In-orbit Experimental of Satellite-induced Code Pseudorange Deviations of BeiDou System

2018 ◽  
Author(s):  
Shaojun Bi ◽  
Changgang Zheng ◽  
Congwei Yang ◽  
Jinjun Zheng ◽  
Chengyan He ◽  
...  
Keyword(s):  
Beidou System ◽  
Code Pseudorange

scholarly journals BeiDou Satellite Unhealthy States and the Impact on System Performance

Sensors ◽  
2018 ◽  
Vol 18 (12) ◽  
pp. 4196 ◽  
Author(s):  
Caibo Hu ◽  
Chuang Shi ◽  
Jinping Chen ◽  
Yidong Lou ◽  
Fei Wang
Keyword(s):  
System Performance ◽  
Satellite Orbit ◽  
Service Area ◽  
The Other ◽  
Classification Method ◽  
Positioning Accuracy ◽  
General Classification ◽  
Broadcast Ephemeris ◽  
Beidou System ◽  
The Impact

The BeiDou system satellites may be unhealthy due to many reasons, affecting system performance in different ways. Therefore, it is important to analyze the causes and characteristics of the satellites’ unhealthy states. In this study, these states are classified into five types based on the broadcast ephemeris. Three criteria are presented, based on which a general classification method is proposed. Data from July 2017 to June 2018 are analyzed to validate the method, from which we know that the average unhealthy duration due to satellite maneuvers is much longer than the duration of unhealthy states related to satellite orbit or clock anomalies, and the other unhealthy states may be caused by inbound or outbound satellites. Statistics show that most of the time, the number of unhealthy satellites is no more than two and the average positioning accuracy in the service area will decrease by no more than 0.75 and 1.2 meters when one or two BDS satellites are unhealthy, respectively.

scholarly journals BeiDou satellite-induced code pseudorange variations: diagnosis and therapy

GPS Solutions ◽  
2014 ◽  
Vol 19 (4) ◽  
pp. 639-648 ◽  
Author(s):  
Lambert Wanninger ◽  
Susanne Beer
Keyword(s):  
Diagnosis And Therapy ◽  
Code Pseudorange

Analysis of BDS-3 distributed autonomous navigation based on BeiDou system simulation platform

2021 ◽  
Vol 67 (1) ◽  
pp. 401-410
Author(s):  
Xiaozhou Ye ◽  
Wenxiang Liu ◽  
Yong Zuo ◽  
Wei Wang ◽  
Haihong Wang ◽  
...  
Keyword(s):  
Autonomous Navigation ◽  
System Simulation ◽  
Simulation Platform ◽  
Beidou System

scholarly journals Time Synchronization and Performance of BeiDou Satellite Clocks in Orbit

2013 ◽  
Vol 2013 ◽  
pp. 1-5 ◽  
Author(s):  
Han Chunhao ◽  
Cai Zhiwu ◽  
Lin Yuting ◽  
Liu Li ◽  
Xiao Shenghong ◽  
...  
Keyword(s):  
Time Synchronization ◽  
Time Transfer ◽  
Time Model ◽  
Error Sources ◽  
Satellite Navigation System ◽  
Beidou System ◽  
Ground Test ◽  
And Performance ◽  
General Relations ◽  
Better Than

The time model of Beidou satellite clocks is analyzed. The general relations of satellite clocks with the system time are studied. The error sources of two-way radio time transfer between satellites and uplink stations are analyzed. The uncertainty of type A is about 0.3 ns in Beidou system. All the satellite clocks in orbit of Beidou satellite navigation system are evaluated by the clock offsets observed by the two-way radio time transfer. The frequency stabilities at a sample time of 10000 s and 1 day for all the satellite clocks are better than . It means that the performance of Beidou satellite clocks in orbit is consistent with the ground test, and the results in orbit are a little better than those in ground vacuum.

A Precise Weighting Approach with Application to Combined L1/B1 GPS/BeiDou Positioning

2014 ◽  
Vol 67 (5) ◽  
pp. 911-925 ◽  
Author(s):  
Changsheng Cai ◽  
Lin Pan ◽  
Yang Gao
Keyword(s):  
Time Window ◽  
A Priori ◽  
Estimation Method ◽  
Satellite System ◽  
Positioning Accuracy ◽  
Satellite Systems ◽  
Beidou System ◽  
Component Estimation ◽  
Navigation Service ◽  
Global Navigation Satellite

The BeiDou system has been providing a regional navigation service since 27 December 2012. The Global Navigation Satellite System (GNSS) user community will benefit from combined Global Positioning System (GPS)/BeiDou positioning due to improved positioning accuracy, reliability and availability. But to achieve the best positioning solutions, precise weights of the GPS and BeiDou observations are important since this involves the processing of measurements from two different satellite systems with different quality. Currently, a priori variances are typically used to determine the weights of different types of observations. However, such an approach may not be precise since many un-modelled errors are not accounted for. The Helmert variance component estimation method is more appropriate in this case to determine the weights of GPS and BeiDou observations. This requires high redundant observations in order to obtain reliable solutions, which will be a concern in the case of insufficient numbers of visible satellites. To address this issue, a weighting approach is proposed by a combination of the Helmert method and a moving-window average filter. In this approach, the filter is applied to combine all epoch-by-epoch weight estimates within a time window. As a result, more precise and reliable weights for GPS and BeiDou observations can be obtained at every epoch. Both static and kinematic tests in open sky and under tree environments are conducted to assess the performance of the new weighting approach. The results indicate significantly improved positioning accuracy.

scholarly journals A Forward GPS Multipath Simulator Based on the Vegetation Radiative Transfer Equation Model

2017 ◽  
Author(s):  
Xuerui Wu ◽  
Shuanggen Jin
Keyword(s):  
Soil Moisture ◽  
Radiative Transfer ◽  
Transfer Equation ◽  
Radiative Transfer Equation ◽  
Signal To Noise Ratio ◽  
Equation Model ◽  
Forest Monitoring ◽  
Specular Scattering ◽  
Vegetation Parameters ◽  
Code Pseudorange

GNSS have been widely used in navigation, positioning and timing. Nowadays, the multipath errors previously considered detrimental may be re-utilized for the remote sensing of geophysical parameters (soil moisture, vegetation and snow depth), e.g. GPS- Multipath Reflectometry (GPS-MR). In this paper, a new element describing bistatic scattering properties of vegetation is incorporated into the traditional GPS-MR model. This new element is the first-order radiative transfer equation model. The new forward GPS multipath simulator is able to explicitly link the vegetation parameters with GPS multipath observables (signal-to-noise-ratio (SNR), code pseudorange and carrier phase observables). The trunk layer and its corresponding scattering mechanisms are ignored since GPS-MR is not suitable for high forest monitoring due to the coherence of direct and reflected signals. Based on this new model linking the GPS observables (SNR, phase and pseudorange) with detailed vegetation parameters, the developed simulator can present how the GPS signals (L1 and L2 carrier frequencies, C/A, P(Y) and L2C modulations) are transmitted (scattered and absorbed) through vegetation medium and received by GPS receivers. Simulation results show that wheat will decrease the amplitudes of GPS multipath observables, if we increase the vegetation moisture contents or the scatters sizes (stem or leaf), the amplitudes of GPS multipath observables (SNR, phase and code) decrease. Although the Specular-Ground component dominates the total specular scattering, vegetation covered ground soil moisture has almost no effects on the final multipath signatures. Our simulated results are consistent with published results for environmental parameter detections with GPS-MR.

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