Detection and Repair of Continuous Cycle Slips in GPS Carrier-Phase Data using QUAD Method

摘要

The cycle slip is a peculiar question in GPS carrier-phase observations. The undetected cycle slips are mainly absorbed by the integer ambiguity parameters and receiver position coordinate parameters, leading to the biased estimates for these parameters. Detection and repair of cycle slips in carrier-phase data are therefore the two major quality-control problems that need to be addressed. Various methods and techniques have been devised for detecting and repairing the cycle slips in the past. Since the principle of detecting cycle slips is based on the location of gross errors, the method called QUasi-Accurate Detection of gross errors (QUAD). is introduced in the present paper to detect and repair the cycle slips in GPS carrier-phase data. As the QUAD method takes real errors of observations as objects to be studied, it can simultaneously identify, locate multiple gross errors in observations, estimate their values and accuracies and then correct them. The mathematical model is summarized and followed by detailed implementation procedures with a simulation example. Two numerical examples are then given to illustrate the feasibility and validity of this method. The results show that: (1) the QUAD method is fit for data processing of both single-frequency and dual-frequency GPS receivers; (2) if the quasi-accurate observations have been selected correctly, the gross errors and cycle slips can be detected simultaneously and easily; (3) the estimators of real errors of the observations with gross errors and cycle slips are relatively close to the "real" values and thus the gross errors and cycle slips can be successfully corrected according to the estimators. Our results indicate that the QUAD method can be reliably used for detection and repair of continuous cycle slips necessary for rapid static positioning and kinematic positioning with quite few observations.