Investigation of ionospheric scintillation effects on RTK in Brazil

The ionospheric irregularities lead to rapid fluctuations in the amplitude and/or phase of radio signals commonly referred to as ionospheric scintillation, which can reduce the accuracy and reliability of Global Navigation Satellite System (GNSS) and even lead to complete loss of signal lock in GNSS receivers. At low latitudes, where anomalous ionospheric disturbances are more frequent, strong scintillation can last up to several hours. This paper investigates the impact of scintillation on the Real Time Kinematic (RTK) positioning of the Global Positioning System (GPS) using ionospheric scintillation data collected in Brazil during the solar maximum year 2014. Significant positioning errors are observed when dynamic RTK processing strategies are used during strong scintillation. The maximum positioning deviations in the east, north and upper directions reach 2.29, 1.84 and 1.37 m, respectively. At the same time, the Double Differential (DD) carrier phase residuals also increase. By contrast, when using static RTK processing strategy during strong scintillation, the positioning error is less than 5 mm at all time. However, there is a significant increase in DD phase residuals. The relationship between the standard deviation of the one-minute carrier phase residuals and the scintillation index S4 is investigated. A significant correlation is found between the phase residuals standard deviation and S4, which thus can be used to indicate the occurrence of scintillation. This study is important for a better understanding of scintillation characteristics and their impact on real-Time differential positioning at low latitudes. It can also be used to develop scintillation mitigation methods for GNSS differential positioning.