scholarly journals Co-Seismic Ionospheric Disturbances Following the 2016 West Sumatra and 2018 Palu Earthquakes from GPS and GLONASS Measurements

2022 ◽  
Vol 14 (2) ◽  
pp. 401
Author(s):  
Mokhamad Nur Cahyadi ◽  
Buldan Muslim ◽  
Danar Guruh Pratomo ◽  
Ira Mutiara Anjasmara ◽  
Deasy Arisa ◽  
...  
Keyword(s):  
Acoustic Waves ◽  
Satellite System ◽  
Strike Slip ◽  
Line Of Sight ◽  
Ionospheric Disturbances ◽  
Sumatra Earthquake ◽  
Satellite Line ◽  
West Sumatra ◽  
Global Navigation Satellite ◽  
Earthquake Moment

The study of ionospheric disturbances associated with the two large strike-slip earthquakes in Indonesia was investigated, which are West Sumatra on 2 March 2016 (Mw = 7.8), and Palu on 28 September 2018 (Mw = 7.5). The anomalies were observed by measuring co-seismic ionospheric disturbances (CIDs) using the Global Navigation Satellite System (GNSS). The results show positive and negative CIDs polarization changes for the 2016 West Sumatra earthquake, depending on the position of the satellite line-of-sight, while the 2018 Palu earthquake shows negative changes only due to differences in co-seismic vertical crustal displacement. The 2016 West Sumatra earthquake caused uplift and subsidence, while the 2018 Palu earthquake was dominated by subsidence. TEC anomalies occurred about 10 to 15 min after the two earthquakes with amplitude of 2.9 TECU and 0.4 TECU, respectively. The TEC anomaly amplitude was also affected by the magnitude of the earthquake moment. The disturbance signal propagated with a velocity of ~1–1.72 km s−1 for the 2016 West Sumatra earthquake and ~0.97–1.08 km s−1 for the 2018 Palu mainshock earthquake, which are consistent with acoustic waves. The wave also caused an oscillation signal of ∼4 mHz, and their azimuthal asymmetry of propagation confirmed the phenomena in the Southern Hemisphere. The CID signal could be identified at a distance of around 400–1500 km from the epicenter in the southwestern direction.

scholarly journals Three-dimensional Tomography of Coseismic Ionospheric Disturbances from the 2016 West Sumatera Earthquake

2021 ◽  
Vol 936 (1) ◽  
pp. 012022
Author(s):  
R W Rahayu ◽  
M N Cahyadi ◽  
B Muslim ◽  
I M Anjasmara ◽  
E Y Handoko ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Temporal Analysis ◽  
Satellite System ◽  
Electron Content ◽  
Ionospheric Disturbances ◽  
Total Electron ◽  
3D Tomography ◽  
West Sumatra ◽  
3D Information ◽  
Global Navigation Satellite

Abstract Global Navigation Satellite System (GNSS) is a navigation system that uses satellite signals to determine its position, which consists of several satellites arranged in a constellation system. GNSS transmits signals to receivers on Earth. The GNSS receiver determines the user’s position, speed, and time by processing the signals transmitted by the satellites. The initial purpose of launching the GNSS was for navigation purposes, but along with its development, GNSS can be used for the purposes of observing deformation of the earth’s crust and in studying the atmosphere. The delayed wave data when passing through the ionosphere can be used to obtain Total Electron Content (TEC) values which then used to study ionospheric disturbances. Ionospheric disturbances are caused by various phenomena, the most common one is the ionospheric disturbances caused by the induction of acoustic and gravitational waves excited by co seismic crustal motions from large earthquakes. Ionospheric disturbances that happened before an earthquake are called Pre-seismic Ionospheric Disturbances and those that occur after an earthquake are called Co-seismic Ionospheric Disturbances (CID). Most studies of ionospheric disturbances still provide information on the timing and value of TEC anomalies in 2D form. Therefore, in this study, a 3D ionosphere profile modelling using computed 3D tomography will be carried out. The 3D information provided is in the form of time, ionosphere altitude and TEC anomaly value by utilizing GNSS data. The TEC anomaly value is obtained from the calculation of linear combination of the ionosphere. This study aims to obtain a spatial and temporal analysis of the CID caused by the West Sumatra Earthquake on March 2, 2016.

scholarly journals A New Method to Improve the Detection of Co-Seismic Ionospheric Disturbances using Sequential Measurement Combination

Sensors ◽  
2019 ◽  
Vol 19 (13) ◽  
pp. 2948 ◽  
Author(s):  
Seonho Kang ◽  
Junesol Song ◽  
Deokhwa Han ◽  
Bugyeom Kim ◽  
Hyoungmin So ◽  
...  
Keyword(s):  
Time Derivative ◽  
Tohoku Earthquake ◽  
Satellite System ◽  
Detection Performance ◽  
Ionospheric Delay ◽  
New Method ◽  
Ionospheric Disturbances ◽  
The 2011 Tohoku Earthquake ◽  
Sequential Measurement ◽  
Global Navigation Satellite

Earthquakes generate energy that propagates into the ionosphere and incurs co-seismic ionospheric disturbances (CIDs), which can be observed in ionospheric delay measurements. In most cases, the CID has a weak signal strength, because the energy in the atmosphere transferred from the earthquake dissipates as it travels toward the ionosphere. It is particularly hard to observe at reference stations that are located far from the epicenter. As the number of Global Navigation Satellite System stations and their positions are restricted, it is important to employ weak CID data in the analysis by improving the detection performance of CIDs. In this study, we suggest a new method of detecting CIDs, which mainly uses a sequential measurement combination of the carrier phase-based ionospheric delay data, with a 1-second interval. The proposed method’s performance was compared with conventional methods, including band-pass filters and a representative time-derivative method, using data from the 2011 Tohoku earthquake. As a result, the maximum CID-to-noise ratio can be increased by a maximum of 13% when the proposed method is used, and consequently, the detection performance of the CID can be improved.

scholarly journals GNSS Multipath Detection Using Continuous Time-Series C/N0

Sensors ◽  
2020 ◽  
Vol 20 (14) ◽  
pp. 4059
Author(s):  
Nobuaki Kubo ◽  
Kaito Kobayashi ◽  
Rei Furukawa
Keyword(s):  
Time Series ◽  
Continuous Time ◽  
Urban Areas ◽  
Satellite System ◽  
Line Of Sight ◽  
Static Tests ◽  
Gnss Receivers ◽  
Multipath Detection ◽  
Global Navigation Satellite ◽  
Multipath Errors

The reduction of multipath errors is a significant challenge in the Global Navigation Satellite System (GNSS), especially when receiving non-line-of-sight (NLOS) signals. However, selecting line-of-sight (LOS) satellites correctly is still a difficult task in dense urban areas, even with the latest GNSS receivers. This study demonstrates a new method of utilization of C/N0 of the GNSS to detect NLOS signals. The elevation-dependent threshold of the C/N0 setting may be effective in mitigating multipath errors. However, the C/N0 fluctuation affected by NLOS signals is quite large. If the C/N0 is over the threshold, the satellite is used for positioning even if it is still affected by the NLOS signal, which causes the positioning error to jump easily. To overcome this issue, we focused on the value of continuous time-series C/N0 for a certain period. If the C/N0 of the satellite was less than the determined threshold, the satellite was not used for positioning for a certain period, even if the C/N0 recovered over the threshold. Three static tests were conducted at challenging locations near high-rise buildings in Tokyo. The results proved that our method could substantially mitigate multipath errors in differential GNSS by appropriately removing the NLOS signals. Therefore, the performance of real-time kinematic GNSS was significantly improved.

scholarly journals An overview of methodologies for real-time detection, characterisation and tracking of traveling ionospheric disturbances developed in the TechTIDE project

2020 ◽  
Vol 10 ◽  
pp. 42
Author(s):  
Anna Belehaki ◽  
Ioanna Tsagouri ◽  
David Altadill ◽  
Estefania Blanch ◽  
Claudia Borries ◽  
...  
Keyword(s):  
Real Time ◽  
Large Scale ◽  
Tracking System ◽  
Warning System ◽  
Satellite System ◽  
Ionospheric Disturbances ◽  
Time Activity ◽  
Travelling Ionospheric Disturbances ◽  
Additional Information ◽  
Global Navigation Satellite

The main objective of the TechTIDE project (warning and mitigation technologies for travelling ionospheric disturbances effects) is the development of an identification and tracking system for travelling ionospheric disturbances (TIDs) which will issue warnings of electron density perturbations over large world regions. The TechTIDE project has put in operation a real-time warning system that provides the results of complementary TID detection methodologies and many potential drivers to help users assess the risks and develop mitigation techniques tailored to their applications. The TechTIDE methodologies are able to detect in real time activity caused by both large-scale and medium-scale TIDs and characterize background conditions and external drivers, as an additional information required by the users to assess the criticality of the ongoing disturbances in real time. TechTIDE methodologies are based on the exploitation of data collected in real time from Digisondes, Global Navigation Satellite System (GNSS) receivers and Continuous Doppler Sounding System (CDSS) networks. The results are obtained and provided to users in real time. The paper presents the achievements of the project and discusses the challenges faced in the development of the final TechTIDE warning system.

scholarly journals Properties and Generation of Large Scale Travelling Ionospheric Disturbances during 8 September 2017

2020 ◽  
Author(s):  
Claudia Borries ◽  
Arthur Amaral Ferreira ◽  
Chao Xiong ◽  
Renato Alves Borges ◽  
Jens Mielich ◽  
...  
Keyword(s):  
Large Scale ◽  
Satellite System ◽  
Auroral Oval ◽  
Ionospheric Disturbances ◽  
High Latitudes ◽  
Travelling Ionospheric Disturbances ◽  
Source Mechanisms ◽  
Magnetometer Data ◽  
Space Weather Event ◽  
Global Navigation Satellite

<p>Large Scale Travelling Ionospheric Disturbances (LSTIDs) are a frequent phenomenon during ionospheric storms, indicating strong electrodynamic processes in high latitudes. LSTIDs are signatures of Atmospheric Gravity Waves (AGW) observed in the changes of the electron density in the ionosphere. During ionospheric storms, large scale AGWs are often generated in the vicinity of the auroral region, where sudden strong heating processes take place.</p><p>Many LSTIDs are observed during the ionosphere storm during the September 2017 Space Weather event. In this presentation, the LSTID occurrence on 8<sup>th</sup> September 2017 is analysed in more detail, based on a TID detection method using ground based Global Navigation Satellite System (GNSS) measurements. Fast LSTIDs are observed in midlatitudes between 0-3 UT and 13-16 UT. Slow LSTIDs are observed between 3-12 UT. A significant strong wave-like TEC perturbation occurred in high latitudes at noon, which vanished at around 50°N. A strong single LSTID in mid-latitudes generated in high latitudes around 18 UT. Consulting IMAGE magnetometer data, ionosonde measurements and Swarm field aligned current measurements, strong heating processes, the extension of the Auroral oval and unusual electrodynamic processes are discussed as source mechanisms for these LSTIDs.</p>

scholarly journals Unambiguous Multipath Mitigation Technique for BOC(n,n) and MBOC-Modulated GNSS Signals

2012 ◽  
Vol 2012 ◽  
pp. 1-13 ◽  
Author(s):  
Khaled Rouabah ◽  
Mustapha Flissi ◽  
Salim Attia ◽  
Djamel Chikouche
Keyword(s):  
Satellite System ◽  
Delay Estimation ◽  
Line Of Sight ◽  
Likelihood Estimator ◽  
Multipath Mitigation ◽  
Binary Offset Carrier ◽  
Efficient Scheme ◽  
The Common ◽  
Global Navigation Satellite ◽  
Mitigation Technique

We propose an efficient scheme for side peaks cancelation and multipath (MP) mitigation in binary offset carrier (n,n) (BOC(n,n)) and multiplexed BOC (MBOC) modulated signals. The proposed scheme reduces significantly the band of variation of MP errors in global navigation satellite system (GNSS). It consists of two versions. The first one is based on the use of maximum likelihood estimator (MLE) of MP signals and reference correlation functions (CFs) like that of pseudorandom noise (PRN) code without BOC subcarrier. In the second version, the former (MLE) is used with the reference BOC(n,n) or MBOC CFs. Unlike traditional BOC(n,n) and MBOC, that have CFs containing multiple peaks leading to potential tracking ambiguities, our proposed scheme does not contain any side peaks. In addition, all the MP signals with medium and long delays have no effect on the estimation of the pseudorange. On the other hand, all the methods proposed for mitigating MP in no-BOC scheme are practical for our scheme due to its CF which is similar to that of the PRN code. The computer simulation results show that the proposed scheme has superior performances in the reduction of the errors produced in the process of the delay estimation of line of sight (LOS) and caused by MP propagation. In fact, the performances of the proposed scheme are better with regard to that of the traditional BOC(n,n) and MBOC. Moreover, in the presence of noise, our proposed scheme keeps better performances than the common side peaks cancelation methods.

scholarly journals Smartphone Shadow Matching for Better Cross-street GNSS Positioning in Urban Environments

2014 ◽  
Vol 68 (3) ◽  
pp. 411-433 ◽  
Author(s):  
Lei Wang ◽  
Paul D Groves ◽  
Marek K Ziebart
Keyword(s):  
Large Scale ◽  
Signal To Noise Ratio ◽  
Three Dimensional ◽  
Satellite System ◽  
Urban Environments ◽  
Line Of Sight ◽  
Measured Signal ◽  
Gnss Positioning ◽  
Global Navigation Satellite ◽  
Dense Urban Environment

Global Navigation Satellite System (GNSS) shadow matching is a new positioning technique that determines position by comparing the measured signal availability and strength with predictions made using a three-dimensional (3D) city model. It complements conventional GNSS positioning and can significantly improve cross-street positioning accuracy in dense urban environments. This paper describes how shadow matching has been adapted to work on an Android smartphone and presents the first comprehensive performance assessment of smartphone GNSS shadow matching. Using GPS and GLONASS data recorded at 20 locations within central London, it is shown that shadow matching significantly outperforms conventional GNSS positioning in the cross-street direction. The success rate for obtaining a cross-street position accuracy within 5 m, enabling the correct side of a street to be determined, was 54·50% using shadow matching, compared to 24·77% for the conventional GNSS position. The likely performance of four-constellation shadow matching is predicted, the feasibility of a large-scale implementation of shadow matching is assessed, and some methods for improving performance are proposed. A further contribution is a signal-to-noise ratio analysis of the direct line-of-sight and non-line-of-sight signals received on a smartphone in a dense urban environment.

scholarly journals Robustly Adaptive EKF PDR/UWB Integrated Navigation Based on Additional Heading Constraint

Sensors ◽  
2021 ◽  
Vol 21 (13) ◽  
pp. 4390
Author(s):  
Debao Yuan ◽  
Jian Zhang ◽  
Jian Wang ◽  
Ximin Cui ◽  
Fei Liu ◽  
...  
Keyword(s):  
Dead Reckoning ◽  
Wide Band ◽  
Satellite System ◽  
Line Of Sight ◽  
Indoor Environments ◽  
Integrated Navigation ◽  
Position Information ◽  
Positioning Systems ◽  
Global Navigation Satellite ◽  
Non Line Of Sight

At present, GNSS (Global Navigation Satellite System) positioning technology is widely used for outdoor positioning services because of its high-precision positioning characteristics. However, in indoor environments, effective position information cannot be provided, because of the signals being obscured. In order to improve the accuracy and continuity of indoor positioning systems, in this paper, we propose a PDR/UWB (Pedestrian Dead Reckoning and Ultra Wide Band) integrated navigation algorithm based on an adaptively robust EKF (Extended Kalman Filter) to address the problem of error accumulation in the PDR algorithm and gross errors in the location results of the UWB in non-line-of-sight scenarios. First, the basic principles of UWB and PDR location algorithms are given. Then, we propose a loose combination of the PDR and UWB algorithms by using the adaptively robust EKF. By using the robust factor to adjust the weight of the observation value to resist the influence of the gross error, and by adjusting the variance of the system adaptively according to the positioning scene, the algorithm can improve the robustness and heading factor of the PDR algorithm, which is constrained by indoor maps. Finally, the effectiveness of the algorithm is verified by the measured data. The experimental results showed that the algorithm can not only reduce the accumulation of PDR errors, but can also resist the influence of gross location errors under non-line-of-sight UWB scenarios.

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