Impact of GPS differential code bias in dual- and triple-frequency positioning and satellite clock estimation

GPS Solutions ◽  
2016 ◽  
Vol 21 (3) ◽  
pp. 897-903 ◽  
Author(s):  
Haojun Li ◽  
Bofeng Li ◽  
Lizhi Lou ◽  
Ling Yang ◽  
Jiexian Wang
Keyword(s):  
Satellite Clock ◽  
Differential Code Bias ◽  
Triple Frequency ◽  
Code Bias ◽  
Clock Estimation

scholarly journals Investigation and Validation of the Time-Varying Characteristic for the GPS Differential Code Bias

2019 ◽  
Vol 11 (4) ◽  
pp. 428 ◽  
Author(s):  
Haojun Li ◽  
Jingxin Xiao ◽  
Weidong Zhu
Keyword(s):  
Single Point ◽  
Time Varying ◽  
International Gnss Service ◽  
Data Set ◽  
Differential Code Bias ◽  
Triple Frequency ◽  
Code Bias ◽  
Constant Part ◽  
The Difference ◽  
Better Than

The time-varying characteristic of the bias in the GPS code observation is investigated using triple-frequency observations. The method for estimating the combined code bias is presented and the twelve-month (1 January–31 December 2016) triple-frequency GPS data set from 114 International GNSS Service (IGS) stations is processed to analyze the characteristic of the combined code bias. The results show that the main periods of the combined code bias are 12, 8, 6, 4, 4.8 and 2.67 h. The time-varying characteristic of the combined code bias, which is the combination of differential code bias (DCB) (P1–P5) and DCB (P1–P2), shows that the real satellite DCBs are also time-varying. The difference between the two sets of the computed constant parts of the combined code bias, with the IGS DCB products of DCB (P1–P2) and DCB (P1–P2) and the mean of the estimated 24-h combined code bias series, further show that the combined code bias cannot be replaced by the DCB (P1–P2) and DCB (P1–P5) products. The time-varying part of inter-frequency clock bias (IFCB) can be estimated by the phase and code observations and the phase based IFCB is the combinations of the triple-frequency satellite uncalibrated phase delays (UPDs) and the code-based IFCB is the function of the DCBs. The performances of the computed the IFCB with different methods in single point positioning indicate that the accuracy for the constant part of the combined code bias is reduced, when the IGS DCB products are used to compute. These performances also show that the time-varying part of IFCB estimated with phase observation is better than that of code observation. The predicted results show that 98% of the predicted constant part of the combined code bias can be corrected and the attenuation of the predicted accuracy is much less evident. However, the accuracy of the predicted time-varying part decreases significantly with the predicted time.

scholarly journals BDS-3 differential code bias estimation with undifferenced uncombined model based on triple-frequency observation

2020 ◽  
Vol 94 (4) ◽  
Author(s):  
Shengfeng Gu ◽  
YinTong Wang ◽  
Qile Zhao ◽  
Fu Zheng ◽  
Xiaopeng Gong
Keyword(s):  
Bias Estimation ◽  
Differential Code Bias ◽  
Model Based ◽  
Triple Frequency ◽  
Code Bias ◽  
Frequency Observation

Multi-GNSS triple-frequency differential code bias (DCB) determination with precise point positioning (PPP)

2018 ◽  
Vol 93 (5) ◽  
pp. 765-784 ◽  
Author(s):  
Teng Liu ◽  
Baocheng Zhang ◽  
Yunbin Yuan ◽  
Zishen Li ◽  
Ningbo Wang
Keyword(s):  
Precise Point Positioning ◽  
Differential Code Bias ◽  
Triple Frequency ◽  
Code Bias ◽  
Point Positioning

Regional BDS satellite clock estimation with triple-frequency ambiguity resolution based on undifferenced observation

GPS Solutions ◽  
2019 ◽  
Vol 23 (2) ◽  
Author(s):  
Xinhao Yang ◽  
Shengfeng Gu ◽  
Xiaopeng Gong ◽  
Weiwei Song ◽  
Yidong Lou ◽  
...  
Keyword(s):  
Ambiguity Resolution ◽  
Satellite Clock ◽  
Triple Frequency ◽  
Clock Estimation

Service and Evaluation of the GPS Triple-Frequency Satellite Clock Offset

2018 ◽  
Vol 71 (5) ◽  
pp. 1263-1273
Author(s):  
Haojun Li ◽  
Weidong Zhu ◽  
Rungen Zhao ◽  
Jiexian Wang
Keyword(s):  
Global Positioning System ◽  
Single Point ◽  
Satellite Clock ◽  
Service Strategy ◽  
North East ◽  
Triple Frequency ◽  
Global Positioning ◽  
Code Bias ◽  
Clock Offset ◽  
Gps Observations

This paper considers the effect of the biases in Global Positioning System (GPS) observations on satellite clock offset estimation. GPS triple-frequency satellite clock and reference observations are discussed. When the reference observation is selected and the corresponding satellite clock offset is computed, satellite clock offsets for all observations are obtained based on the computed satellite clock offset and the biases between the reference observation and other observations. The characteristics of these biases are analysed, and a service strategy for the GPS triple-frequency satellite clock offset is presented. To evaluate the computed GPS satellite clock offset, the performance in single-point positioning is validated. The positioning results show that the average relative improvements are about 20%, 28% and 19% for north, east and vertical components, when the Differential Code Bias (DCB) (P1-P2), DCB (P1-P5) and modelled Inter-Frequency Clock Bias (IFCB) are corrected. The effect of DCB (P1-P2), DCB (P1-P5) and modelled IFCB on the altitude direction is more evident than on the horizontal directions.

scholarly journals A Method to Accelerate the Convergence of Satellite Clock Offset Estimation Considering the Time-Varying Code Biases

2021 ◽  
Vol 13 (14) ◽  
pp. 2714
Author(s):  
Shuai Liu ◽  
Yunbin Yuan
Keyword(s):  
Real Time ◽  
Convergence Speed ◽  
Time Varying ◽  
Satellite Clock ◽  
Filter Convergence ◽  
Long Time ◽  
Code Bias ◽  
Clock Estimation ◽  
The Stability ◽  
Clock Offset

Continuous and stable precision satellite clock offsets are an important guarantee for real-time precise point positioning (PPP). However, in real-time PPP, the estimation of a satellite clock is often interrupted for various reasons such as network fluctuations, which leads to a long time for clocks to converge again. Typically, code biases are assumed to stay constant over time in clock estimation according to the current literature. In this contribution, it is shown that this assumption reduces the convergence speed of estimation, and the satellite clocks are still unstable for several hours after convergence. For this reason, we study the influence of different code bias extraction schemes, that is, taking code biases as constants, extracting satellite code biases (SCBs), extracting receiver code biases (RCBs) and simultaneously extracting SCBs and RCBs, on satellite clock estimation. Results show that, the time-varying SCBs are the main factors leading to the instability of satellite clocks, and considering SCBs in the estimation can significantly accelerate the filter convergence and improve the stability of clocks. Then, the products generated by introducing SCBs in the clock estimation based on undifferenced observations are applied to PPP experiments. Compared with the original undifferenced model, clocks estimated using the new method can significantly accelerate the convergence speed of PPP and improve the positioning accuracy, which illustrates that our estimated clocks are effective and superior.

scholarly journals The Effect of BDS-3 Time Group Delay and Differential Code Bias Corrections on Positioning

2020 ◽  
Vol 11 (1) ◽  
pp. 104
Author(s):  
Peipei Dai ◽  
Jianping Xing ◽  
Yulong Ge ◽  
Xuhai Yang ◽  
Weijin Qin ◽  
...  
Keyword(s):  
Group Delay ◽  
Assessment System ◽  
Convergence Time ◽  
Single Frequency ◽  
Positioning Accuracy ◽  
Differential Code Bias ◽  
Receiver Clock ◽  
Code Bias ◽  
Point Positioning ◽  
The Impact

The timing group delay parameter (TGD) or differential code bias parameter (DCB) is an important factor that affects the performance of GNSS basic services; therefore, TGD and DCB must be taken seriously. Moreover, the TGD parameter is modulated in the navigation message, taking into account the impact of TGD on the performance of the basic service. International GNSS Monitoring and Assessment System (iGMAS) provides the broadcast ephemeris with TGD parameter and the Chinese Academy of Science (CAS) provides DCB products. In this paper, the current available BDS-3 TGD and DCB parameters are firstly described in detail, and the relationship of TGD and DCB for BDS-3 is figured out. Then, correction models of BDS-3 TGD and DCB in standard point positioning (SPP) or precise point positioning (PPP) are given, which can be applied in various situations. For the effects of TGD and DCB in the SPP and PPP solution processes, all the signals from BDS-3 were researched, and the validity of TGD and DCB has been further verified. The experimental results show that the accuracy of B1I, B1C and B2a single-frequency SPP with TGD or DCB correction was improved by approximately 12–60%. TGD will not be considered for B3I single-frequency, because the broadcast satellite clock offset is based on the B3I as the reference signal. The positioning accuracy of B1I/B3I and B1C/B2a dual-frequency SPP showed that the improvement range for horizontal components is 60.2% to 74.4%, and the vertical components improved by about 50% after the modification of TGD and DCB. In addition, most of the uncorrected code biases are mostly absorbed into the receiver clock bias and other parameters for PPP, resulting in longer convergence time. The convergence time can be max increased by up to 50% when the DCB parameters are corrected. Consequently, the positioning accuracy can reach the centimeter level after convergence, but it is critical for PPP convergence time and receiver clock bias that the TGD and DCB correction be considered seriously.

GPS satellite clock estimation using global atomic clock network

GPS Solutions ◽  
2021 ◽  
Vol 25 (3) ◽  
Author(s):  
Jian Yao ◽  
Sungpil Yoon ◽  
Bryan Stressler ◽  
Steve Hilla ◽  
Mark Schenewerk
Keyword(s):  
Atomic Clock ◽  
Satellite Clock ◽  
Clock Network ◽  
Clock Estimation

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

2018 ◽  
Vol 10 (11) ◽  
pp. 1736 ◽  
Author(s):  
Xin Xie ◽  
Rongxin Fang ◽  
Tao Geng ◽  
Guangxing Wang ◽  
Qile Zhao ◽  
...  
Keyword(s):  
Density Ratio ◽  
Assessment System ◽  
Triple Frequency ◽  
Signal Characteristics ◽  
Open Service ◽  
Code Bias ◽  
Block Iif ◽  
Navigation Signals ◽  
Gps Block Iif

The international GNSS monitoring and assessment system (iGMAS) tracking network has been established by China to track multi-GNSS satellites. A key feature of iGMAS stations is the capability to fully track new navigation signals from the recently deployed BDS-3 satellites. In addition to the B1I and B3I signals inherited from BDS-2 satellites, the BDS-3 satellites are capable of transmitting new open service signals, including B1C at 1575.42 MHz, B2a at 1176.45 MHz, and B2b at 1207.14 MHz. In this contribution, we present a comprehensive analysis and characterization of GNSS signals tracked by different receivers and antennas equipped in the iGMAS network, especially as they relate to BDS-3 signals. Signal characteristics are analyzed in terms of the carrier-to-noise density ratio for the different signals as measured by the receiver, as well as pseudo-range noise and multipath. Special attention is given to discussion of the satellite-induced code bias, which has been identified to exist in the code observations of BDS-2, and the inter-frequency clock bias (IFCB), which has been observed in the triple-frequency carrier phase combinations of GPS Block IIF and BDS-2 satellites. The results indicate that the satellite-induced code bias is negligible for all signals of BDS-3 satellites, while small IFCB variations with peak amplitudes of about 1 cm can be recognized in BDS-3 triple-carrier combinations.

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