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Global and regional sea level variations are important indicators of climate change and are derived from accurate sea surface height measurements and precisely determined orbits of altimetry satellites. To validate and improve the quality of these orbits, comparisons with external solutions are important. Since orbit solutions of different institutions are not necessarily provided at the same time instants, interpolation is required for comparison. In this study, we investigate the appropriate interpolation method and its degree to reduce interpolation errors to sub-millimetre levels. We also assess the magnitude of errors occurring at transformations when expressing orbit differences not only in the terrestrial reference frame (Cartesian coordinates), but also in local orbital and ellipsoidal coordinates. The analyses conducted in this study provide good results for Hermite interpolation of degrees 7–11 and Newton interpolation of at least degree 9 with a three-dimensional interpolation error of 0.6 mm and a scattering of 0.2 mm on average for satellite coordinates given with an accuracy of 1 mm in the SP3 format. These interpolation settings limit transformation errors between coordinate systems to ±0.01 mm and incorrect mapping of interpolation errors into certain components in the target system to ±0.02 mm. The spectral analysis of orbit differences is affected up to 0.1 mm in magnitude with appropriate interpolation settings. Extending the number of decimal digits of the satellite position and velocity in SP3 files by one digit benefits the orbit comparisons and reduces the interpolation error by 90% from 0.6 to 0.06 mm. The results are obtained using piece-wise interpolation and a validity interval inside the interpolation interval to minimise the effects of the Runge phenomenon. [ABSTRACT FROM AUTHOR]

Due to factors that include systematic sensor delay, it is difficult for synthetic aperture radar (SAR) satellite stereo positioning to meet the requirements of large-scale mapping. In traditional stereo positioning methods, ground control points (GCP) are required to eliminate errors. In this study, a method is proposed to improve the stereo positioning accuracy without GCP. First, the factors influencing the Gaofen-3 (GF-3) satellite stereo positioning accuracy were analysed. The errors were divided into systematic fixed errors, spatial and temporal variation errors, and random errors. Subsequently, a systematic geometric error compensation model and a stereo adjustment model were constructed, and a method to improve the multiscene and multimode stereo positioning accuracy without GCP was proposed. Finally, the effects of different intersection angles on the accuracy of stereo positioning were compared and analysed, and the optimal intersection angle of the SAR satellite was quantitatively analysed. The effectiveness and accuracy of this method were verified using GF-3 high-resolution image data. The experimental results indicate that the proposed method can improve the SAR satellite stereo positioning accuracy. The plane positioning accuracy improved by 95.1%, and the elevation positioning accuracy improved by 97.9%. In general, the plane and elevation positioning accuracies of the GF-3 satellite were better than 3 m and 2 m, respectively. The stereo-positioning accuracy of the SAR satellite was the best and most stable when the intersection angle was between 40° and 50°. [ABSTRACT FROM AUTHOR]

The spatial gradient induced by the Equatorial Plasma Bubble (EPB) in low latitude regions is a major challenge for the Ground Based Augmentation System (GBAS). To facilitate the implementation and operation of GBAS Approach Service Type (GAST)-D at Hong Kong International Airport, the impact of EPB induced spatial gradients needs to be analyzed. Previous simulations using a two-dimensional trapezoid model neglected the three-dimensional structure of the EPB, assuming ionospheric delay on a thin shell at a specific altitude. To address this limitation, this paper adopts a cube above the magnetic equator to characterize the EPB threat model. The ionospheric delay difference between satellite signals passing through the EPB model is limited by the upper bound spatial gradient derived with the data collected from Hong Kong Satellite Positioning Reference Station Network. The simulation results reveal that ionospheric monitors in GAST D can satisfy the Category II/III approach requirement, i.e., the probability of missed detection P MD for the differential range error Er larger than 2.75 m is lower than 1 × 10 - 9 . The potentially hazardous event with the largest Er of 2.47 m and P MD of 1.86 × 10 - 9 occurs when the satellite signal moves parallel to the equator near the Equatorial Ionization Anomaly (EIA) region, and its significant portion traverses in the EPB depletion region. [ABSTRACT FROM AUTHOR]

The BeiDou-3 navigation satellite system (BDS-3) has officially provided positioning, navigation, and timing (PNT) services to global users since 31 July 2020. With the application of inter-satellite link technology, global integrity monitoring becomes possible. Nevertheless, the content of integrity monitoring is still limited by the communication capacity of inter-satellite links and the layout of ground monitoring stations. Low earth orbit (LEO) satellites have advantages in information-carrying rate and kinematic velocity and can be used as satellite-based monitoring stations for navigation satellites. Large numbers of LEO satellites can provide more monitoring data than ground monitoring stations and make it easier to obtain full-arc observation data. A new challenge of redundant data also arises. This study constructs multi-source observation links with satellite-to-ground, inter-satellite, and satellite-based observation data, proposes an integrity monitoring method with optimization of observation links, and verifies the performance of integrity monitoring with different observation links. The experimental results show four findings. (1) Based on the integrity status of BDS-3, the proposed system-level integrity mode can realize full-arc anomaly diagnosis in information and signals according to the observation conditions of the target satellite. Apart from basic navigation messages and satellite-based augmentation messages, autonomous messages and inter-satellite ranging data can be used to evaluate the state of the target satellite. (2) For a giant LEO constellation, only a small number of LEO satellites need to be selected to construct a minimum satellite-based observation unit that can realize multiple returns of navigation messages and reduce the redundancy of observation data. With the support of 12 and 30 LEO satellites, the minimum number of satellite-based observation links is 1 and 4, respectively, verifying that a small amount of LEO satellites could be used to construct a minimum satellite-based observation unit. (3) A small number of LEO satellites can effectively improve the observation geometry of the target satellite. An orbit determination observation unit, which consists of chosen satellite-to-ground and/or satellite-based observation links based on observation geometry, is proposed to carry out fast calculations of satellite orbit. If the orbit determination observation unit contains 6 satellite-to-ground monitoring links and 6/12/60 LEO satellites, the value of satellite position dilution of precision (SPDOP) is 38.37, 24.60, and 15.71, respectively, with a 92.95%, 95.49%, and 97.12% improvement than the results using 6 satellite-to-ground monitoring links only. (4) LEO satellites could not only expand the resolution of integrity parameters in real time but also augment the service accuracy of the navigation satellite system. As the number of LEO satellites increases, the area where UDRE parameters can be solved in real time is constantly expanding to a global area. The service accuracy is 0.93 m, 0.88 m, and 0.65 m, respectively, with augmentation of 6, 12, and 60 LEO satellites, which is an 8.9%, 13.7%, and 36.3% improvement compared with the results of regional service. LEO satellites have practical application values by improving the integrity monitoring of navigation satellites. [ABSTRACT FROM AUTHOR]

The Length of Day (LOD) and the Universal Time (UT1) play crucial roles in satellite positioning, deep space exploration, and related fields. The primary method for predicting LOD and UT1 is least squares fitting combined with autoregressive (AR) models. Polynomial Curve Fitting (PCF) has greater accuracy in capturing long-term trends compared to standard least squares fitting. In this study, PCF combined with Weighted Least Squares (WLS) is employed to fit and extrapolate the periodic and trend components of the LOD series after removing tidal influences. Additionally, considering the time-varying characteristics of the LOD series, a Long Short-Term Memory (LSTM) network is utilized to predict the residuals derived from the fitting process. The 14 C04 LOD series released by the International Earth Rotation and Reference System Service (IERS) is used as the base series, with 70 LOD and UT1-UTC prediction experiments conducted during the period from 1 September 2021–31 December 2022. The results indicate that the PCF+WLS+LSTM method is well-suited for medium- and long-term (90–360 days) prediction of the LOD and UT1-UTC. Significant improvements in prediction accuracy were obtained for periods ranging from 90–360 days, particularly beyond 150 days, where the average accuracy improved by over 20% compared to IERS Bulletin A. Specifically, the largest prediction accuracy increase for LOD and UT1-UTC was 49.5% and 59.2%, respectively. [ABSTRACT FROM AUTHOR]

The paper considers the problem of ensuring stable radio communication during an Earth–Mars flight using relay satellites. We have analyzed the orbits of relay satellites that are in resonance with the Earth–Mars flight trajectory, which makes it possible to provide a channel of communication with Earth for each mission using such trajectory. A single-stage relay scheme is considered using a regenerative transponder that performs complete processing of the received signal, including demodulation, decoding, subsequent coding, modulation, and transfer to the operating frequency. An independent assessment of power budgets of the communication channels "mission-oriented spacecraft–relay satellite" and "relay satellite–ground receiving network" has been performed. The requirements for the possible regions of the relay satellite positioning in the Earth–Mars flight stage are formulated. Families of resonant orbits providing the given quality of communication on the trajectory of the mission-oriented spacecraft using the relay satellite are defined. The most promising variants of relay satellite orbits have been identified based on the following criteria: the maximum transmitted data during the flight and the maximum data rate at the maximum distance from the Earth. [ABSTRACT FROM AUTHOR]

This paper presents the design, development, and investigation of a novel piezoelectric inertial motor whose target application is the low Earth orbit (LEO) temperature conditions. The motor utilizes the inertial stick–slip principle, driven by the first bending mode of three piezoelectric bimorph plates, and is compact and lightweight, with a total volume of 443 cm3 and a mass of 28.14 g. Numerical simulations and experimental investigations were conducted to assess the mechanical and electromechanical performance of the motor in a temperature range from −20 °C to 40 °C. The results show that the motor's resonant frequency decreases from 12,810 Hz at −20 °C to 12,640 Hz at 40 °C, with a total deviation of 170 Hz. The displacement amplitude increased from 12.61 μm to 13.31 μm across the same temperature range, indicating an improved mechanical response at higher temperatures. The motor achieved a maximum angular speed up to 1200 RPM and a stall torque of 13.1 N·mm at an excitation voltage amplitude of 180 Vp-p. The simple and scalable design, combined with its stability under varying temperature conditions, makes it well suited for small satellite applications, particularly in precision positioning tasks such as satellite orientation and free-space optical (FSO) communications. [ABSTRACT FROM AUTHOR]

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The ionosphere, partially ionized by solar radiation, is rich in free electrons and ions, affecting satellite navigation signals by altering their speed and path. This interaction often leads to signal delays of 5–10 m, complicating accurate positioning in satellite-based systems. This paper investigates the influence of global ionospheric models (GIMs) with varying Temporal Resolutions (TR) on satellite positioning accuracy and convergence time under different solar activities, represented by the years 2009 (low solar activity) and 2014 (high solar activity). The study utilizes Global Positioning System (GPS) data from three GIMs: CODG, representing the Center for Orbit Determination in Europe (CODE) GNSS model with a 2-h TR; bcom, with a 1-h TR; and b5mg, with a 5-min TR. Analysis was conducted using the GNSS Analysis Software for Multi-constellation and Multi-frequency Precise Positioning across 46 international GNSS service stations under single and dual-frequency strategies. The results indicate that precise point positioning convergence time improved by approximately 18 % and 78 % using single and dual frequencies, depending on the GIM applied. Consequently, positioning accuracy after convergence improved by about 16 % and 27 % in the horizontal and up components for ionospheric-constrained single-frequency PPP models and by 68 % and 79 % in the horizontal and up components for dual-frequency PPP models. Furthermore, vertical total electron content analysis at the MARS station revealed significant variations correlating with solar activity, underscoring the importance of selecting appropriate GIMs for accurate GNSS positioning. Future studies, including multi-solar events, are recommended for comprehensive analysis. [ABSTRACT FROM AUTHOR]

The GF-7 satellite, China's inaugural sub-meter-level stereoscopic mapping satellite, has been deployed for a wide range of applications, including natural resource investigation, environmental monitoring, fundamental surveying, and the development of global geospatial information resources. The satellite's stable platform and reliable imaging systems are crucial for achieving high-quality imaging and precise attitude measurements. However, the satellite's operation is affected by both internal and external factors, which induce vibrations in the satellite platform, thereby affecting image quality and mapping accuracy. To address this challenge, this paper proposes a novel method for constructing a satellite platform vibration model based on geographic location information. The model is developed by integrating composite data from star sensors and gyroscopes (gyro) with subsatellite point location data. The experimental methodology involves the composite processing of gyro data and star sensor optical axis angles, integration of the processed data through time-matching and normalization, and denoising of the integrated data, followed by trigonometric fitting to capture the periodic characteristics of platform vibrations. The positions of the satellite substellar points are determined from the satellite orbit data. A rigorous geometric imaging model is then used to construct a vibration model with geographic location correlation in combination with the satellite subsatellite point positions. The experimental results demonstrate the following: (1) Over the same temporal range, there is a significant convergence in the waveform similarities between the gyro data and the star sensor optical axis angles, indicating a strong correlation in the jitter information; (2) The platform vibration exhibits a robust correlation with the satellite's geographic location along its orbit. Specifically, the model reveals that the GF-7 satellite experiences the maximum vibration amplitude between 5° S and 20° S latitude during its ascending phase, and the minimum vibration amplitude between 5° N and 20° N latitude during the descending phase. The model established in this study offers theoretical support for optimizing satellite attitude and mitigating platform vibrations. [ABSTRACT FROM AUTHOR]

This study utilizes ionospheric total electron contents (TECs) data from China and its surrounding areas to compute the regional ionospheric semi‐variance using the Gaussian variogram. The regional ionospheric model is then constructed by introducing an additional stochastic term, named adjusted Spherical Harmonics Adding KrigING method (SHAKING), in which the stochastic Vertical Total Electron Content estimated using Kriging interpolation based on Ionospheric Variogram Model Parameters (IVMP) predict model. In the IVMP prediction model, two notable periodic patterns, that is, diurnal and annual signals with periods of 365.25/i days and 24/j hours, are recognized as Fourier series decompositions. These patterns capture the regular daily and yearly periodic variations in variogram parameters, and the IVMP prediction model is established using harmonic estimation methods. IVMP‐SHAKING is employed to generate the regional ionospheric map in China using multi‐GNSS data from 27 reference stations during days of the year 150–250 in 2022, with 14 rover stations used for evaluation. Results indicate that the proposed model exhibits a standard deviation of 4.85 TECu compared to the difference of slant TEC extracted from rover stations. Compared to existing models, including BDS‐3 broadcast ionospheric model (BDGIM), GPS broadcast model (Klobuchar), Galileo broadcast model (NeQuickG) and post‐processing Global Ionospheric Map released by IGS (IGSG), the accuracy of IVMP‐SHAKING improves by 6%–52%. Additionally, the Standard Point Positioning performance with different ionospheric corrections is analyzed on test stations. Results demonstrate that the horizontal and vertical positioning accuracy of the IVMP‐SHAKING model improves by 31%–55% and 16%–33%, respectively, compared to other three solutions. Plain Language Summary: This study looks at data on the total amount of electrons in the ionosphere (called Total Electron Content (TEC)) in China and nearby regions. We use this data to understand how TEC varies across the region using a statistical method called Gaussian variogram. Then, we create a model of the ionosphere called the Adjusted Spherical Harmonics Adding Kriging method (or SHAKING). This new model considers regular patterns in TEC variations throughout the day and year. We tested this model using data from 27 fixed stations and 14 mobile stations during a specific time period in 2022. The contribution of this paper is twofold. Firstly, we analyzed the spatial correlation of the ionosphere in China and developed a predictive model for this spatial correlation. Subsequently, based on this predictive model, we established a model for ionospheric delay and applied it to Global Navigation Satellite System positioning. Key Points: The study introduces a novel ionospheric approach, IVMP‐SHAKING, which based on Gaussian variogram model and Kriging interpolationIVMP‐SHAKING incorporates Fourier series decomposition to capture diurnal and annual periodic patterns in ionospheric variogram parametersEvaluation against existing models like BDGIM, Klobuchar, and IGSG demonstrates that IVMP‐SHAKING outperforms them by a significant margin [ABSTRACT FROM AUTHOR]

Despite growth in the use of electronic monitoring (EM), and Global Positioning Satellite (GPS) tracking in particular over the last 20 years, limited research has examined the effectiveness of these approaches on community supervision outcomes (e.g. likelihood of failure on community supervision). This study makes use of data from over 59,000 probation cases collected over a 40-year time span in a midwestern state. Using Propensity Score Matching (PSM), the study compares the rates of unsuccessful sentence completion among those who were supervised with and without any EM (and also GPS specifically). Results reveal that after matching cases on a variety of relevant controls (e.g. demographics, risk level, current offense type), those receiving EM while on probation were significantly more likely to fail to complete their term of supervision, with similar results for those who received GPS, specifically. Limitations of the study and implications for the use of EM/GPS with probationers as a potential alternative to prison are discussed. [ABSTRACT FROM AUTHOR]

Structure from motion (SfM) photogrammetry coupled with multiview stereo (MVS) techniques are widely used for generating topographic data for monitoring change in surface elevation. However, study sites on remote glaciers and ice caps often offer suboptimal conditions, including large survey areas, complex topography, changing weather and light conditions, poor contrast over ice and snow, and reduced satellite positioning performance. Here, we provide a review of methodological considerations for conducting aerial photography surveys under challenging field conditions. We generate topographic reconstructions, outlining the entire workflow, from data acquisition to SfM-MVS processing, using case studies focused around two small glaciers in Arctic Canada. We provide recommendations for the selection of photographic and positioning hardware and guidelines for flexible survey design using direct measurements of camera positions, thereby removing the need for ground control points. The focus is on maximising hardware performance despite inherent limitations, with the aim of optimising the quality and quantity of the source data, including image information and control measurements, despite suboptimal conditions. [ABSTRACT FROM AUTHOR]

Underground mining involves numerous risks, such as collapses, gas leaks, and explosions, posing significant threats to worker safety. In this work, we develop an indoor localization system that uses Bluetooth for coarse positioning and ultrasonic arrays for precision calibration. This system is particularly useful for automated mining operations in underground environments where satellite positioning signals are unavailable. The indoor localization system consists of ultrasonic receiver arrays and an improved multi-transmitter-multi-receiver algorithm, enabling accurate localization within the mining environment. Geometric Dilution of Precision (GDOP) analysis is incorporated to optimize the network layout, and an inertial navigation module is integrated to track the posture of moving objects, enabling precise trajectory determination over large areas, such as coal mines. In the experiment, three traditional methods were compared, and the proposed tracking approach demonstrated a positioning accuracy within 10 cm, reducing error by 20% compared to conventional techniques. This high-precision indoor localization method proves beneficial for underground mining applications. [ABSTRACT FROM AUTHOR]

The correction of the trajectory of a two-impulse launch of a spacecraft into a high circular orbit of an artificial Moon satellite is considered, taking into account errors in determining the position and speed of the satellite, as well as errors in issuing speed impulses in magnitude and direction. Trajectory corrections with one and two correction impulses are considered. Results of analysis are presented. Conclusions are drawn about the practical application of such trajectories. [ABSTRACT FROM AUTHOR]

The properties of satellite dwarf galaxies provide important empirical insights for verifying cosmological models on galaxy scales. Their phase-space correlations, in particular, offer interesting insights into a broad range of models, since they are dominated by gravity and are largely independent of the specific dark matter flavor or baryonic processes that are considered. Next to the much-debated planes-of-satellites phenomenon, the lopsided distribution of satellites relative to their host galaxy has been studied observationally and in cosmological simulations. The degree to which observed lopsidedness is consistent with expectations from simulations is still unclear. We quantified the level of lopsidedness in isolated observed satellite systems under six different metrics. We studied 47 systems from the MATLAS survey beyond the local volume (LV) as well as 21 LV satellite systems from the ELVES survey. The satellite systems are complete to an estimated absolute magnitude of M ∼ −9. We find that the so-called wedge metric, counting the number of dwarfs in wedges with varying opening angles, is best suited to capture a system's overall lopsidedness. Under this metric, our analysis reveals that ∼16 percent of the tested satellite systems exhibit a statistically significant degree of lopsidedness when compared to systems with randomly generated satellite position angles. This presents a notable excess over the expected 5% (2σ level) of significantly lopsided systems in a sample with no overall inherent lopsidedness. To gain the most rounded picture, however, a combination of metrics that are sensitive to different features of lopsidedness should be used. Combining all tested metrics, the number of significantly lopsided systems increases to ∼21 percent. Contrary to recent results from the literature, we find more lopsided systems among the red early-type galaxies in the MATLAS survey compared to the mostly blue late-type hosts in ELVES. We further find that satellite galaxies at larger distances from the host, potentially recently accreted, are likely the primary contributors to the reported excess of lopsidedness. Our results set the groundwork that allows a comparison with similar systems in cosmological simulations to assess the consistency with the standard model. [ABSTRACT FROM AUTHOR]

Drones traditionally rely on satellite signals for positioning and altitude. However, when in a special denial environment, satellite communication is interrupted, and the traditional positioning and height determination methods face challenges. We made a dataset at the height of 80–200 m and proposed a multi-scale input network. The positioning index RDS achieved 76.3 points, and the positioning accuracy within 20 m was 81.7%. This paper proposes a method to judge the height by image alone, without the support of other sensor data. One height judgment can be made per single image. Based on the UAV image–satellite image matching positioning technology, by calculating the actual area represented by the UAV image in real space, combined with the fixed parameters of the optical camera, the actual height of the UAV flight is calculated, which is 80–200 m, and the relative error rate of height is 18.1%. [ABSTRACT FROM AUTHOR]

In recent years, the Global Positioning System has commonly activated flex power, including global flex power and regional flex power. The activation and deactivation periods of satellite flex power are distinguished, and the impact of flex power on the estimation of the differential code biases (DCBs), ionospheric delays and positioning are analyzed. The results indicate that the DCBs are more stable when taking flex power into account. The impact of flex power on the inter-frequency DCBs is 0.19 ns, and on ionosphere estimation is 0.68 TECU. The impact of flex power on the intra-frequency DCBs for L1 and L2 is 0.17 ns and 0.25 ns, respectively. Single point positioning is affected by flex power in the E, N and U components by 0.04 m, 0.12 m and 0.17 m, respectively. [ABSTRACT FROM AUTHOR]

This project is based on the Beidou satellite navigation and positioning technology developed by China. The integrated analysis method is used to obtain the monitoring data of high-precision power cables in high-altitude areas with high-precision millimeters to realize the whole process of monitoring various disasters. An early warning system for power line swing and tower bottom geological hazards is established. The track data of cable swing is obtained by using single-frequency dynamic data post-processing (PPK) based on synchronous power grid monitoring. The applicability and trajectory accuracy of the scheme are evaluated by combining theory with practical engineering. This provides essential technical support for the mechanism and prevention of cable sloshing. The experimental simulation shows that the monitoring efficiency of the system is high. [ABSTRACT FROM AUTHOR]

The low Earth orbit (LEO) satellite internet network (LEO-SIN) has become a heated issue for the next generation of mobile communications, serving as a crucial means to achieve global wide-area broadband coverage and, especially, mobile phone directly to satellite cell (MPDTSC) communication. The ultra-high-speed movement of LEO satellites relative to the Earth results in serious Doppler effects, leading to signal de-synchronization at the user end (UE), and relative high-speed motion leading to frequent satellite handovers. Satellite ephemeris, which indicates the satellite's position, has the potential to determine the position of the transmit (Tx) within the LEO-SIN, thereby enhancing the reliability and efficiency of satellite communication. The adoption of ephemeris in the LEO-SIN has met some new challenges: (1) how UEs can acquire ephemerides before signal synchronization is complete, (2) how to minimize the frequency of ephemeris broadcasting, and (3) how to decrease the overhead of ephemeris broadcasting. To address the above challenges, this paper proposes a method for extrapolating the LEO-SIN orbit based on multi-satellite ephemeris coordination (MSEC) and the multi-stream fractional autoregressive integrated moving average (MS-FARIMA). First, a multi-factor global error analysis model for ephemeris-extrapolation error is established, which decomposes it into three types; namely, random error (RE), trending error (TE), and periodic error (PE), with a focus on increasing the extrapolation accuracy by improving RE and TE. Second, RE is eliminated by utilizing the ephemerides from multiple satellites received at the same UE at the same time, as well as multiple ephemerides from the same satellite at different times. Subsequently, we propose a new FARIMA algorithm with the innovation of a multi-stream data time-series forecast (TSF), which effectively improves ephemeris extrapolation errors. Finally, the simulation results show that the proposed method reduces ephemeris extrapolation errors by 33.5% compared to existing methods, which also contributes to a performance enhancement in the Doppler frequency offset (DFO) estimation of MPDTSC. [ABSTRACT FROM AUTHOR]

Ambiguity resolution (AR) can markedly enhance the precision of precise point positioning (PPP) and accelerate the convergence process. The decoupled clock model represents a pivotal approach for ambiguity resolution, yet current research on this topic is largely confined to GPS. Consequently, in this study, we extend the investigation of the decoupled clock model to multi-GNSS. Firstly, based on the conventional model, we derive the multi-GNSS decoupled clock estimation model and the precise point positioning with ambiguity resolution (PPP-AR) model. Secondly, we provide a detailed explanation of the estimation process for the multi-GNSS decoupled clock estimation. To validate the efficacy of the proposed model, we conduct multi-GNSS decoupled clock estimation and PPP-AR experiments using six days of observation data. The results demonstrate that the decoupled clocks of GPS, Galileo, and BDS-3 can all achieve high accuracy, thus fully meeting the requirement of ambiguity resolution. In terms of positioning performance, the joint three systems have higher positioning accuracy, reaching 3.10 cm and 6.13 cm in horizontal and vertical directions, respectively. Furthermore, the convergence time (CT) and time to first fix (TTFF) are shortened, to 23.13 min and 13.65 min, respectively. The experimental findings indicate that the proposed multi-GNSS decoupled clock model exhibits high precision and rapid positioning service capabilities. [ABSTRACT FROM AUTHOR]

To address airflow interference and inertial altitude dispersion during high-speed aircraft flight, a novel algorithm integrating cubature Kalman filter (CKF), air data observation system, and inertial navigation system (INS) is proposed for real-time aircraft air data estimation through sensor data fusion. The algorithm utilizes nonlinear equations and models interactions among the inertial system, satellite positioning system, and air data system to integrate sensor data for computing aircraft velocity and altitude, followed by estimation of parameters such as angle of attack and sideslip. Experimental results demonstrate the high accuracy and stability of the proposed method in estimating airflow angle and Mach number. [ABSTRACT FROM AUTHOR]

For the time and frequency signals of Beidou satellites, a high-accuracy phase frequency detection technology based on phase group synchronization is proposed. Using the Beidou receiver and satellite signals as the frequency standard and the measured signals, respectively. The Beidou receiver and the satellite signals are sent to the phase coincidence detector of the different frequencies to generate a phase coincidence point pulse, which is sent to the different frequency phase detector as a control signal to generate the phase differences between the Beidou receiver and satellite signals, and then complete the high-accuracy phase synchronization between the Beidou receiver and satellite signals. Experimental results show that when the delay resolution reaches ps level, the phase synchronization accuracy of the system can reach 10 ps, which has the characteristics of small phase noise, low development cost, simple circuit structure, and high synchronization accuracy compared with the traditional phase synchronization technologies. Therefore, it would be widely used in satellite positioning, astrometry, precision navigation, aerospace, satellite launch, power transmission, communications, radar, and other high-tech fields. [ABSTRACT FROM AUTHOR]

The Global Navigation Satellite System (GNSS) is a key asset for tropospheric monitoring. Currently, GNSS meteorology relies primarily on geodetic-grade stations. However, such stations are too costly to be densely deployed, which limits the contribution of GNSS to tropospheric monitoring. In 2016, Google released the raw GNSS measurement application programming interface for smartphones running on Android version 7.0 and higher. Given that nowadays there are billions of Android smartphones worldwide, utilizing those devices for atmospheric monitoring represents a remarkable scientific opportunity. In this study, smartphone GNSS data collected in Germany as part of the Application of Machine Learning Technology for GNSS IoT Data Fusion (CAMALIOT) crowdsourcing campaign in 2022 were utilized to investigate this idea. Approximately 20 000 raw GNSS observation files were collected there during the campaign. First, a dedicated data processing pipeline was established that consists of two major parts: machine learning (ML)-based data selection and ionosphere-free precise point positioning (PPP)-based zenith total delay (ZTD) estimation. The proposed method was validated with a dedicated smartphone data collection experiment conducted on the rooftop of the ETH campus. The results confirmed that ZTD estimates of millimeter-level precision could be achieved with smartphone data collected in an open-sky environment. The impacts of observation time span and utilization of multi-GNSS observations on ZTD estimation were also investigated. Subsequently, the crowdsourced data from Germany were processed by PPP with the ionospheric delays interpolated using observations from surrounding satellite positioning service of the German National Survey (SAPOS) GNSS stations. The ZTDs derived from ERA5 and an ML-based ZTD product served as benchmarks. The results revealed that an accuracy of better than 10 mm can be achieved by utilizing selected high-quality crowdsourced smartphone data. This study demonstrates high-precision ZTD determination with crowdsourced smartphone GNSS data and reveals success factors and current limitations. [ABSTRACT FROM AUTHOR]

In GNSS/IMU integrated navigation systems, factors like satellite occlusion and non-line-of-sight can degrade satellite positioning accuracy, thereby impacting overall navigation system results. To tackle this challenge and leverage historical pseudorange information effectively, this paper proposes a graph optimization-based GNSS/IMU model with virtual constraints. These virtual constraints in the graph model are derived from the satellite's position from the previous time step, the rate of change of pseudoranges, and ephemeris data. This virtual constraint serves as an alternative solution for individual satellites in cases of signal anomalies, thereby ensuring the integrity and continuity of the graph optimization model. Additionally, this paper conducts an analysis of the graph optimization model based on these virtual constraints, comparing it with traditional graph models of GNSS/IMU and SLAM. The marginalization of the graph model involving virtual constraints is analyzed next. The experiment was conducted on a set of real-world data, and the results of the proposed method were compared with tightly coupled Kalman filtering and the original graph optimization method. In instantaneous performance testing, the method maintains an RMSE error within 5% compared with real pseudorange measurement, while in a continuous performance testing scenario with no available GNSS signal, the method shows approximately a 30% improvement in horizontal RMSE accuracy over the traditional graph optimization method during a 10-second period. This demonstrates the method's potential for practical applications. [ABSTRACT FROM AUTHOR]

The accuracy of the results of satellite measurements is influenced by many factors. One of them is the multipath phenomenon resulting from reflections of the satellite signal, mainly from objects in the vicinity of the GNSS antenna. The multipath remains a domain source of ranging errors in satellite positioning. Despite the groups of multipath mitigation methods, it is impossible to totally eliminate the influence of this error on the measurement results. This error has two main effects in the case of carrier phase differential positioning. First, the multipath increases the initial search space for correct ambiguities. Secondly, the accuracy of the vector solution between the reference station and the rover receiver is affected. The authors of this article analyzed the presence of multipath in the Polish network of permanent GNSS stations ASG-EUPOS. Data from the year 2021 were used for the analysis. Two computational strategies were adopted to determine the multipath. The pseudorange multipath observable combination (MP) for L1, L2 and L5 signals was used for code measurements. In the case of the carrier phase, multipath analyses of double-differenced L1, L2, and L5 carriers between neighbouring stations were performed. Based on the research, the average multipath level for the Polish GNSS reference stations network was determined. Stations where the levels of particular combinations exceed the assumed values were successively determined. Finally, multipath models in the form of sidereal maps were created. Based on these models, six stations were identified and recommended for further analysis concerning the impact of multipath on GNSS measurements. [ABSTRACT FROM AUTHOR]

The study introduces the concept of regional GPS orbit determination, whereby GPS satellite positions are determined using GPS measurements from locally or regional distributed stations. The importance and characteristics of regional GPS orbit are briefly discussed. The technique used to determine the regional GPS satellite position is coined Inverse Single Point Positioning (ISPP). Code-based pseudorange is used and improved using residual correction model. Two designs of station distribution are selected in this study, which only cover stations in Malaysia and stations situated 8000 km from a reference point in Malaysia. The root-mean-squared-error (RMSE) of ISPP when compared against final ephemeris were 660.65 m and 27.61 m, while the 3D RMSE of positioning were 1.612 m and 1.324 m for the first and second designs, respectively, lower than the accuracy of broadcast ephemeris. Three parameters are identified as factors affecting accuracy of ISPP, namely geometry of station distribution, nature of measurement used, and technique of orbit determination. Further research will be required to fully realize a functional regional GPS orbit. [ABSTRACT FROM AUTHOR]

To An innovative irrigation system was proposed for facility cultivation tomatoes using weight feedback, in order to improve the accuracy of irrigation. Among them, the weighing feedback module was used to monitor the water requirements of tomato plants. Multi-source information acquisition and transmission were to collect and transmit the environmental information in the greenhouse. An irrigation decision module was to issue the irrigation commands for the switch of water pumps. A water-fertilizer actuation module was to configure and transport the nutrient into the crops. Initially, a satellite positioning module was employed to ascertain the latitude and longitude of the irrigation site, which was facilitated the automatic calculation of the sunrise, sunset, and solar noon times. Four phases of dynamic irrigation were autonomously segmented the day, according to the water absorption of coco coir strips and the diurnal transpiration patterns of tomato plants within the greenhouse. Furthermore, general mode of irrigating nutrient or desalination mode of irrigating pure water (or low-concentration nutrient solution) was formulated, according to the greenhouse temperature and humidity information, as well as the feedback on the root information of tomato plants that obtained from drainage conductivity. Experimental design was involved the radiation accumulation and timed irrigation as controls, in order to validate the applicability, in terms of cultivation, irrigation, and application benefits. The results indicate that the weight feedback system increased irrigation volume by about 1.8%, compared with the radiation accumulation. The fertilizer usage, drainage ratio, and drainage EC value were reduced by 7.3%, 7.9%, and 9.3%, respectively. The irrigation volume, fertilizer usage, drainage ratio, and drainage EC value decreased by approximately 11.3%, 20.0%, 17.9%, and 4.9%, respectively, compared with the timed irrigation. Cultivation results show that when the coconut coir strip-cultivated tomatoes were irrigated under this weight feedback irrigation system, there were no significant differences (P>0.05) in the stem thickness, relative chlorophyll content of leaves, sugar content, and single ear mass, compared with the radiation accumulation. Additionally, the plant height increased by 4.8%. There were no significant differences (P>0.05) in the plant height, stem thickness, relative chlorophyll content of leaves, sugar content, and single ear mass, compared with timed irrigation. It was expected that 15 solar greenhouses (1.22 hm²) were contributed to save 27.6 thousand yuan per month and 22.6 thousand yuan per hectares per month using the weight feedback system, compared with the radiation accumulation; The park can save 22.47 thousand yuan per month in application benefits, compared with the timed irrigation and 18.47 thousand yuan per hectares per month. As such, the previous cumbersome calculation of water demand was greatly simplified to achieve the precise detection of tomato water and precision irrigation for the Rockwool cultivation and the mixed substrate potted cultivation. [ABSTRACT FROM AUTHOR]

In order to solve the problem of converting a large amount of original GNSS receiver observation data into RINEX format files independent of the receiver during satellite positioning measurement in railway line engineering plane control networks, this paper used the C # language for secondary development of the program. The GNSS receiver observation data of Trimble Company was taken as the research object, and the syntax rules of the batch processing file of the GNSS receiver original observation data which provided by the company decoding program Convert To RINEX were analyzed. Then, the batch processing file calling method of the program was used to develop the Trimble GNSS observation data batch processor. After engineering verification, this batch of processor software could conveniently and quickly convert the massive raw data of Trimble GNSS receivers into RINEX format files independent of the receivers, and can be applied to various large-scale satellite measurement projects such as railway line engineering plane control network satellite positioning measurement. [ABSTRACT FROM AUTHOR]

Addressing the positioning challenges for mountainous railways, based on the Yichang -Fuling High-speed Railway project, this paper discussed the application effects of ground-based augmentation and satellite-based augmentation technologies of the Beidou Satellite Navigation System. Firstly, it introduced the background of the difficulties in positioning mountain railways and analyzed the importance of satellite positioning in the safe operation and line management of railways. Then, it described in detail the spatial positioning accuracy testing methods based on ground-based augmentation systems and satellite-based augmentation systems. The test results show that, the positioning accuracy of the Beidou ground-based augmentation positioning system is excellent, with an internal consistency median error of less than 1 cm and an external consistency median error of 2 cm or less. The average convergence time of the Beidou satellitebased augmentation system is within 3 minutes, with an internal consistency median error of 2 cm or less, and an external consistency median error of less than 3 cm. The research results indicate that the combined ground and satellite-based augmentation positioning of the Yichang - Fuling High-speed Railway can meet the requirements of railway surveying and has broad development prospects in the practical application of mountain railways. [ABSTRACT FROM AUTHOR]

The article presents how the values of (3D) coordinates of land reference points affect the results of gravimetric measurements made from the ship in sea areas. These measurements are the basis for 3D maritime inertial navigation, improving ships' operational safety. The campaign verifying the network absolute point coordinates used as a reference point for relative marine gravity measurements was described. The obtained values were compared with catalogue values. In verification of network points 3D position the satellite data Global Satellite Navigation System (GNSS) and ground supporting systems (GBAS) was used. In this example, the height difference of the land reference point was 0.32 m. As a consequence, the offset budget of the marine campaign was affected in the range of up to 0.35 mGal. The influence on gravity free-air anomaly was not constant over the entire area covered by the campaign. [ABSTRACT FROM AUTHOR]

Additional ionospheric information is essential for mitigating errors in single‐frequency (SF) Global Navigation Satellite Systems (GNSS) positioning. The increasing number of low‐cost dual‐frequency (DF) receiver users faces limitations in tracking DF observables compared to traditional geodetic receivers. Consequently, ionospheric correction algorithms (ICAs) are also essential for low‐cost DF devices in hybrid‐frequency positioning. To evaluate the performance of commonly used ICAs during solar cycle 25, our study presents a global statistical investigation of the contribution of five broadcast ionospheric models (BIMs) and the International GNSS Service (IGS) combined real‐time global ionospheric maps (IRTG) to the positioning domain, covering both quiet and perturbed ionospheric conditions. The BIMs investigated include the GPS Klobuchar (GPSK), Galileo NequickG (NEQG), NTCM‐GlAzpar (NTCMG), BDS‐2 Klobuchar (BDSK), and BeiDou Global Ionospheric delay correction Model (BDGIM). Experimental results from standard point positioning indicate that IRTG demonstrates superior overall accuracy compared to all BIMs, with a mean 3D root mean squared (RMS) of 2.76 m during perturbed period. Specifically, GPSK, NTCMG, NEQG, BDGIM, and BDSK exhibit RMS values of 2.03, 1.67, 1.72, 1.62, and 2.36 m during quiet conditions, and 4.02, 3.17, 2.86, 3.14, and 4.44 m during perturbed conditions, respectively. Among the BIMs, NEQG demonstrates superior performance at middle and high latitudes but exhibits lower accuracy than NTCMG and BDGIM at low latitudes during daytime under quiet conditions. BDGIM performs slightly better than NTCMG at low latitudes but slightly worse at high latitudes. BDSK shows notable improvement for high‐ and mid‐latitude regions since 3 June 2020. Plain Language Summary: The ionospheric delay caused by free electrons in the ionosphere is a significant source of error in single‐frequency Global Navigation Satellite Systems (GNSS) positioning. To correct for this, broadcast ionospheric models (BIMs) developed by GPS, BDS, and Galileo, as well as real‐time global ionospheric maps (RT‐GIMs) provided by the International GNSS Service (IGS), are widely used. This study comprehensively analyzed the contribution of five BIMs and the IGS combined RT‐GIMs (IRTG) to GNSS positioning during different ionospheric conditions in solar cycle 25. Using data from 34 IGS stations worldwide over 123 days in 2020 and 2023, we conducted standard point positioning experiments. Overall, the average order of decreasing accuracy during quiet conditions were BeiDou Global Ionospheric delay correction Model (BDGIM), NTCMG, NEQG, GPSK, and BDSK, while during perturbed conditions, the order was IRTG, NEQG, BDGIM, NTCMG, GPSK, and BDSK. Key Points: We investigated the contribution of five broadcast ionospheric models (BIMs) and IRTG to Global Navigation Satellite Systems positioning across latitudinal and diurnal variations during solar cycle 25IRTG outperforms all BIMs. Among all BIMs, BeiDou Global Ionospheric delay correction Model, and NeQuickG perform the best during the quiet and perturbed period, respectivelyAlthough BDSK shows notable improvement for high latitudes since June 2020, it still exhibits the worst position performance among all BIMs [ABSTRACT FROM AUTHOR]

This paper provides a complete model for satellite tracking that uses Two Line Elements (TLE) data to accurately predict and track satellite locations over time. The three-phase graphical user interface of the model allows for real-time viewing of satellite positions and critical tracking data: input, prediction, and output. This work offers a comprehensive method for tracking and visualizing satellites in low Earth orbit (LEO), geostationary orbit, and remote sensing orbit utilizing TLE data. Precise latitude and longitude calculations allow for ongoing trajectory mapping, which makes it easier to track satellite movement dynamically. Accuracy and clarity are further enhanced by visualizing satellite swaths. Along their courses, satellite names are added to make identification easier. This integrated method has significant benefits for applications including space exploration, telecommunication, and environmental monitoring. Moreover, it makes constellation dynamics and satellite interactions more understandable, developing satellite-based technologies for a variety of useful uses. [ABSTRACT FROM AUTHOR]

One of the key challenges in Multi-Spectral Automatic Diagnostic (MAD) robot design is the precise targeting of narrow-angle cameras on a specific part of the equipment. The paper shows that a low-cost MAD robot, whose navigation system is based on open-source ArduRover firmware and a pair of low-cost Ublox F9P GNSS receivers, can inspect the 8 × 4 degree ultraviolet camera bounding the targeting error within 0.5 degrees. To achieve this result, we propose a new targeting procedure that can be implemented without any modifications in ArduRover firmware and outperforms more expensive solutions based on LiDAR SLAM and UWB. This paper will be interesting to the developers of robotic systems for power equipment inspection because it proposes a simple and effective solution for MAD robots' camera targeting and provides the first quantitative analysis of the GNSS reception conditions during power equipment inspection. This analysis is based on the experimental results collected during the inspection of the overhead power transmission lines and equipment inspections on the open switchgear of different power plants. Moreover, it includes not only satellite, dilution of precision, and positioning/heading estimation accuracy but also the direct measurements of angular errors that could be achieved on operating power plants using GNSS-only camera targeting. [ABSTRACT FROM AUTHOR]

Satellite navigation positioning has become an indispensable component of everyday life, where precise pinpointing and rapid convergence are crucial in delivering timely and accurate location information. However, due to the damping of integer ambiguities and system residual errors, the rapid convergence of Precise Point Positioning (PPP) implementation is a significant challenge. To address this, this paper proposes a novel Carrier Phase Zero-Baseline Self-Differencing Precise Point Positioning (CZS-PPP) technique and its ionosphere-free fusion model. By employing the proposed CZS-PPP approach in separate scenarios involving BDS-3, GPS, and dual-system settings, we systematically validate the efficacy of the method. The experimental results indicate that the convergence time of the method is less than 4 min in a single-system scenario. Furthermore, in a dual-system scenario, the method can achieve rapid convergence in less than 3 min. The CZS-PPP technique presented demonstrates the elimination of integer ambiguities and the effective suppression of system residuals, in comparison to the conventional method. The proposed approach has demonstrated remarkable performance across different systems, offering a promising new pathway for achieving PPP fast convergence in BDS/GNSS. [ABSTRACT FROM AUTHOR]

This paper presents an innovative approach aimed at enhancing satellite position determination accuracy within a geostationary equatorial orbit (GEO) by integrating a regional navigation satellite system (RNSS) with a global navigation satellite system (GNSS). In a GEO, incoming GNSS signals are typically constrained to a specific direction on the other side of the Earth, resulting in a significant dilution of precision (DOP) and, consequently, a significant radial error. By incorporating an RNSS, signals from more diverse directions are available, improving observability and enhancing navigation precision. Taking the quasi-zenith satellite system (QZSS) as a representative RNSS, this paper demonstrates the feasibility of receiving signals from GEO satellites across a substantial range. Link budget analyses were conducted using the precise side-lobe patterns of the QZSS, revealing that QZSS signals can be consistently observed across most arcs in a GEO. Two comprehensive simulations were conducted: a point solution and an extended Kalman filter-based orbit determination. The results affirm the anticipated improvement in navigation precision indicated by the DOP analysis. It is essential to note that whereas RNSS signals can be received from any longitude in a GEO, enhanced navigation precision relies on the distance from the satellite to the RNSS. Considering the availability of multiple RNSS options, the concept presented in this research can be adapted to any longitude within a GEO, thereby promoting stable, high-precision navigation. [ABSTRACT FROM AUTHOR]

The global community, with coordination from the United Nations, is energized to pursue the Sustainable Development Goals (SDGs), a list of 17 important aspirations that summarize the key challenges of our era. The SDGs apply to every nation and represent an international effort to eliminate extreme poverty, ensure access to safe drinking water, strengthen food security, and produce clean and reliable energy, among other pursuits. Space technology is already being used around the world to advance progress toward the SDGs and monitor their related Indicators. This paper explores how six technologies related to space—satellite Earth observation, satellite communication, satellite navigation and positioning, human spaceflight and microgravity research, space technology transfer, and basic scientific research—are being used to realize the vision that the SDGs represent. The paper also discusses the obstacles that limit the application of these technologies for the SDGs and provides an overview of potential paths to overcome these barriers. The paper finally studies the historical and potential roles that four distinct types of entities involved in global sustainable development—governments, non- and inter-governmental organizations, entrepreneurial companies, and universities— have played or may play in the application of space technologies towards the SDGs. • Six space technology areas are shown to support the U.N. Sustainable Development Goals. • Examples of space projects that support the SDGs are found in many sectors. • New designs for technology are needed to improve effectiveness of space applications for the SDGS. [ABSTRACT FROM AUTHOR]

Against the background of the intensive development and implementation of satellite technologies for position determination, navigation, and time synchronization, one of the central threats to critical industries is the creation of intentional interference to the signals of global navigation satellite systems. It is shown that the use of small-sized antenna arrays in navigation systems consisting of satellite constellations of GPS, GLONASS, GALILEO, BEIDOU, QZSS, or their combinations makes it possible to detect and suppress interfering signals by forming zeros of the antenna array directional pattern in the directions of their arrival. The interfering signal suppression is supplemented with detection procedures while maintaining the ability of navigation by using from one to four satellite systems according to criteria of the required number of satellites in the line of sight and the permissible geometric factor. The process of suppressing the interfering signal from four directions is illustrated by three scenarios, the initial data for which are signals from 35 satellites in the line of sight collected in real-time from five systems. It has been shown that the use of five systems and 35 satellites ensures the suppression of the interfering signal. At the same time, 22 satellites are involved in solving the navigation problem, 13 satellites are below the detection threshold, and the geometric factor is 1.18. When using GPS, GLONASS, and 19 satellites, the interfering signal is suppressed. In this case, 10 satellites are involved in solving the navigation problem, 9 are below the detection threshold, and the geometric factor is 2.1. When using only GPS, the interfering signal suppression is also ensured. This time 7 satellites are involved in solving the navigation problem, 4 are below the detection threshold, and the geometric factor is 1.76. [ABSTRACT FROM AUTHOR]

Global navigation satellite system (GNSS) provides users with all-weather, continuous, high-precision positioning, navigation, and timing (PNT) services. In the operation and use of GNSS, the influence of the space environment is a factor that must be considered. For example, during geomagnetic storms, a series of changes in the Earth's magnetosphere, ionosphere, and upper atmosphere affect GNSS's positioning performance. To investigate the positioning performance of global satellite navigation systems during geomagnetic storms, this study selected three geomagnetic storm events that occurred from September to December 2023. Utilizing the global positioning system (GPS)/Beidou navigation satellite system (BDS) dual-system, kinematic precise point positioning (PPP) experiments were conducted, and the raw observational data from 100 stations worldwide was analyzed. The experimental results show that the positioning accuracy of some stations in high-latitude areas decreases significantly when using the conventional Geometry Free (GF) cycle-slip detection threshold during geomagnetic storms, which means that the GF is no longer applicable to high-precision positioning services. Meanwhile, there is no significant change in the satellite signal strengths received at the stations during the period of the decrease in positioning accuracy. Analyzing the cycle-slip rates for stations where abnormal accuracy occurred, it was observed that stations experiencing a significant decline in positioning accuracy exhibited serious cycle-slip misjudgments. To improve the kinematic PPP accuracy during magnetic storms, this paper proposes an adaptive threshold for cycle-slip detection and designs five experimental strategies. After using the GF adaptive threshold, the station positioning accuracy improved significantly. It achieved the accuracy level of the quiet period, while the cycle-slip incidence reached the average level. During magnetic storms, the ionosphere changes rapidly, and the use of the traditional GF constant threshold will cause serious cycle-slip misjudgments, which makes the dynamic accuracy in high latitude areas and some mid-latitude areas uncommon, while the use of the GF adaptive threshold can alleviate this phenomenon and improve the positioning accuracy in the high-latitude regions and some of the affected mid-latitude areas during the magnetic storms. [ABSTRACT FROM AUTHOR]

Mobile robots have been widely engaged in many fields. To obtain the precise and consistent localization of mobile robots, the Global Navigation Satellite System (GNSS) is often employed. With the continuous development and modernization of GNSS, more tracked satellites can be used for multi-GNSS positioning calculation, which can improve the positioning performance and enhance accuracy. However, it also increases computational complexity. Therefore, a satellite selection method, which selects a subset from all visible satellites, is necessary. In multi-GNSS positioning, the geometric dilution of precision (GDOP) is an essential metric for satellite selection. However, the traditional traversal method requires a large amount of solution resources. In this paper, we proposed an improved genetic algorithm for satellite selection. By defining the maturity factor (MF) to guide the crossover and mutation operators, the search performance is guaranteed while reducing unnecessary crossover and mutation operations, thus reducing the search time. By adopting the previous epoch optimal individual inheritance strategy, the satellite selection results of subsequent epochs under continuous epochs have been improved. The experimental results verify the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

Rapid progress in satellite technology has led to a noticeable surge in availability of Earth observation satellite images, which are being collected daily from satellites deployed worldwide. However, even with advanced satellite positioning equipment, there are still diverse level of remaining positional errors. This is a hindrance to satellite image utilization. Therefore, positional errors between satellite images must be corrected before utilization. Relative geometric correction of satellite images is a technique that adjusts geometric displacements based on their relative positional relationships in image or object space. In this study, we propose homography-based bundle adjustment for relative geometric correction of multi-sensor satellite images. Our method aims to estimate optimal ground plane on which images are projected and quickly generate result image. For experiments, orthorectified satellite images with various resolutions and georeferencing information were employed as input data. The experiment results showed that the average error, which was initially 4.96 pixels before relative geometric correction, was decreased to 1.73 pixels after applying the proposed method. [ABSTRACT FROM AUTHOR]

Newly developed coupled-cluster (CC) methods enable simulations of ionization potentials and spectral functions of molecular systems in a wide range of energy scales ranging from core-binding to valence. This paper discusses the results obtained with the real-time equation-of-motion CC cumulant (RT-EOM-CC) approach and CC Green's function (CCGF) approaches in applications to the water and water dimer molecules. We compare the ionization potentials obtained with these methods for the valence region with the results obtained with the coupled-cluster with singles, doubles, and perturbative triples formulation as a difference of energies for N and N − 1 electron systems. All methods show good agreement with each other. They also agree well with the experiment with errors usually below 0.1 eV for the ionization potentials. We also analyze unique features of the spectral functions, associated with the position of satellite peaks, obtained with the RT-EOM-CC and CCGF methods employing single and double excitations, as a function of the monomer OH bond length and the proton transfer coordinate in the dimer. Finally, we analyze the impact of the basis set effects on the quality of calculated ionization potentials and find that the basis set effects are less pronounced for the augmented-type sets. [ABSTRACT FROM AUTHOR]

Combining multiple devices for localization has important applications in the military field. This paper exploits the land-based short-wave platforms and satellites for fusion localization. The ionospheric reflection height error and satellite position errors have a great impact on the short-wave localization and satellite localization accuracy, respectively. In this paper, an iterative constrained weighted least squares (ICWLS) algorithm is proposed for these two kinds of errors. The algorithm converts the nonconvex equation constraints to linear constraints using the results of the previous iteration, thus ensuring convergence to the globally optimal solution. Simulation results show that the localization accuracy of the algorithm can reach the corresponding Constrained Cramér–Rao Lower Bound (CCRLB). Finally, the localization results of the two methods are fused using Kalman filtering. Simulations show that the fused localization accuracy is improved compared to the single-means localization. [ABSTRACT FROM AUTHOR]

The application of robotics has great implications for future food security, sustainable agricultural development, improving resource efficiency, reducing chemical pesticide use, reducing manual labor, and maximizing field output. Aiming at the problems of high labor intensity and labor shortage in the fields of pesticide application, weeding, and field information collection, a multifunctional and electric field management robot platform is designed, which has four switching steering modes (Ackermann steering, four-wheel steering, crab steering, and zero-radius steering), and its wheel-track can be automatically adjusted. Commonly used spraying booms, weeders, crop information collectors, and other devices can be easily installed on the robot platform. A multi-sensor integrated navigation system including a satellite positioning system, an RGB camera, and a multi-line lidar is designed to realize the unmanned driving of the robot platform in a complex field environment. Field tests have shown that the robot can follow the set route, and tests under simulated conditions have indicated that it can also dynamically correct paths based on crop rows by using a visual system. Results from multiple trials showed that the trajectory tracking accuracy meets the requirements of various field management operations. [ABSTRACT FROM AUTHOR]

The Seafloor Geodetic Observation–Array (SGO-A), operated by the Japan Coast Guard, relies on the Global Navigation Satellite System–Acoustics combination (GNSS-A) technique, which integrates satellite positioning systems and undersea acoustic ranging to determine seafloor crustal deformation at the centimeter level for earthquake disaster prevention. Recently, we found distortion in the SGO-A 10-kHz carrier wave that degraded the accuracy. Carrier wave distortion can cause errors on the scale of several centimeters to twenty centimeters, which greatly impedes centimeter-level observations. This study investigated this carrier wave degradation by an underwater acoustic communication experiment conducted in 2022, using a transducer similar to that used by SGO-A. Also, we reproduced degraded waveforms through a grid search-like method for quantitatively evaluating the extent to which the interior of the equipment contributed to deterioration. Our results underscore the importance of careful consideration in signal processing, as the observed waveform degradation is not solely attributed to hardware structures but also to internal electrical circuits. The findings suggest that conventional signal identification methods may lead to errors, providing motivation for a shift towards experimental and experiential timing-based waveform identification approaches to enhance accuracy in GNSS-A systems. [ABSTRACT FROM AUTHOR]

In the autonomous navigation of mobile robots, precise positioning is crucial. In forest environments with weak satellite signals or in sites disturbed by complex environments, satellite positioning accuracy has difficulty in meeting the requirements of autonomous navigation positioning accuracy for robots. This article proposes a vision SLAM/UWB tightly coupled localization method and designs a UWB non-line-of-sight error identification method using the displacement increment of the visual odometer. It utilizes the displacement increment of visual output and UWB ranging information as measurement values and applies the extended Kalman filtering algorithm for data fusion. This study utilized the constructed experimental platform to collect images and ultra-wideband ranging data in outdoor environments and experimentally validated the combined positioning method. The experimental results show that the algorithm outperforms individual UWB or loosely coupled combination positioning methods in terms of positioning accuracy. It effectively eliminates non-line-of-sight errors in UWB, improving the accuracy and stability of the combined positioning system. [ABSTRACT FROM AUTHOR]