Analysis of Multi-GNSS PPP Initialization using Dual- and Triple-frequency Data

2017 ◽  
Author(s):  
John Aggrey ◽  
Sunil Bisnath
Keyword(s):  
Frequency Data ◽  
Triple Frequency

scholarly journals Improved Cycle Slip Repair with GPS Triple-Frequency Measurements by Minifying the Influences of Ionospheric Variation and Pseudorange Errors

2021 ◽  
Vol 13 (4) ◽  
pp. 556
Author(s):  
Dehai Li ◽  
Yamin Dang ◽  
Yunbin Yuan ◽  
Jinzhong Mi
Keyword(s):  
Success Rate ◽  
Cycle Slip ◽  
Frequency Data ◽  
Success Rates ◽  
Precise Positioning ◽  
Ionospheric Effects ◽  
Triple Frequency ◽  
Basic Work ◽  
Cycle Slip Detection ◽  
Phase Data

In advance of precise positioning with phase data, cycle slip detection (CSD) is a basic work that should be implemented in phase data possessing. When the cycle slip occurred, cycle slip repair (CSR) can be taken to rebuild the continuity of phase data. Unfortunately, the large pseudorange errors can contaminate the combinations with the pseudoranges and phases such as the Hatch–Melbourne–Wubbena combination (HMW) and cause false CSD or wrong CSR results. On the other hand, the severe ionospheric time variation can deteriorate the epoch-difference geometry-free phase (GF), and tremendously interfere with the performances of CSD and CSR. To handle the aforementioned limitations, a global position system (GPS) triple-frequency CSR method (GTCSR) is proposed with two efficient treatments: (1) the significant ionospheric variations are corrected, and the influences from the residual ionospheric effects are minimized along with the observational noises; and (2) the impacts of large pseudorange errors are refrained by designing a discrimination function with a geometry-free and ionosphere-free phase to identify the correct cycle slip values. Consequently, CSR tests were conducted with three monitoring stations at different regions. First, during a strong geomagnetic storm, without correcting the ionospheric variation of CSR (WICSR) displayed obvious failures, and many epochs of cycle slip values from WICSR deviated from the known values. However, the results of the GTCSR were correct, and GTCSR presented a higher success rate than that of WICSR. Furthermore, for the real triple-frequency data, by adding gross errors of 2.5 m on all epoch-difference pseudoranges epoch by epoch, the conventional triple-frequency CSR with the optimized combinations (CTCSR) and the CSD with HMW (HMWCSD) showed many mistakes, where the results of CTCSR and HMWCSD on numerous epochs were inconsistent with the actual situations, but the success rate of GTCSR was significantly higher than those of CTCSR and HMWCSD. In summary, in the condition of the cutoff elevation being larger than 10 degrees, improved performances and higher success rates were achieved from GTCSR under environments of large pseudorange errors and severe ionospheric variations.

scholarly journals Beyond three frequencies: An extendable model for single-epoch decimeter-level point positioning by exploiting Galileo and BeiDou-3 signals

2020 ◽  
Author(s):  
Jianghui Geng ◽  
Jiang Guo
Keyword(s):  
High Precision ◽  
Autonomous Driving ◽  
Convergence Time ◽  
Frequency Data ◽  
Positioning Accuracy ◽  
Safety Standards ◽  
Triple Frequency ◽  
Wide Lane ◽  
Point Positioning ◽  
Single Epoch

GNSS is indispensable to self-driving vehicles by delivering decimeter-level or better absolute positioning solutions. Such a high precision normally requires a convergence time spanning seconds to minutes, which is however unrealistic in extremely difficult driving conditions where GNSS signals are obstructed frequently. Such convergences, no matter how short, will greatly risk and discredit autonomous driving in satisfying stringent life-safety standards. In this study, we therefore developed an extendable GNSS precise point positioning (PPP) model to exploit the advanced Galileo/BeiDou-3 more-than-three-frequency signals with the goal of achieving instant or single-epoch 10-30 cm positioning accuracy and over 99% availability for the horizontal components over wide areas. In particular, uncombined Galileo/BeiDou-3 signals on all available frequencies were injected simultaneously into PPP to perform single-epoch wide-lane ambiguity resolution (PPP-WAR) after phase bias calibrations on raw observations. Experimenting on the Galileo five-frequency data from 36 stations in Australia, we found that instant PPP-WAR was accomplished at more than 99.5% of all epochs; we achieved an instant positioning accuracy of 0.10 and 0.11 m (1) for the east and north components, respectively, using Galileo E1/E5a/E5/E5b/E6 signals from less than 10 satellites, while 0.16 and 0.23 m using BeiDou-3 B1C/B1I/B2a/B2b/B3I signals from only 5-6 satellites per epoch observed by 10 stations within China. Moreover, we carried out vehicle-borne experiments collecting multi-frequency Galileo/BeiDou-3 signals in case of overpass and tunnel adversities. With 7 Galileo/BeiDou-3 satellites per epoch on average, instant PPP-WAR reached a mean positioning accuracy of 0.23 and 0.24 m for the horizontal components, which can be further improved to 0.14 and 0.12 m when multi-epoch filtering is preferably enabled. More encouragingly, though this positioning accuracy can also be ensured with triple-frequency data, the data redundancy favored by even more frequencies can reduce the high-precision recovery time from up to 4 s to 2 s in case of total signal blockages. With the rapidly ongoing deployment of Galileo, BeiDou-3 and other GNSS constellations, we can envision an instant global positioning service characterized by around 20-cm horizontal accuracy and over 99% availability for self-driving vehicles.

Optimal Solution to Multi-Frequency BDS Code-Multipath Combination Measurement

2019 ◽  
Vol 72 (5) ◽  
pp. 1297-1314
Author(s):  
Tian Jin ◽  
Bingjie Hu ◽  
Yining Sun ◽  
Zhigang Huang ◽  
Qian Wang ◽  
...  
Keyword(s):  
Rapid Development ◽  
Optimal Solution ◽  
Satellite System ◽  
Frequency Data ◽  
International Gnss Service ◽  
Triple Frequency ◽  
Multipath Combination ◽  
Beidou System ◽  
Global Navigation Satellite ◽  
Gnss Observations

Global Navigation Satellite System (GNSS) observations contain various errors, the separation and measurement of which is a popular research topic. Multipath effect on code measurements is investigated through the multipath combination, but carrier multipath error is small, and it is difficult to distinguish from other errors, such as hardware delay, carrier noise and satellite inherent biases. However, as the number of frequency points increases during the rapid development of GNSSs, it is possible to analyse the abovementioned errors in detail. Triple-frequency combination can be used to eliminate the first order ionospheric error, and a quad-frequency combination has one degree of freedom, which may be used to minimise carrier error effects. For this reason, an optimum method has been developed for multi-frequency GNSS code-multipath combination measurements, which has been verified by exploiting BeiDou System (BDS), three frequency data from an International GNSS Service (IGS) station and a city canyon as well as actual sampled quad-frequency data. By comparative analysis, we found that the fluctuations of an optimum triple-frequency combination are smaller than that of the non-optimum combination, which decreases the influence of inherent errors and biases on carrier phase. At the same time, second-order ionospheric error can be effectively eliminated as well. This provides a new code-multipath combination measurement optimisation methodology for future multi-frequency BDS and other GNSSs.

Profil Pasien Katarak Senilis Pada Usia 40 Tahun Keatas di RSI Siti Rahmah Tahun 2017

2019 ◽  
Vol 1 (1) ◽  
pp. 15-21
Author(s):  
Rada Puspita ◽  
Haves Ashan ◽  
Fidiariani Sjaaf
Keyword(s):  
High School ◽  
Secondary Data ◽  
Study Data ◽  
Vision Impairment ◽  
High School Education ◽  
Frequency Data ◽  
Private Companies ◽  
The World ◽  
Age Range ◽  
Cataract Patients

Vision impairment is estimated to affect 285 million people in the world, where 16-20% experience blindness, from the number of blindness suffered at the age of 40-50 years. Cataract seninis is all lens opacities that are found in old age that is above 40 years. The purpose of identifying and collecting frequency data Profile of Senilis cataract patients at the age of 40 years and above at RSI Siti Rahmah Padang in 2017. The research method is descriptive type of research, this study data taken is secondary data, In this study data was taken from the Medical Record at RSI Siti Rahmah Padang. When the study was conducted in February-August 2018, the population of this study were all cataract patients at the age of 40 years and above at RSI Siti Rahmah Padang in 2017 with 80 samples. Data analysis is univariate presented in the form of a frequency distribution table. Results From 80 respondents as many as 40 people (50%) were in the age range of 60-69 years, as many as 42 people (52.5%) patients were male, as many as 31 people (38.8%) patients with high school education and 35 people (43.8%) patients work as private companies. Conclusion In general, most patients are at the age of 60-69 years, the most sex is men, the highest education is high school and most patients are private.

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