Detection of ionospheric anomalies based on FFT Averaging Ratio (FAR) algorithm

Global Navigation Satellite Systems (GNSS) is a collection of satellite systems, which is used to locate users´ positions. Radio wave propagation effects on GNSS signals play a major role in precise position, velocity and time determination. In the atmosphere, the signal is subjected to influence by ionosphere and troposphere. In the ionospheric region, the Total Electron Content (TEC) content varies, causing fluctuations in GNSS signals. These ionospheric scintillations are difficult to detect. For high integrity and precision, these scintillations should be reduced. In this paper, a new algorithm called the FFT Averaging Ratio (FAR) algorithm has been proposed and implemented with low latitude multi-frequency GNSS station data at Koneru Lakshmaiah University (16.44° N, 80.62° E), Guntur, Andhra Pradesh, India. Power Spectral Density (PSD) was calculated for the FFT output and a decision criterion was obtained. A threshold value was obtained by the chi square inversion method and compared with the decision criterion. It was observed that FAR algorithm was able to detect ionospheric anomalies well.