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-phasernobservations. The undetected cycle slips are mainlyrnabsorbed by the integer ambiguity parameters and receiverrnposition coordinate parameters, leading to the biasedrnestimates for these parameters. Detection and repair ofrncycle slips in carrier-phase data are therefore the twornmajor quality-control problems that need to be addressed.rnVarious methods and techniques have been devised forrndetecting and repairing the cycle slips in the past. Sincernthe principle of detecting cycle slips is based on thernlocation of gross errors, the method calledrn"QUasi-Accurate Detection of gross errors (QUAD)" isrnintroduced in the present paper to detect and repair therncycle slips in GPS carrier-phase data. As the QUADrnmethod takes real errors of observations as objects to bernstudied, it can simultaneously identify, locate multiplerngross errors in observations, estimate their values andrnaccuracies and then correct them. The mathematicalrnmodel is summarized and followed by detailedrnimplementation procedures with a simulation example.rnTwo numerical examples are then given to illustrate thernfeasibility and validity of this method. The results showrnthat: (1) the QUAD method is fit for data processing ofrnboth single-frequency and dual-frequency GPS receivers;rn(2) if the quasi-accurate observations have been selectedrncorrectly, the gross errors and cycle slips can be detectedrnsimultaneously and easily; (3) the estimators of real errorsrnof the observations with gross errors and cycle slips arernrelatively close to the "real" values and thus the grossrnerrors and cycle slips can be successfully correctedrnaccording to the estimators. Our results indicate that thernQUAD method can be reliably used for detection andrnrepair of continuous cycle slips necessary for rapid staticrnpositioning and kinematic positioning with quite fewrnobservations.