Yang Jiang, Yan Zhang, Zhitao Lyu, Shuai Guo, Yang Gao
Precise smartphone-based positioning service is challenging in dense urban areas due to significant multipath effects in GNSS signals received by smartphone devices. The raw GNSS measurements will be contaminated by non-line-of-sight (NLOS) signals, severely deteriorating the smartphone positioning accuracy. Many methods have been proposed to mitigate the GNSS NLOS problem, including 3D mapping-aided GNSS, RAIM, and machine learning-based methods. But these methods have limitations such as the need for 3D city models or external devices, high false-alarm chances, and training processes. In this study, we have developed a new approach to improve smartphone positioning accuracy in dense urban areas by coupling the smartphone GNSS and camera sensors, which are already available in most smartphones. Wholly based on themselves, the proposed method tightly integrates GNSS pseudorange, carrier-phase and Doppler measurements, and a visual odometry (VO). The GNSS measurements undergo preprocessing, DD normal equations, and velocity estimations. The smartphone images are processed using a KLT optical flow method, where GNSS velocities are applied to estimate the coordinate rotation and scale between them based on a sliding-window least-squares scheme using Horn’s method. Importantly, a quad-tree-based outlier searching (QTOS) algorithm is applied to ensure the healthiness of estimation processes throughout the integration. The data from DD GNSS normal equations, GNSS velocities, and VO velocities are input to an FGO algorithm for final positioning estimations. A field test in the dense urban area of Calgary showed an improvement of 25% in horizontal accuracy and a reduction of velocity estimation error by 30%, where the chance of positioning outliers (> 30 m) is significantly reduced by 76%. Therefore, the proposed method provides an effective solution for precise smartphone positioning in dense urban areas without the need for external data sources or training.
{"title":"Tightly Integrated Smartphone GNSS and Visual odometry for Enhanced Urban Pedestrian Positioning","authors":"Yang Jiang, Yan Zhang, Zhitao Lyu, Shuai Guo, Yang Gao","doi":"10.33012/2023.19464","DOIUrl":"https://doi.org/10.33012/2023.19464","url":null,"abstract":"Precise smartphone-based positioning service is challenging in dense urban areas due to significant multipath effects in GNSS signals received by smartphone devices. The raw GNSS measurements will be contaminated by non-line-of-sight (NLOS) signals, severely deteriorating the smartphone positioning accuracy. Many methods have been proposed to mitigate the GNSS NLOS problem, including 3D mapping-aided GNSS, RAIM, and machine learning-based methods. But these methods have limitations such as the need for 3D city models or external devices, high false-alarm chances, and training processes. In this study, we have developed a new approach to improve smartphone positioning accuracy in dense urban areas by coupling the smartphone GNSS and camera sensors, which are already available in most smartphones. Wholly based on themselves, the proposed method tightly integrates GNSS pseudorange, carrier-phase and Doppler measurements, and a visual odometry (VO). The GNSS measurements undergo preprocessing, DD normal equations, and velocity estimations. The smartphone images are processed using a KLT optical flow method, where GNSS velocities are applied to estimate the coordinate rotation and scale between them based on a sliding-window least-squares scheme using Horn’s method. Importantly, a quad-tree-based outlier searching (QTOS) algorithm is applied to ensure the healthiness of estimation processes throughout the integration. The data from DD GNSS normal equations, GNSS velocities, and VO velocities are input to an FGO algorithm for final positioning estimations. A field test in the dense urban area of Calgary showed an improvement of 25% in horizontal accuracy and a reduction of velocity estimation error by 30%, where the chance of positioning outliers (> 30 m) is significantly reduced by 76%. Therefore, the proposed method provides an effective solution for precise smartphone positioning in dense urban areas without the need for external data sources or training.","PeriodicalId":498211,"journal":{"name":"Proceedings of the Satellite Division's International Technical Meeting","volume":"79 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135483918","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Global Positioning System (GPS) Based Positioning, Navigation, and Timing (PNT) services support the United States transportation sector in safely transporting people and goods and enabling efficiencies resulting in benefits to national and economic security. GPS signals are broadcasted from a constellation of satellites orbiting in Medium Earth Orbit (MEO) and their signal strength at the user receiver is very low in signal power density magnitude and thus susceptible to unintentional and intentional signal disruption or manipulation from undesired sources. Two recent real-world events in the transportation sector highlight the impacts related to the susceptibility of these GPS signal disruptions and the constant need to improve the GPS Interference Detection and Mitigation (IDM) posture of the Department of Transportation with the goal to restore GPS based PNT services to the expected levels of availability and reliability. This IDM mission goal contributes to an overall resilient PNT services posture when GPS is quickly restored to the expected normal operating conditions. On January 21, 2022, the GPS signal-in-space around the city of Denver, CO was degraded by the presence of unwanted emissions south of the Denver International Airport1 . Numerous aircraft, train stations, emergency response communication towers and medical messaging services detected and experienced varying levels of GPS signal reception degradation for a period of approximately 33 hours until the unwanted emissions source was positively identified and shut down. On October 17, 2022, the GPS signal-in-space around the cities of Dallas and Fort Worth, TX was degraded by the presence of unwanted emissions southwest from the Dallas-Ft. Worth International Airport. Numerous aircraft in the terminal and air route airspace detected and experience GPS signal reception degradation for a period of approximately 44 hours. Ground infrastructure recordings of GPS signal degradation effects were absent during the active event affecting aircraft. The unwanted emissions source ceased without positively being identified.
{"title":"U.S. Department of Transportation (DOT) Global Positioning System (GPS) Interference Detection and Mitigation (IDM) Program","authors":"James S. Aviles, Karen L. Van Dyke","doi":"10.33012/2023.19248","DOIUrl":"https://doi.org/10.33012/2023.19248","url":null,"abstract":"Global Positioning System (GPS) Based Positioning, Navigation, and Timing (PNT) services support the United States transportation sector in safely transporting people and goods and enabling efficiencies resulting in benefits to national and economic security. GPS signals are broadcasted from a constellation of satellites orbiting in Medium Earth Orbit (MEO) and their signal strength at the user receiver is very low in signal power density magnitude and thus susceptible to unintentional and intentional signal disruption or manipulation from undesired sources. Two recent real-world events in the transportation sector highlight the impacts related to the susceptibility of these GPS signal disruptions and the constant need to improve the GPS Interference Detection and Mitigation (IDM) posture of the Department of Transportation with the goal to restore GPS based PNT services to the expected levels of availability and reliability. This IDM mission goal contributes to an overall resilient PNT services posture when GPS is quickly restored to the expected normal operating conditions. On January 21, 2022, the GPS signal-in-space around the city of Denver, CO was degraded by the presence of unwanted emissions south of the Denver International Airport1 . Numerous aircraft, train stations, emergency response communication towers and medical messaging services detected and experienced varying levels of GPS signal reception degradation for a period of approximately 33 hours until the unwanted emissions source was positively identified and shut down. On October 17, 2022, the GPS signal-in-space around the cities of Dallas and Fort Worth, TX was degraded by the presence of unwanted emissions southwest from the Dallas-Ft. Worth International Airport. Numerous aircraft in the terminal and air route airspace detected and experience GPS signal reception degradation for a period of approximately 44 hours. Ground infrastructure recordings of GPS signal degradation effects were absent during the active event affecting aircraft. The unwanted emissions source ceased without positively being identified.","PeriodicalId":498211,"journal":{"name":"Proceedings of the Satellite Division's International Technical Meeting","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135484039","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The objective of this proposed research is to develop methods that aid navigation through cis-lunar space that do not rely on the limited availability of the DSN. Such methods would utilize the weak signals from the antenna sidelobes of the well-established GNSS constellation and the signals that would originate from the current set of proposed LNSS orbits being considered, shown in Figure 1. Prior work in utilizing weak GNSS signals in a highly elliptical orbit (HEO) with Direct Positioning Estimation (DPE) methods has informed the research within this paper which investigates positioning at even further altitudes beyond the GPS constellation. Artemis I ephemerides and GPS antenna patterns are used to simulate the link budget expected from the satellite geometry for one day of the Artemis mission for the portion beyond the altitude of the GPS constellation and into the cis-lunar space. From this simulation, two portions of the Artemis I mission are determined to be ideal locations for further simulation in order to perform DPE methods in future work.
{"title":"Using Spacecraft Data to Investigate Navigating Cis-Lunar Space","authors":"Faith Cornish, Kirsten Strandjord","doi":"10.33012/2023.19281","DOIUrl":"https://doi.org/10.33012/2023.19281","url":null,"abstract":"The objective of this proposed research is to develop methods that aid navigation through cis-lunar space that do not rely on the limited availability of the DSN. Such methods would utilize the weak signals from the antenna sidelobes of the well-established GNSS constellation and the signals that would originate from the current set of proposed LNSS orbits being considered, shown in Figure 1. Prior work in utilizing weak GNSS signals in a highly elliptical orbit (HEO) with Direct Positioning Estimation (DPE) methods has informed the research within this paper which investigates positioning at even further altitudes beyond the GPS constellation. Artemis I ephemerides and GPS antenna patterns are used to simulate the link budget expected from the satellite geometry for one day of the Artemis mission for the portion beyond the altitude of the GPS constellation and into the cis-lunar space. From this simulation, two portions of the Artemis I mission are determined to be ideal locations for further simulation in order to perform DPE methods in future work.","PeriodicalId":498211,"journal":{"name":"Proceedings of the Satellite Division's International Technical Meeting","volume":"2012 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135484112","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A spectral approach for blind acquisition and Doppler tracking of low Earth orbit (LEO) satellite signals is applied to National Oceanic and Atmospheric Administration (NOAA) satellites. The approach accounts for the high LEO satellites’ dynamic channel, by deriving an appropriate model for the received signal frequency spectrum. A frequency-domain-based Doppler discriminator is utilized along with a Kalman filter-based Doppler tracking algorithm. Experimental results are presented showing successful acquisition and Doppler tracking of NOAA LEO satellite signals. Next, the approach is demonstrated in multi-constellation LEO acquisition and tracking, showing Hz-level Doppler tracking of 4 Starlink, 2 OneWeb, 1 Iridium NEXT, 1 Orbcomm, and 1 NOAA LEO satellites. Carrier phase observables were constructed from the tracked Doppler and fused through a nonlinear least-squares estimator to localize a stationary receiver. Starting with an initial estimate 3,600 km away from the receiver’s true position, the proposed approach is shown to achieve a two-dimensional (2D) error of 5.1 m.
{"title":"Blind Doppler Tracking and Positioning with NOAA LEO Satellite Signals","authors":"Sharbel Kozhaya, Haitham Kanj, Zaher M. Kassas","doi":"10.33012/2023.19463","DOIUrl":"https://doi.org/10.33012/2023.19463","url":null,"abstract":"A spectral approach for blind acquisition and Doppler tracking of low Earth orbit (LEO) satellite signals is applied to National Oceanic and Atmospheric Administration (NOAA) satellites. The approach accounts for the high LEO satellites’ dynamic channel, by deriving an appropriate model for the received signal frequency spectrum. A frequency-domain-based Doppler discriminator is utilized along with a Kalman filter-based Doppler tracking algorithm. Experimental results are presented showing successful acquisition and Doppler tracking of NOAA LEO satellite signals. Next, the approach is demonstrated in multi-constellation LEO acquisition and tracking, showing Hz-level Doppler tracking of 4 Starlink, 2 OneWeb, 1 Iridium NEXT, 1 Orbcomm, and 1 NOAA LEO satellites. Carrier phase observables were constructed from the tracked Doppler and fused through a nonlinear least-squares estimator to localize a stationary receiver. Starting with an initial estimate 3,600 km away from the receiver’s true position, the proposed approach is shown to achieve a two-dimensional (2D) error of 5.1 m.","PeriodicalId":498211,"journal":{"name":"Proceedings of the Satellite Division's International Technical Meeting","volume":"42 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135483148","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
L. Musumeci, N. Batzilis, G. Caparra, S. Circiu, P. Crosta, D. Ibañez, X. Otero, N. Sirikan, S. Wallner, I. Fernandez-Hernandez, D. López Rodrigo
This article will provide an extensive collection of results from the OSNMA testing activities conducted at ESA/ESTEC including relevant setup, processing tools, data collection and testing methodologies to assess relevant KPIs such as position accuracy and availability, OSNMA data availability on a global scale, Time To First authenticated data and fix. OSNMA testing activities at ESA/ESTEC cover the monitoring of failed authentications, the global OSNMA performance as monitored by the Galileo Experimental Sensor Stations (GESS), and the assessment of local user performance in rural and urban environments. Concerning the tools, the main OSNMA system qualification tool used by the ESA is the FOC Test User Receiver, implementing real time OSNMA processing including: • parallel PVT engine with and without OSNMA, • wide grade of user configurability to emulate different receiver operational use cases, • optimized OSNMA data extraction and processing logic to maximize performance in challenging environments, • automated testing capabilities to characterize Time To First Fix (TTFF) and TTTF-Authenticated Data (TTFF-AD) for different receiver start-up assumptions. Beyond, additional receiver technology implementing OSNMA were involved in the characterization of the OSNMA performance in mobile rural and urban environments.
{"title":"OSNMA User Performance Assessment at ESA/ESTEC – System Qualifications Tools and Methodologies","authors":"L. Musumeci, N. Batzilis, G. Caparra, S. Circiu, P. Crosta, D. Ibañez, X. Otero, N. Sirikan, S. Wallner, I. Fernandez-Hernandez, D. López Rodrigo","doi":"10.33012/2023.19224","DOIUrl":"https://doi.org/10.33012/2023.19224","url":null,"abstract":"This article will provide an extensive collection of results from the OSNMA testing activities conducted at ESA/ESTEC including relevant setup, processing tools, data collection and testing methodologies to assess relevant KPIs such as position accuracy and availability, OSNMA data availability on a global scale, Time To First authenticated data and fix. OSNMA testing activities at ESA/ESTEC cover the monitoring of failed authentications, the global OSNMA performance as monitored by the Galileo Experimental Sensor Stations (GESS), and the assessment of local user performance in rural and urban environments. Concerning the tools, the main OSNMA system qualification tool used by the ESA is the FOC Test User Receiver, implementing real time OSNMA processing including: • parallel PVT engine with and without OSNMA, • wide grade of user configurability to emulate different receiver operational use cases, • optimized OSNMA data extraction and processing logic to maximize performance in challenging environments, • automated testing capabilities to characterize Time To First Fix (TTFF) and TTTF-Authenticated Data (TTFF-AD) for different receiver start-up assumptions. Beyond, additional receiver technology implementing OSNMA were involved in the characterization of the OSNMA performance in mobile rural and urban environments.","PeriodicalId":498211,"journal":{"name":"Proceedings of the Satellite Division's International Technical Meeting","volume":"10 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135483154","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Xiaowei Lan, Hongwen Wang, Kun Fang, Yanbo Zhu, Zhipeng Wang
The utilization of onboard GNSS receivers and the potential broadcasting of dual-frequency navigation signals for low earth orbit (LEO) satellites represent effective means for improving ionospheric modeling performance in the future. Regional ionospheric corrections can be provided by the single-frequency (SF) service of Satellite-Based Augmentation System (SBAS), and further improvement relies on effective utilizations of LEO-related observations, which travel only a portion of the ionosphere. In addressing this challenge, the ionosphere is simplified as multiple thin layers, and bottom-side LEO-related observations are compensated by the established topside ionospheric grid. Subsequently, observations from GPS and LEO are integrated, and the entire ionospheric grid of SBAS is estimated using Kriging. The performance improvement of the BeiDou SBAS (BDSBAS) ionospheric grid is evaluated in a simulated environment based on the NeQuick-2 model. The evaluation involves the GPS constellation and a LEO constellation comprising 192 satellites. The results indicate that the better performance is achieved when the bottom-side observations from LEO satellites are first compensated and then mapped to vertical delays. Accordingly, the optimal cut-off elevation angle for these observations is determined to be 15°. Under these conditions, the root mean square (RMS) of the vertical delay estimation errors for 117 ionospheric grid points (IGPs) decreases by an average of 16.47% throughout the day, with a maximum reduction of up to 38.39% compared to using only GPS observations. Additionally, it is observed that the inclusion of LEO-related observations has the most significant improvement on the southern edge IGPs of BDSBAS during periods of high solar activity throughout the day.
{"title":"Evaluation for BDSABS Ionospheric Grid Augmented by LEO Constellations","authors":"Xiaowei Lan, Hongwen Wang, Kun Fang, Yanbo Zhu, Zhipeng Wang","doi":"10.33012/2023.19177","DOIUrl":"https://doi.org/10.33012/2023.19177","url":null,"abstract":"The utilization of onboard GNSS receivers and the potential broadcasting of dual-frequency navigation signals for low earth orbit (LEO) satellites represent effective means for improving ionospheric modeling performance in the future. Regional ionospheric corrections can be provided by the single-frequency (SF) service of Satellite-Based Augmentation System (SBAS), and further improvement relies on effective utilizations of LEO-related observations, which travel only a portion of the ionosphere. In addressing this challenge, the ionosphere is simplified as multiple thin layers, and bottom-side LEO-related observations are compensated by the established topside ionospheric grid. Subsequently, observations from GPS and LEO are integrated, and the entire ionospheric grid of SBAS is estimated using Kriging. The performance improvement of the BeiDou SBAS (BDSBAS) ionospheric grid is evaluated in a simulated environment based on the NeQuick-2 model. The evaluation involves the GPS constellation and a LEO constellation comprising 192 satellites. The results indicate that the better performance is achieved when the bottom-side observations from LEO satellites are first compensated and then mapped to vertical delays. Accordingly, the optimal cut-off elevation angle for these observations is determined to be 15°. Under these conditions, the root mean square (RMS) of the vertical delay estimation errors for 117 ionospheric grid points (IGPs) decreases by an average of 16.47% throughout the day, with a maximum reduction of up to 38.39% compared to using only GPS observations. Additionally, it is observed that the inclusion of LEO-related observations has the most significant improvement on the southern edge IGPs of BDSBAS during periods of high solar activity throughout the day.","PeriodicalId":498211,"journal":{"name":"Proceedings of the Satellite Division's International Technical Meeting","volume":"440 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135483155","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
According to the 41st session of the ICAO assembly, the very low strength of GNSS signals received from satellites makes GNSS vulnerable to radio frequency interference (RFI), and other undesirable disturbances, which poses a threat to aviation safety. In the field of civil aviation, the performance of GNSS is directly related to NACp, NUCp and other data widely used in Automatic Dependent Surveillance-Broadcast (ADS-B) system, where GNSS RFI can be reflected and located by their numerical changes. Interference detection and location based on ADS-B is a new way to solve GNSS RFI problem in civil aviation. Current researches focus on improving the performance of the algorithm, but there are few studies on the impact mechanism of GNSS RFI. This paper analyzes the influence of GNSS RFI on ADS-B data in principle, and provides theoretical support for algorithm, detects and locates RFI using genetic algorithm. The performance of the proposed detection and location algorithm is verified with the interference events in Chengdu, China in March 2021. It has made an attempt to the application of civil aviation surveillance and navigation fusion and to deal with GNSS RFI. This research provides theoretical reference and technical support for the detection and location of GNSS RFI in civil aviation.
{"title":"Civil Aviation GNSS Interference Detection and Location Based on Genetic Algorithm Using ADS-B Data","authors":"Jinqi Li, Hongxia Wang, Zhiqiang Dan, Jiahao Xu, Zhipeng Wang, Yanbo Zhu","doi":"10.33012/2023.19392","DOIUrl":"https://doi.org/10.33012/2023.19392","url":null,"abstract":"According to the 41st session of the ICAO assembly, the very low strength of GNSS signals received from satellites makes GNSS vulnerable to radio frequency interference (RFI), and other undesirable disturbances, which poses a threat to aviation safety. In the field of civil aviation, the performance of GNSS is directly related to NACp, NUCp and other data widely used in Automatic Dependent Surveillance-Broadcast (ADS-B) system, where GNSS RFI can be reflected and located by their numerical changes. Interference detection and location based on ADS-B is a new way to solve GNSS RFI problem in civil aviation. Current researches focus on improving the performance of the algorithm, but there are few studies on the impact mechanism of GNSS RFI. This paper analyzes the influence of GNSS RFI on ADS-B data in principle, and provides theoretical support for algorithm, detects and locates RFI using genetic algorithm. The performance of the proposed detection and location algorithm is verified with the interference events in Chengdu, China in March 2021. It has made an attempt to the application of civil aviation surveillance and navigation fusion and to deal with GNSS RFI. This research provides theoretical reference and technical support for the detection and location of GNSS RFI in civil aviation.","PeriodicalId":498211,"journal":{"name":"Proceedings of the Satellite Division's International Technical Meeting","volume":"49 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135483183","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Accurate and timely prediction of Total Electron Content (TEC) in the ionosphere is of paramount importance for various applications such as GNSS positioning and navigation, communication systems, and space weather monitoring. While recent years have witnessed the application of various deep learning techniques to this task, these methods often treat vertical total electron content (VTEC) maps as either images or sequences, disregarding the inherent non-Euclidean (spherical) nature of VTEC maps. Addressing this limitation, our study offers a novel perspective by introducing graph structures to represent VTEC data. This paper presents a groundbreaking approach, GNNTrans, which amalgamates the strengths of graph convolutional networks and transformer architectures to predict TEC. GNNTrans adeptly captures the intricate spatial and temporal dependencies intrinsic to VTEC maps. Through an ablation study, the results demonstrate graph structures and Graph Neural Networks (GNN) are superior to conventional Convolutional Neural Network (CNN) methods in extracting non-Euclidean spatial information from VTEC maps, achieving root mean square errors (RMSE) of 2.58 and 2.66. Additionally, experiments demonstrate GNNTrans’s supremacy over the CODE one-day forecasting product across various dimensions, reducing the RMSE to 3.34 and 1.49 in 2014 and 2018 respectively, in contrast to C1P’s values of 8.74 and 6.41. GNNTrans exhibits remarkable performance in predicting TEC variations across diverse conditions, thus holding promise for heightened accuracy and reliability in ionospheric TEC forecasting.
{"title":"Ionospheric VTEC Map Forecasting based on Graph Neural Network with Transformers","authors":"Ruirui Liu, Yiping Jiang","doi":"10.33012/2023.19292","DOIUrl":"https://doi.org/10.33012/2023.19292","url":null,"abstract":"Accurate and timely prediction of Total Electron Content (TEC) in the ionosphere is of paramount importance for various applications such as GNSS positioning and navigation, communication systems, and space weather monitoring. While recent years have witnessed the application of various deep learning techniques to this task, these methods often treat vertical total electron content (VTEC) maps as either images or sequences, disregarding the inherent non-Euclidean (spherical) nature of VTEC maps. Addressing this limitation, our study offers a novel perspective by introducing graph structures to represent VTEC data. This paper presents a groundbreaking approach, GNNTrans, which amalgamates the strengths of graph convolutional networks and transformer architectures to predict TEC. GNNTrans adeptly captures the intricate spatial and temporal dependencies intrinsic to VTEC maps. Through an ablation study, the results demonstrate graph structures and Graph Neural Networks (GNN) are superior to conventional Convolutional Neural Network (CNN) methods in extracting non-Euclidean spatial information from VTEC maps, achieving root mean square errors (RMSE) of 2.58 and 2.66. Additionally, experiments demonstrate GNNTrans’s supremacy over the CODE one-day forecasting product across various dimensions, reducing the RMSE to 3.34 and 1.49 in 2014 and 2018 respectively, in contrast to C1P’s values of 8.74 and 6.41. GNNTrans exhibits remarkable performance in predicting TEC variations across diverse conditions, thus holding promise for heightened accuracy and reliability in ionospheric TEC forecasting.","PeriodicalId":498211,"journal":{"name":"Proceedings of the Satellite Division's International Technical Meeting","volume":"29 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135483403","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Phyo C. Thu, Pornchai Supnithi, Lin Min Min Myint, Jirapoom Budtho, Susumu Saito
Equatorial plasma bubbles (EPBs) refer to ionospheric irregularities in low-latitude regions, commonly observed after sunset. They originate at the magnetic equator and then potentially spread to mid-latitude region. As cm-level positioning techniques are increasingly important to various segments of society, the performance degradation of these systems due to EPB at low latitudes needs to be investigated. In this work, we analyze the EPB effects on the performances of real-time kinematic (RTK) positioning at the short, medium, and long baselines at low-latitude stations in Thailand. The low-latitudes local ionospheric disturbances such EPBs are shown to degrade the positioning accuracy of RTK in different seasons in 2022. It is found that the positioning errors are higher during the disturbance periods and more severe at the long baselines than the shorter ones, especially during the equinoctial months.
{"title":"Effects of Equatorial Plasma Bubbles Over Real-Time Kinematic Positioning in Low-Latitude Region","authors":"Phyo C. Thu, Pornchai Supnithi, Lin Min Min Myint, Jirapoom Budtho, Susumu Saito","doi":"10.33012/2023.19465","DOIUrl":"https://doi.org/10.33012/2023.19465","url":null,"abstract":"Equatorial plasma bubbles (EPBs) refer to ionospheric irregularities in low-latitude regions, commonly observed after sunset. They originate at the magnetic equator and then potentially spread to mid-latitude region. As cm-level positioning techniques are increasingly important to various segments of society, the performance degradation of these systems due to EPB at low latitudes needs to be investigated. In this work, we analyze the EPB effects on the performances of real-time kinematic (RTK) positioning at the short, medium, and long baselines at low-latitude stations in Thailand. The low-latitudes local ionospheric disturbances such EPBs are shown to degrade the positioning accuracy of RTK in different seasons in 2022. It is found that the positioning errors are higher during the disturbance periods and more severe at the long baselines than the shorter ones, especially during the equinoctial months.","PeriodicalId":498211,"journal":{"name":"Proceedings of the Satellite Division's International Technical Meeting","volume":"49 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135483604","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yichen Liu, Urs Hugentobler, Bingbing Duan, Nikolay Mikhaylov, Jeffrey Simon
This study investigates the reparameterization of the uncombined triple-frequency PPP-AR model, mainly in terms of the receiver hardware bias estimation. We explore the impact of the number of estimated receiver bias parameters as a function of pseudorange noise, i.e., the trade-off between estimating too many bias parameters on cost of a high stochastic error posing a challenge on ambiguity resolution on one hand, and estimating too few bias parameters on cost of ignored inconsistencies on the other hand. We implemented 4 different bias estimation strategies and compared their performance in positioning and ambiguity resolution against each other in the presence of phase bias across various pseudorange noise levels. The results show that with accurately initialized reference ambiguities, for code noise levels below 0.3 meters, estimating four biases (one each for P3, L1, L2, L3 signals) outperforms other strategies, while for code noise levels exceeding 0.3 meters, estimating two biases is sufficient. Conversely, with inaccurately estimated reference ambiguities, estimating four biases constantly prevails across all code noise levels. In ideal conditions, i.e., bias-free scenario, however, estimating only one bias is the optimal choice. This research enables readers to get insight into bias estimation strategies in the uncombined triple-frequency PPP-AR model and their impact on positioning performance and ambiguity resolution across different code noise levels. The conclusions can act as a guideline supporting the user implementation of the optimum representation of hardware biases in the uncombined PPP-AR model.
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