Analysis of BeiDou Satellite Measurements with Code Multipath and Geometry-Free Ionosphere-Free Combinations

Abstract

Using GNSS observable from some stations in the Asia-Pacific area, the carrier-to-noise ratio (CNR) and multipath combinations of BeiDou Navigation Satellite System (BDS), as well as their variations with time and/or elevation were investigated and compared with those of GPS and Galileo. Provided the same elevation, the CNR of B1 observables is the lowest among the three BDS frequencies, while B3 is the highest. The code multipath combinations of BDS inclined geosynchronous orbit (IGSO) and medium Earth orbit (MEO) satellites are remarkably correlated with elevation, and the systematic “V” shape trends could be eliminated through between-station-differencing or modeling correction. Daily periodicity was found in the geometry-free ionosphere-free (GFIF) combinations of both BDS geostationary Earth orbit (GEO) and IGSO satellites. The variation range of carrier phase GFIF combinations of GEO satellites is −2.0 to 2.0 cm. The periodicity of carrier phase GFIF combination could be significantly mitigated through between-station differencing. Carrier phase GFIF combinations of BDS GEO and IGSO satellites might also contain delays related to satellites. Cross-correlation suggests that the GFIF combinations’ time series of some GEO satellites might vary according to their relative geometries with the sun.

Characterization of GNSS Signals Tracked by the iGMAS Network Considering Recent BDS-3 Satellites

“…For the IFCB variations, which have been identified to exist in BDS-2 and GPS Block IIF satellites [24,26], the small bias variations with peak amplitudes of about 1 cm can been found in BDS-3 triple-frequency carrier phase combinations. However, no apparent bias variations were observed for BDS-3e satellites in Zhang et al [5] and Pan et al [27].…”

“…With the availability of three-frequency signals for GPS Block IIF satellites, inter-frequency clock bias (IFCB) was found, which was defined as the difference of the satellite clock offsets determined from two different ionosphere-free (IF) linear combinations of L1/L2 and L1/L5 carrier phase observations, and could most likely be attributed to inconsistency among frequency-dependent phase biases within a satellite [24,25]. According to previous studies, the IFCB between the BDS-2 B1/B2 and B1/B3 ionosphere-free satellite clocks showed a peak-to-peak amplitude of about 4 cm and, more noticeably, 10-40 cm for GPS Block IIF satellites [26,27]. In contrast, no apparent IFCB variations could be identified for the three signals of Galileo and QZSS satellites [28].…”

Considering Inter-Frequency Clock Bias for BDS Triple-Frequency Precise Point Positioning

“…Full consistency of three carriers can be ensured for QZSS and Galileo, and thus the IFCB in multi-frequency integrated precise positioning can be ignored for them [15][16][17]. Several studies also relate to the IFCB of BDS-2 satellites [18,19]. Compared with their results, a wider range of IFCB variations is obtained because the datasets spanning a longer period of time are involved in the analysis.…”

Combining GPS, BeiDou, and Galileo Satellite Systems for Time and Frequency Transfer Based on Carrier Phase Observations

“…In the case of GPS alone, the ionosphere-free combination can be used for the dual-frequency carrier phase and pseudo-range observations to eliminate the first-order effects of the ionosphere [34][35][36][37][38]. After the ionosphere-free combination is formed, the observation equation of the CP technique can be written as follows [39,40]:…”