Quality Control for Differential Kinematic GPS Positioning

Kinematic differential GPS positioning is used to achieve accurate, real-time positions and velocities of a moving platform on land, in the air and at sea. In a dynamic environment, however, the deviations or biases from the assumed system and observation models are often significant. This results in a degradation of the accuracy and reliability of the estimated positions and velocities. Therefore, quality control methods are inevitably needed in a real-time positioning system to insure the system is functioning properly. In this thesis, the statistical quality control methods for use in kinematic GPS positioning are investigated. The general recursive formulas for bias influence analysis and reliability analysis in Kalman filtering are derived and the bias influence characteristics and the minimum detectable bias (MDB) values of some typical biases in differential kinematic GPS positioning are studied. A real-time statistical testing and implementation procedure for use in kinematic GPS positioning is given based on the state space two-stage Kalman filtering technique, hypothesis testing theory and reliability analysis. This procedure is for the detection of common biases such as cycle slips in carrier phases and outliers in phase rates and pseudoranges, and for the elimination of their influences on the kinematic GPS positioning results. All the derived formulas and algorithms were implemented in a software package called QUALIKIN on a 386 microcomputer. The application of the statistical quality control methods and testing of the software was performed on two GPS data sets collected in land semi-kinematic mode over a well-controlled traverse. Analysis of the results indicates that, with a data rate of one second or higher, the testing procedure developed herein can correctly detect, identify and estimate carrier phase cycle slips between consecutive epochs occurring at the one cycle level on multiple satellites under low and medium vehicle dynamics. The detection and adaptation of phase rate and pseudorange outliers is also possible. The magnitude of the detectable outliers is dependent on the corresponding measurement accuracy, satellite geometry and the number of the outliers present. Further studies iii of quality control methods are recommended. Among them are the extension of the testing procedure to incorporate the system bias detection and adaptation for high dynamic surveying and navigation systems, application of the theory to integrated systems such as GPS/INS, and investigation of the carrier phase ambiguity initialization methods in the kinematic mode. iv ACKNOWLEDGMENTS I would like to express my deep gratitude to my supervisor, Professor …