Assessment of the Multi-GNSS PPP Performance Using Precise Products from the Wuhan Analysis Centre (original) (raw)
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Comparative analysis of multi-constellation GNSS single-frequency precise point positioning
Survey Review, 2017
We develop new single-frequency PPP models, which combine the observations of the current GNSS constellations, including GPS, GLONASS, Galileo and BeiDou. Four single-frequency GNSS PPP models are developed, namely, the undifferenced single-frequency GNSS PPP model, the undifferenced ionosphere-free (IF) code and phase model known as quasi-phase model, the between-satellite-single-difference model (BSSD) and the between-satellite-singledifference ionosphere-free (BSSDIF) model. The IGS final precise products are used to account for the orbital and clock errors. For both undifferenced and BSSD models, the IGS final global ionospheric maps (GIM) model is used to correct the ionospheric delay. The GNSS inter-system biases are treated as additional unknowns in the estimation process for the undifferenced models, while a loosely coupled technique is used for the BSSD models. Various GNSS combinations are considered in the assessment for each PPP model, including GPS/GLONASS, GPS/Galileo, GPS/BeiDou and quad-constellation GNSS observations. It is shown that the multi-GNSS observations enhance the PPP solution accuracy in comparison with the GPS-only solution. Furthermore, the use of IF-PPP technique enhances the positioning accuracy by 25, 20, 24, 20 and 19% compared with the GIM-based PPP model for the GPS-only, GPS/GLONASS, GPS/Galileo, GPS/BeiDou and quad-GNSS combinations, respectively, for 1 h of GNSS data processing. In addition, an average of 15% positioning accuracy improvement can be obtained when the BSSD techniques are used compared with the undifferenced techniques. However, for 6 h of processing, comparable positioning accuracy can be obtained from all four singlefrequency models.
Improving Precise Point Positioning Performance Using Multi-Frequency Multi-Constellation GNSS
2019
Precise Point Positioning (PPP) is a technique for determining the precise coordinates of a stand-alone Global Navigation Satellite System (GNSS) receiver without relying on simultaneous measurements from a network or nearby reference receiver. PPP can provide decimetre level accuracy for kinematic positioning and cm-level accuracy for static surveying, provided that long duration dual-frequency measurements are used with the most precise satellite orbit and clock products. However, its main drawback is a long convergence time of typically half an hour to reach cm-level accuracy with static data, and decimetre level accuracy with kinematic data. The ongoing modernisation of GPS and GLONASS, accompanied by the development of Galileo, Beidou and regional navigation satellite systems (RNSS) including Quazi Zenith Satellite System (QZSS) and the Indian Regional Navigation Satellite System (IRNSS), with an operational name NAVIC, provides opportunities for developing novel PPP models wit...
Precise Point Positioning (PPP) is traditionally based on dual-frequency observations of GPS or GPS/GLONASS satellite navigation systems. Recently, new GNSS constellations, such as the European Galileo and the Chinese BeiDou are developing rapidly. With the new IGS project known as IGS MGEX which produces highly accurate GNSS orbital and clock products, multi-constellations PPP becomes feasible. On the other hand, the un-differenced ionosphere-free is commonly used as standard precise point positioning technique. However, the existence of receiver and satellite biases, which are absorbed by the ambiguities, significantly affected the convergence time. Between- satellite-single-difference (BSSD) ionosphere free PPP technique is traditionally used to cancel out the receiver related biases from both code and phase measurements. This paper introduces multiple ambiguity datum (MAD) PPP technique which can be applied to separate the code and phase measurements removing the receiver and satellite code biases affecting the GNSS receiver phase clock and ambiguities parameters. The mathematical model for the three GNSS PPP techniques is developed by considering the current full GNSS constellations. In addition, the current limitations of the GNSS PPP techniques are discussed. Static post-processing results for a number of IGS MGEX GNSS stations are presented to investigate the contribution of the newly GNSS system observations and the newly developed GNSS PPP techniques and its limitations. The results indicate that the additional Galileo and BeiDou observations have a marginal effect on the positioning accuracy and convergence time compared with the existence combined GPS/GLONASS PPP. However, reference to GPS PPP, the contribution of BeiDou observations can be considered geographically dependent. In addition, the results show that the BSSD PPP models slightly enhance the convergence time compared with other PPP techniques. However, both the standard un-differenced and the developed multiple ambiguity datum techniques present comparable positioning accuracy and convergence time due to the lack of code and phase-based satellite clock products and the mathematical correlation between the positioning and ambiguity parameters.
A simplified and unified model of multi-GNSS precise point positioning
Advances in Space Research, 2015
Additional observations from other GNSS s can augment GPS precise point positioning (PPP) for improved positioning accuracy, reliability and availability. Traditional multi-GNSS PPP model requires the estimation of inter-system bias (ISB) parameter. Based on the scaled sensitivity matrix (SSM) method, a quantitative approach for assessing parameter assimilation, we theoretically prove that the ISB parameter is not correlated with coordinate parameters and it can be assimilated into clock and ambiguity parameters. Thus, removing ISB from multi-GNSS PPP model does not affect coordinate estimation. Based on this analysis, we develop a simplified and unified model for multi-GNSS PPP, where ISB parameter does not need to be estimated and observations from different GNSS systems are treated in a unified way. To verify the new model, we implement the algorithm to the self-developed software to process 1 year GPS/GLONASS data of 53 IGS (International GNSS Service) worldwide stations and 1 month GPS/BDS data of 15 IGS MGEX (Multi-GNSS Experiment) stations. Two types of GPS/GLONASS and GPS/BDS combined PPP solution are performed, one is based on traditional model and the other implements the new model. RMSs of coordinate differences between the two type of solutions are few lm for daily static PPP and less than 0.02 mm for GPS/GLONASS kinematic PPP in the North, East and Up components, respectively. Considering the millimeter-level precision of current GNSS PPP solutions, these statistics demonstrate equivalent performance of the two solution types.
Measurement Science and Technology, 2020
The development of a global navigation satellite system (GNSS) brings the benefit of positioning, navigation and timing (PNT) services with three or even more available frequency signals. This paper developed five-system multi-frequency precise point positioning (PPP) models based on mathematical and stochastic models. Static positioning performances were evaluated and analyzed with multi-GNSS experiment (MGEX) network datasets and a vehicle-borne kinematic experiment was conducted to verify the kinematic PPP performances. In addition, the receiver clock, zenith tropospheric delay (ZTD), inter-frequency bias (IFB) and differential code bias (DCB) estimates were discussed. Results show that the triple-frequency PPP performances perform slightly better than the dual-frequency solutions, apart from the GPS-related PPP models based on a single ionosphere-free (IF) combined measurement. By introducing the external ionospheric products, the mean convergence time is reduced. For instance, the mean convergence time of ionosphere-constrained (IC) multi-frequency PPP is reduced by 7.4% from 35.7 to 33.1 min and by 19.0% from 7.8 to 6.3 min, for Galileo-only and five-constellation solutions, respectively, compared with dual-frequency IF PPP models. Similarly, the kinematic PPP can also achieve improved performances with more frequency signals and multi-GNSS observations.
With expanding satellite-based navigation systems, multi-Global Navigation Satellite System (GNSS) Precise Point Positioning (PPP) presents an advantage over a single navigation system, which improves position accuracy and enhances availability of satellites and signals. The York GNSS PPP software was developed using C++ in the Microsoft.Net platform to utilize the existing multi-GNSS satellite constellations based on the software processor used by the Natural Resources Canada (NRCan) PPP online service. The software was built as a robust, scalable, modular tool that meets the highest of scientific standards compared to existing online PPP engines. There exists a correlation between receiver stations from heterogeneous networks, such as the IGS, in GNSS PPP processing and the increase in magnitude of the pseudorange and carrier-phase biases in both GPS + GLONASS and GLONASS-only PPP solutions. The correlation is due to mixed receiver and antenna hardware as well as firmware versions. Unlike GPS, GLONASS observations are affected by the Frequency Division Multiple Access (FDMA) satellite signal structure, which introduces inter-frequency channel biases and other system biases. The GLONASS pseudorange inter-channel frequency biases show a strong correlation with different receiver types, firmware versions and antenna types. This research estimated the GLONASS pseudorange inter-frequency channel biases using 350 IGS stations, based on 32 receiver types and 4 antenna types over a period of one week. An improvement of 19% was observed after calibrating for the pseudorange ICBs, in the horizontal components respectively, considering a 20 minutes convergence period
GNSS Satellite Clock Real-Time Estimation and Analysis for Its Positioning
Lecture Notes in Electrical Engineering, 2014
Real-time and high-precision Multi-GNSS positioning technical has been playing an important role in the determination of low earth orbiter (LEO) and monitoring of geologic hazards. The key concern should be on the achievement of the high-precision satellite orbit and clock products. In this paper, real-time clock estimation strategy was introduced. Based on the mean square root filtering method, dates via 35 global uniformly distributed IGS observations were used to estimate real-time satellite clock errors of GPS and CLONASS, which was proved 0.2 ns and 0.8 ns respectively. The outcomes were verified again via precise point positioning. Consequently, compared with the positioning accuracy via only GPS, that of GPS and GLONASS improved 26 % in X direction, 40 % in Y direction and 2 % in Z direction. The convergence time shorten 2 to 4 times as well. Keywords GPS Á GLONASS Á Real-time clock estimation Á Combination positioning Á Mean square root filtering 62.1 Instruction Precise point positioning (PPP) of Global navigation satellite system (GNSS) can achieve centimetre-level accuracy for static positioning and decimetre-level for kinematic respectively. Its precision depends mainly on the quality of satellite orbit
Analyzing GNSS data in precise point positioning software
GPS Solutions, 2010
This work demonstrates that precise point positioning (PPP) can be used not only for positioning, but for a variety of other tasks, such as signal analysis. The fact that the observation model used for accurate error modeling has to take into consideration the several effects present in GPS signals, and that observations are undifferenced, makes PPP a powerful data analysis tool sensitive to a variety of parameters. The PPP application developed at the University of New Brunswick, which is called GAPS (GPS Analysis and Positioning Software), has been designed and built in order to take advantage of available precise products, resulting in a data analysis tool for determining parameters in addition to position, receiver clock error, and neutral atmosphere delay. These other estimated parameters include ionospheric delays, code biases, satellite clock errors, and code multipath among others. In all cases, the procedures were developed in order to be suitable for real-time as well as post-processing applications. One of the main accomplishments in the development described here is the use of very precise satellite products, coupled with a very complete observation error modeling to make possible a variety of analyses based on GPS data. In this paper, several procedures are described, their innovative aspects are pointed out, and their results are analyzed and compared with other sources. The procedures and software are readily adaptable for using data from other global navigation satellite systems.