Indian Regional Navigation Satellite System (IRNSS) is developed for providing positioning, velocity and timing information to Indian users within the error of 10 m. Amplitude scintillation is the rapid fluctuations in amplitude of navigation signal due to small scale irregularities in electron density presents in ionosphere. Strong scintillation can degrade the accuracy of navigation system and generate the errors in precise positioning services. S4 index is the statistical measurement of amplitude scintillation which reflects scintillation event. The characteristics of amplitude scintillation on IRNSS/SBAS/GPS receiver with all seven satellites during heavy rainy days at the low altitude station IITRAM, Ahmedabad are investigated. The raw data are collected from the IRNSS/GPS/SBAS receiver with L1, L5 and S band at the Ahmedabad city with average altitude of 53 m in Gujarat. Here, real time monitoring system for amplitude scintillation and positioning error is designed for all three bands. S4 values for three bands are calculated and analyzed to define the scintillation event for the period of 14 days. The position errors of heavy rainy days are also found. This study also focuses on time duration over which the carrier to noise ratio acquires zero value, effect of elevation angle of satellite on carrier to noise ratio and ionospheric delay. We found that L1 band suffers more from scintillation compare to L5 and S band. Day to day investigation of amplitude scintillation is carried out here. The results of this investigation would be utilized for understanding of amplitude scintillation effect during rainy weather condition in low altitude station.