Multifrequency Cycle Slip Detection And Correction Method Based On Robust M Estimation

Due to the advantages of low noise and high accuracy of carrier phase observation,it is widely used in high-precision GNSS positioning and navigation services.Comparing with the pseudorange observation,there are still unknown integer ambiguities and cycle slips in carrier phase observations.Before applying carrier phase observations in precise positioning services,cycle slips must be detected and eliminated.This paper mainly focuses on the problem of cycle slip detection in GNSS data preprocessing.Firstly,a new robust M estimation algorithm is proposed for detecting cycle slips in MW combination.The algorithm is specially designed for the random sequence with has time dependency,and is more suitable for the cycle-slip detection.Furthermore,following the principle of equivalence weight,an iterative algorithm for solving the robust estimation problem is given.Secondly,according to the proposed robust M estimation algorithm above,a new double-frequency cycle-slip detection scheme is designed.Compared with the classical TurboEdit method,this scheme combined the integer prior of the slip into the traditional weekly jump judgment criterion.Experiments show that even with large pseudorange noise and large multipath effect,the algorithm is still able to detect slips of only one or two cycles in the MW combination accurately and reliably.Combining with the ionospheric residual combination,we can detect and correct those cycle slips nearly in real time.Finally,a new optimizing algorithm to find coefficients in three-frequency combinations is proposed,by which three optimal linear combinations are given.And a new estimation method for real-time ionospheric delay variation is given.The optimal combinations and the new estimation method are used to design a new real time cycle slips detection and correction scheme.The new scheme can detect the slips of arbitrary cycles at all frequencies in real time.And using the least squares algorithm,we can detect and correct cycle slips reliably.Experiments show that the new algorithm is barely affected by pseudorange noise and ionospheric delay,which has high detection accuracy.