Accuracy assessment of Precise Point Positioning with multi-constellation GNSS data under ionospheric scintillation effects

GPS and GLONASS are currently the Global Navigation Satellite Systems (GNSS) with full operational capacity. The integration of GPS, GLONASS and future GNSS constellations can provide better accuracy and more reliability in geodetic positioning, in particular for kinematic Precise Point Positioning (PPP), where the satellite geometry is considered a limiting factor to achieve centimeter accuracy. The satellite geometry can change suddenly in kinematic positioning in urban areas or under conditions of strong atmospheric effects such as for instance ionospheric scintillation that may degrade satellite signal quality, causing cycle slips and even loss of lock. Scintillation is caused by small scale irregularities in the ionosphere and is characterized by rapid changes in amplitude and phase of the signal, which are more severe in equatorial and high latitudes geomagnetic regions. In this work, geodetic positioning through the PPP method was evaluated with integrated GPS and GLONASS data collected in the equatorial region under varied scintillation conditions. The GNSS data were processed in kinematic PPP mode and the analyses show accuracy improvements of up to 60% under conditions of strong scintillation when using multi-constellation data instead of GPS data alone. The concepts and analyses related to the ionospheric scintillation effects, the mathematical model involved in PPP with GPS and GLONASS data integration as well as accuracy assessment with data collected under ionospheric scintillation effects are presented.

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A Strategy to Mitigate the Ionospheric Scintillation Effects on BDS Precise Point Positioning: Cycle-Slip Threshold Model

Remote Sensing ◽

10.3390/rs11212551 ◽

2019 ◽

Vol 11 (21) ◽

pp. 2551

Author(s):

Xiaomin Luo ◽

Yidong Lou ◽

Shengfeng Gu ◽

Weiwei Song

Keyword(s):

Hong Kong ◽

Precise Point Positioning ◽

Threshold Model ◽

Geomagnetic Latitude ◽

Satellite System ◽

Ionospheric Scintillation ◽

Navigation Satellite ◽

Cycle Slip ◽

Cycle Slips ◽

Point Positioning

Because of the special design of BeiDou navigation satellite system (BDS) constellation, the effects of ionospheric scintillation on operational BDS generally are more serious than on the global positioning system (GPS). As BDS is currently providing global services, it is increasingly important to seek strategies to mitigate the scintillation effects on BDS navigation and positioning services. In this study, an improved cycle-slip threshold model is proposed to decrease the high false-alarm rate of cycle-slips under scintillation conditions, thus avoiding the frequent unnecessary ambiguity resets in BDS precise point positioning (PPP) solution. We use one-year (from 23 March 2015 to 23 March 2016) BDS dataset from Hong Kong Sha Tin (HKST) station (22.4°N, 114.2°E; geomagnetic latitude: 15.4°N) to model the cycle-slip threshold and try to make it suitable for three types of BDS satellites and multiple scintillation levels. The availability of our mitigation strategy is validated by using three months (from 1 September 2015 to 30 November 2015) BDS dataset collected at 10 global navigation satellite system (GNSS) stations in Hong Kong. Positioning results demonstrate that our mitigated BDS PPP can prevent the sudden fluctuations of positioning errors induced by the ionospheric scintillation. Statistical results of BDS PPP experiments show that the mitigated solution can maintain an accuracy of about 0.08 m and 0.10 m in the horizontal and vertical components, respectively. Compared with standard BDS PPP, the accuracy of mitigated PPP can be improved by approximately 24.1%, 38.2%, and 47.9% in the east, north, and up directions, respectively. Our study demonstrates that considering different scintillation levels to establish appropriate cycle-slip threshold model in PPP processing can efficiently mitigate the ionospheric scintillation effects on BDS PPP.

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Accuracy Assessment and Improvement of GNSS Precise Point Positioning Under Ionospheric Scintillation

Lecture Notes in Electrical Engineering - China Satellite Navigation Conference (CSNC) 2019 Proceedings ◽

10.1007/978-981-13-7759-4_36 ◽

2019 ◽

pp. 400-411

Author(s):

Zhenlong Fang ◽

Wenfeng Nie ◽

Tianhe Xu ◽

Zhizhao Liu ◽

Shiwei Yu

Keyword(s):

Precise Point Positioning ◽

Accuracy Assessment ◽

Ionospheric Scintillation ◽

Point Positioning

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Development and Positioning Accuracy Assessment of Precise Point Positioning Algorithms Based on GLONASS Code-Pseudorange Measurements

Journal of Positioning Navigation and Timing ◽

10.11003/jpnt.2014.3.4.155 ◽

2014 ◽

Vol 3 (4) ◽

pp. 155-161

Author(s):

Mi-So Kim ◽

Kwan-Dong Park ◽

Jihye Won

Keyword(s):

Precise Point Positioning ◽

Accuracy Assessment ◽

Positioning Accuracy ◽

Point Positioning ◽

Code Pseudorange

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Investigation of ionospheric scintillation effects on BDS precise point positioning at low-latitude regions

GPS Solutions ◽

10.1007/s10291-018-0728-8 ◽

2018 ◽

Vol 22 (3) ◽

Cited By ~ 14

Author(s):

Xiaomin Luo ◽

Yidong Lou ◽

Qinqin Xiao ◽

Shengfeng Gu ◽

Biyan Chen ◽

...

Keyword(s):

Precise Point Positioning ◽

Ionospheric Scintillation ◽

Low Latitude ◽

Point Positioning

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GNSS-Warp Software for Real-Time Precise Point Positioning

Artificial Satellites ◽

10.1515/arsa-2015-0005 ◽

2015 ◽

Vol 50 (2) ◽

pp. 59-76 ◽

Cited By ~ 10

Author(s):

Hadaś Tomasz

Keyword(s):

Real Time ◽

Precise Point Positioning ◽

Static Mode ◽

Time Service ◽

The Real ◽

North East ◽

Satellite Geometry ◽

Point Positioning ◽

Performance Validation ◽

Mode A

Abstract On April 1, 2013 IGS launched the real-time service providing products for Precise Point Positioning (PPP). The availability of real-time makes PPP a very powerful technique to process GNSS signals in real-time and opens a new PPP applications opportunities. There are still, however, some limitations of PPP, especially in the kinematic mode. A significant change in satellite geometry is required to efficiently de-correlate troposphere delay, receiver clock offset, and receiver height. In order to challenge PPP limitations, the GNSS-WARP (Wroclaw Algorithms for Real-time Positioning) software has been developed from scratch at Wroclaw University of Environmental and Life Science in Poland. This paper presents the GNSS-WARP software itself and some results of GNSS data analysis using PPP and PPP-RTK (Real-Time Kinematic) technique. The results of static and kinematic processing in GPS only and GPS + GLONASS mode with final and real-time products are presented. Software performance validation in postprocessing mode confirmed that the software can be considered as a state-ofthe- art software and used for further studies on PPP algorithm development. The real-time positioning test made it possible to assess the quality of real-time coordinates, which is a few millimeters for North, East, Up in static mode, a below decimeter in kinematic mode. The accuracy and precision of height estimates in kinematic mode were improved by constraining the solution with an external, near real-time troposphere model. The software also allows estimation of real-time ZTD, however, the obtained precision of 11.2 mm means that further improvements in the software, real-time products or processing strategy are required.

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Enabling robust and accurate navigation for UAVs using real-time GNSS precise point positioning and IMU integration

The Aeronautical Journal ◽

10.1017/aer.2020.80 ◽

2020 ◽

Vol 125 (1283) ◽

pp. 87-108

Author(s):

C. Chi ◽

X. Zhan ◽

S. Wang ◽

Y. Zhai

Keyword(s):

Real Time ◽

Precise Point Positioning ◽

Three Dimensional ◽

Coupled System ◽

Measurement Unit ◽

Satellite Geometry ◽

Tightly Coupled ◽

Point Positioning ◽

Gnss Measurements ◽

The One

ABSTRACTAccurate navigation is required in many Unmanned Aerial Vehicle (UAV) applications. In recent years, GNSS Precise Point Positioning (PPP) has been recognised as an efficient approach for providing precise positioning services. In contrast to the widely used Real-Time Kinematic (RTK), PPP is independent of reference stations, which greatly broadens its scope of application. However, the accuracy and reliability of PPP can be significantly decreased by poor GNSS satellite geometry and outage. In response, a real-time four-constellation GNSS PPP is applied to improve the geometry in this work, and PPP is tightly coupled with an Inertial Measurement Unit (IMU) to smooth the position and velocity output, thus improving the robustness of the navigation solution. Experimental flight tests are carried out using a UAV in an open-sky area, and GNSS-challenged environments are simulated. The results show that the four-constellation GNSS PPP/IMU integration reduces the Root-Mean-Square (RMS) Three-Dimensional (3D) positioning and velocity error by 76.4% and 67.1%, respectively, in open sky with respect to the one-GNSS PPP. Under scenarios where GNSS measurements are insufficient, the coupled system can still provide continuous solutions. Moreover, the coupled PPP/IMU system can also maintain the convergence of PPP during GNSS-challenged periods and can greatly shorten the re-convergence period of PPP when the UAV returns to the open sky.

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Calibration of regional ionospheric delay with uncombined precise point positioning and accuracy assessment

Journal of Earth System Science ◽

10.1007/s12040-012-0206-6 ◽

2012 ◽

Vol 121 (4) ◽

pp. 989-999 ◽

Cited By ~ 8

Author(s):

LI WEI ◽

CHENG PENGFEI ◽

BEI JINZHONG ◽

WEN HANJIANG ◽

WANG HUA

Keyword(s):

Precise Point Positioning ◽

Accuracy Assessment ◽

Ionospheric Delay ◽

Point Positioning

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REVISITING THE ROLE OF OBSERVATION SESSION DURATION ON PRECISE POINT POSITIONING ACCURACY USING GIPSY/OASIS II SOFTWARE

Boletim de Ciências Geodésicas ◽

10.1590/s1982-21702016000300023 ◽

2016 ◽

Vol 22 (3) ◽

pp. 405-419 ◽

Cited By ~ 5

Author(s):

Adem G. Hayal ◽

D. Ugur Sanli

Keyword(s):

Precise Point Positioning ◽

Accuracy Assessment ◽

Relative Positioning ◽

International Gnss Service ◽

Session Duration ◽

Previous Formulation ◽

Single Station ◽

Analysis Strategies ◽

Point Positioning

The accuracy of GPS precise point positioning (PPP) was previously modelled as a function of the observing session duration T. The NASA, JPL's software GIPSY OASIS II (GOA-II) along with the legacy products was used to process the GPS data. The original accuracy model is not applicable anymore because JPL started releasing its products using new modelling and analysis strategies as of August 2007, and the legacy products are no longer available. The developments mainly comprise the new orbit and clock determination strategy, second order ionosphere modelling, and single station ambiguity resolution. Previously, the PPP accuracy was studied using v 4.0 of the GOA-II. The accuracy model showed coarser results compared to that of the relative positioning. Here, we processed the data of the International GNSS Service (IGS) stations to refine the accuracy of GOA-II PPP from version 6.3. Considering the above changes we refined the accuracy of PPP. First we modified the previous model used for the accuracy assessment. Then we tested out this model using straightforward polynomial and logarithmic models. The tests indicate the previous formulation still satisfactorily models the accuracy using refined coefficient values Sn = 7.8 mm , Se = 6.8 mm , Sv = 29.9 mm for T ≥ 2 h.

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