlob) Model, BeiDou System (BDS2) Model and NeQuick 2 Model over a low latitude NavIC station in forecasting the ionospheric delays. The experimental results of SAKARMA for NavIC have revealed that the MAPE for proposed SAKARMA model is 9-17% (accuracy: 83-91%), while 34-53% (accuracy: 47-66%) for the Klobuchar model. Thus, the results illustrate that the proposed SAKARMA model is capable of predicting the ionospheric delays for single frequency GNSS/NavIC users.

Highlights

The proposed coefficients-based time series model, i.e. SAKARMA model is evaluated for both spatio temporal datasets using the Assimilated Indian Regional Vertical Total Electron Content (AIRAVAT) vertical TEC (VTEC) maps over Indian region and NAVIC observations at single low latitude station
Developing/improving the performance of ionospheric broadcasting models to alert and correct the ionospheric corrections is crucial for the real-time single frequency Global Navigation Satellite System (GNSS)/Navigation with Indian Constellation (NavIC) users
A new ionospheric model for Single Frequency GNSS User Applications using Klobuchar model driven by Auto Regressive Moving Average (SAKARMA) method is proposed

Summary

INTRODUCTION

Klobuchar [1] has developed a global ionospheric delay model known as ionospheric broadcasting model (IBM) for the benefit of single frequency Global Positioning System (GPS) users It provides ionospheric corrections in real time applications with only 8 coefficients in the GPS navigation message. Han et al, Yuan et al, Filjar et al, Lee et al, Shukla et al, Wang et al, etc., [4], [9]–[13] have worked on different aspects by adding several parameters for improving the performance of Klobuchar model The effectiveness of these Klobuchar-like models developed by the addition of several new parameters could yield an accuracy not exceeding 70% during geomagnetic disturbed conditions; which definitely is not sufficient for safety critical single frequency GNSS user applications that demand high accuracy.

DATA AND PROPOSED IONOSPHERIC SAKARMA MODEL

RESULTS AND DISCUSSION

CONCLUSION