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The Quality Assessment of Non-Integer-Hour Data in GPS Broadcast Ephemerides and Its Impact on the Accuracy of Real-Time Kinematic Positioning Over the South China Sea

The abnormal effect in the GPS broadcast ephemeris could cause significant influence on the real-time navigation and positioning solution by using orbit and clock error data provided by GPS broadcast ephemeris. In this paper, three types of non-integer-hour navigation data in GPS broadcast ephemeris were described, firstly. Compared with GPST integer hour data, we find that there are two kinds of data block of non-integer-hour navigation containing gross error with different levels of precision, which can reflect from User Range Accuracy (URA) in the broadcast ephemeris. This gross error would cause a large deviation when using GPS broadcast ephemeris for orbit calculation, and leads to a decrease in kinematic positioning accuracy. Secondly, an improved weighted method which according to the consistency relationship between the URA value and the orbital precision is proposed to improve the positioning accuracy by controlling the influence of gross errors in broadcast ephemeris. Finally, the correction algorithm proposed in this paper is applied to real-time kinematic positioning with shipborne GPS data over the South China Sea. The results show that the proposed positioning algorithm can efficiently reduce the influence of the gross error in the broadcast ephemeris, and improve the accuracy of the navigation and positioning greatly.