A Single-Difference Multipath Hemispherical Map for Multipath Mitigation in BDS-2/BDS-3 Short Baseline Positioning

Abstract

The BeiDou Navigation Satellite System (BDS) features a heterogeneous constellation so that it is difficult to mitigate the multipath in the coordinate-domain. Therefore, mitigating the multipath in the observation-domain becomes more important. Sidereal filtering is commonly used for multipath mitigation, which needs to calculate the orbit repeat time of each satellite. However, that poses a computational challenge and damages the integrity at the end of the multipath model. Therefore, this paper proposes a single-difference model based on the multipath hemispherical map (SD-MHM) to mitigate the BDS-2/BDS-3 multipath in a short baseline. The proposed method is converted from double-difference residuals to single-difference residuals, which is not restricted by the pivot satellite transformation. Moreover, it takes the elevation and the azimuth angles of the satellite as the independent variables of the multipath model. The SD-MHM overcomes the unequal observation time of some satellites and does not require specific hardware. The experimental results show that the SD-MHM reduces the root mean square of the positioning errors by 56.4%, 63.9%, and 67.4% in the east, north, and vertical directions; moreover, it contributes to an increase in the baseline accuracy from 1.97 to 0.84 mm. The proposed SD-MHM has significant advantages in multipath mitigation compared with the advanced sidereal filtering method. Besides, the SD-MHM also features an excellent multipath correction capability for observation data with a period of more than seven days. Therefore, the SD-MHM provides a universal strategy for BDS multipath mitigation.

A Study on the Detecting Cycle Slips and a Repair Algorithm for B1/B3

“…By combining and comparing the B1/B3 dual-frequency code multipath [21] before and after repairing, it is established that the formulas are as follows [22,23]:…”

“…Figure 4a-c represent the GF combination values of PRN 4, PRN 6 and PRN22, respectively, after the cycle slips were repaired. Figure5a-cshow the MW combination values after the cycle slips were repaired.…”

GNSS multipath suppression technology based on postcorrelation and independent component analysis

“…These methods are mainly used in data postprocessing, which is difficult to apply in real-time positioning. The data processing method also includes the method developed from the time domain repetition period based on the satellite constellation, such as sidereal filtering (SF) [ 9 ] and advanced sidereal filtering (ASF) [ 10 ], this kind of method has difficulties such as large amount of modeling and complicated correction; and the modeling method based on multipath spatial repeatability such as multipath hemispherical map (MHM) [ 11 ], trend surface analysis-based multipath hemispherical map (T-MHM) [ 12 ] and single-difference multipath hemispherical map (SD-MHM) [ 13 ]. In addition, with the development of neural networks and machine learning, there are many new methods to identify line of sight (LOS) and non line of sight (NLOS) signals, including NLOS multipath classification of GNSS signal correlation output using machine learning [ 14 ], machine learning based LOS/NLOS classifier for GNSS shadow matching [ 15 ], neural networks based GPS spoofing detection [ 16 ].…”

Correction Model of BDS-3 Satellite Pseudorange Multipath Delays and Its Impact on Single-Frequency Precise Point Positioning

“…ese errors can be corrected by the existing algorithms [11][12][13]. However, some errors, such as pseudorange multipath delays, have not yet been corrected by an agreed upon method [14,15]. e downlink navigation signals of satellites are transmitted under nonideal conditions, and the surrounding environment has a great influence on the received signals [2].…”