Abstract
BDS (Beidou Navigation Satellite System) integrates the legacy PNT (Positioning, Navigation, Timing) service and the authorized SBAS (Satellite-Based Augmentation Services) service. To support the requirement of decimeter-level positioning, four types of differential corrections are developed in the BDS SBAS, including the State Space Representation (SSR)-based satellite orbit/clock corrections, the Observation Space Representation (OSR)-based ionospheric grid corrections, and the partition comprehensive corrections. In this study, we summarize the features of these differential corrections, including their definition and usages. The function model of precise point positioning (PPP) for dual- and single-frequency users using the four types of BDS SBAS corrections are proposed. Datasets are collected from 34 stations over one month in 2019, and PPP is performed for all the datasets. Results show that the root mean square (RMS) of the positioning errors for static/kinematic dual-frequency (DF) PPP are of 12 cm/16 cm in horizontal and 18 cm/20 cm in vertical component, while for single-frequency (SF) PPP are of 14 cm/32 cm and 22 cm/40 cm, respectively. With regard to the convergence performance, the horizontal and vertical positioning errors of kinematic DF-PPP can converge to 0.5 m in less than 15 min and 20 min, respectively. As for the kinematic SF-PPP, it could converge to 0.8 m in horizontal and 1.0 m in vertical within 30 min, where the ionosphere-constrained PPP performs better than the UofC PPP approach, owing to the contribution of the ionospheric grid corrections.
Highlights
The system-level services provided by Global Navigation Satellite System (GNSS) include Legacy PNT and satellite-based augmentation services (SBAS)
As shown by Chen et al [7,19] and Zhang et al [20], the new Beidou navigation system (BDS) SBAS corrections are generated in a superimposition way: In the first step satellite, orbit/clock corrections are estimated in an iterative way; and the estimated real-time orbit/clock corrections are used to correct the orbit/clock errors in the broadcast ephemeris during the second step where the partial comprehensive corrections (PCC) is estimated for each satellite/partition pairs
Where ρibrd,s is the geometric distance from station to satellite computed from the broadcast ephemeris, and dρ is the line of sight observation correction converted from the SBAS satellite orbit correction; δtibrd is the satellite clock calculated from the broadcast ephemeris, and ∆ti is the real-time SBAS satellite clock correction; STDim,s is the slant tropospheric delay using the same model as in the BDS SBAS; ∆Φi is the real-time SBAS partition comprehensive correction of carrier-phase, respectively
Summary
The system-level services provided by Global Navigation Satellite System (GNSS) include Legacy PNT (positioning, navigation, and timing) and satellite-based augmentation services (SBAS). The US-American Wide Area Augmentation System (WAAS) [1], the European Geostationary Navigation Overlay Service (EGNOS) [2], the Japanese Multi-functional Transport Satellite Satellite-based Augmentation System (MSAS) [3], and the Russian Satellite Differential Corrections and Monitoring (SDCM) [4], etc These systems are designed to operate as separate services beyond GPS or GLONASS systems. For the BDS SBAS system, Cao et al first evaluate the single point positioning (SPP) performance based on the equivalent satellite clock. For the BDS partition comprehensive corrections, some initial precise point positioning results are given [8], comprehensive PPP models based on these corrections are not discussed, especially for the single-frequency users. Main points of this paper are discussed and concluded
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