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GPS/GLONASS Combined Precise Point Positioning with Receiver Clock Modeling.

Wang F, Chen X, Guo F - Sensors (Basel) (2015)

Bottom Line: The results indicate that the positioning accuracy as well as convergence time can benefit from the receiver clock modeling.Compared to the GPS-only PPP, solutions of the GPS/GLONASS combined PPP are much better no matter if the receiver clock offsets are modeled or not, indicating that the positioning accuracy and reliability are significantly improved with the additional GLONASS satellites in the case of insufficient number of GPS satellites or poor geometry conditions.However, the refinement of ISB model weakens the correlation between coordinates and ISB estimates and finally enhance the PPP performance in the case of poor observation conditions.

View Article: PubMed Central - PubMed

Affiliation: School of Geodesy and Geomatics, Wuhan University, 129 Luoyu Road, Wuhan 430079, China. fhwang@sgg.whu.edu.cn.

ABSTRACT
Research has demonstrated that receiver clock modeling can reduce the correlation coefficients among the parameters of receiver clock bias, station height and zenith tropospheric delay. This paper introduces the receiver clock modeling to GPS/GLONASS combined precise point positioning (PPP), aiming to better separate the receiver clock bias and station coordinates and therefore improve positioning accuracy. Firstly, the basic mathematic models including the GPS/GLONASS observation equations, stochastic model, and receiver clock model are briefly introduced. Then datasets from several IGS stations equipped with high-stability atomic clocks are used for kinematic PPP tests. To investigate the performance of PPP, including the positioning accuracy and convergence time, a week of (1-7 January 2014) GPS/GLONASS data retrieved from these IGS stations are processed with different schemes. The results indicate that the positioning accuracy as well as convergence time can benefit from the receiver clock modeling. This is particularly pronounced for the vertical component. Statistic RMSs show that the average improvement of three-dimensional positioning accuracy reaches up to 30%-40%. Sometimes, it even reaches over 60% for specific stations. Compared to the GPS-only PPP, solutions of the GPS/GLONASS combined PPP are much better no matter if the receiver clock offsets are modeled or not, indicating that the positioning accuracy and reliability are significantly improved with the additional GLONASS satellites in the case of insufficient number of GPS satellites or poor geometry conditions. In addition to the receiver clock modeling, the impacts of different inter-system timing bias (ISB) models are investigated. For the case of a sufficient number of satellites with fairly good geometry, the PPP performances are not seriously affected by the ISB model due to the low correlation between the ISB and the other parameters. However, the refinement of ISB model weakens the correlation between coordinates and ISB estimates and finally enhance the PPP performance in the case of poor observation conditions.

No MeSH data available.


Related in: MedlinePlus

Receiver clock offset and ISB of GPS/GLONASS combined PPP.
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sensors-15-15478-f006: Receiver clock offset and ISB of GPS/GLONASS combined PPP.

Mentions: Figure 6 shows the estimated receiver clock offsets and the GPS-GLONASS time scale differences for the first 3 h on HOB2 and WTZR stations. As shown in Figure 6, the estimated receiver clock biases of both Models do not change frequently, which further confirms the feasibility of receiver clock modeling. Since the receiver clock bias parameters are estimated with different schemes, the estimates consequently perform different characteristics. Take the Model 2 for example, the receiver clock estimates run with larger variations since the potential short-term correlations among the receiver clock biases are ignored. However, the receiver clock estimates run much smoother if they are modeled as a linear model in a specific segment. One may notice that, the receiver clock estimates in Figure 6 show similar features as the vertical coordinates in Figure 5. This can be attributed to the correlation between the receiver clock bias and station height as mentioned in Section 3.1. As to the time scale differences, estimates from both models are close to each other because the same appropriate model is utilized in Figure 6.


GPS/GLONASS Combined Precise Point Positioning with Receiver Clock Modeling.

Wang F, Chen X, Guo F - Sensors (Basel) (2015)

Receiver clock offset and ISB of GPS/GLONASS combined PPP.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4541840&req=5

sensors-15-15478-f006: Receiver clock offset and ISB of GPS/GLONASS combined PPP.
Mentions: Figure 6 shows the estimated receiver clock offsets and the GPS-GLONASS time scale differences for the first 3 h on HOB2 and WTZR stations. As shown in Figure 6, the estimated receiver clock biases of both Models do not change frequently, which further confirms the feasibility of receiver clock modeling. Since the receiver clock bias parameters are estimated with different schemes, the estimates consequently perform different characteristics. Take the Model 2 for example, the receiver clock estimates run with larger variations since the potential short-term correlations among the receiver clock biases are ignored. However, the receiver clock estimates run much smoother if they are modeled as a linear model in a specific segment. One may notice that, the receiver clock estimates in Figure 6 show similar features as the vertical coordinates in Figure 5. This can be attributed to the correlation between the receiver clock bias and station height as mentioned in Section 3.1. As to the time scale differences, estimates from both models are close to each other because the same appropriate model is utilized in Figure 6.

Bottom Line: The results indicate that the positioning accuracy as well as convergence time can benefit from the receiver clock modeling.Compared to the GPS-only PPP, solutions of the GPS/GLONASS combined PPP are much better no matter if the receiver clock offsets are modeled or not, indicating that the positioning accuracy and reliability are significantly improved with the additional GLONASS satellites in the case of insufficient number of GPS satellites or poor geometry conditions.However, the refinement of ISB model weakens the correlation between coordinates and ISB estimates and finally enhance the PPP performance in the case of poor observation conditions.

View Article: PubMed Central - PubMed

Affiliation: School of Geodesy and Geomatics, Wuhan University, 129 Luoyu Road, Wuhan 430079, China. fhwang@sgg.whu.edu.cn.

ABSTRACT
Research has demonstrated that receiver clock modeling can reduce the correlation coefficients among the parameters of receiver clock bias, station height and zenith tropospheric delay. This paper introduces the receiver clock modeling to GPS/GLONASS combined precise point positioning (PPP), aiming to better separate the receiver clock bias and station coordinates and therefore improve positioning accuracy. Firstly, the basic mathematic models including the GPS/GLONASS observation equations, stochastic model, and receiver clock model are briefly introduced. Then datasets from several IGS stations equipped with high-stability atomic clocks are used for kinematic PPP tests. To investigate the performance of PPP, including the positioning accuracy and convergence time, a week of (1-7 January 2014) GPS/GLONASS data retrieved from these IGS stations are processed with different schemes. The results indicate that the positioning accuracy as well as convergence time can benefit from the receiver clock modeling. This is particularly pronounced for the vertical component. Statistic RMSs show that the average improvement of three-dimensional positioning accuracy reaches up to 30%-40%. Sometimes, it even reaches over 60% for specific stations. Compared to the GPS-only PPP, solutions of the GPS/GLONASS combined PPP are much better no matter if the receiver clock offsets are modeled or not, indicating that the positioning accuracy and reliability are significantly improved with the additional GLONASS satellites in the case of insufficient number of GPS satellites or poor geometry conditions. In addition to the receiver clock modeling, the impacts of different inter-system timing bias (ISB) models are investigated. For the case of a sufficient number of satellites with fairly good geometry, the PPP performances are not seriously affected by the ISB model due to the low correlation between the ISB and the other parameters. However, the refinement of ISB model weakens the correlation between coordinates and ISB estimates and finally enhance the PPP performance in the case of poor observation conditions.

No MeSH data available.


Related in: MedlinePlus