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Abstract:
The performance of the radio communication-relied applications, e.g., Global Navigation Satellite System (GNSS), is closely related to the activities of the ionosphere. Ionospheric irregularities within the ionosphere cause GNSS signals scintillation, loss lock, and cycle slips and thus further degrade the performance of GNSS applications, e.g., Precise Point Positioning (PPP). In this contribution, we evaluated the performance of ROTI (Rate of change of TEC Index) derived from phase observations of geodetic receivers in monitoring ionospheric scintillation in the aspect of correlation, integrity, and reliability. The results show that ROTI calculated from 1s-data (1s/sample) has better performance (integrity of 90%, correlation with S4 of 0.8-0.9, reliability of 88%) than that from 30s-data (30s/sample) (integrity of 60%, correlation with S4 of 0.7-0.8, reliability of 80%), suggesting sampling rate a key to the performance of ROTI in monitoring ionospheric scintillation. In addition, we investigated the impacts of ionospheric irregularities on the performance of kinematic PPP in China. The results show that the ionospheric irregularities caused increased positioning errors (decimeter- to meter-level), enlarged phase residuals (decimeter-level), and increased cycle slips in PPP processing in low-latitude regions of China. By proposing a novel strategy, we present direct evidence of the falsely detected cycle slips in 30s-data by the traditional cycle slip detection threshold in PPP processing. We reveal that the abundant falsely detected cycle slips are dominantly responsible for the degradation of kinematic PPP solutions during the period of ionospheric irregularities. Our results advance maintaining the robustness of GNSS applications in ionospheric disturbed environments.
