scholarly journals A Real-Time Detection Method for BDS Signal in Space Anomalies

Sensors ◽  
2019 ◽  
Vol 19 (6) ◽  
pp. 1437 ◽  
Author(s):  
Chun Cheng ◽  
Yuxin Zhao ◽  
Liang Li ◽  
Lin Zhao
Keyword(s):  
Real Time ◽  
Estimation Method ◽  
Satellite System ◽  
Statistical Characteristics ◽  
Estimation Accuracy ◽  
Navigation Systems ◽  
Long Latency ◽  
Characteristics Analysis ◽  
Satellite Navigation Systems ◽  
Range Error

Signal In Space (SIS) anomalies in satellite navigation systems can degrade satellite-based navigation and positioning performance. The occurrence of SIS anomalies from the BeiDou navigation satellite System (BDS) may be more frequent than for the Global Positioning System (GPS). In order to guarantee the integrity of BDS users, detecting and excluding SIS anomalies is indispensable. The traditional method through the comparison between the final precision ephemeris and the broadcast ephemeris is limited by the issue of long latency of precision ephemeris release. Through the statistical characteristics analysis of Signal In Space User Range Error (SISURE), we propose a real-time Instantaneous SISURE (IURE) estimation method by using the Kalman filtering-based carrier-smoothed-code to detect and exclude BDS SIS anomalies, in which the threshold for BDS IURE anomaly detection are obtained from the integrity requirement. The experimental results based on 1 Hz data from ground observations show that the proposed method has an estimation accuracy of 1.1 m for BDS IURE. The test results show that the proposed method can effectively detect the SIS anomalies caused by either orbit faults or clock faults.

scholarly journals Learning-Type Anchors-Driven Pose Estimation for the Autolanding Fixed-Wing UAVs

2021 ◽  
Author(s):  
Dengqing Tang ◽  
Lincheng Shen ◽  
Xiaojiao Xiang ◽  
Han Zhou ◽  
Tianjiang Hu
Keyword(s):  
Real Time ◽  
Pose Estimation ◽  
Stereo Vision ◽  
Vision System ◽  
Estimation Method ◽  
Satellite System ◽  
Training Dataset ◽  
Estimation Accuracy ◽  
The Impact ◽  
Outdoor Experiments

<p>We propose a learning-type anchors-driven real-time pose estimation method for the autolanding fixed-wing unmanned aerial vehicle (UAV). The proposed method enables online tracking of both position and attitude by the ground stereo vision system in the Global Navigation Satellite System denied environments. A pipeline of convolutional neural network (CNN)-based UAV anchors detection and anchors-driven UAV pose estimation are employed. To realize robust and accurate anchors detection, we design and implement a Block-CNN architecture to reduce the impact of the outliers. With the basis of the anchors, monocular and stereo vision-based filters are established to update the UAV position and attitude. To expand the training dataset without extra outdoor experiments, we develop a parallel system containing the outdoor and simulated systems with the same configuration. Simulated and outdoor experiments are performed to demonstrate the remarkable pose estimation accuracy improvement compared with the conventional Perspective-N-Points solution. In addition, the experiments also validate the feasibility of the proposed architecture and algorithm in terms of the accuracy and real-time capability requirements for fixed-wing autolanding UAVs.</p>

scholarly journals Learning-Type Anchors-Driven Pose Estimation for the Autolanding Fixed-Wing UAVs

2021 ◽  
Author(s):  
Dengqing Tang ◽  
Lincheng Shen ◽  
Xiaojiao Xiang ◽  
Han Zhou ◽  
Tianjiang Hu
Keyword(s):  
Real Time ◽  
Pose Estimation ◽  
Stereo Vision ◽  
Vision System ◽  
Estimation Method ◽  
Satellite System ◽  
Training Dataset ◽  
Estimation Accuracy ◽  
The Impact ◽  
Outdoor Experiments

<p>We propose a learning-type anchors-driven real-time pose estimation method for the autolanding fixed-wing unmanned aerial vehicle (UAV). The proposed method enables online tracking of both position and attitude by the ground stereo vision system in the Global Navigation Satellite System denied environments. A pipeline of convolutional neural network (CNN)-based UAV anchors detection and anchors-driven UAV pose estimation are employed. To realize robust and accurate anchors detection, we design and implement a Block-CNN architecture to reduce the impact of the outliers. With the basis of the anchors, monocular and stereo vision-based filters are established to update the UAV position and attitude. To expand the training dataset without extra outdoor experiments, we develop a parallel system containing the outdoor and simulated systems with the same configuration. Simulated and outdoor experiments are performed to demonstrate the remarkable pose estimation accuracy improvement compared with the conventional Perspective-N-Points solution. In addition, the experiments also validate the feasibility of the proposed architecture and algorithm in terms of the accuracy and real-time capability requirements for fixed-wing autolanding UAVs.</p>

scholarly journals High-Accuracy Real-Time Kinematic Positioning with Multiple Rover Receivers Sharing Common Clock

2021 ◽  
Vol 13 (4) ◽  
pp. 823
Author(s):  
Lin Zhao ◽  
Jiachang Jiang ◽  
Liang Li ◽  
Chun Jia ◽  
Jianhua Cheng
Keyword(s):  
Real Time ◽  
Ambiguity Resolution ◽  
Temporal Stability ◽  
Estimation Method ◽  
Satellite System ◽  
Integer Ambiguity ◽  
Dual Frequency ◽  
Kinematic Positioning ◽  
Real Time Kinematic ◽  
Satellite Visibility

Since the traditional real-time kinematic positioning method is limited by the reduced satellite visibility from the deprived navigational environments, we, therefore, propose an improved RTK method with multiple rover receivers sharing a common clock. The proposed method can enhance observational redundancy by blending the observations from each rover receiver together so that the model strength will be improved. Integer ambiguity resolution of the proposed method is challenged in the presence of several inter-receiver biases (IRB). The IRB including inter-receiver code bias (IRCB) and inter-receiver phase bias (IRPB) is calibrated by the pre-estimation method because of their temporal stability. Multiple BeiDou Navigation Satellite System (BDS) dual-frequency datasets are collected to test the proposed method. The experimental results have shown that the IRCB and IRPB under the common clock mode are sufficiently stable for the ambiguity resolution. Compared with the traditional method, the ambiguity resolution success rate and positioning accuracy of the proposed method can be improved by 19.5% and 46.4% in the restricted satellite visibility environments.

scholarly journals Precise time and frequency transfer combined BeiDou’s RDSS and RNSS signals

2019 ◽  
Vol 2019 (1) ◽  
Author(s):  
Wenxue Liu ◽  
Hong Yuan ◽  
Jian Ge ◽  
Ying Xu
Keyword(s):  
Satellite Orbit ◽  
Satellite Navigation ◽  
Satellite System ◽  
Signal Frequency ◽  
Navigation Systems ◽  
Satellite Navigation System ◽  
Frequency Transfer ◽  
Satellite Navigation Systems ◽  
Satellite Service ◽  
Precise Time

Abstract Unlike other satellite navigation systems such as GPS (Global Positioning System), the BeiDou satellite navigation system broadcasts RDSS (Radio Determination Satellite Service) and RNSS (Radio Navigation Satellite Service) signals simultaneously on its GEO (geostationary earth orbit) satellites and provides related navigation services. This paper studies the method of using the RDSS and RNSS signals of BeiDou to achieve accurate frequency and time transmission. We analyze the generation mechanism of RDSS signal and RNSS signal of BeiDou GEO satellite, establish a mathematical model of RDSS and RNSS signal frequency transfer, and derive an equation based on BeiDou’s RDSS and RNSS signals for accurate frequency and time transmission. We also verified the relevant performance of the method through computer simulation. The results show that the combination of RDSS and RNSS signals from the BeiDou satellite system provides a new solution for its application in precise time and frequency transmission. This method is different from other satellite navigation systems such as GPS and is unique to the BeiDou system, with high accuracy and low dependence on satellite orbit accuracy.

scholarly journals Application of GNSS Methods for Monitoring Offshore Platform Deformation

2018 ◽  
Vol 34 ◽  
pp. 01019
Author(s):  
Khin Cho Myint ◽  
Abd Nasir Matori ◽  
Adel Gohari
Keyword(s):  
Phase Measurement ◽  
Satellite System ◽  
Deformation Monitoring ◽  
Offshore Platform ◽  
Offshore Platforms ◽  
Navigation Systems ◽  
Correlated Errors ◽  
Carrier Phase Measurement ◽  
Satellite Navigation Systems ◽  
Global Navigation Satellite

Global Navigation Satellite System (GNSS) has become a powerful tool for high-precision deformation monitoring application. Monitoring of deformation and subsidence of offshore platform due to factors such as shallow gas phenomena. GNSS is the technical interoperability and compatibility between various satellite navigation systems such as modernized GPS, Galileo, reconstructed GLONASS to be used by civilian users. It has been known that excessive deformation affects platform structurally, causing loss of production and affects the efficiency of the machinery on board the platform. GNSS have been proven to be one of the most precise positioning methods where by users can get accuracy to the nearest centimeter of a given position from carrier phase measurement processing of GPS signals. This research is aimed at using GNSS technique, which is one of the most standard methods to monitor the deformation of offshore platforms. Therefore, station modeling, which accounts for the spatial correlated errors, and hence speeds up the ambiguity resolution process is employed. It was found that GNSS combines the high accuracy of the results monitoring the offshore platforms deformation with the possibility of survey.

scholarly journals Establishment of a Real-Time Local Tropospheric Fusion Model

2019 ◽  
Vol 11 (11) ◽  
pp. 1321 ◽  
Author(s):  
Yibin Yao ◽  
Xingyu Xu ◽  
Chaoqian Xu ◽  
Wenjie Peng ◽  
Yangyang Wan
Keyword(s):  
Real Time ◽  
Meteorological Data ◽  
Rapid Development ◽  
Water Vapor Pressure ◽  
Auxiliary Information ◽  
Satellite System ◽  
Tropospheric Delay ◽  
Navigation Systems ◽  
Delay Model ◽  
Fusion Model

The tropospheric delay is one major error source affecting the precise positioning provided by the global navigation satellite system (GNSS). This error occurs because the GNSS signals are refracted while travelling through the troposphere layer. Nowadays, various types of model can produce the tropospheric delay. Among them, the globally distributed GNSS permanent stations can resolve the tropospheric delay with the highest accuracy and the best continuity. Meteorological models, such as the Saastamoinen model, provide formulae to calculate temperature, pressure, water vapor pressure and subsequently the tropospheric delay. Some grid-based empirical tropospheric delay models directly provide tropospheric parameters at a global scale and in real time without any auxiliary information. However, the spatial resolution of the GNSS tropospheric delay is not sufficient, and the accuracy of the meteorological and empirical models is relatively poor. With the rapid development of satellite navigation systems around the globe, the demand for real-time high-precision GNSS positioning services has been growing dramatically, requiring real-time and high-accuracy troposphere models as a critical prerequisite. Therefore, this paper proposes a multi-source real-time local tropospheric delay model that uses polynomial fitting of ground-based GNSS observations, meteorological data, and empirical GPT2w models. The results show that the accuracy in the zenith tropospheric delay (ZTD) of the proposed tropospheric delay model has been verified with a RMS (root mean square) of 1.48 cm in active troposphere conditions, and 1.45 cm in stable troposphere conditions, which is significantly better than the conventional tropospheric GPT2w and Saastamoinen models.

scholarly journals Assessment of risks in implementing automated satellite navigation systems

2014 ◽  
Vol 60 (Special Issue) ◽  
pp. S16-S24 ◽  
Author(s):  
M. Žitňák ◽  
M. Macák ◽  
M. Korenko
Keyword(s):  
Satellite Navigation ◽  
Satellite System ◽  
Navigation Systems ◽  
Agricultural Practice ◽  
Unit Costs ◽  
Signal Type ◽  
Fmea Method ◽  
Satellite Navigation Systems ◽  
The Individual ◽  
A Company

One of the ways of increasing the efficiency and safety of work is the implementation of navigation systems in agricultural practice. Satellite navigation as a means of reducing the unit costs and increasing the safety can have a significant economic impact on a company when properly used. The objective of measurement was to assess the accuracy of a satellite system AutoTrack working with a correction signal SF2. Its provider specifies an accuracy of &plusmn; 5 cm for this signal type. The accuracy of machine work was compared for two scenarios, i.e. with and without satellite navigation. Further, the navigation of machines focused predominantly on AgGPS EZ-Guide Plus and AutoTrac Universal. The FMEA method was used to determine the risk of probable failures that can occur on machines while working. This work describes the individual failures that can occur on navigation systems of machines and analyses their impact on operator&rsquo;s safety.

Multi-GNSS real-time orbit and clock quality changes over time 

2021 ◽  
Author(s):  
Kamil Kazmierski ◽  
Radoslaw Zajdel ◽  
Krzysztof Sośnica
Keyword(s):  
Real Time ◽  
Orbital Plane ◽  
Satellite System ◽  
Quality Level ◽  
Navigation Systems ◽  
Positioning Errors ◽  
Time Regime ◽  
Changes Over Time ◽  
Strategy Changes

&lt;p&gt;Navigation systems have substantially evolved in the last decade. The multi-GNSS constellation including GPS, GLONASS, Galileo, and BeiDou consists of more than a hundred active satellites. To fully exploit their potential, users should be able to take advantage of those systems not only in postprocessing mode employing final solutions but also in real-time. It is also important to make satellite signals highly useful in a real-time regime not only in standard positioning mode but also with the precise positioning technique. That is why real-time products are highly desirable. One of the IGS Analysis Centers that support multi-GNSS real-time solution is CNES which provides not only orbits and clocks but also code and phase biases and VTEC global maps. Over the last few years, real-time products have been changing similarly to navigation systems, which come along with observation availability and calculation strategy changes.&lt;/p&gt;&lt;p&gt;We utilize the signal-in-space ranging error (SISRE) as the main orbit and clock quality indicator. Additionally, SLR observations are used as an independent source of information about orbit quality. Three years of data, between 2017 and 2020, are used to check the progress in the quality of the delivered products to the users through the internet streams provided by CNES.&lt;/p&gt;&lt;p&gt;The progress in the product quality in the test period is obvious and it depends on the satellite system, block or satellite type, time, and the height of the Sun above the orbital plane. The most accurate orbits are available for GPS, however, the very stable atomic clocks of Galileo compensate for systematic errors in Galileo orbits. Consequently, the SISRE for Galileo is lower than that for GPS, equaling 1.6 and 2.3 cm for Galileo and GPS, respectively. The SISRE value for GLONASS, despite the good quality of the orbits, is disturbed by the lower quality of the onboard clocks and is equal to 4-6 cm. The same quality level is for BeiDou-2 MEO and IGSO satellites. Products for BeiDou-2 GEO satellites are less accurate and with poor availability due to a large number of satellite maneuvers, thus they are not very useful for real-time positioning.&lt;/p&gt;&lt;p&gt;For positioning purposes, the presented results may be interesting especially in the context of the proper observation weighting in the multi-GNSS combinations. It is worth mentioning that the quality of the real-time products is not constant and neglecting this fact may bring undesirable positioning errors, especially for long processing campaigns.&lt;/p&gt;

Geodetic technologies for monitoring ballast compaction parameters during the construction and overhaul of railways using global navigation satellite system

2020 ◽  
Vol 961 (7) ◽  
pp. 8-13
Author(s):  
V.V. Scherbakov ◽  
A.P. Karpik ◽  
I.V. Scherbakov ◽  
M.N. Barsuk ◽  
I.A. Buntsev
Keyword(s):  
Monitoring System ◽  
Dynamic Control ◽  
Geophysical Methods ◽  
Satellite System ◽  
Dynamic Mode ◽  
Navigation Systems ◽  
Residual Deformations ◽  
Satellite Navigation Systems ◽  
Global Navigation Satellite

The development of a monitoring system based on global satellite navigation systems (GNSS) of ballast compaction quality during the construction and overhaul of railways is covered in the article. Traditional geodetic methods for determining the quality of ballast compaction are tedious. Non-geodetic methods (dynamic control systems, empirical models and geophysical methods) are not widely used on railways due to the low reliability of the ballast compaction quality, as well as the high complexity of the work. The proposed method and device of a quality control system for ballast compaction are based on the measurement of draft and residual deformations during compaction in dynamic mode. The current coordinates are determined using GNSS with dual-antenna positioning receivers performing advanced functions, including determining the relative position of the antennas in plan and height. The monitoring system developed at the Siberian State University of Railway Engineering enables real-time determining parameters which characterize the quality of compaction with high accuracy and the ability of controlling the compaction process according to the current parameters.

scholarly journals Research on Dynamic Inertial Estimation Technology for Deck Deformation of Large Ships

Sensors ◽  
2019 ◽  
Vol 19 (19) ◽  
pp. 4167
Author(s):  
Bo Ren ◽  
Tianjiao Li ◽  
Xiang Li
Keyword(s):  
Kalman Filter ◽  
Estimation Method ◽  
Inertial Navigation ◽  
Engineering Application ◽  
Estimation Accuracy ◽  
Navigation Systems ◽  
Inertial Navigation Systems ◽  
Weapon Systems ◽  
Dynamic Estimation ◽  
Curvature And Torsion

Many kinds of weapon systems and launching equipment on the deck of large ships are easily affected by deck deformation. In order to ensure the accuracy of weapon systems and the safety of taking off and landing of carrier aircraft, a dynamic estimation method combining the main inertial navigation systems (INS) and the sub-inertial navigation systems (SINS) is designed to estimate the curvature and torsion of any trajectory on the deck. Our contributions start from the fact that the area of concern extends from the fixed points to any trajectory on the deck. The dynamic filter algorithm of wavelet combined with Kalman filter is used to process the acquired data. The wavelet method is used to remove the outliers in the acquired data, and the Kalman filter effectively reduces the influence of white noise, so that the estimation accuracy is guaranteed. The simulation results clearly show that the deck deformation of large ships can be obtained accurately in real-time over the observed area which proved that this dynamic inertial measurement method is feasible in practical engineering application.

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