MULTIPATH REDUCTION ON REPETITION IN TIME SERIES FROM THE PERMANENT GPS PHASE RESIDUALS

摘要

In this research, the newly developed Hilbert Huang Transformation method is applied to decompose the time-shifted post-fit GPS phase signal residuals into a range of fluctuating components from high-to low-frequencies. Global Positioning System (GPS) satellite constellation returns to the same configuration in a sidereal day (23 h 56 m 4 s); however, daily GPS position estimates are usually based on the solar day. After processing GPS data of several days, the steady time shifts of the satellite constellation with respect to the station appear in the patterns of the post-fit phase residuals with time shift by 3 m 56 s per day. The effects of environmental multipath delays may be filtered out by the HHT method. We can, however, observe some multipath effects in the data from a static GPS antenna which occupies the same site over several days (or permanently), because the geometry between the GPS satellites and any (permanent) reflectors at that site repeats every sidereal day. In this paper, it was found that the time-shifted post-fit double-difference phase residuals are highly dependent on the GPS antenna site. The correlation coefficients are more than 0.94.