Predictive Data Optimization of Doppler Collision Events for NavIC System

Abstract

Navigation with Indian Constellation (NavIC) is satellite-based navigation system developed by Indian Space Research Organization (ISRO), India. It consists of seven satellites, among them, three are geostationary (GEO) satellites, and the rest are geosynchronous satellites. There are several factors that effect the positional accuracy of the NavIC system, and among them, one of the important parameter is Doppler collision (DC). The occurrence of the DC depends upon the usage of geostationary (GEO) satellites in position estimation. The DC may occur when the relative Doppler shift between two satellites is less than the bandwidth of receiver code tracking loop. To analyze the DC events, the required navigational data are collected from IRKS-GPS-SBAS (IGS) receiver located at low latitude station. There are variations in the values of Doppler shift of GEO satellites and have a significant impact on the Doppler collision prediction. To predict the DC accurately, the data optimization is very much essential for precise positioning applications. This paper presents the predictive data optimization of DC events by using various filtering methods such as moving average, Savitzky–Golay and median filter. Among three methods, Savitzky–Golay method provides better data optimization to predict short-term DC events as compared with other methods.