The amplitude of systematic multipath variation (SMV) exists in multipath combination series may exceed 0.5 m for some geostationary earth orbit (GEO) satellites, which is larger than the normal noise level of GPS code observation.
The analysis of multipath combinations (MPC) suggests more multipath present for BDS than GPS for the CA code (B1 MPC is 0.597 m, L1 MPC is 0.326 m), but less multipath for the P code (B2 MPC is 0.421 m, L2 MPC is 0.673 m).
The Multipath (MP) combination, Melbourne-Wübbena (MW) combination and wide-lane uncalibrated phase delays (UPDs) are calculated to verify the existence and magnitude of the satellite-induced code bias for the BDS-3 satellites.
Zhang et al. (2017) analyzed the originate characteristic of code bias in BDS MW-defined combination and concluded that the origin of errors may from transmitting satellite sides for IGSO and MEO satellites, and the biases for GEO satellites originate from both ground- and satellite sides, mainly from ground multipath.
Then, the low-frequency component of multipath (MP) combination series is extracted using a zero phase-shift low-pass filter and applied to help minimize this error based on the repetition of code bias.
We present an analysis of code bias based on multipath (MP) combination observations.
The proposed method uses the SMV extracted from multipath (MP) combination series with adaptive wavelet transform as correction for current day observation in post-processing use or as following day correction in real-time use.
In this paper, with real GPS and BDS triple-frequency observations, we analyse the influence of the carrier-phase multipath in three typical triple-frequency combinations: extra-wide-lane (EWL) combination, ionosphere estimation with ambiguity-corrected EWL/wide-lane (WL) combinations and the geometry-free and ionosphere-free (GIF) combination for narrow-lane (NL ARR.
Due to the presence of micro-multipath propagation, the combination of the direct path and the multipath in both forward and return links yields the following four combinations of the two-way propagation: path I (l 1 l 1), path II (l 2 l 2), path III (l 1 l 2), and path IV(l 2 l 1).
