scholarly journals Evaluation of BDS-2 and BDS-3 Satellite Atomic Clock Products and Their Effects on Positioning

2021 ◽  
Vol 13 (24) ◽  
pp. 5041
Author(s):  
Shengfeng Gu ◽  
Feiyu Mao ◽  
Xiaopeng Gong ◽  
Yidong Lou ◽  
Xueyong Xu ◽  
...  
Keyword(s):  
Atomic Clock ◽  
Satellite System ◽  
Atomic Clocks ◽  
Satellite Clock ◽  
Satellite Navigation System ◽  
Broadcast Ephemeris ◽  
Third Phase ◽  
Improved Stability ◽  
One Year ◽  
Better Than

The BeiDou Navigation Satellite System (BDS) has completed third phase construction and currently provides global services, with a mixed constellation of BDS-2 and BDS-3. The newly launched BDS-3 satellites are equipped with rubidium and passive hydrogen maser (PHM) atomic clocks. The performance of atomic clocks is one of the cores of satellite navigation system, which will affect the performance of positioning, navigation and timing (PNT). In this paper, we systematically analyze the characteristics of BDS-2 and BDS-3 atomic clocks, based on more than one year of precise satellite clock products and broadcast ephemeris. Firstly, the results of overlapping Allan variations demonstrate that BDS-3 Rb and PHM clocks improve better in stability than BDS-2 Rb clock and are comparable to GPS IIF Rb and Galileo PHM clocks. Accordingly, the STDs of BDS-3 broadcast satellite clock are better than GPS and BDS-2, which are at the same level with that of Galileo. Secondly, the inter-system bias (ISB) between BDS-2 and BDS-3 is analyzed by satellite clock datum comparison and precise point positioning (PPP). Surprisingly, the discrepancy between BDS-2 and BDS-3 satellite clock datum has a great difference between products that could reach up to about 10 ns for WHU satellite clock products and broadcast ephemeris. Moreover, the ISBs between BDS-2 and BDS-3 satellite clocks are quite stable over one-year periods. Thirdly, due to the improved stability of BDS-3 atomic clock, the 68% positioning accuracy is better than 0.65 m at 10 min for BDS-3 PPP, based on broadcast ephemeris. Besides, the non-negligible bias between BDS-2 and BDS-3 will greatly affect the BDS precise data processing. The accuracy of positioning is greatly improved when considering the ISB.

High-Accuracy Optical Frequency Atomic Clock

2021 ◽  
Vol 30 (3) ◽  
pp. 2-7
Author(s):  
Myoung-Sun HEO ◽  
Dai-Hyuk YU ◽  
Won-Kyu LEE
Keyword(s):  
Atomic Clock ◽  
Satellite System ◽  
High Accuracy ◽  
Optical Frequency ◽  
Atomic Clocks ◽  
Navigation Satellite ◽  
Fundamental Constants ◽  
Quantum Metrology ◽  
Order Of Magnitude ◽  
Global Navigation Satellite

Frequencies have been the most accurately measured physical quantity since the second was defined in 1967 based on the microwave atomic transition of a Cs atom. Recently, atomic clocks using optical frequency transitions have shown an order of magnitude better accuracy than microwave clocks. Thanks to their high accuracy and resolution, atomic clocks have become a new tool for investigations involving fundamental science and technology, such as the search for dark matter, gravitational wave detection, the temporal variation of fundamental constants, relativistic geodesy, quantum metrology, and the advanced Global Navigation Satellite System (GNSS). In addition, a redefinition of the second based on the optical frequency is expected. In this paper, we review the principles and applications of optical clocks.

scholarly journals Removing day-boundary discontinuities on GNSS clock estimates: methodology and results

GPS Solutions ◽  
2021 ◽  
Vol 25 (2) ◽  
Author(s):  
Adrià Rovira-Garcia ◽  
José Miguel Juan ◽  
Jaume Sanz ◽  
Guillermo González-Casado ◽  
Javier Ventura-Traveset ◽  
...  
Keyword(s):  
Carrier Phase ◽  
Atomic Clock ◽  
Satellite System ◽  
Daily Basis ◽  
Integer Ambiguity ◽  
Atomic Clocks ◽  
International Gnss Service ◽  
Present Contribution ◽  
Statistical Characterization ◽  
Phase Measurements

AbstractGlobal navigation satellite system (GNSS) satellites are equipped with very stable atomic clocks that can be used for assessing the models and strategies involved in the estimation processes, where the clock estimates should present high stability. For instance, GNSS products (including satellite and receiver clocks) are computed on daily basis, i.e., with the data of each day being processed independently from other days. This choice produces the well-known day-boundary discontinuities (DBDs) on clock estimates that stem from the estimation process, rather than to the nature of the atomic clock itself. The aim of the present contribution is to propose a strategy to estimate the satellite and receiver clock offsets that is capable to reduce the DBDs observed in the products of different analysis centers (ACs) within the International GNSS Service (IGS), ultimately improving the accuracy of clock estimates. Our approach relies on the use of unambiguous, undifferenced and uncombined carrier phase measurements collected by a network of permanent receivers on ground. The strategy considers the carrier phase hardware delays and assumes their possible variations along time. Our daily data processing aims to maintaining the natural continuity over days of the carrier phase measurements after integer ambiguity resolution (IAR), even if IAR is performed on daily batches. We compare our clock estimations with those computed by different IGS ACs, evaluating the linear behavior of the satellite atomic clocks on the day change. The results show the removal of DBD on clock estimates computed with the continuous and unambiguous carrier phase measurements. This DBD improvement may benefit the statistical characterization of long-term phenomena correlated with the on-board clocks.

scholarly journals Analysis and Assessment of BDS-2 and BDS-3 Broadcast Ephemeris: Accuracy, the Datum of Broadcast Clocks and Its Impact on Single Point Positioning

2020 ◽  
Vol 12 (13) ◽  
pp. 2081 ◽  
Author(s):  
Guoqiang Jiao ◽  
Shuli Song ◽  
Yangyang Liu ◽  
Ke Su ◽  
Na Cheng ◽  
...  
Keyword(s):  
Single Point ◽  
Satellite Orbit ◽  
Satellite System ◽  
Satellite Orbits ◽  
Satellite Clock ◽  
Single Point Positioning ◽  
Broadcast Ephemeris ◽  
North East ◽  
Point Positioning ◽  
Broadcast Orbit

For the global ordinary users, the broadcast ephemeris plays important roles in positioning, navigation and timing (PNT) services. With the construction of a new generation of the BeiDou navigation satellite system (BDS), the development of BDS has entered the era of globalization. It is meaningful for global users to analyze and assess the BDS-2 and BDS-3 broadcast ephemeris. Therefore, the satellite orbits and clock offsets calculated by broadcast ephemeris are compared with the precise orbit and clock offset products provided by three analysis centers (i.e., Helmholtz Centre Potsdam German Research Center for Geosciences (GFZ), Wuhan University (WHU) and Shanghai Astronomical Observatory (SHA)), and the corresponding signal-in-space range error (SISRE) and the orbit-only SISRE are analyzed to assess the accuracy of BDS broadcast ephemeris. Due to the upgrade of BDS-3 satellite hardware technology and inter-satellite links payload and the development of satellite orbit determination algorithm, the accuracy of broadcast orbit and clock offsets has been greatly improved. The root mean square (RMS) of BDS-3 broadcast orbit errors is improved by 86.30%, 89.47% and 76.86%, and the standard deviation (STD) is improved by 79.41%, 77.00% and 76.78% compared with BDS-2 in the radial, along-track and cross-track directions. The corresponding RMS and STD of all BDS-3 satellite clock offsets are improved by 40.34% and 52.49% than that of BDS-2, respectively. Meanwhile, the mean RMS and STD are 1.78 m and 0.40 m for BDS-2 SISRE, 1.72 m and 0.34 m for BDS-2 orbit-only SISRE, 0.50 m and 0.14 m for BDS-3 SISRE, and 0.17 m and 0.04 m for BDS-3 orbit-only SISRE. It is noteworthy that the average broadcast-minus-precise (BMP) clock values of BDS-2 and BDS-3 are inconsistent, which can indirectly prove that the datum of broadcast clock offsets for BDS-2 and BDS-3 are inconsistent. The inconsistency of the datum of satellite clock offsets and receiver hardware delay bias between BDS-2 and BDS-3 will result in the inter-system bias (ISB) on the receiver segment. For JAVAD TRE_3 receivers, the ISB is relatively small and thus can be ignored. However, for the TRIMBLE ALLOY, SEPT POLARX5, CETC-54-GMR-4016, CETC-54-GMR-4011, GNSS-GGR and UB4B0-13478 receivers, estimating ISB can improve the positioning accuracy of single point positioning (SPP) by 20.15%, 19.81% and 12.76% in north, east and up directions, respectively.

An Integrity Monitoring Algorithm for GNSS Satellite Atomic Clocks

2019 ◽  
Vol 72 (06) ◽  
pp. 1533-1549
Author(s):  
X.M. Huang ◽  
X. Zhao ◽  
J.Y. Li ◽  
X.W. Zhu ◽  
G. Ou
Keyword(s):  
Numerical Simulations ◽  
Global Navigation Satellite System ◽  
Atomic Clock ◽  
Measurement Model ◽  
Satellite System ◽  
Atomic Clocks ◽  
Navigation Satellite ◽  
Integrity Monitoring ◽  
Global Navigation Satellite ◽  
Monitoring Algorithm

An algorithm for Global Navigation Satellite System satellite atomic clock integrity monitoring based on an extended measurement model is proposed. A detection statistic achieved by parity transformation is used to detect clock anomalies, and the concept of the optimal accumulation number, with a method to find it, is provided. Numerical simulations are adopted to verify the validity of detecting two typical anomalies.

Broadcast Ephemeris Accuracy Analysis for GPS Based on Precise Ephemeris

2014 ◽  
Vol 602-605 ◽  
pp. 3667-3670 ◽  
Author(s):  
Rui Xi Jia ◽  
Xiao Yu Li ◽  
Chang Feng Xia ◽  
Dong Yang Jin
Keyword(s):  
Navigation System ◽  
Satellite Navigation ◽  
Accuracy Analysis ◽  
Satellite Navigation System ◽  
Broadcast Ephemeris ◽  
Important Index ◽  
Precise Ephemeris ◽  
Better Than

The accuracy of broadcast ephemeris is an important index of a satellite navigation system. The theory and method of precise ephemeris assessing broadcast ephemeris are introduced. The accuracy of GPS satellite broadcast ephemeris is assessed with the precise ones provided by IGS. The orbital coordinates of GPS broadcast ephemeris from 18th to 24th October 2013 are calculated. The analysis shows that during this time the GPS satellite broadcast ephemeris is reliable, accurate and safe as the whole, meanwhile the broadcast ephemeris accuracy is about 1 meter, better than nominal accuracy of 5 meters.

Analysis of Influence of Ephemeris-Time Information on Accuracy of Solving a Navigation Problem by Signals of GLONASS System

2020 ◽  
Vol 25 (5) ◽  
pp. 465-474
Author(s):  
V.O. Zhilinskiy ◽  
◽  
D.S. Pecheritsa ◽  
L.G. Gagarina ◽  
◽  
...  
Keyword(s):  
High Precision ◽  
Satellite Navigation ◽  
Satellite System ◽  
Navigation Systems ◽  
Navigation Problem ◽  
Satellite Navigation System ◽  
Study Results ◽  
Accuracy Of Measurements ◽  
Huge Impact ◽  
Time Information

The Global Navigation Satellite System has a huge impact on both the public and private sectors, including the social-economic development, it has many applications and is an integral part of many domains. The application of the satellite navigation systems remains the most relevant in the field of transport, including land, air and maritime transport. The GLONASS system consists of three segments and the operation of the entire system depends on functioning of each component, but primarily, the accuracy of measurements depends on the basis forming of the control segment and management, responsible for forming ephemeris-time information. In the work, the influence of ephemeris-time information on the accuracy of solving the navigation problem by the signals of the GLONASS satellite navigation system has been analyzed. The influence of both ephemeris information and the frequency information, and of the time corrections has been individually studied. The accuracy of the ephemeris-time information is especially important when solving the navigation problem by highly precise positioning method. For the analysis the following scenarios of the navigation problem solving have been formed: using high-precision and broadcast ephemeris-time information, a combination of broadcast (high-precision) ephemeris-time information, and high-precision (broadcast) satellite clock offsets and two scenarios with simulation of the calculation of the relative correction to the radio signal carrier frequency. Based on the study results it has been concluded that the contribution of the frequency-time corrections to the error of location determination is of the greatest importance and a huge impact on the error location, while the errors of the ephemeris information are insignificant

The Role of Chess in the Intellectual Development of Childrens from Primary School

2019 ◽  
pp. 58-62
Author(s):  
Vlad Stegariu ◽  
Simona Andreea Popușoi ◽  
Beatrice Abălașei ◽  
Nicolae Lucian Voinea ◽  
Ioan Stelescu ◽  
...  
Keyword(s):  
Cognitive Development ◽  
Primary School ◽  
Intellectual Development ◽  
Resources Allocation ◽  
Control Group ◽  
Cognitive Resources ◽  
One Year ◽  
Better Than ◽  
Chess Playing

Chess playing has a significant role in participants’ resources allocation, both at a psychological level, but mostly concerning the cognitive resources. The aim of the present study was to examine the effect of chess playing on the intellectual development of primary-class students. 67 children were tested using the Raven Standard Progressive Matrices and were distributed in three different groups according to their experience with chess, namely: the control group (formed by students with no experience with chess playing), the beginners group (students with less than one year in chess playing training) and the advanced group (children with more than two years experience with chess). Results indicated that chess playing had a significant effect on the SPM performance, indicating that those in the advanced group performed significantly better than those in the control or in the beginners group. Conclusions of this study tap into the benefits of playing chess with a focus on the children’s’ cognitive development.

scholarly journals NLOS Multipath Classification of GNSS Signal Correlation Output Using Machine Learning

Sensors ◽  
2021 ◽  
Vol 21 (7) ◽  
pp. 2503
Author(s):  
Taro Suzuki ◽  
Yoshiharu Amano
Keyword(s):  
Machine Learning ◽  
Satellite System ◽  
Training Data ◽  
Support Vector ◽  
Positioning Errors ◽  
Automated Method ◽  
Global Navigation Satellite ◽  
Better Than ◽  
Signal Correlation

This paper proposes a method for detecting non-line-of-sight (NLOS) multipath, which causes large positioning errors in a global navigation satellite system (GNSS). We use GNSS signal correlation output, which is the most primitive GNSS signal processing output, to detect NLOS multipath based on machine learning. The shape of the multi-correlator outputs is distorted due to the NLOS multipath. The features of the shape of the multi-correlator are used to discriminate the NLOS multipath. We implement two supervised learning methods, a support vector machine (SVM) and a neural network (NN), and compare their performance. In addition, we also propose an automated method of collecting training data for LOS and NLOS signals of machine learning. The evaluation of the proposed NLOS detection method in an urban environment confirmed that NN was better than SVM, and 97.7% of NLOS signals were correctly discriminated.

scholarly journals An In-Depth Assessment of the New BDS-3 B1C and B2a Signals

2021 ◽  
Vol 13 (4) ◽  
pp. 788
Author(s):  
Qinghua Zhang ◽  
Yongxing Zhu ◽  
Zhengsheng Chen
Keyword(s):  
Carrier Phase ◽  
Density Ratio ◽  
Signal Strength ◽  
Satellite Orbit ◽  
Satellite System ◽  
Earth Orbit ◽  
Base Line ◽  
Signal Characteristics ◽  
Better Than

An in-depth and comprehensive assessment of new observations from BDS-3 satellites is presented, with the main focus on the Carrier-to-Noise density ratio (C/N0), the quality of code and carrier phase observations for B1C and B2a signal. The signal characteristics of geosynchronous earth orbit (GEO), inclined geosynchronous satellite orbit (IGSO) and medium earth orbit (MEO) satellites of BDS-3 were grouped and compared, respectively. The evaluation results of the new B1C and B2a signals of BDS-3 were compared with the previously B1I/B2I/B3I signals and the interoperable signals of GPS, Galileo and quasi-zenith satellite system (QZSS) were compared simultaneously. As expected, the results clearly show that B1C and B2a have better signal strength and higher accuracy, including code and carrier phase observations. The C/N0 of the B2a signal is about 3 dB higher than other signals. One exception is the code observation accuracy of B3I, which value is less than 0.15 m. The carrier precision of B1C and B2a is better than that of B1I/B2I/B3I. Despite difference-in-difference (DD) observation quantity or zero-base line evaluation is adopted, while B1C is about 0.3 mm higher carrier precision than B2a. The BDS-3 MEO satellite and GPS, Galileo, and QZSS satellites have the same level of signal strength, code and phase observation accuracy at the interoperable frequency, namely 1575.42 MHz and 1176.45 MHz which are very suitable for the co-position application.

GPS satellite clock estimation using global atomic clock network

GPS Solutions ◽  
2021 ◽  
Vol 25 (3) ◽  
Author(s):  
Jian Yao ◽  
Sungpil Yoon ◽  
Bryan Stressler ◽  
Steve Hilla ◽  
Mark Schenewerk
Keyword(s):  
Atomic Clock ◽  
Satellite Clock ◽  
Clock Network ◽  
Clock Estimation
Sign in / Sign up

Export Citation Format

Share Document