scholarly journals Decaying Post-Seismic Deformation Observed on the Korean Peninsula Following the 2011 Tohoku-Oki Earthquake

Sensors ◽  
2021 ◽  
Vol 21 (13) ◽  
pp. 4493
Author(s):  
Dong-Hyo Sohn ◽  
Byung-Kyu Choi ◽  
Sungshil Kim ◽  
Sun-Cheon Park ◽  
Won-Jin Lee ◽  
...  
Keyword(s):  
Korean Peninsula ◽  
Epicentral Distance ◽  
Satellite System ◽  
Temporal Variations ◽  
Crustal Movement ◽  
Geologic Structure ◽  
Earthquake Motion ◽  
The Difference ◽  
Global Navigation Satellite ◽  
Seismic Deformation

We investigated decaying post-seismic deformation observed on the Korean Peninsula associated with the 2011 Mw 9.0 Tohoku-Oki earthquake using Global Navigation Satellite System (GNSS). The GNSS velocity vectors were estimated in five periods from 2005 to 2019. A co-seismic offset of the Korean Peninsula caused by the 2011 earthquake was inversely proportional to epicentral distances. According to the temporal variations of two components (magnitude and direction) of the GNSS velocity vector with the epicentral distance, the difference between the eastern and western regions for the two components becomes smaller over time. For approximately nine years after the 2011 event, the direction for the crustal movement in South Korea showed a recovery pattern returning to the pre-earthquake motion. In addition, the recovery patterns of the crustal movement were observed differently with the regional geologic structure (e.g., the crustal thickness) and each period. Our estimates of the decay in post-seismic deformation of the Korean Peninsula suggest that post-seismic relaxation will be complete within 5–20 years after the 2011 earthquake. The results suggest that the crustal movement on the Korean Peninsula is gradually recovering to its pre-earthquake motion.

scholarly journals Modeling and Analysis of BDS-2 and BDS-3 Combined Precise Time and Frequency Transfer Considering Stochastic Models of Inter-System Bias

2021 ◽  
Vol 13 (4) ◽  
pp. 793
Author(s):  
Guoqiang Jiao ◽  
Shuli Song ◽  
Qinming Chen ◽  
Chao Huang ◽  
Ke Su ◽  
...  
Keyword(s):  
Stochastic Models ◽  
Satellite System ◽  
Modeling And Analysis ◽  
System Bias ◽  
Frequency Transfer ◽  
Global Navigation ◽  
The Difference ◽  
The Stability ◽  
Global Navigation Satellite ◽  
Precise Time

BeiDou global navigation satellite system (BDS) began to provide positioning, navigation, and timing (PNT) services to global users officially on 31 July, 2020. BDS constellations consist of regional (BDS-2) and global navigation satellites (BDS-3). Due to the difference of modulations and characteristics for the BDS-2 and BDS-3 default civil service signals (B1I/B3I) and the increase of new signals (B1C/B2a) for BDS-3, a systemically bias exists in the receiver-end when receiving and processing BDS-2 and BDS-3 signals, which leads to the inter-system bias (ISB) between BDS-2 and BDS-3 on the receiver side. To fully utilize BDS, the BDS-2 and BDS-3 combined precise time and frequency transfer are investigated considering the effect of the ISB. Four kinds of ISB stochastic models are presented, which are ignoring ISB (ISBNO), estimating ISB as random constant (ISBCV), random walk process (ISBRW), and white noise process (ISBWN). The results demonstrate that the datum of receiver clock offsets can be unified and the ISB deduced datum confusion can be avoided by estimating the ISB. The ISBCV and ISBRW models are superior to ISBWN. For the BDS-2 and BDS-3 combined precise time and frequency transfer using ISBNO, ISBCV, ISBRW, and ISBWN, the stability of clock differences of old signals can be enhanced by 20.18%, 23.89%, 23.96%, and 11.46% over BDS-2-only, respectively. For new signals, the enhancements are −50.77%, 20.22%, 17.53%, and −3.69%, respectively. Moreover, ISBCV and ISBRW models have the better frequency transfer stability. Consequently, we recommended the optimal ISBCV or suboptimal ISBRW model for BDS-2 and BDS-3 combined precise time and frequency transfer when processing the old as well as the new signals.

scholarly journals Testing Multi-Frequency Low-Cost GNSS Receivers for Geodetic Monitoring Purposes

Sensors ◽  
2020 ◽  
Vol 20 (16) ◽  
pp. 4375
Author(s):  
Veton Hamza ◽  
Bojan Stopar ◽  
Tomaž Ambrožič ◽  
Goran Turk ◽  
Oskar Sterle
Keyword(s):  
Low Cost ◽  
Base Point ◽  
Satellite System ◽  
Gnss Receivers ◽  
The Difference ◽  
Short Baselines ◽  
Height Component ◽  
Global Navigation Satellite ◽  
High Level ◽  
Positional Precision

Global Navigation Satellite System (GNSS) technology is widely used for geodetic monitoring purposes. However, in cases where a higher risk of receiver damage is expected, geodetic GNSS receivers may be considered too expensive to be used. As an alternative, low-cost GNSS receivers that are cheap, light, and prove to be of adequate quality over short baselines, are considered. The main goal of this research is to evaluate the positional precision of a multi-frequency low-cost instrument, namely, ZED-F9P with u-blox ANN-MB-00 antenna, and to investigate its potential for displacement detection. We determined the positional precision within static survey, and the displacement detection within dynamic survey. In both cases, two baselines were set, with the same rover point equipped with a low-cost GNSS instrument. The base point of the first baseline was observed with a geodetic GNSS instrument, whereas the second baseline was observed with a low-cost GNSS instrument. The results from static survey for both baselines showed comparable results for horizontal components; the precision was on a level of 2 mm or better. For the height component, the results show a better performance of low-cost instruments. This may be a consequence of unknown antenna calibration parameters for low-cost GNSS antenna, while statistically significant coordinates of rover points were obtained from both baselines. The difference was again more significant in the height component. For the displacement detection, a device was used that imposes controlled movements with sub-millimeter accuracy. Results, obtained on a basis of 30-min sessions, show that low-cost GNSS instruments can detect displacements from 10 mm upwards with a high level of reliability. On the other hand, low-cost instruments performed slightly worse as far as accuracy is concerned.

scholarly journals Spaceborne GNSS-R Observation of Global Lake Level: First Results from the TechDemoSat-1 Mission

2019 ◽  
Vol 11 (12) ◽  
pp. 1438 ◽  
Author(s):  
Liwen Xu ◽  
Wei Wan ◽  
Xiuwan Chen ◽  
Siyu Zhu ◽  
Baojian Liu ◽  
...  
Keyword(s):  
Satellite System ◽  
Temporal Variations ◽  
Strong Correlations ◽  
Lake Levels ◽  
The Caspian Sea ◽  
First Results ◽  
The Uk ◽  
Global Navigation Satellite ◽  
Inland Water Bodies ◽  
First Time

Spaceborne global navigation satellite system reflectometry (GNSS-R) data collected by the UK TechDemoSat-1 (TDS-1) satellite is applied to retrieve global lake levels for the first time. Lake levels of 351 global lakes (area greater than 500 km2 and elevation lower than 3000 m each) are estimated using TDS-1 Level 1b data over 2015–2017. Strong correlations (overall R2 greater than 0.95) are observed among lake levels derived from TDS-1 and other altimetry satellites such as CryoSat-2, Jason, and Envisat (the latter two are collected by Hydroweb), although with large root-mean-square error (RMSE) (tens of meters) mainly due to the fact that TDS-1 is not dedicated for altimetry measuring purpose. Examples of the Caspian Sea and the Poyang Lake show consistent spatial and temporal variations between TDS-1 and other data sources. The results in this paper provide supportive information for further application of GNSS-R constellations to measure altimetry of inland water bodies.

scholarly journals Analysis and Comparison of GPS Precipitable Water Estimates between Two Nearby Stations on Tahiti Island

Sensors ◽  
2019 ◽  
Vol 19 (24) ◽  
pp. 5578
Author(s):  
Fangzhao Zhang ◽  
Jean-Pierre Barriot ◽  
Guochang Xu ◽  
Marania Hopuare
Keyword(s):  
Mapping Function ◽  
Precipitable Water ◽  
Satellite System ◽  
Tropospheric Delay ◽  
Horizontal Distance ◽  
International Gnss Service ◽  
Weighted Mean Temperature ◽  
The Difference ◽  
Global Navigation Satellite ◽  
The Impact

Since Bevis first proposed Global Positioning System (GPS) meteorology in 1992, the precipitable water (PW) estimates retrieved from Global Navigation Satellite System (GNSS) networks with high accuracy have been widely used in many meteorological applications. The proper estimation of GNSS PW can be affected by the GNSS processing strategy as well as the local geographical properties of GNSS sites. To better understand the impact of these factors, we compare PW estimates from two nearby permanent GPS stations (THTI and FAA1) in the tropical Tahiti Island, a basalt shield volcano located in the South Pacific, with a mean slope of 8% and a diameter of 30 km. The altitude difference between the two stations is 86.14 m, and their horizontal distance difference is 2.56 km. In this paper, Bernese GNSS Software Version 5.2 with precise point positioning (PPP) and Vienna mapping function 1 (VMF1) was applied to estimate the zenith tropospheric delay (ZTD), which was compared with the International GNSS Service (IGS) Final products. The meteorological parameters sourced from the European Center for Medium-Range Weather Forecasts (ECMWF) and the local weighted mean temperature ( T m ) model were used to estimate the GPS PW for three years (May 2016 to April 2019). The results show that the differences of PW between two nearby GPS stations is nearly a constant with value 1.73 mm. In our case, this difference is mainly driven by insolation differences, the difference in altitude and the wind being only second factors.

scholarly journals Comparing Winds near Tropical Oceanic Precipitation Systems with and without Lightning

2020 ◽  
Vol 12 (23) ◽  
pp. 3968
Author(s):  
Timothy J. Lang
Keyword(s):  
Satellite System ◽  
Lightning Flash ◽  
Wind Speeds ◽  
Tropical Oceans ◽  
Ocean Winds ◽  
The Difference ◽  
Microphysical Processes ◽  
Global Navigation Satellite ◽  
Matching Criteria ◽  
Rain Rates

In order to examine how robust updraft strength and ice-based microphysical processes aloft in storms may affect convective outflows near the surface, ocean winds were compared between tropical maritime precipitation systems with and without lightning. The analysis focused on Cyclone Global Navigation Satellite System (CYGNSS) specular point tracks, using straightforward spatiotemporal matching criteria to pair CYGNSS-measured wind speeds with satellite-based precipitation observations, Advanced Scatterometer (ASCAT) wind speeds, and lightning flash data from ground-based and space-based sensors. Based on the results, thunderstorms over the tropical oceans are associated with significantly heavier rain rates (~200% greater) than non-thunderstorms. However, wind speeds near either type of precipitation system do not differ much (~0.5 m s−1 or less). Moreover, the sign of the difference depends on the wind instrument used, with CYGNSS suggesting non-thunderstorm winds are slightly stronger, while ASCAT suggests the opposite. These observed wind differences are likely related to lingering uncertainties between CYGNSS and ASCAT measurements in precipitation. However, both CYGNSS and ASCAT observe winds near precipitation (whether lightning-producing or not) to be stronger than background winds by at least 1 m s−1.

scholarly journals MATHEMATICAL ANALYSIS OF THE ALGORITHMS USED IN MODERNIZED METHODS OF BUILDING MEASUREMENTS WITH RTN GNSS TECHNOLOGY

2015 ◽  
Vol 21 (4) ◽  
pp. 848-866 ◽  
Author(s):  
Robert Krzyżek
Keyword(s):  
Real Time ◽  
Mathematical Analysis ◽  
Classical Method ◽  
Satellite System ◽  
Building Structures ◽  
Base Points ◽  
Measurement Results ◽  
Innovative Solution ◽  
The Difference ◽  
Global Navigation Satellite

The use of RTN GNSS surveying technology (Real Time Kinematic Global Navigation Satellite System) for direct measurements of building structures is extremely difficult, and often impossible. Therefore, the real-time technology is supported by indirect methods of measurements. One such solution is the method of line-line intersection. Having determined the position (the coordinates) of the so-called base points on the extension of the wall faces of a building, and having calculated the coordinates of intersection of the lines of relationships between the base points, the coordinates of corners of a building structure are obtained, which are relatively unreliable. In order to increase the reliability of these coordinates, the author proposes to add an innovative solution called vector translation to the classical method of line-line intersection. This paper proves the thesis on the increased reliability of determining the coordinates of corners of buildings by conducting an appropriate mathematical analysis of these formulas, using the algorithm developed by the author. The performed analysis shows that this innovative solution results in a smaller difference between the adjusted coordinates relative to the theoretical ones, than the difference captured from the "raw" measurement results with respect to the theoretical values.

scholarly journals Investigation of method of elimination of interference situation effect on GPS navigation receiver operation by smoothing of pseudorange measurements by pseudophase increment

2020 ◽  
pp. 46-53
Author(s):  
V. Y. Vovasov ◽  
D. A. Sukharev
Keyword(s):  
High Precision ◽  
Experimental Studies ◽  
Satellite System ◽  
Mobile Object ◽  
Time Interval ◽  
Urgent Task ◽  
Long Time ◽  
The Difference ◽  
Navigation Signals ◽  
Global Navigation Satellite

The wide application of high-precision GNSS (global navigation satellite system) positioning technologies for unmanned mobile object management requires the acquisition of solutions with subdecimeter accuracy and the reduction of the convergence period to such accuracy from the beginning of measurements to 20–25 minutes. Unfortunately, the accuracy of the obtained navigation solutions and the time of convergence to high-precision solutions are influenced by re-reflection of GNSS signals from the ground, buildings and structures, as well as interference from different sources of radio emissions of the urban environment. Therefore, it is an urgent task to implement methods of eliminating the influence of the interference situation on the operation of the navigation receiver of GNSS signals and investigating their effectiveness. The paper considers the results of investigation of the method of elimination of interference situation effect on GPS signal navigation receiver operation using smoothing of raw pseudorange measurements by pseudophase increment. Justification of the difference of measurement of pseudo-range by carrier phase and pseudo-range by code is given as a criterion of efficiency of estimation of interference situation influence in the area of navigation signals reception. As a result of the analysis of experimental studies, it has been shown that using the described method, starting from 900 seconds, the values of the smoothed parameter do not deviate from the averaged measurements over a long time interval by more than 0.1 meters, which indicates the efficiency of the method of smoothing by phase increments and is potentially promising for highly accurate measurements.

scholarly journals Kalman Filter-Based Fusion of Collocated Acceleration, GNSS and Rotation Data for 6C Motion Tracking

Sensors ◽  
2021 ◽  
Vol 21 (4) ◽  
pp. 1543
Author(s):  
Yara Rossi ◽  
Konstantinos Tatsis ◽  
Mudathir Awadaljeed ◽  
Konstantin Arbogast ◽  
Eleni Chatzi ◽  
...  
Keyword(s):  
Kalman Filter ◽  
Motion Tracking ◽  
Translational Motion ◽  
Substantial Reduction ◽  
Ground Truth ◽  
Feedback System ◽  
Satellite System ◽  
Robot Arm ◽  
The Difference ◽  
Global Navigation Satellite

The ground motion of an earthquake or the ambient motion of a large engineered structure not only has translational motion, but it also includes rotation around all three axes. No current sensor can record all six components, while the fusion of individual instruments that could provide such recordings, such as accelerometers or Global Navigation Satellite System (GNSS) receivers, and rotational sensors, is non-trivial. We propose achieving such a fusion via a six-component (6C) Kalman filter (KF) that is suitable for structural monitoring applications, as well as earthquake monitoring. In order to develop and validate this methodology, we have set up an experimental case study, relying on the use of an industrial six-axis robot arm, on which the instruments are mounted. The robot simulates the structural motion resulting atop a wind-excited wind turbine tower. The quality of the 6C KF reconstruction is assessed by comparing the estimated response to the feedback system of the robot, which performed the experiments. The fusion of rotational information yields significant improvement for both the acceleration recordings but also the GNSS positions, as evidenced via the substantial reduction of the RMSE, expressed as the difference between the KF predictions and robot feedback. This work puts forth, for the first time, a KF-based fusion for all six motion components, validated against a high-precision ground truth measurement. The proposed filter formulation is able to exploit the strengths of each instrument and recover more precise motion estimates that can be exploited for multiple purposes.

scholarly journals Quantitative Evaluation of Environmental Loading Induced Displacement Products for Correcting GNSS Time Series in CMONOC

2020 ◽  
Vol 12 (4) ◽  
pp. 594 ◽  
Author(s):  
Li ◽  
Huang ◽  
Chen ◽  
Dam ◽  
Fok ◽  
...  
Keyword(s):  
Time Series ◽  
Mainland China ◽  
Vertical Component ◽  
Satellite System ◽  
Environmental Loading ◽  
Noise Characteristics ◽  
The Difference ◽  
Land Data Assimilation System ◽  
Global Navigation Satellite ◽  
Gnss Time Series

Mass redistribution within the Earth system deforms the surface elastically. Loading theory allows us to predict loading induced displacement anywhere on the Earth’s surface using environmental loading models, e.g., Global Land Data Assimilation System. In addition, different publicly available loading products are available. However, there are differences among those products and the differences among the combinations of loading models cannot be ignored when precisions of better than 1 cm are required. Many scholars have applied these loading corrections to Global Navigation Satellite System (GNSS) time series from mainland China without considering or discussing the differences between the available models. Evaluating the effects of different loading products over this region is of paramount importance for accurately removing the loading signal. In this study, we investigate the performance of these different publicly available loading products on the scatter of GNSS time series from the Crustal Movement Observation Network of China. We concentrate on five different continental water storage loading models, six different non-tidal atmospheric loading models, and five different non-tidal oceanic loading models. We also investigate all the different combinations of loading products. The results show that the difference in RMS reduction can reach 20% in the vertical component depending on the loading correction applied. We then discuss the performance of different loading combinations and their effects on the noise characteristics of GNSS height time series and horizontal velocities. The results show that the loading products from NASA may be the best choice for corrections in mainland China. This conclusion could serve as an important reference for loading products users in this region.

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