Algorithm for Real-Time Cycle Slip Detection and Repair for Low Elevation GPS Undifferenced Data in Different Environments

Abstract

Real-time cycle slip detection and repair is one of the key issues in global positioning system (GPS) high precision data processing and application. In particular, when GPS stations are in special environments, such as strong ionospheric disturbance, sea, and high-voltage transmission line interference, cycle slip detection and repair in low elevation GPS observation data are more complicated than those in normal environments. For low elevation GPS undifferenced carrier phase data in different environments, a combined cycle slip detection algorithm is proposed. This method uses the first-order Gauss–Markov stochastic process to model the pseudorange multipath in the wide-lane phase minus narrow-lane pseudorange observation equation, and establishes the state equation of the wide-lane ambiguity with the pseudorange multipath as a parameter, and it uses the Kalman filter for real-time estimation and detects cycle slips based on statistical hypothesis testing with a predicted residual sequence. Meanwhile, considering there are certain correlations among low elevation, observation epoch interval, and ionospheric delay error, a second-order difference geometry-free combination cycle slip test is constructed that takes into account the elevation. By combining the two methods, real-time cycle slip detection for GPS low elevation satellite undifferenced data is achieved. A cycle slip repair method based on spatial search and objective function minimization criterion is further proposed to determine the correct solution of the cycle slips after they are detected. The whole algorithm is experimentally verified using the static and kinematic measured data of low elevation satellites under four different environments: normal condition, high-voltage transmission lines, dynamic condition in the sea, and ionospheric disturbances. The experimental results show that the algorithm can detect and repair cycle slips accurately for low elevation GPS undifferenced data, the difference between the float solution and the true value for the cycle slip does not exceed 0.5 cycle, and the differences obey the normal distribution overall. At the same time, the wide-lane ambiguity and second-order difference GF combination sequence calculated by the algorithm is smoother, which give further evidence that the algorithm for cycle slip detection and repair is feasible and effective, and has the advantage of being immune to the special observation environments.

Initial Study of Adaptive Threshold Cycle Slip Detection on BDS/GPS Kinematic Precise Point Positioning during Geomagnetic Storms

“…In PPP data preprocessing, cycle-slip detection and repair are vital issues to achieve high-precision positioning and fast parameter convergence [38][39][40][41]. There are various cycleslip detection methods regarding non-differential combinatorial observables, including the high-order difference method, polynomial fitting method, Kalman filtering method, Melbourne Wubeena (MW) combinatorial observables method, geometric phase-free method, etc.…”

Quality Assessment of Various CHC NAV GNSS Receiver Models

“…Integrity is one of the factors used to assess GNSS performance where it measures the confidence in the accuracy of the information provided by the overall process. Integrity is a general performance characteristic that refers to a user's ability to trust the provided value of a specific location or velocity quantity (e.g., horizontal and vertical position) [12] and [13].…”

A hierarchical combination algorithm for real-time cycle slip detection and repair in low satellite elevation and ionospheric scintillation conditions

“…Filtering techniques employ filters to smooth signals and detect cycle slips by analyzing the residuals postfiltering. These encompass high-order differencing 21,22 and Kalman filtering [23][24][25] , etc. High-order differencing stands out for its simplicity and absence of complex matrix operations, rendering it straightforward to implement.…”