Multipath analysis of code measurements for BeiDou geostationary satellites

摘要

Having non-negligible impact on the code range observables, multipath delay is one of the error sources that limit GNSS positioning accuracy. Due to the relatively stationary geometry, multipath effects for signals from geostationary earth orbit (GEO) satellites are even more difficult to mitigate by merely increasing the observing periods or averaging over multiple epochs. To investigate the characteristics of code, multipath effects for the BeiDou Navigation Satellite System (BDS) GEO satellites, a linear combination of observations reflecting code multipath was employed and BDS multipath time series over long periods were analyzed with the Fourier transform, correlation and wavelet transform. The amplitudes of GEO multipath series vary from < 1.0 m to around 2.0 m, and the periods of the dominant daily repeating components fall between 86,130 and 86,280 s. The low-frequency components were extracted, and most cross-correlation coefficients between the low-frequency components of two consecutive days are larger than 0.7. When the low-frequency components of the first day are subtracted from the multipath time series of the second day, a decrease of more than 25 % is found in terms of the code standard deviations. By correcting the observables with low-frequency multipath of the previous day, the precisions of code-only single-point positioning using ionosphere-free linear combination of BDS first and second or first and third frequencies can be improved. Precision improvements in north, east and up components for two stations in Perth, Australia were shown to be 0.2, 0.5 and 0.4 m, and 0.3, 0 and 0.5 m, respectively.