Characterization of amplitude scintillation and distribution of positioning error for IRNSS/GPS/SBAS receiver

Indian regional navigation satellite system (IRNSS) or Navigation with Indian Constellation (NaVIC) is the satellite-based navigation system, established and controlled by the Indian Space Research Organization. It provides services of positioning, velocity, and timing for civilian and military applications. Ionospheric irregularities cause the fuctuations in the amplitude and phase of the received navigation signals; this phenomenon is known as scintillation. Scintillation can create the error in precise positioning and degrades the position accuracy of the navigation system. It varies with solar activity, geographical location, seasonal variation, day–night time, and elevation angle of satellites. The S4 index is one of the key parameters to estimate the amplitude scintillation to recognize the quality of the navigation signal. In this paper, amplitude scintillation characteristics are studied with IRNSS/GPS/SBAS in the Ahmedabad region which is at the average altitude of 53 m. S4 index is calculated and analyzed using the real-time navigation data of one week. Here, IRNSS/GPS/SBAS receiver with L1, L5, and S-band, is used to collect the data at low altitude station (IITRAM, Ahmedabad). The position error of normal sunny days is calculated using IRNSS/GPS/SBAS receiver. The probability of position error is also derived and found that it follows the gamma distribution function and validate it statistically using a chi-square test. This study also focuses on the efect of elevation of the satellite on the value of carrier to noise ratio at the location of IITRAM.