An Efficient Cycle-Slip Repair Model With High Success Rate for BDS Triple- Frequency Observations

Abstract

An improved cycle-slip repair model is proposed for BDS triple-frequency undifferenced observations. Two extra-wide-lane code-phase combinations and one additional geometry-free (GF) carrierphase combination are employed. To ensure the GF phase combination follows a normal distribution, the residual ionospheric variation of the GF phase combination is corrected in real-time using the previous observation sequence without cycle slip. The integer least squares principle, based on the least-squares ambiguity decorrelation adjustment, is used to solve the fixed value of cycle slip. The corresponding covariance matrix of floating cycle-slip estimations used for construction is updated in real time to improve the fixed efficiency of cycle slip. Moreover, for reliable repair of cycle slip for triple-frequency observations, the critical ratio value between the second-best and best cycle-slip candidates for different residual ionosphere accuracies and different repair success rates are given based on large amounts of simulated data. Lastly, a set of active ionosphere and low-sampling-rate real data was used for evaluation and analysis of the algorithm. Results showed the success rate of cycle-slip repair is 99.997%, even under active ionosphere conditions, with low satellite elevation and low sampling rate. Unfortunately, one cycle-slip group (1, 1, 1) of the C14 satellite was not detected successfully and repaired correctly because of insensitivity to the GF phase combination under bad observation conditions. INDEX TERMS Cycle slip, triple-frequency observations, BDS, integer least squares, ionospheric delay.