Differential Positioning Algorithm for GBAS Based on Extended Kalman Filtering

In order to improve the accuracy of positioning calculation of the user segment of the ground based augmentation system (GBAS), a differential positioning calculation algorithm based on extended Kalman filtering (EKF) is proposed. The carrier-phase smoothing pseudorange and cycle slip detection method are given here, and the differential correction algorithm for the GBAS is studied. The pseudorange is smoothed by carrier-phase, and the smoothed differential pseudorange data are taken as the measurement of the Kalman filtering. The carrier-phase smoothing technology and the Kalman filtering are used to suppress the influence of the random error on the position calculation result. Taking the GBAS platform built in the laboratory as the object of study, the carrier-phase smoothing pseudorange algorithm and the differential position calculation algorithm based on Kalman filtering are verified and analyzed. The experimental results show that the accuracy of the pseudo- range positioning has been improved after the carrier-phase smoothing. Meanwhile, the differential positioning algorithm which is based on Kalman filtering improves the accuracy of the position calculation. The root mean square values (RMS) of the positioning errors are increased by more than 25% compared with the RMS of the least square positioning calculation method.