Limits...
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

Positioning error and GDOP of GPS/GLONASS combined PPP with different ISB models (case two: limited number of GPS and GLONASS satellites, an average of 6 satellites included).
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4541840&req=5

sensors-15-15478-f009: Positioning error and GDOP of GPS/GLONASS combined PPP with different ISB models (case two: limited number of GPS and GLONASS satellites, an average of 6 satellites included).

Mentions: Case two: Likewise, the same data used in Section 3.2 were processed with the above three schemes. As mentioned in Section 3.2, only a few satellites (3G + 3R) are available in this case. Figure 9 shows the positioning results and the corresponding GDOP for the first two hours on HOB2, and the correlation coefficients between the ISB and other parameters are shown in Figure 10. Due to the limited number of satellites and poor geometry, the positioning accuracy decreases to a few decimeters. Comparing with the positioning errors of the three schemes, we can find that the latter two schemes outperform the first one, indicating the GPS/GLONASS combined PPP can benefit from the inter-system bias modeling. This is true at the initial stage, especially the improvement of convergence. The correlation coefficients in Figure 10 show that the coordinates as well as receiver clock biases are highly correlated with the ISB estimates in the case of an insufficient number of satellites and poor geometry. Once the ISBs are modeled as random walk noise or white noise, the correlation coefficients can be obviously reduced. That means the parameters can be better separated from each other, and consequently we can obtain more accurate and reliable solutions.


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

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

Positioning error and GDOP of GPS/GLONASS combined PPP with different ISB models (case two: limited number of GPS and GLONASS satellites, an average of 6 satellites included).
© Copyright Policy
Related In: Results  -  Collection

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

sensors-15-15478-f009: Positioning error and GDOP of GPS/GLONASS combined PPP with different ISB models (case two: limited number of GPS and GLONASS satellites, an average of 6 satellites included).
Mentions: Case two: Likewise, the same data used in Section 3.2 were processed with the above three schemes. As mentioned in Section 3.2, only a few satellites (3G + 3R) are available in this case. Figure 9 shows the positioning results and the corresponding GDOP for the first two hours on HOB2, and the correlation coefficients between the ISB and other parameters are shown in Figure 10. Due to the limited number of satellites and poor geometry, the positioning accuracy decreases to a few decimeters. Comparing with the positioning errors of the three schemes, we can find that the latter two schemes outperform the first one, indicating the GPS/GLONASS combined PPP can benefit from the inter-system bias modeling. This is true at the initial stage, especially the improvement of convergence. The correlation coefficients in Figure 10 show that the coordinates as well as receiver clock biases are highly correlated with the ISB estimates in the case of an insufficient number of satellites and poor geometry. Once the ISBs are modeled as random walk noise or white noise, the correlation coefficients can be obviously reduced. That means the parameters can be better separated from each other, and consequently we can obtain more accurate and reliable solutions.

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