Beidou Satellite Research Articles

An adaptive robust strategy based on hypothesis testing for satellite clock bias short-term forecasting

The study of short-term forecasting of satellite clock bias (SCB) is important to promote the development of real-time precise point positioning, and the Kalman filter model has certain advantages over other models in the single forecast model. However, the filtering performance will be degraded by the model bias, and a fading factor is constructed to control the effect brought by the model bias. Considering that the fading factor may cause the covariance matrix to be abnormally inflated or even invalid when the observed information is unreliable, the chi-square test is introduced as a test indicator. At the current epoch moment, the fading factor or robust estimation is conditionally applied based on the result of the hypothesis test. An improved IGGIII weight function is used by the robust estimation, which simplifies the solution of the parametric robust solution. BeiDou satellite navigation system-3 satellite clock bias data with different clock types were selected for the analysis of fitting accuracy and forecasting accuracy, and the experimental results showed that the proposed algorithm can well eliminate the anomalous perturbation phenomenon caused by model deviation and improve the fitting accuracy. The comparison of forecast accuracy between the proposed strategy and GM(1,1), quadratic polynomial, and autoregressive integrated moving average (ARIMA) models at 3, 6, and 12 h intervals reveals that the proposed strategy consistently demonstrates optimal forecast accuracy.

Simulating VLBI observations to BeiDou and Galileo satellites in L-band for frame ties

Abstract Using the very long baseline interferometry (VLBI) technique to observe Earth-orbiting satellites is a topic of increasing interest for the establishment of frame ties. We present a simulation study on VLBI observations to BeiDou and Galileo satellites in L-band to investigate the accuracy of inter-technique frame ties between VLBI and global navigation satellite system (GNSS). We employ a global network of 16 antennas equipped with dedicated L-band receivers capable of observing BeiDou’s B1 and B3 navigation signals and Galileo’s E1 and E6 navigation signals. Through extensive Monte Carlo simulations, we simulate 24-h sessions to determine the optimal ratio of satellite to quasar scans. The optimal schedule uses about 80–90% satellite sources. We find that the 10–20% observations of quasar sources improve the estimation of the troposphere and, consequently, the estimation of the antenna position. Combining the normal equations from seven 24-h sessions, we derive a 7-day solution. The average antenna position repeatability is 7.3 mm. We identify the limitations of the results as the tropospheric turbulence, inaccuracies in the satellite orbit determination, and the lack of a more homogeneously distributed global network. This simulation study supports the understanding in the topic of building a frame tie using VLBI observations to GNSS satellites.

Design of a 3D space early warning system for high precision positioning technology of Beidou and analysis of differential positioning accuracy

The Beidou satellite navigation system has achieved certain results in positioning accuracy, but due to factors such as system errors, its accuracy still does not fully meet the requirements of high-precision measurement. Therefore, this study proposes a design method for a three-dimensional space early warning system, aiming to combine the positioning function of the BeiDou satellite navigation system and differential positioning technology to improve positioning accuracy. By utilizing differential positioning technology, multiple reference stations are arranged around the receiving device, and the positioning information received by these stations is used for accuracy correction. This method can effectively offset errors such as atmospheric errors, clock errors, and multipath effects between receivers, making the obtained positioning results more accurate. Through the design and implementation of a three-dimensional space early warning system, positioning errors can be predicted and monitored, and abnormal positioning situations can be detected and corrected in a timely manner, thereby improving the overall reliability of positioning. The system designed in this article can effectively improve positioning accuracy, meet the requirements of modern measurement technology for positioning accuracy, and demonstrate the superiority of the system through experimental verification and differential positioning accuracy analysis.

Research on Improvement of Data Synchronization Method for Distribution Network Differential Protection Based on 5G

To enhance the reliability of traditional current protection systems in the evolving landscape of future power grids, this paper proposes a differential protection data synchronization approach that leverages satellite and 5G network timing. This method addresses the risk of inadvertent operation due to 5G communication jitter. It employs the BeiDou satellite system for synchronizing the timing of 5G base stations and terminals. This synchronization extends to the 5G terminal and the protection device, thereby mitigating time deviations caused by air interface delays and reducing the 5G network’s end-to-end delay by approximately 4 ms on average. A simulation was conducted to assess the reliability and effectiveness of the proposed method under normal satellite signal conditions. The results indicated a significant improvement in protection accuracy, with the method reducing the protection activation time by approximately 5–7 ms compared to the 5G timing data synchronization method. This advancement offers technical support for the safe and stable operation of new power systems.

The Evolution and Potential of Precision Agriculture in China Anchored In "3S" Technology.

Agriculture serves as a linchpin for the national economy. With the accelerated evolution of information technology and emergent high-tech innovations, the digitization of agriculture has emerged as a pivotal trajectory for contemporary agricultural advancement. Conventional practices encompassing planting, fertilization, and harvesting are transitioning towards more quantitative, localized, and technologically-driven precision agriculture. Concurrently, with the global surge in "precision agriculture", Chinese academicians have progressively delved into its study. Over the past three decades, the "3S" technology-centric "precision agriculture" in China has witnessed commendable advancements, exemplified by innovations such as the Global Agricultural Remote Sensing Quick Report System and the Beidou Satellite Navigation System-based autonomic agricultural machinery operation. However, the modernization of Chinese agriculture exhibits certain limitations, including limited adoption, suboptimal integration, and a scarcity of high-caliber experts. Given the swift progression of Chinese scientific and economic domains, the "3S" technology is poised to surmount these challenges, enhancing the modernization of Chinese agriculture. Hence, "precision agriculture" anchored in "3S" technology retains significant growth prospects within China.

Research Progress of Wireless Positioning Methods Based on RSSI

Location-based services are now playing an integral role in the development of emerging industries, such as the Internet of Things, artificial intelligence and smart cities. Although GPS, Beidou and other satellite positioning technologies are becoming more and more mature, they still have certain limitations. In order to meet the needs of high-precision positioning, wireless positioning is proposed as a supplementary technology to satellite positioning, in which the Received Signal Strength Indication (RSSI) is one of the most popular positioning methods. In this paper, the application scenarios, evaluation methods and related localization methods of wireless positioning based on RSSI are studied. Secondly, the relevant optimization methods are analyzed and compared from different angles, and the methods of RSSI data acquisition are described. Finally, the existing problems and future development trends in RSSI positioning methods are expounded, which has certain reference significance for further research on RSSI localization.

Performance Evaluation of Strapdown Inertial Navigation and Beidou Satellite Navigation System Based on Intelligent Image Processing Technology

Performance Evaluation of Strapdown Inertial Navigation and Beidou Satellite Navigation System Based on Intelligent Image Processing Technology

Two-Level Integrity-Monitoring Method for Multi-Source Information Fusion Navigation

To address the issue of integrity monitoring for a multi-source information fusion navigation system, a theoretical framework of two-level integrity monitoring is proposed. Firstly, at the system level, a system-integrity-monitoring method based on the Kalman filter weighted least-squares form is established to detect and isolate faulty navigation sources. Secondly, at the sensor level, considering the redundancy of the faulty navigation sources, this paper presents the design of a multi-mode comprehensive fault-detection method for non-redundant navigation sources. Additionally, an extended-dimension matrix optimized sensor-fault detection and verification method for redundant navigation sources is proposed. Finally, integrity risk allocation criteria are established based on the effectiveness of navigation sources to calculate the system protection level and trigger integrity alarms. The two-level integrity-monitoring method was tested on a multi-source information fusion navigation system integrated with an inertial navigation system (INS), global positioning system (GPS), BeiDou satellite navigation system (BDS), Doppler velocity log (DVL), barometric altimeter (BA), and terrain-aided navigation (TAN). Test results demonstrate that the proposed method can effectively isolate the faulty navigation source within 10 s. Furthermore, it can detect the faulty sensors within the faulty navigation sources, thereby enhancing the reliability and robustness of the multi-source information fusion navigation system.

Prediction of regional carbon emissions using deep learning and mathematical–statistical model

Detecting carbon emissions is the key to carbon peaking and carbon neutrality goals. Existing research has focused on utilizing data-driven method to study carbon emissions off a single object. This study proposes a regional carbon emissions prediction method. The area objects are divided into dynamic objects for vehicles and static objects for buildings. For the dynamic object, carbon emissions is modeled using the vehicle location provided by the BeiDou satellite navigation system (BDS). For the static object, the neural network R3det (rotation remote sensing target detection) is used to identify the buildings in remote sensing images, and then the trained ARIMA time series model is used to predict the carbon emissions. The model is tested in an industrial park in Tangshan, Hebei Province in China. The result of the regional three-dimensional emission map shows that the method provided a novel and feasible idea for carbon emissions prediction.

GPS signal jamming effect in Svalbard Island and its elimination by using GLONASS, Galileo and Beidou satellites

The Svalbard Islands are located in the Arctic Ocean, halfway between Norway and the North Pole. Because of this, the Svalbard Islands exhibit a number of special properties that make it an interesting region for studying interactions between the atmosphere, sea ice, and ocean. In this study, satellite signals of three points (NABG, NYA2 and NYAL) on the island of Svalbard in the Barents Sea were examined. On January 8, 2022, signal jamming effects appeared at all three points. From these two points (NYA2, NYAL), it was obvious that GLONASS, Galileo and Beidou satellites were also recorded in the receivers as well as GPS satellites. For this reason, the effect of the jamming effect on the GPS signals on the position accuracy was investigated using both static and kinematic methods. In addition, both static and kinematic processing at these two points was performed with GLONASS-Galileo-Beidou satellite combinations in order to eliminate the GPS jamming effect. Although the GPS jamming effect is not obtained in large values ​​in the static process, when only GPS satellites are used in the kinematic process, it reaches approximately 5 meters as the maximum horizontal coordinate difference. The maximum height difference recorded was approximately 15 meters. The difference in coordinates between the kinematic and static processes, as determined through the use of GLONASS, Galileo, and Beidou satellites, was around 5 cm. However, in terms of height values, it reached up to about 10 cm. In the Svalbard Islands, when GPS signals are exposed to interference, satisfactory results were obtained by using GLONASS-Galileo-Beidou satellites.

Retrieval of high-precision precipitable water vapour maps using Sentinel-1A and Beidou satellite data

ABSTRACTPrecipitable water vapour (PWV) is a primary factor that affects climate and weather. The accurate retrieval of PWV is crucial for weather prediction and meteorological research. Interferometric Synthetic Aperture Radar (InSAR) has been rapidly developed in recent years and proven effective in PWV retrieval in the regions of good coherence. However, there are large areas of natural terrain where signals decoherence that limit the precision of PWV retrieval. Besides, due to the differential interference processing of InSAR data, the results of its retrieval are differential PWV (ΔPWV). In this study, the StaMPS-InSAR was used to overcome the problem of weak detection ability in low coherence regions. A series of 11 Sentinel-1A images were selected to retrieve space-continuous ΔPWV. Beidou Satellite Navigation System (BDS) can retrieve high-precision PWV. Hence, the BDS data was utilized to convert the InSAR-derived ΔPWV to PWV. Compared with the BDS-derived PWV, the root mean square error (RMSE) of the experimental results is 1.3 mm with a spatial resolution as fine as 20 m. The correlation coefficient between the deviations and Liquid Cloud Water is 0.65, indicating a positive correlation. We demonstrate the advantage of the proposed method for retrieving PWV in computational efficiency by comparing it with the SBAS-InSAR. With the increasing stack size of the SAR images, our method can reduce the taking time for processing. The proportion can reach 12.6% when the stack size of SAR images is 20. By the spatio-temporal analysis of the results, we found some characteristics of PWV in mountain areas especially. The results have certain reference value for the space-continuous PWV retrieval and the study of PWV spatio-temporal characteristics.

Exploring the behavior feature of complex trajectories of ships with Fourier transform processing: a case from fishing vessels

The significant uncertainty and complexity of vessels at sea poses challenges for regulatory bodies in the fishing industry. This paper presents a method for identifying fishing vessel trajectory characteristics involving the Fourier series transform. The model utilizes the Fourier series and Gaussian mixture clustering to address the complexity and uncertainty issues in fishing vessel trajectories. First, the vessel trajectories undergo a process of dimensionality expansion and projection along the temporal axis. The relationship between trajectories and complex plane projection was elucidated in this process. Second, a vessel trajectory identification model involving Fourier transformation was constructed. Subsequently, the phase spectrum was assigned binary values using differentiation, and the phase spectrum characteristics of the transformed trajectories through Fourier transformation were analyzed. Finally, six encoding formats for fishing vessel motion trajectories in phase spectrum encoding are introduced, along with the determination of uncertain vessel motion range through mixed Gaussian clustering. This method has been validated using a dataset comprising 7,000 fishing vessel trajectories collected from the Beidou satellite positioning system. The results demonstrate that the range of uncertain vessel motion was able to be obtained with the assistance of Gaussian mixture clustering, with an 80% probability position of approximately 1,000 m and a 50% probability position of around 2,000 m. Effective identification of fishing vessel operating and navigational states was achieved, leading to the determination of a safety distance for fishing vessels in the range of 1,000m–2,000 m. This research holds important reference value for fishery regulatory agencies in terms of supervising fishing vessels and maintaining a safe navigational distance.

Application of Kalman filter in wharf surface displacement of Beidou automatic monitoring

To meet the requirements for real-time dynamic monitoring of wharf surface displacement, an automatic monitoring system based on Beidou satellite navigation was constructed, and it was applied to monitor the surface displacement of a wharf in Tianjin Port. Next, the sensible system noise of the Kalman filter state equation was determined by the simulation experiment. Finally, the monitoring data were processed and analyzed by Kalman filter. The results show that the accuracy of the monitoring data can be improved by more than 30% by Kalman filtering, particularly the elevation direction accuracy can reach more than 40%. The plane and elevation accuracy can be less than 1.5mm, after the Beidou automatic monitoring data has been processed by Kalman filtering, and this meets the needs for most engineering deformation monitoring. In a word, the Beidou automatic monitoring system is characterized by continuity, real-time and high precision, and can be applied to most engineering deformation monitoring requirements.

Preliminary performance analysis of BeiDou-2/GPS navigation systems over the low latitude region

Abstract On a regional or worldwide scale, satellite-based navigation systems can offer three-dimensional Position, Velocity, and Timing (PVT) services to an indefinite number of users. BeiDou-2 is China’s regional navigation satellite system that encompasses the Asia-Pacific region. BeiDou-2’s space section comprises GEO, MEO, and IGSO satellites, making it unique among the navigation systems. This research focuses on key aspects, including satellite visibility and signal strength, as a function of the elevation angle across the low latitude region (Indian region). In addition, the results were compared with those obtained using the GPS. The data is acquired from a GNSS receiver located at the Hyderabad station (latitude:17°24′28″, longitude:78°31′04″). The results show that BeiDou-2 satellites have better visibility than GPS satellites at all elevation angles. However, visibility is low at high elevations; therefore, multiple systems are required to obtain user information. As the elevation angle increases, the carrier-to-noise density ratio (C/No) also increases. Additionally, the standard deviation (STD) was calculated and compared to that of the GPS. Despite the average signal strength of GPS satellites remaining high throughout the elevation range, the STD of BeiDou-2 satellites was found to be low. These results indicate that further work is needed to improve the interoperability of multiple navigation systems and to provide more accurate location information to Indian users.

Adapting empirical solar radiation pressure model for BDS-3 medium Earth orbit satellites

For the precise orbit determination (POD) of global navigation satellite systems (GNSS) constellation, it is very difficult to precisely model the solar radiation pressure (SRP) force acting on GNSS satellites. For GPS satellites, the ECOM model developed by the Center for Orbit Determination in Europe has been utilized by most of International GNSS Service (IGS) analysis centers. However, it should be adapted and optimized to the characteristics of satellites of each GNSS system or even individual satellites. It was extended to the ECOM2 model for GLONASS satellites and then for Galileo satellites by employing a box–wing model. Since November 2020, the third generation of the BeiDou satellite system (BDS-3) has been in its full operation and there are about 200 globally distributed IGS ground stations tracking BDS-3 signals, which creates a great potential to evaluate and optimize its SRP modeling. From the POD processing carried out in this study, we found significant fluctuations of up to 20 cm in overlapping orbit differences for satellites over eclipses in the radial direction and of about 20 and 50 cm in the cross and along directions for ECOM2 and ECOM models. Then, based on numerical analyses we demonstrate that the fourth- and sixth-order sine terms in the Sun direction can significantly reduce the overlapping orbit differences of ECOM. Therefore, an adapted SRP model by adding the fourth- and sixth-order sine periodical terms in the Sun direction to the ECOM model is presented. The adapted model is then validated for BDS-3 POD and orbit prediction. Results show that fluctuations in the amplitude of overlapping estimated orbits using ECOM models are reduced from 20 to < 10 cm in the radial-track component and satellite laser ranging residuals are reduced to half by the adapted SRP model. For the predicted BDS-3 satellite orbits, the RMS values over deep eclipses can be improved from about 7, 14 and 26 cm to about 3, 5 and 12 cm, in the radial, cross and along directions, respectively, compared to the ECOM model.

Distributed new energy information acquisition model of distribution network based on Beidou communication

Abstract Aiming at the low efficiency of distributed new energy information collection in distribution network and the poor encryption of information transmission process, a distributed new energy information collection model based on Beidou communication is proposed. The new energy information acquisition terminal, data acquisition and transmission equipment, Beidou satellite communication module and dispatching master terminal are designed respectively to form the hardware module of the distribution network distributed new energy information acquisition model. Use Beidou communication to collect new energy information, realize the encrypted transmission of new energy information based on Beidou short message, and complete the construction of distribution network distributed new energy information collection model based on Beidou communication. The experimental results show that the bandwidth allocation effect of the Beidou benchmark station of the model is good, the Beidou communication distance is long, the data encryption can be completed in a small space by using the model, the transmission efficiency of new energy data is high, and the data integrity can be effectively guaranteed.

Indoor and Outdoor Fusion Positioning Technology Based on BeiDou Satellite Navigation

In order to solve the inaccuracy and discontinuity of BeiDou differential indoor and outdoor navigation and positioning, this article highlights an indoor and outdoor fusion positioning method based on BeiDou differential and WIFI. This positioning method combines the micro-inertial navigation positioning technology with a single positioning method such as Bluetooth, WIFI fingerprint, ZigBee, ultra-wideband UWB, etc., to correct the BeiDou pseudo range equation to reduce the spatial pseudo range error. And it can integrate BeiDou differential pseudo range equation and linear filtering algorithm to achieve precise positioning of navigation. The research results show that the method realizes the positioning of the indoor and outdoor interactive area by fusing the satellite pseudo-range equation and the base station pseudo-range equation. And it realizes the seamless integration of indoor and outdoor precise positioning, which improves the positioning accuracy and reliability.

A Multipath Error Reduction Method for BDS Using Tikhonov Regularization with Parameter Optimization

Multipath error is an important factor restricting the relative positioning accuracy of the Beidou Navigation Satellite System (BDS). Because of the complexity of the reflection environment, the mathematical modeling of multipath errors is quite difficult. The sidereal filtering algorithm corrects multipath errors by using the feature of period repetition, which can greatly reduce its influence and improve the accuracy of positioning and attitude measurement. In view of the constellation heterogeneity of BDS, it is more complicated to apply sideral filtering. Based on the reconstructed single-difference residual of the carrier phase, the multipath repetition time of the Beidou satellite is estimated using the idea of segmentation. The Tikhonov regularization method and the classical wavelet method are used to extract the multipath of the single-difference residual of the carrier phase, and the “clean” sequence of the single-difference residual is obtained. The experimental results show that it is feasible to extract the multipath error correctly by Tikhonov regularization, and the multipath error is smoother than the original residual measurement. Furthermore, the estimation method of the regularization parameter is further optimized. After using the optimized Tikhonov regularization method with sidereal filtering, the mean RMS improvements of GEO, IGSO, and MEO satellites are 45.9%, 38.2%, and 37.5%, respectively. The positioning accuracy on E, N, and U components is improved by 24.8%, 26.3%, and 42.7%, respectively. The attitude resolution accuracy is improved by 22.9% in the yaw angle and 12.6% in the pitch angle. The proposed method can be an alternative BDS multipath error modeling and mitigation approach.

BDS Orbit Maneuver Detection Based on Epoch-Updated Orbits Estimated by SRIF

The orbit maneuver detection is crucial in Global Navigation Satellite System (GNSS) precise orbit determination, which is necessary for adjusting data processing strategies. The frequency of orbit maneuvers for the BeiDou Navigation System is significantly higher than that of other navigation systems, especially for geosynchronous orbit (GEO) and inclined geosynchronous orbit (IGSO) satellites. We propose a novel real-time and postprocessing method for detecting orbit maneuvers for BeiDou satellites based on the orbit differences between the epoch-updated orbit estimated using square root information (SRIF) and the predicted orbit according to the precise orbit estimated during non-maneuver period, as well as the orbital state difference during maneuver and non-maneuver periods. This method has significant advantages over using observation residuals and it is not affected by observation outliers, thus improving the accuracy and timeliness of orbit maneuver detection. We demonstrated that 32 orbit maneuver events of BeiDou satellites were successfully detected in 2022, of which 1 was for medium Earth orbit (MEO), 7 were for IGSO with an average detected maneuvering time of 7–8 min, and 24 were for GEO satellites with an average detected time of 4–5 min. Moreover, our method can be easily integrated into current real-time filter-based precise orbit determination (POD) processing without any extra task line, which simplifies the overall data processing. The data used in this method can be accessed easily, including GNSS observation data, broadcast ephemeris, and other open-source information files.

Radiation environment and effect detection based on global navigation constellation

Abstract Combining the anomalies and environmental monitoring data of the early stage Beidou satellites, the space radiation environment spatial/temporal distribution and space radiation effect risk characteristics are analyzed, and the dynamic characteristics of space environmental factors, such as hot plasma, high-energy electron and solar proton are summarized. The systematic joint monitoring for surface charging, internal charging, single event effect and total dose effect with corresponding space environment factors is proposed. The detector types, measurement parameters range and engineering constraints are allocated, and the engineering application and scientific research of detection data are prospected.