科研之友
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摘要
We discuss the impact of a traveling ionospheric disturbance (TID) on cycle slip detection for the geometry-free (GF) combination. Based on the GF combination algorithm, we deduce for the first time the computational formula for the component of the residual introduced by TID. We confirm the theoretical equation according to the real TIDs extracted from the GPS data after the 2011 Tohoku earthquake. According to the theoretical equation, we compute the ionospheric residual by TID for various GNSS (including GPS, GLONASS and BDS) combinations. The results present several interesting findings: (1) The TID exerts the maximum residual on the GPS L1&L5 combination, whereas the effects on GPS L2&L5 and BDS B2&B3 combinations are smaller than 0.1 cycles and can be negligible, (2) the residual by large-scale TID (LSTID) is less than 0.1 cycles for all the GNSS combinations and can be negligible, (3) for 30 s sampled data, the residual by medium-scale TID (MSTID) can exceed 0.3 cycles with small period and large amplitude of TID, possibly leading to the invalidity of the algorithm and (4) for data with a sampling rate of 10 s or higher, the TID residual can be negligible.
