BDS code bias periodical mitigation by low-pass filtering and its applications in precise positioning

Abstract

The code-phase divergences, which are minimal for GPS, GLONASS, and Galileo satellites, are commonly found in BeiDou Navigation Satellite System (BDS) Geostationary Orbit (GEO), Inclined GeoSynchronous Orbit (IGSO) and Medium Earth Orbit (MEO) satellites. Several precise positioning applications which use code observations are severely affected by these code biases. We present an analysis of code bias based on multipath (MP) combination observations. To mitigate the effect of BDS code bias on precise positioning, we proposed a periodical correction method using a low-pass filter for BDS GEO, IGSO and MEO satellites. The auto-correlation of MP series over long periods is analyzed to obtain the periods of the dominant repeating components for three types of BDS satellites. The periods of the dominant daily repeating components are close to 86,160 s for BDS GEO and IGSO satellites while 603,120 s for MEO satellites. The zero phase-shift low-pass filter was used to extract the low-frequency components of MP series and then low-frequency components are applied to mitigate the code bias periodically. The developed correction methods can make a more remarkable improvement for the accuracy of MP series, compared to the current elevation-dependent correction models. Data sets collected at 50 Global Navigation Satellite System (GNSS) ground stations including 15 of the International GNSS Monitoring and Assessment System (iGMAS) and 35 of the Multi-GNSS Experiment (MGEX) stations are employed for this study. To analyze the influence of code bias on precise positioning and validate the effectiveness of the correction methods, some applications such as single point positioning (SPP), wide-lane (WL) ambiguity analysis and Uncalibrated Phase Delays (UPDs) estimation are conducted. After applying the proposal correction method to the code observations, SPP solutions outperform the uncorrected ones in term of positioning accuracy. The positioning accuracy decreased by 0.28 and 0.1 m in the north and east components and the improvements are more significant for the U components decreased by 0.42 m. In addition, the systematic variations of Melbourne-Wübbena (MW) combination are greatly removed and the convergence time of the MW series are decreased. Moreover, significant improvement is also achieved in terms of the usage rate and residuals of UPDs estimation.

Smart Grazing in Tibetan Plateau: Development of a Ground-Air-Space Integrated Low-Cost Internet of Things System for Yak Monitoring

“…GPS is a well-known and most widely used satellite positioning system, and BDS is the latest deployed navigation system. Li et al presented an analysis of code bias based on multipath combination observations, which improved the singlepoint positioning results, and the vertical component decreased by 0.42 m and by 0.28 and 0.1 m in north and east direction [13]. Wei et al designed a remote monitoring system to track vehicles based on the combination of BDS and GSM, only spent little money on low price hardware and mobile network GSM fees [14].…”

A Simulation Study on Triple Frequency Ambiguity Resolution for Reference Stations Using Different Strategy Regarding Elevation angles

“…GPS plans L5 signal full operation since 2020. [1] Therefore many researchers have already investigated efficient coefficients. In general, two independent ambiguities, which have meter level wave lengths, could be fixed even if with integer rounding in several epochs.…”

“…Since the difficulty to overcome other errors for short wave length, many studies have been assumed the measurement errors for several baseline lengths. [1] In addition to previous researches, we have investigated measurement errors regarding to elevation angles in [4]. The errors depend on elevation angle as well as the baseline length.…”