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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

Correlation coefficients between ISB and other parameters (case one: sufficient number of GPS and GLONASS satellites, an average of 15 satellites included).
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sensors-15-15478-f008: Correlation coefficients between ISB and other parameters (case one: sufficient number of GPS and GLONASS satellites, an average of 15 satellites included).

Mentions: Case one: The same data used in Section 3.1 were processed with the above three schemes. In this case, an average of 15 GPS/GLONASS satellites are available. Figure 7 shows the positioning results and the corresponding geometric dilution of precision (GDOP) for the first 2 h on HOB2. The other stations show the similar results and thus are not presented herein. After a short time convergence, both the horizontal and vertical components reach an accuracy of a few centimeters (±5 cm). One may notice that the performances of the three different schemes are almost the same. In other words, the positioning accuracy is not seriously affected by the different models of inter-system bias. This is reasonable when we acknowledge the fact that the correlation coefficients between IBS and other parameters are quite small due to the sufficient number of satellites and the pretty good geometry. As shown in Figure 8, the correlation coefficients between ISB and receiver clock bias show the largest values (about 0.05), whereas the correlation coefficients between ISB and the other parameters (such as coordinates and tropospheric delay) are close to zeroes. Moreover, the correlation coefficients seem to be unaffected by the adjustment of inter-system bias models.


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

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

Correlation coefficients between ISB and other parameters (case one: sufficient number of GPS and GLONASS satellites, an average of 15 satellites included).
© Copyright Policy
Related In: Results  -  Collection

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

sensors-15-15478-f008: Correlation coefficients between ISB and other parameters (case one: sufficient number of GPS and GLONASS satellites, an average of 15 satellites included).
Mentions: Case one: The same data used in Section 3.1 were processed with the above three schemes. In this case, an average of 15 GPS/GLONASS satellites are available. Figure 7 shows the positioning results and the corresponding geometric dilution of precision (GDOP) for the first 2 h on HOB2. The other stations show the similar results and thus are not presented herein. After a short time convergence, both the horizontal and vertical components reach an accuracy of a few centimeters (±5 cm). One may notice that the performances of the three different schemes are almost the same. In other words, the positioning accuracy is not seriously affected by the different models of inter-system bias. This is reasonable when we acknowledge the fact that the correlation coefficients between IBS and other parameters are quite small due to the sufficient number of satellites and the pretty good geometry. As shown in Figure 8, the correlation coefficients between ISB and receiver clock bias show the largest values (about 0.05), whereas the correlation coefficients between ISB and the other parameters (such as coordinates and tropospheric delay) are close to zeroes. Moreover, the correlation coefficients seem to be unaffected by the adjustment of inter-system bias models.

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