Research on the Impact of the Decrease in Observation Stations on SBAS

The Satellite-Based Augmentation System (SBAS) realizes the correction and error envelope of the signal in space by broadcasting the ephemeris and satellite clock corrections and integrity parameters. During the research process, it was discovered that due to the interruption of the pseudo range observation data, the number of GPS satellites’ visible stations decreased instantaneously. This problem not only increased the correction error, but also caused glitches in the User Differential Range Error (UDRE), which affected the continuity of system. In order to solve this problem, an algorithm is proposed: at the epoch where the number of visible stations decreases, the Kalman Filter amplifies the observation noise covariance matrix to reduce the weight of observations, and gradually restore the observation noise covariance matrix over time before the effect of the decrease in the number of visible stations is eliminated. The results show that the algorithm can suppress the correction error amplitude caused by the instantaneous decrease in the number of observation stations by up to 90%, and can effectively suppress part of the UDRE glitches at the same time.