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• Significant ionospheric disturbances during the 2021 Typhoon Chanthu were observed by GPS and GLONASS. • The ionospheric disturbances following the Typhoon are accompanied and propagated with the "N"-type wave. • The propagation velocity and center frequency of ionospheric disturbances are within the range of gravity waves. Severe typhoons often result in substantial economic and human losses. Therefore, near-real-time monitoring and forecasting of severe typhoons have a significant importance. In this paper, characteristics of ionospheric disturbances during the 2021 Typhoon Chanthu are estimated and investigated from GPS and GLONASS measurements. We calculate high-precision de-trended and filtered ionospheric vertical total electron content (VTEC) data based on GPS and GLONASS data from intensive Global Navigation Satellite System (GNSS) observations at 30-second intervals in Taiwan. Based on the VTEC values, we analyze the characteristics of ionospheric disturbances caused by Typhoon Chanthu, such as the time of appearance of ionospheric disturbances, changes in the magnitude of these disturbances, alterations in two-dimensional disturbances, fluctuations in the speed of disturbance propagation, and shifts in the frequency spectrum. The results reveal that both GPS-TEC and GLONASS-TEC exhibit noticeable disturbances during the specified timeframe. These disturbances are accompanied by the occurrence of "N"-type anomalies in TEC. Notably, at the occurrence of the disturbance, the elevation angle of GPS PRN32 and GLONASS PRN1 satellites is approximately 50°-55°, and their respective distances from the typhoon eye are roughly 350 km and 150 km. The propagation velocity and center frequency of the ionospheric disturbances are located in the range of gravity waves. Specifically, the disturbances propagation speeds of GPS PRN32 and GLONASS PRN1 are approximately 129.36 m/s and 128.33 m/s, respectively, while the center frequencies are about 1.17 mHz and 1.43 mHz. The ionospheric perturbations observed by GPS and GLONASS exhibit certain similarities, which provide valuable insights into the relationship between typhoons and ionospheric disturbances. [ABSTRACT FROM AUTHOR]

In this paper, the micro-phasor measurement system is developed to support phasor identification of distribution transformers for the distribution mapping management system (DMMS) of Taiwan Power Company (TPC). The one pulse per second signal (1PPS) from the global positioning system (GPS) is used to synchronize the voltage sampling between reference and measurement sides. By receiving 1PPS from GPS, the phasor measurement of three-phase voltage at the reference site of the substation is stored in the master station with a time-stamp. This paper proposes a timing synchronous module with an embedded temperature compensated crystal oscillator (TCXO) to generate highly accurate timing for field measurement of underground distribution facilities. Mobile communication network is used to compare measurement results between reference and field sides of voltage angle that define distribution transformer phasor. This paper also designs and develops an application for mobile devices by importing DMMS database, which is used to search the attributes of the distribution transformers for measurement at the field. After the transformer phasor is identified, the results are stored in the mobile device to update the attributes of distribution transformers in DMMS. [ABSTRACT FROM AUTHOR]

Typhoon is one of the major hazards in ocean coastal areas, but traditional techniques are inadequate to monitor typhoons due to limited or high‐cost observations, like radio sounding and meteorological radar. Previous studies have found that typhoons can cause ionospheric disturbances, but the relationship and characteristics are still unclear. In this paper, about 400 stations observations of the Global Positioning System (GPS) network in Taiwan are used to extract ionospheric disturbances during multiple typhoons. The detailed characteristics of the ionospheric disturbances are investigated using a fourth‐order Butterworth filter following the 2016 Nepartak, 2019 Lekima, 2019 Mitag, and 2020 Hagupit typhoons. The results show that significant ionospheric disturbances were observed during the typhoons, and the larger disturbances are mostly located 400–1200 km far from the typhoon eye. The estimated horizontal propagation velocity of the ionospheric disturbances is about 127–194 m/s. The locations of the ionospheric disturbances between the typhoon eye and the landfall site are related to the typhoon path. The azimuth distribution of the ionospheric disturbance around the typhoon eye is affected by the GPS elevation angles. At 500–700 km from the typhoon eye, the mean ionospheric disturbances are 0.17 TECU (TEC Unit) and 0.15 TECU for super typhoon Nepartak and Lekima, and 0.13 TECU and 0.18 TECU for typhoon Mitag and Hagupit. The higher the intensity of the typhoon is, the greater the magnitude of the ionospheric disturbance is. Key Points: Significant ionospheric disturbances are observed following multiple typhoons from GPS‐derived Total Electron Content dataThe directivities of positive and negative ionospheric disturbances are found in different azimuthsThe magnitude of ionospheric disturbances is related to the typhoon intensity with a positive proportion [ABSTRACT FROM AUTHOR]

Background: Taiwan's higher education institutions prioritize interdisciplinary knowledge and cultural competence in cultural design, emphasizing the value of immersion in the local environment to develop cultural competence. However, challenges arise from the disappearance of traditional local lifestyles and limitations of traditional outdoor lectures such as group size and learning environment. Mobile augmented reality technology serves as a personal learning tool to overcome these challenges, enabling learners to uncover hidden knowledge in scenic locations and improving learning efficiency. Objective: The study utilized learning analytics to investigate the impact of using mobile augmented reality on enhancing learners' cultural competence. Methods: The study used both qualitative and quasi‐experimental quantitative research to evaluate the effects of mobile augmented reality on cultural competence. A total of 78 third‐year university students participated in the study, with 37 of them using mobile augmented reality to learn about culture. The researchers utilized both the Mann–Whitney U test and interviews to compare the effectiveness of mobile augmented reality with that of a 'real' tour guide in field courses. Results: The experimental results indicate that learners were able to continuously seek and find information about local culture through field exploration with mobile augmented reality, resulting in similar effects to those of attending a live lecture. Conclusions: It showed that incorporating mobile AR into field visits can create gamified and active learning scenarios that enhance immersion and drive active learning in local culture. The results in greater cultural knowledge and understanding, leading to the development of cultural competence in students. Lay Description: What is already known about this topic: There is a heightened emphasis on cultivating and demonstrating cultural competence across various fields due to the significantly grow of cultural and creative industries.Relying solely on traditional classroom teaching for learning about local culture may result in a diminished impact, as a comprehensive understanding of culture necessitates a keen sense of life.To address the limitations of traditional classroom lectures, educators continuously strive to enhance teaching methodologies by developing innovative approaches, such as experiential learning and community‐based learning, which involve hands‐on activities and real‐world engagement to foster increased learning motivation and improved effectiveness.Augmented reality (AR), a technology that overlays virtual images onto real scenes in real time, has gained extensive usage in diverse fields such as medicine, national defence, education, and entertainment, offering interactive gaming experiences and providing an opportunity to experience the culture and past lives of locals in the field, enhancing learners' understanding of cultural history and creating immersive encounters during visits.Particularly in digital learning, the integration of AR enables learners to engage with additional content through mobile devices, fostering an immersive and gamified learning experience. What this paper adds: The use of the AR app for learning about the local culture yielded comparable outcomes to traditional guided tours.Participants actively engaged in self‐directed learning and demonstrated a sense of initiative while utilizing AR.The flexibility and autonomy provided by field learning, which extended beyond the course period, allowed participants to revisit the field and explore at their own pace using AR.Demonstrates that participants took control and responsibility for their own learning, leading to an enhancement in learner autonomy.Participants who utilized the Roaming Jingliao AR system to explore cultural scenarios exhibited enhanced knowledge and attitudes regarding cultural competence, specifically in areas such as cultural understanding, rice food cultural knowledge, Songjiang folk arts, and skills and practices, which can be attributed to the immersive and autonomous nature of AR‐based knowledge learning in outdoor guided courses, minimizing the influence of external environmental factors and facilitating a deeper understanding of the content compared to traditional guided tours. Implications for practice and/or policy: The findings of this study highlight the importance of considering the limitations associated with a relatively small sample size when conducting research within a university curriculum. To enhance the validity and reliability of future studies, practitioners and policymakers should prioritize the inclusion of larger and more diverse samples, enabling a more comprehensive understanding of the impact of AR technology on cultural learning and informing evidence‐based practices and policies.The study's focus on a specific group of participants and their contextual background highlights the need for future research to include participants from diverse educational settings and cultural backgrounds, ensuring that the findings are more applicable and relevant to a broader population. Practitioners and policymakers should consider the importance of inclusivity and diversity when designing and implementing cultural learning interventions using AR technology.The recognition of technological limitations highlights the importance of considering the specific AR system used in cultural learning interventions. Practitioners and policymakers should be cautious when adopting AR technologies and recognize that different AR systems or platforms may yield different outcomes. Future research should focus on evaluating the effectiveness of various AR systems and platforms to inform decision‐making regarding the selection and implementation of AR technologies for cultural learning initiatives. [ABSTRACT FROM AUTHOR]

This paper provides an overview of the contributions of the space-based global navigation satellite system (GNSS) radio occultation (RO) measurements from the FORMOSAT-7/COSMIC2 (F7/C2) mission in advancing our understanding of ionospheric plasma physics in the purview of space weather. The global positioning system (GPS) occultation experiment (GOX) onboard FORMOSAT-3/COSMIC (F3/C), with more than four and half million ionospheric RO soundings during April 2006–May 2020, offered a unique three-dimensional (3D) perspective to examine the global electron density distribution and unravel the underlying physical processes. The current F7/C2 carries TGRS (Tri-GNSS radio occultation system) has tracked more than 4000 RO profiles within ±35° latitudes per day since 25 June 2019. Taking advantage of the larger number of low-latitude soundings, the F7/C2 TGRS observations were used here to examine the 3D electron density structures and electrodynamics of the equatorial ionization anomaly, plasma depletion bays, and four-peaked patterns, as well as the S4 index of GNSS signal scintillations in the equatorial and low-latitude ionosphere, which have been previously investigated by using F3/C measurements. The results demonstrated that the denser low-latitude soundings enable the construction of monthly global electron density maps as well the altitude-latitude profiles with higher spatial and temporal resolution windows, and revealed longitudinal and seasonal characteristics in greater detail. The enhanced F7/C2 RO observations were further applied by the Central Weather Bureau/Space Weather Operation Office (CWB/SWOO) in Taiwan and the National Oceanic and Atmospheric Administration/Space Weather Prediction Center (NOAA/SWPC) in the United States to specify the ionospheric conditions for issuing alerts and warnings for positioning, navigation, and communication customers. A brief description of the two models is also provided. [ABSTRACT FROM AUTHOR]

The recent advances in satellite based ionosphere monitoring provided more evidence about earthquake (EQ) precursors from lithosphere ionosphere coupling mechanism. In this paper, we investigate ionospheric anomalies associated with the December 19, 2009, Taiwan EQ (Mw = 6.4), that occurred on UT = 13:02 h. Seismo ionospheric anomalies are evaluated during 31 days (20 day before followed by 10 days after the EQ) in the data of French Satellite Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions (DEMETER) and validated from Global Navigation Satellite System (GNSS) retrieved Total Electron Content (TEC). The day time values of ISL (Langmuir Probe) and IAP (Ion Analyzer) from DEMETER point to significant ionospheric perturbations within 5 days associated with EQ day. Moreover, GNSS stations of International GNSS Service (IGS) within EQ preparation zone also validate anomalies in ionosphere prior/after the Mw 6.4, Taiwan EQ. Moreover, spatial and temporal analyses of daily ionospheric indices from DEMETER and GNSS point to simultaneous enhancement in electron density, ion density, electron temperature and TEC related to the main shock during quiet geomagnetic storm (Dst < − 30 nT, Kp ≤ 3). All these evidence aids in promoting the lithosphere- ionosphere coupling over the epicenter of Mw 6.4 during the preparation period from DEMETER and GNSS TEC. [ABSTRACT FROM AUTHOR]

Variations of the ionosphere can significantly disrupt synthetic aperture radar (SAR) acquisitions and interferometric measurements of ground deformation. In this paper, we show how the ionosphere can also strongly modify C-band interferograms despite its smaller influence at higher frequencies. Thus, ionospheric phase screens should not be neglected: their compensation improves the estimation of ground deformation maps. The split-spectrum method is able to estimate the dispersive ionospheric component of the interferometric phase; we describe the implementation of this method for the burst modes TOPS and ScanSAR to estimate and remove ionospheric phase screens. We present Sentinel-1 interferograms of the 2016 Taiwan earthquake and ALOS-2 interferograms of the 2015 Nepal earthquake, which show strong ionospheric phase gradients, and their corrected versions. Finally, to validate the results and better understand the origin of these ionospheric variations, we compare the estimated differential ionosphere with global Total Electron Content maps and local Global Positioning System measurements. [ABSTRACT FROM PUBLISHER]

This paper describes the implementation of the Wide Area Differential Global Positioning System (WADGPS) system in order to evaluate the operational performance of a satellite based aviation navigation system within Taipei Flight Information Region (FIR). The main objective of the WADGPS is to provide real time integrity information regarding the use of GPS for civil aviation applications. This paper uses the e-GPS observation stations operated by the Taiwan Ministry of Interior (MOI) as the WADGPS reference stations to collect the L1-L2 dual-frequency GPS measurements. A WADGPS master station is also implemented to process all GPS measurements sent from each reference station, and then generate the vector corrections. These vector corrections consist of the satellite ephemeris and clock errors, and a grid of ionospheric delays. The data stream also includes confidence bounds for the corrections and "Use/Do Not Use" messages to provide integrity. These messages are then passed to the WADGPS user through the Internet. This paper discusses the WADGPS system architecture and the system performance analysis. A five-day operation performance in Taipei Flight Information Region (FIR) is presented in this paper. The results show that the WADGPS can improve the accuracy performance of GPS positioning and fulfill the integrity performance required by Non-Precision Approach (NPA) defined by the International Civil Aviation Organization (ICAO). [ABSTRACT FROM AUTHOR]

The Linbeiken area is located in the village of Pingding, Taiwan. Since the Mindulle and Aere Typhoons in 2004, and as a result of the landslide triggered by the continuous heavy rainfall on 9 June 2006, there has been a persistent collapse of side slopes in the area. This paper describes the equipment that was installed to collect on-site topographic and hydrological information in the Linbeiken area upstream of the Pingding River and to monitor changes in the landslide area, as well as the measurements that were collected during the 2008 Typhoon Sinlaku. A case study of a landslide in Pingding, Taiwan was used to monitor the accurate coordinate changes in the potential landslide areas during typhoons. The goal of this study was to establish warning indexes, and to strengthen the software and hardware at the local disaster response center in the hope of gaining a full idea of the surface movement in landslide areas in future flood seasons. This is important for boosting the preparedness to adapt to landslide hazards, for improving disaster warnings, and for reporting efficiently to better protect the lives and property of local residents. The results show that the landslide disaster monitoring and warning system in Taiwan, as applied during Typhoon Sinlaku in 2008, is both effective and comprehensive. [ABSTRACT FROM AUTHOR]

In urban environments, Global Positioning System (GPS) signals are often reflected or blocked by buildings causing multipath effects and Non-Line-Of-Sight (NLOS) reception. These effects degrade GPS positioning performance. Although improved receiver and antenna design can reduce the multipath effect to some extent, NLOS elimination is limited due to sensor cost. Measurements based modelling methods have shown promise to reduce NLOS, while positioning accuracy is limited by the correct classification of the signal reception types. These limitations are addressed in this paper by developing an integrated algorithm using matching, Particle Swam Optimized Adaptive Neuro Fuzzy Inference System (PSO-ANFIS) and a spatial city model. The user's location is determined by matching the high accuracy signal reception type determined by PSO-ANFIS with satellite visibility of each candidate position determined by the ray-tracing and a 3D city model. The results from a field test in an urban area in Taiwan show that the PSO-ANFIS based algorithm achieves a classification accuracy of 96%, 88%, and 91% for LOS, multipath and NLOS signals, respectively, which is superior to the other classification algorithms. The final horizontal positioning accuracies in terms of the Root Mean Square Error (RMSE) are 3.20 m using a commercial receiver and 1.88 m using a geodetic receiver. The proposed algorithm has consistent improvements of 88% and 70% respectively compared to the traditional Weighted Least Square (WLS) based positioning method, and is the best compared to the other state-of-the art methods with the improvements ranging from 15% to 77% depending on the test conditions. [ABSTRACT FROM AUTHOR]

The Choushui River Alluvial Fan (CRAF) is a major agricultural area in Taiwan with heavy groundwater usage. The extraction of groundwater here has caused land subsidence, which is now a significant global environmental issue. This study analyzes land subsidence in the CRAF by integrating hydrogeological data from 233 groundwater monitoring stations across four aquifers (CRAF Groundwater_NET) and data from 50 continuous GNSS stations (CRAF GNSS_NET). We developed an automated processing flow for GNSS static surveying within CRAF GNSS_NET, and further employed a time-series fitting method to examine the long-term trends and annual changes for both GNSS and groundwater level data. Our analysis of the time-series data from the past decade identifies areas of significant groundwater level depletion and subsidence hotspots. We explore the relationship between groundwater level variations and surface displacements within CRAF, utilizing GNSS data to analyze horizontal and vertical displacement trends, as well as annual changes. We integrate these findings with hydrogeological data to understand regional subsidence patterns. Our results indicate that CRAF is characterized by distinct hydrogeological features. The study finds that the amplitudes of annual changes in both groundwater level and vertical displacement generally increase from northeast to southwest in the analyzed region. One particular area shows significant groundwater level decline, with the most severe rate recorded at 0.54 m/year. Similarly, GNSS analysis indicates pronounced subsidence trends in the same area, with rates ranging from 4.2 to 5.2 cm/year. These findings highlight the critical need for the development of effective groundwater management strategies to ensure sustainable use of groundwater resources and to implement mitigation measures against land subsidence in similar multipleaquifer settings. [ABSTRACT FROM AUTHOR]

National leveling height networks have recently been set up in Taiwan, and global positioning system (GPS) observations were carried out at the benchmarks of the networks. The purpose of this paper is to develop an improved local geoid model for Taiwan by integrating a local gravimetric geoid model with the GPS and leveling height data. To overcome the problems of datum inconsistencies and possible systematic errors in height data of different types, the least squares collocation technique was applied. The result from fit of the improved geoid model to the control data at 300 benchmarks shows that a mean accuracy of geoidal heights at a 2 cm level is obtainable. [ABSTRACT FROM AUTHOR]

The world's first Global Positioning System Radio Occultation (GPS-RO) constellation, the joint Taiwan-U.S. Formosa Satellite No. 3 - Constellation Observing System for Meteorology, Ionosphere & Climate (FORMOSAT-3/COSMIC) has demonstrated the value of GPS-RO data in terrestrial weather, space weather, and climate study. The RO measurement technique was dubbed as "the most accurate and stable thermometer in space" because of its high accuracy, high vertical resolution, and high stability, which does not require calibration. Since its launch in 2006, FORMOSAT-3/COSMIC has accumulated over 6.9 million atmospheric and 4.6 million ionospheric RO sounding profiles. Encouraged by the success of FORMOSAT-3/COSMIC, Taiwan's National Space Organization (NSPO, https://www.nspo.narl.org.tw/index.php?ln=en) and the U.S. National Oceanic and Atmospheric Administration (NOAA) started the planning for the FORMOSAT-7/COSMIC-2 mission in 2008 as a follow-on program to FORMOSAT-3/COSMIC. The FORMOSAT-7/COSMIC-2 satellite constellation, consisting of six small satellites, was successfully launched in June 2019 as the world's first operational RO satellite constellation focusing over the tropics. After fourteen years in service, providing valuable data to operational and research communities, FORMOSAT-3/COSMIC was officially decommissioned ten months after FORMOSAT-7/COSMIC-2 has been sent to space, and replaced by the FORMOSAT-7/COSMIC-2. As expected, the first results from FORMOSAT-7/COSMIC-2 showed positive impact on operational weather prediction and has observed interesting phenomenon in the ionosphere. In this paper, we will summarize the progress from FORMOSAT-7/COSMIC-2 up to date. [ABSTRACT FROM AUTHOR]

The global positioning system (GPS) receiver has been one of the most important navigation systems for more than two decades. Although the GPS system was originally designed for near-Earth navigation, currently it is widely used in highly dynamic environments (such as low Earth orbit (LEO)). A space-capable GPS receiver (GPSR) is capable of providing timing and navigation information for spacecraft to determine the orbit and synchronize the onboard timing; therefore, it is one of the essential components of modern spacecraft. However, a space-grade GPSR is technology-sensitive and under export control. In order to overcome export control, the National Space Organization (NSPO) in Taiwan completed the development of a self-reliant space-grade GPSR in 2014. The NSPO GPSR, built in-house, has passed its qualification tests and is ready to fly onboard the Triton satellite. In addition to providing navigation, the GPS/global navigation satellite system (GNSS) is facilitated to many remote sensing missions, such as GNSS radio occultation (GNSS-RO) and GNSS reflectometry (GNSS-R). Based on the design of the NSPO GPSR, the NSPO is actively engaged in the development of the Triton program (a GNSS reflectometry mission). In a GNSS-R mission, the reflected signals are processed to form delay Doppler maps (DDMs) so that various properties (including ocean surface roughness, vegetation, soil moisture, and so on) can be retrieved. This paper describes not only the development of the NSPO GPSR but also the design, development, and special features of the Triton's GNSS-R mission. Moreover, in order to verify the NSPO GNSS-R receiver, ground/flight tests are deemed essential. Then, data analyses of the airborne GNSS-R tests are presented in this paper. [ABSTRACT FROM AUTHOR]

Precipitable water vapor (PWV) and zenith total delay (ZTD) are highly correlated indicators used for forecasting rainfall effectively. These two factors are widely used when establishing qualitative and quantitative rainfall forecast models. Another indicator, however, convective available potential energy (CAPE), is also highly correlated with the occurrence of rainfall, but has not been combined with PWV or ZTD in previous studies. Therefore, a novel rainfall forecast model based on support vector regression that combines CAPE and Global Navigation Satellite System (GNSS)-derived PWV is proposed in this paper. Moreover, annual, seasonal scales, and hourly autocorrelation for predictors were also considered, and wavelet coherence (WTC) was introduced to further reveal the correlation relationships between CAPE, PWV and rainfall in both time and frequency domains. Hourly PWV, CAPE, temperature (T) and rainfall over a time span of three years were collected from four stations in Singapore and Taiwan to evaluate the performance of the proposed model. The root mean square error (RMSE) and mean absolute error (MAE) between the measured and forecasted rainfall were calculated for each year and averaged. Subsequently, the average RMSE and MAE were determined for the annual seasonal rainfall. The annual average RMSE value was 0.71 mm and the average annual seasonal RMSE value was 0.69 mm. The annual average MAE value was 0.21 mm and the annual seasonal was 0.22 mm. The average correlation coefficient (R2) for the annual value was 0.94 and the annual seasonal R2 value was 0.93. These results indicate that the forecast accuracy at the seasonal scale is basically consistent with annual scale. Additionally, a measure called comparable RMSE (CRMS) was introduced to evaluate the forecasting accuracy across all grades of rainfall. This analysis showed that the accuracy of moderate rainfall (MR) and heavy rainfall (HR) forecasts is similar, but slight rainfall (SR) forecasts are the most accurate among seasons and schemes. • A short-term rainfall forecast method is proposed using convective available potential energy (CAPE) and GNSS-derived PWV. • The forecast accuracy of seasonal scales is consistent with annual scale. • Results showed that the forecast accuracy of moderate rainfall and heavy rainfall were comparable while that of slight rainfall was highest. [ABSTRACT FROM AUTHOR]

The FORMOSA Satellite Series No. 3/Constellation Observing System for Meteorology, Ionosphere and Climate (FORMOSAT-3/COSMIC) spacecraft constellation consisting of six low-earth-orbiting satellites is the world's first operational Global Positioning System (GPS) radio occultation mission. The mission has been jointly developed by the National Space Organization of Taiwan and the University Corporation for Atmospheric Research of the U.S. in collaboration with the Jet Propulsion Laboratory, NASA, and the Naval Research Laboratory for three onboard payloads, including a GPS Occultation Receiver, a triband beacon, and a tiny ionospheric photometer. The FORMOSAT-3/COSMIC mission was successfully launched from Vandenberg into the same orbit plane of the designated 516-km circular parking orbit altitude on April 15, 2006. After the six satellites completed the in-orbit checkout activities, the mission was started immediately at the parking orbit for in-orbit checkout, calibration, and experiment of three onboard payloads. Individual spacecraft thrust burns for orbit raising were performed to begin the constellation deployment of the satellites into six separate orbit planes. All six FORMOSAT-3/COSMIC satellites are maintained in a good state of health except spacecraft flight model no. 2, which has had power shortages. Five out of the six satellites had reached their final mission orbits of 800 km as of November 2007. This paper provides an overview of the constellation spacecraft design, constellation mission operations, constellation deployment time-line evolution, associated spacecraft mass property and moment of inertia results, orbit-raising challenges, and lessons learned during the orbit-raising operations. [ABSTRACT FROM AUTHOR]

The 2013 Ruisui earthquake represents the first unequivocal evidence of the activity of the Central Range fault (CRF) in central Longitudinal Valley, Taiwan. Using a joint Bayesian finite‐fault source inversion of Global Navigation Satellite System and strain time series, we infer that coseismic rupture occurred between 4 and 19 km depth with maximum slip of 0.5 m located near the hypocenter. We then apply a variational Bayesian independent component analysis approach to displacement signals to infer a 3‐months long afterslip located in the near‐source region. This observation represents the first evidence of aseismic slip on the CRF. Combining geodetic and seismological analysis with simulations based on rate‐and‐state friction mechanics, we analyze the interplay between seismic and aseismic deformation during the earthquake sequence. We observe that afterslip is the dominant postseismic deformation mechanism, with >95% of the moment being released aseismically in the postseismic phase and also likely represents the driving force controlling aftershock productivity. Finally, we infer the presence of a shallow velocity strengthening zone (∼0–4 km depth) associated with spatially heterogeneous slip during the postseismic phase with maximum slip of 0.18 m located above the zone of maximum coseismic deformation. Plain Language Summary: Tectonic faults display a broad range of slip patterns, ranging from fast slip (earthquakes) to episodic or continuous aseismic slip. Aseismic transient slip events are now widely observed in active regions and play an important role in stress redistribution in the Earth's crust. The Central Range fault (CRF) is the second most active fault in the Longitudinal Valley, in eastern Taiwan. During the past 15 years, the fault hosted large to destructive earthquakes, but little is known about the presence and the role of aseismic events on the fault deformation. The 2013 Ruisui earthquake reveals for the first time the presence of transient slip regions on the CRF, capable of sustaining aseismic deformation over months. Besides, slow stress relaxation on the fault plane may have also influenced the behavior of seismicity following the mainshock. Monitoring and characterizing the sources of aseismic slip is fundamental to identify areas with high seismic hazard on the fault and to gain more knowledge about the interactions between seismic and aseismic processes. Key Points: We present the first evidence for the detection of postseismic deformation on the Central Range fault, in the Longitudinal Valley (Taiwan)Afterslip represents the dominant deformation mechanism during the postseismic phase and controlled aftershock productionThe velocity strengthening region may have acted like a barrier, resisting the rupture propagation toward the surface during the earthquake [ABSTRACT FROM AUTHOR]

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In this study, a low-cost, software-defined Global Positioning System (GPS) and Satellite-Based Augmentation System (SBAS) Reflectometry (GPS&SBAS-R) system has been built and proposed to measure ocean-surface wave parameters on board the research vessel New Ocean Researcher 1 (R/V NOR-1) of Taiwan. A power-law, ocean-wave spectrum model has been used and applied with the Small Perturbation Method approach to solve the electromagnetic wave scattering problem from rough ocean surface, and compared with experimental seaborne GPS&SBAS-R observations. Meanwhile, the intensity scintillations of high-sampling GPS&SBAS-R signal acquisition data are thought to be caused by the moving of rough surfaces of the targeted ocean. We found that each derived scintillation power spectrum is a Fresnel-filtering result on ocean-surface elevation fluctuations and depends on the First Fresnel Zone (FFZ) distance and the ocean-surface wave velocity. The determined ocean-surface wave speeds have been compared and validated against nearby buoy measurements. [ABSTRACT FROM AUTHOR]

This study presents a new landslide monitoring system, which is designed to be cost-effective, robust, flexible, and scalable, aiming for long-term and real-time monitoring and large-scale deployment in harsh and remote environments. This wireless monitoring system consists of the hybrid sensor node (including the GNSS receiver and MEMS accelerometer), the GNSS antenna, the power supply system, and the data center with a big-data infrastructure. The system was deployed at Songmao and Lushan landslide-prone sites, Taiwan, and its effectiveness was also examined through monitoring real landslide events. It was found that continuous monitoring, combining displacement and vibration data, enables us to see how and when the landslide is triggered by the rainfall, together with the potential sliding direction, and the associated aftermath behavior, even after the rainfall stops. The entire landslide movement, from initiation to the subsequent continuous movement, can be captured in detail through the DGNSS analyses. The potential landslide direction is derived based on the directivity from the Horizontal to Vertical Spectral Ratio (HVSR) analyses on the seismic measurements by the 3-axis accelerometers. The monitoring results also agree with other measurements from the borehole inclinometer/extensometer and total station. At these two sites, the groundwater level exhibited a distinct time lag in rising after the rainfall started and the subsequent sudden increase triggered the landslides. On the contrary, the drawdown of the groundwater level was relatively slow, which is due to the anisotropic permeability of the slate, and therefore promotes the continued slope movement even after the rainfall ceased. Water-softening on the slate along the sliding surface, which was just fractured by landslide movement, could be one of the associated underlying mechanisms. [ABSTRACT FROM AUTHOR]

Typhoons often occur and may cause huge loss of life and damage of infrastructures, but they are still difficult to precisely monitor and predict by traditional in-situ measurements. Nowadays, ionospheric disturbances at a large-scale following typhoons can be monitored using ground-based dual-frequency Global Positioning System (GPS) observations. In this paper the responses of ionospheric total electron content (TEC) to Typhoon Maria on 10 July 2018 are studied by using about 150 stations of the GPS network in Taiwan. The results show that two significant ionospheric disturbances on the southwest side of the typhoon eye were found between 10:00 and 12:00 UTC. This was the stage of severe typhoon and the ionospheric disturbances propagated at speeds of 118.09 and 186.17 m/s, respectively. Both traveling ionospheric disturbances reached up to 0.2 TECU and the amplitudes were slightly different. The change in the filtered TEC time series during the typhoon was further analyzed with the azimuth. It can be seen that the TEC disturbance anomalies were primarily concentrated in a range of between −0.2 and 0.2 TECU and mainly located at 135–300° in the azimuth, namely the southwest side of the typhoon eye. The corresponding frequency spectrum of the two TEC time series was about 1.6 mHz, which is consistent with the frequency of gravity waves. Therefore, the upward propagating gravity wave was the main cause of the traveling ionospheric disturbance during Typhoon Maria. [ABSTRACT FROM AUTHOR]

Taiwan is a highly informational country, and a robust traffic network is not only critical to the national economy, but is also an important infrastructure for economic development. This paper aims to integrate government open data and global positioning system (GPS) technology to build an instant image-based traffic assistant agent with user-friendly interfaces, thus providing more convenient real-time traffic information for users and relevant government units. The proposed system is expected to overcome the difficulty of accurately distinguishing traffic information and to solve the problem of some road sections not providing instant information. Taking the New Taipei City Government traffic open data as an example, the proposed system can display information pages at an optimal size on smartphones and other computer devices, and integrate database analysis to instantly view traffic information. Users can enter the system without downloading the application and can access the cross-platform services using device browsers. The proposed system also provides a user reporting mechanism, which informs vehicle drivers on congested road sections about road conditions. Comparison and analysis of the system with similar applications shows that although they have similar functions, the proposed system offers more practicability, better information accessibility, excellent user experience, and approximately the optimal balance (a kind of symmetry) of the important items of the interface design. [ABSTRACT FROM AUTHOR]

The total electron content (TEC) profiles from the FORMOsa SATellite mission‐3/Constellation Observing System for the Meteorology, Ionosphere, and Climate (COSMIC) and the Fengyun‐3C (FY‐3C) radio occultation (RO) missions during 2006 and 2019 are used to establish the models for deriving the ionospheric sporadic E (Es) critical frequency (foEs). Smax is derived as the maximum vertical gradient of TEC disturbance, which is extracted from a RO TEC profile using the singular spectrum analysis method. Three candidate conversion models are obtained by fitting Smax with foEs observed by collocated ionosondes, and the one with the best performance, the COSMIC&FY‐3C (CF) model, is applied for deriving foEs (foEsCF) from the TEC data of the two missions jointly. For comparison, the C model, which is of similar form as the CF model while being established without using the FY‐3C data, is applied for deriving foEs (foEsC) from the COSMIC TEC data only. The validations over four independent ionosonde stations demonstrate that mean improvements of 0.11 MHz (32%) in the absolute bias and 0.24 MHz (17%) in the root mean square error are obtained by foEsCF compared with foEsC. The spatiotemporal distributions of Es intensity during 2015 and 2019, presented respectively by foEsCF and foEsC, are further compared. The CF model provides more abundant and more detailed information about Es intensity distribution, which is most distinct at high latitudes where the contribution of FY‐3C RO TEC data is significant. Our results reveal that with the aging of the COSMIC satellites, FY‐3C TEC data is a valuable supplementary RO data source for Es‐related studies. Plain Language Summary: Ionospheric sporadic E (Es) layers have significant impacts on radio communication and the propagation of global navigation satellite system signals, and the degrees of the impacts are closed related to the distributions and the intensity of Es layers. The radio occultation (RO) total electron content (TEC) profiles can be used for detecting the existence and the intensity of Es layers due to that the Es layers can bring to sudden enhancements of TEC values. In this study, based on the TEC data from FORMOsa SATellite mission‐3/Constellation Observing System for the Meteorology, Ionosphere, and Climate (COSMIC) and Fengyun‐3C (FY‐3C) RO missions and the collocated ionosonde observations during 2006 and 2019, an optimal model for deriving the Es intensity is promoted, and is compared with another model established using the same method but without using the FY‐3C data. The model using the FY‐3C data shows a better performance for deriving the Es intensity and provides more abundant and more detailed information about Es intensity distributions, especially in high‐latitude regions. The results contribute to understanding the value of FY‐3C RO TEC data for Es layer‐related studies, which is most significant during the last years of COSMIC mission lifespan, when the aging of the satellites brings to the decline in the COSMIC RO data volume. Key Points: The COSMIC&FY‐3C (CF) model, a model for deriving the sporadic E (Es) critical frequency from radio occultation (RO) total electron content data, is promoted by using the Constellation Observing System for the Meteorology, Ionosphere, and Climate (COSMIC) and the Fengyun‐3C (FY‐3C) data jointlyImprovements in the absolute bias and root mean square error of Es critical frequency are obtained by the CF model due to the contribution of FY‐3C RO dataDuring 2015 and 2019, the integrity of Es intensity distribution is improved by using the RO data from the two missions jointly [ABSTRACT FROM AUTHOR]

We explored the driving factors of nonlinear signals in vertical coordinate sequences of stations in a Taiwan global navigation satellite system (GNSS) network, including atmospheric loading (ATML), hydrological loading (HYDL), and non-tidal ocean loading (NTOL) effects. At the same time, we used the finite element analysis software MIDAS to quantify the vertical displacements of different types of monuments due to the thermal expansion effect, including deep drilled braced (DDB) and short drilled braced (SDB). By quantitatively comparing the correction results of GNSS time series with different single mass loading models, we found that there was little difference in the correction of different environmental loading products. We compared different combinations of each loading product to correct the GNSS time series, and finally selected the best combination suitable for Taiwan GNSS network, that is, ATML (GFZ_ECMWF IB) + HYDL (IMLS_MERRA2) + NTOL (IMLS_MPIOM06). We found that the spatial and temporal models of ATML and NTOL are very similar, with non-tidal atmospheric loading and non-tidal ocean loading working together, a pattern that may be related to tropical cyclones. Both models also showed good correction effect on GNSS stations in the western plain of Taiwan, but with limited correction effect in the eastern part of Taiwan. This may be due to the influence of the subtropical monsoon climate in Taiwan and the barrier of the central mountain range, resulting in obvious differences between eastern and western Taiwan. The hydrological loading was found to act in the opposite way to the thermal expansion effect in the temporal domain, indicating that some displacements in hydrological loading may cancel out displacements caused by the thermal expansion effect. This aspect of displacement is not included in the hydrological loading model but should be considered when accurately estimating the temporal and spatial variation of water storage capacity in Taiwan using GNSS observed displacements. [ABSTRACT FROM AUTHOR]

We summarize the status of the FORMOSAT-7/COSMIC-2 (COSMIC-2) mission which has completed its first three years in orbit. COSMIC-2 is a joint U.S./Taiwan program consisting of six satellites in low-inclination orbits with the following payloads: Global Navigation Satellite System radio occultation, in-situ ion velocity meter, and tri-band radio frequency beacon. The constellation is in its final orbit configuration and reached mission full operating capability in September 2021. An extensive calibration/validation campaign has to date enabled the release of all baseline neutral atmosphere products and nearly all baseline ionosphere products. The mission is providing usually more than 5000 neutral atmosphere RO profiles per day with a precision better than 2 μrad from 30–60 km altitude. Each day, nearly 12,000 combined total electron content occultations and arcs are generated with absolute accuracy of better than 3 TECU. IVM density precision is at or below the 1% requirement. Neutral atmosphere and ionosphere latency, measured from time of observation to product creation time, is below 30 min median. Data products are delivered in near real-time to operational weather and space weather centers and made available openly to the research community. New ionosphere products specifying the presence and absence of scintillation are under development and planned for future release. [ABSTRACT FROM AUTHOR]

Although a dynamic or semi-dynamic datum has been adopted in some countries, it remains a challenge if a long-term stable datum is to be established in a tectonic active area. This study presents an approach to realistically reflect the time dependent behaviors of ground reference points while maintaining the long-term stability of a datum. An adaptive approach coupled with the Euler motion model is proposed for dividing an area into blocks. A least-squares collocation is then applied for modeling the residual velocities in each block. A case study using the data from 375 continuously operated GNSS stations in Taiwan is presented. It is illustrated that the complex surface kinematics in this region can be divided into three blocks. Significant reductions up to 64% of residual velocities were obtained. This shows that a stable datum can be established in a region with active and complicated surface kinematics by implementing the proposed. [ABSTRACT FROM AUTHOR]

The southern Ryukyu subduction zone is one of the potential sources for tsunamigenic earthquakes. Despite a great seismic risk, the deformation pattern remains poorly known, primarily due to the absence of seafloor constraints. With GNSS‐acoustic measurements over years, we characterize the convergence rate across this margin growing from 92 mm/yr offshore eastern Taiwan to 123 mm/yr near the Gagua Ridge. The new data suggest the subduction interface is capable of hosting Mw 7.5–8.4 earthquakes. The orientations of seafloor movement and P‐axes in the Nanao Basin are both subnormal to the trench, notably deviate from the direction of plate convergence. By considering the combined effect of plate convergence and backarc rifting, different trends between the forearc convergence, P‐axes, and seafloor movement may indicate some degree of slip‐partitioning. The trench‐parallel component is likely accommodated in part by earthquakes near Taiwan, lower plate deformation, and strike‐slip faults within the accretionary wedge. Plain Language Summary: The southern Ryukyu margin near Taiwan accommodates the relative plate motion and backarc rifting. This region has suffered from tsunamis and large earthquakes with magnitudes of about eight in the history, yet insufficient offshore data still hamper our ability to fully characterize fault slip behaviors. We demonstrate how a seafloor geodetic technique, with the combination of the Global Navigation Satellite System and acoustic ranging, can help us constraining fault slip behaviors and assessing seismic risks. We infer a fraction of oblique plate motion is accommodated by the subduction interface capable of hosting earthquakes with moment magnitudes ranging from 7.5 to 8.4. Incorporating seismological observations, we find different trends of the compressive axes of earthquakes, seafloor movement, and the forearc convergence, which may indicate some degree of strain partitioning. The trench‐parallel motion is partially taken up by seismic slip near Taiwan, subducting plate deformation, and strike‐slip faults within the forearc. More near‐trench observations are crucial to assessing seismic hazard and evaluating strain partitioning along the southern Ryukyu Trench. Key Points: Rapid convergence across the southern Ryukyu margin increases eastward from 92 mm/yr offshore Taiwan to 123 mm/yr near the Gagua RidgeOblique convergence is accommodated in part by the plate interface fault capable of hosting earthquakes with Mw 7.5–8.4Different trends between the forearc convergence, P‐axes, and seafloor movement may indicate some degree of slip partitioning [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we examine pre-earthquake ionospheric anomalies by the total electron content (TEC) derived from a ground-based receiver of the global positioning system (GPS). A network of eight GPS receivers is used to construct daily latitude-time-TEC (LTT) plots to monitor the crest of equatorial ionization anomaly (EIA) in the Taiwan area. Three parameters of the strength, location, and formation time of the EIA crest are extracted. A 15-day running medians of the three parameters and the associated upper and lower quartiles are utilized as the references for identifying abnormal signals for all of the 150 M 5.0 earthquakes in the Taiwan area during 2001–2007. Results show that the EIA crest significantly moves equatorward (poleward) and appears in an earlier (later) time of the afternoon period a few days before (after) the earthquakes along the Taiwan longitude. The two parameters of the EIA crest location and occurrence time can be employed to detect ionospheric earthquake precursors. The results further imply that atmospheric electric fields generated around the epicenter of a forthcoming earthquake during the preparation period are essential. [Copyright &y& Elsevier]

The FORMOSAT-3/COSMIC spacecraft constellation consisting of six LEO satellites is the world's first operational GPS Radio Occultation (RO) mission. The mission is jointly developed by Taiwan's National Space Organization (NSPO) and the United States' UCAR in collaboration with NSF, USAF, NOAA, NASA, NASA's Jet Propulsion Laboratory, and the US Naval Research Laboratory. The FORMOSAT-3/COSMIC satellites were successfully launched from Vandenberg US AFB in California at 0140 UTC 15 April 2006 into the same orbit plane of the designated 516 km altitude. The mission goal is to deploy the six satellites into six orbit planes at 800 km altitude with a 30-degree separation for evenly distributed global coverage. All six FORMOSAT-3/COSMIC satellites are currently maintaining a satisfactory good state-of-health. Five out of six satellites have reached their final mission orbit of 800 km as of November 2007. The data as received by FORMOSAT-3/COSMIC satellites constellation have been processed in near real time into 2500 good ionospheric profiles and 1800 good atmospheric profiles per day. These have outnumbered the worldwide radiosondes (∼900 mostly over land) launched from the ground per day. The processed atmospheric RO data have been assimilated into the Numerical Weather Prediction (NWP) models for real-time weather prediction and typhoon/hurricane forecasting by many major weather centers in the world. This paper describes the FORMOSAT-3/COSMIC satellite constellation system performance and the mission results that span the period from April 2006 to October 2007; and reviews the prospect of a future follow-on mission. [ABSTRACT FROM AUTHOR]

The extraction of a digital elevation model (DEM) from airborne lidar point clouds is an important task in the field of geoinformatics. In this paper, we describe a new automated scheme that utilizes the so-called "climbing-and-sliding" method to search for ground points from lidar point clouds for DEM generation. The new method has the capability of performing a local search while preserving the merits of a global treatment. This is done by emulating the natural movements of climbing and sliding in order to search for ground points on a terrain surface model. To improve efficiency and accuracy, the scheme is implemented with a pseudo-grid data and includes a back selection step for densification. The test data include a dataset released from the ISPRS Working Group III/3 and one for a mountainous area located in southern Taiwan. The experimental results indicate that the proposed method is capable at producing a high fidelity terrain model. [ABSTRACT FROM AUTHOR]

Ground subsidence induced by heavy withdrawal of underground water has resulted in environmental hazard and potential risk in Taiwan, particularly in the Chuo-Shui River alluvial fan where the Yun-Lin section of the Taiwan High Speed Rail is being constructed. In this paper, seasonal effects of ground subsidence occurring in the study area are investigated. The rate of ground subsidence was estimated using a regression analysis of a series of weekly GPS height solutions. The average rate of ground subsidence in the study area over the period of 1995- 2001 was 3 cm/year, with a high correlation coefficient of 0.9. Based on data collected at the piezometer, the variation of ground subsidence rate appears to be associated with an unstable underground water level, which drop gradually during winter and either remains constant or rises during summer time. As a result, ground subsidence rates vary considerably from 1.5 cm/year for the summer data to 9.0 cm/year for the winter data. The seasonal effect of the GPS height variation is borne out by correlation coefficients ranging from 0.3 to 0.7. [ABSTRACT FROM AUTHOR]

Ocean tide loading (OTL) displacements are sensitive to the shallow structure of the solid Earth; hence, the high-resolution spatial pattern of OTL displacement can provide knowledge to constrain the shallow Earth structure, especially in coastal areas. In this study, we investigate the sensitivity of the modeled M2 OTL displacement over Taiwan Island to perturbations of three physical quantities, namely, the density, bulk modulus, and shear modulus in the upper mantle and crust. Then, we compare the sensitivity of the modeled M2 OTL displacement to Earth models with the sensitivity to ocean tide models using root mean square (RMS) differences. We compute the displacement Green's function and OTL displacement relative to the center of mass of the solid Earth (CE) reference frame, analyze the sensitivity to the three physical quantities in the CRUST1.0 model and the Preliminary Reference Earth Model (PREM), and present their spatial patterns. We find that displacement Green's functions and OTL displacements are more sensitive to the two elastic moduli than the density in the upper mantle and crust. Moreover, their distinctive sensitivity patterns suggest that the three physical quantities might be constrained independently. The specific relationships between the perturbed structural depths and the distance ranges of peak sensitivities from the observation points to the coastline revealed by the shear modulus can mitigate the nonuniqueness problem in inversion. In particular, the horizontal tidal components observed by the Global Positioning System (GPS) can yield better results in inversions than the vertical component owing to the smaller OTL model errors and the higher structural sensitivity (except for the shear modulus in the asthenosphere). [ABSTRACT FROM AUTHOR]

The FORMOSAT-7/COSMIC-2 Global Navigation Satellite System (GNSS) Radio Occultation (RO) satellite constellation was launched in June 2019 as a successor of the FORMOSAT-3/COSMIC mission. The Central Weather Bureau (CWB) of Taiwan has received FORMOSAT-7/COSMIC-2 GNSS RO data in real time from the Taiwan Analysis Center for COSMIC. With the global numerical prediction system at CWB, a parallel semioperational experiment assimilating the FORMOSAT-7/COSMIC-2 bending angle data with all other operational observation data has been conducted to evaluate the impact of the FORMOSAT-7/COSMIC-2 data. The first seven-month results show that the quality of the early FORMOSAT-7/COSMIC-2 data has been satisfactory for assimilation. Consistent and significant positive impacts on global forecast skills have been observed since the start of the parallel experiment, with the most significant impact found in the tropical region, reflecting the low-inclination orbital design of the satellites. The impact of the FORMOSAT-7/COSMIC-2 RO data is also estimated using the ensemble forecast sensitivity to observation impact (EFSOI) method, showing an average positive impact per observation similar to other existing GNSS RO datasets, while the total impact is impressive by virtue of its large amount. Sensitivity experiments suggest that the quality control processes built in the Gridpoint Statistical Interpolation (GSI) system for RO data work well to achieve a positive impact by the low-level FORMOSAT-7/COSMIC-2 RO data, while more effort on observation error tuning should be focused to obtain an optimal assimilation performance. This study demonstrates the usefulness of the FORMOSAT-7/COSMIC-2 RO data in global numerical weather prediction during the calibration/validation period and leads to the operational use of the data at CWB. Significance Statement: The importance of the Global Navigation Satellite System Radio Occultation measurement has been widely acknowledged by the numerical weather prediction community. Following the successful FORMOSAT-3/COSMIC mission, the FORMOSAT-7/COSMIC-2 constellation, consisting of also six radio occultation satellites, was launched on 25 June 2019. As a collaborator of the mission, we prepared early to investigate the anticipated impact of the FORMOSAT-7/COSMIC-2 data on weather prediction as soon as the preliminary data were available. Statistically significant improvement in global forecast skills is clearly shown, with the most significant impact found in the tropics, consistent with the primary goal of the mission. The real-time tropospheric and stratospheric FORMOSAT-7/COSMIC-2 radio occultation data have been officially released since March 2020, available for use in operational weather prediction worldwide. [ABSTRACT FROM AUTHOR]

The evident disturbance of global positioning system (GPS) positioning results responding to the 2017 tropical cyclone (TC) Hato is observed in both Hong Kong and Taiwan regions. The GPS solutions of 10 baselines, i.e., five from Hong Kong and five from Taiwan, with baseline lengths ranging from 4.8 to 46.6 km, are analyzed during the TC period from August 16 to 26, 2017. The precipitable water vapor (PWV) variation in temporal and spatial domains is also investigated in terms of 2–5 h scale‐averaged wavelet power and normalized magnitude of spatial gradient. The results indicate that there is a close correlation between positioning disturbance and the spatiotemporal variation of PWV during the TC period. The daily Spearman's correlation coefficient on TC‐impacted day is 0.65 for Hong Kong baselines, ∼1.97 times as large as the mean value 0.33 of the non‐TC‐impacted period. Furthermore, the positioning performance started to degrade when the normalized magnitude of the spatial gradient of PWV experienced a rapid increase. The degradation lasted for ∼7 h, and the degrading trend for Hong Kong baselines is 9.86 mm/h on average. For Taiwan baselines, the degradation lasted for ∼31 h, and the degrading trend is 1.20 mm/h on average. In addition, the GPS three‐dimensional positioning average accuracy on the TC‐impacted day, July 22, 2017, degraded by 255% over the 10 baselines with respect to that of the other non‐TC‐impacted days. Key Points: The performance of global positioning system (GPS) positioning is degraded by 255% during the 2017 tropical cyclone HatoThe Spearman's correlation coefficient between degradation and precipitable water vapor (PWV) variation is 0.65 on average in Hong KongThe degrading trend in Hong Kong and Taiwan is 9.86 mm/h and 1.20 mm/h on average when the PWV has a high‐dynamic spatial variation [ABSTRACT FROM AUTHOR]

Collision of the Luzon Volcanic Arc is the primary causative factor behind the creation of Taiwan Island. Additionally, the indention of the Peikang basement highs in the Taiwan Strait and the back arc spreading of the Okinawa Trough are responsible for the characteristic tectonics in Taiwan. Identification of active tectonic boundaries is important for understanding neotectonics in Taiwan. We analyzed Global Positioning System (GPS) horizontal velocity data in Taiwan with a hierarchical cluster analysis method. We also developed a statistical scheme introducing information entropy to quantitatively assess the fuzziness of the obtained cluster boundaries, which enables us to distinguish a trustworthy discontinuity. The hierarchical representation, which is expressed by a dendrogram, suggests the relative importance of tectonic sources in this region. The major clusters, which appear at higher hierarchy, are likely to represent major tectonic features such as the Longitudinal Valley fault and lateral extrusion in southwest Taiwan. Those at lower hierarchy suggest velocity discontinuities associated with local geological structures such as active faults. For example, boundaries in east offshore Taiwan and southern Taiwan are identified without using geological information by this analysis. In addition to the identification of these clear tectonic boundaries, our statistical cluster assessment shows the existence of fuzzy cluster boundaries along the Coastal Plain and the Western Foothills, reflecting continuum deformation in west Taiwan. Key Points: Hierarchical cluster analysis of GPS data in Taiwan enables extraction of locations of cluster boundaries and hierarchical structures of crustal deformationObtained cluster boundaries reflect regional and local tectonics in TaiwanIntroduction of information entropy into stability assessment of clustering enables quantitative estimation of the stability of cluster boundaries [ABSTRACT FROM AUTHOR]

Advancements in information, communication, and sensor technologies have led to new opportunities in medical care and education. Patients in general prefer visiting the nearest clinic, attempt to avoid waiting for treatment, and have unequal preferences for different clinics and doctors. Therefore, to enable patients to compare multiple clinics, this study proposes a ubiquitous multicriteria clinic recommendation system. In this system, patients can send requests through their cell phones to the system server to obtain a clinic recommendation. Once the patient sends this information to the system, the system server first estimates the patient's speed according to the detection results of a global positioning system. It then applies a fuzzy integer nonlinear programming-ordered weighted average approach to assess four criteria and finally recommends a clinic with maximal utility to the patient. The proposed methodology was tested in a field experiment, and the experimental results showed that it is advantageous over two existing methods in elevating the utilities of recommendations. In addition, such an advantage was shown to be statistically significant. [ABSTRACT FROM AUTHOR]

The impact of global positioning system (GPS) radio occultation (RO) soundings on the prediction of severe mei-yu frontal rainfall near Taiwan in June 2012 was investigated in this study using a developed local bending angle (LBA) operator. Two operators for local refractivity (REF) and nonlocal refractivity [excess phase (EPH)] were also used for comparisons. The devised LBA simplifies the calculation of the Abel transform in inverting model local refractivity without a loss of accuracy. These operators have been implemented into the three-dimensional variational data assimilation system of the Weather Research and Forecasting (WRF) Model to assimilate GPS RO soundings available from the Formosa Satellite Mission 3/Constellation Observing Systems for Meteorology, Ionosphere and Climate ( FORMOSAT-3/COSMIC). The RO data are found to be beneficial to the WRF forecast of local severe rainfall in Taiwan. Characteristics of assimilation performance and innovation for the three operators are discussed. Both of the local operators performing assimilation at observation levels appear to produce mostly larger positive moisture increments than do the current nonlocal operators performing assimilation on the mean height of each model vertical level. As the information of the initial increments has propagated farther south with the frontal flow, the simulation for LBA shows better prediction of rainfall peaks in Taiwan on the second day than both REF and EPH, with a maximum improvement of about 25%. The positive impact of the RO data results partially from several RO observations near Mongolia and north China. This study provides an intercomparison among the three RO operators, and shows the feasibility of regional assimilation with LBA. [ABSTRACT FROM AUTHOR]

This study successfully uses satellite altimetry, including Topex/Poseidon and Jason-2, retrieved by novel retrackers to monitor vertical land motions in Southwestern Taiwan. Satellite altimetry was originally designed to measure open oceans, so waveform retracking should be applied to overcome the complex waveforms reflected from lands. Modified threshold and improved subwaveform threshold retrackers were used in the study to improve the accuracy of altimetric land surface heights (LSHs) in Southwestern Taiwan. Results indicate that the vertical motion rates derived from both retrackers coincide with those calculated by 1843 precise leveling points, with a correlation coefficient of 0.96 and mean differences of 0.43 and 0.52 cm/yr (standard deviations: 0.61 and 0.69 cm/yr). In addition, wet troposphere delay by precise point positioning with the use of Global Navigation Satellite System data was employed to evaluate the impact of the delay on the estimates of vertical motion rates compared with that traditionally derived from the European Center for Medium-Range Weather Forecasts model when the microwave radiometer is non-functional over lands. The accuracies of retracked altimetric land motion rates corrected by wet troposphere delays derived from both models show no remarkable differences in the Tuku and Yuanchang areas because the accuracy of retracked altimetric LSHs is significantly worse than that of wet troposphere delays. [ABSTRACT FROM AUTHOR]

The 2010 March 4, Jia-Shian (Mw 6.3) earthquake in SW Taiwan caused moderate damage and no surface rupture was observed, reflecting a deep source that is relatively rare in western Taiwan. We develop finite-source models using a combination of seismic waveform (strong motion and broadband), Global Positioning System (GPS) and synthetic aperture radar interferometry (InSAR) data to understand the rupture process and slip distribution of this event. The rupture centroid source depth is 19 km based on a series of moment tensor solution tests with improved 1-D Green's functions. The preferred fault model strikes 322° and dips 27° to the NE and the mainshock is a thrust event with a small left-lateral component. The finite-source model shows a primary slip asperity that is about 20 km in diameter at a depth range from 22 to 13 km, with peak slip of 42.5 cm, a total scalar seismic moment of 3.25 × 1018 N m (Mw 6.34) and with an average static stress drop of 0.24 MPa. The rupture velocity of this event is faster than the mid-crustal shear wave velocity in Taiwan, which suggests the possibility of a supershear event which has not been previously observed in Taiwan. Systematic resolution and sensitivity tests are performed to confirm the slip distribution, rupture velocity, the choice of weighting and smoothing for the joint inversions, and the consistency of the slip distribution. The first 24 hours of aftershocks appeared along the upper periphery of the main coseismic slip asperity. Both the mainshock and aftershocks are located in a transition zone where the depth of seismicity and an inferred regional basal décollement increases from central to southern Taiwan. The difference between the current orientation of plate convergence in Taiwan (120º) and the P axis of this event (052º) and nearby measurements of recent crustal strain directions (050° to 080°), as well as the relatively low static stress drop, suggest that the Jia-Shian event involves the reactivation of a deep and weak pre-existing NW–SE geological structure. [ABSTRACT FROM AUTHOR]

The article looks at English composition instruction methods for English as a Foreign Language (EFL) learners. It reports on a study of the use of a mobile device application with augmented reality (AR) features based on the use of Global Positioning System (GPS) technology as a tool by Taiwanese university students to help them complete a descriptive essay assignment for an English composition course. It says the results suggested that the use of the technology helped students improve their writing skills by expanding their knowledge of both content and language.

Widespread persistent coseismic groundwater level changes induced by the M 7.9 Wenchuan earthquake were recorded in 80 wells in Taiwan, located approximately 2,000 km from the epicenter. The timing and magnitude of these changes, ranging from −40 to +23 cm, have been examined by statistical evaluation. The coseismic fall dominated in the plain area, but in the mountainous area most changes are coseismic rises. Both the coseismic rise and the coseismic fall were observed in wells of different depths at two monitoring stations. The processes of the coseismic changes can be shown by the high-frequency well water level data. Analysis of the 1 Hz water level data and the broadband seismogram revealed that a temporary water level change, ranging from 0.2 to 2.3 cm, occurred at the arrival of high-energy Love waves and Rayleigh waves. However, a water level change of 0.3-6.4 cm occurred in 7-20 min after the passing of high-energy surface waves. It is doubtful that such a change could be induced directly by ground shaking. The cross-formational flow due to fracturing or unclogging of sediment pores was possibly too slow to cause the coseismic change. Further studies are required to understand the mechanism of coseismic groundwater level changes induced by a distant earthquake. [ABSTRACT FROM AUTHOR]

Lanyu and Lutao Islands to the southeast of Taiwan are located in the northern extension of the Luzon Arc. Crustal deformation of these islands provides a key to understand the collision of the Luzon Arc against Taiwan. To clarify the style and the rate of vertical movement during the Holocene, uplifted coral reefs fringing these two islands were investigated. Living corals were also investigated for comparison with fossil corals. It was found that Isopora palifera lives dominantly in the upper slope of the present-day fringing coral reefs in Lanyu Island at an average depth of 101 ± 46 cm (one standard deviation) below mean sea level. Using I. palifera as an accurate indicator of paleo-sea levels, Holocene relative sea-level changes were reconstructed. Lanyu Island has been uplifted continuously at a rate of 2.0 mm yr, at least during the late Holocene from 2,269 cal. yr BP to the present. Lutao Island has been uplifted at an average rate of 1.2 mm yr, since at least 5,749 cal. yr BP, although it is unclear whether the uplift was continuous. The present observations, combined with the GPS displacement field and deep crustal structure, suggest that the continuous uplift is related to aseismic slip on the Longitudinal Valley Fault. [ABSTRACT FROM AUTHOR]

During 1992–2007, excessive pumping of groundwater caused large-scale aquifer-system compaction and land subsidence in the Choshui River Alluvial Fan, especially in the area of Yunlin county. The subsidence impedes surface-water runoff and endangers the operation of Taiwan High Speed Rail. Leveling, Global Positioning System (GPS), multi-level compaction monitoring well, and Differential Interferometric Synthetic Aperture Radar (DInSAR) are used to study the extent of subsidence in Yunlin and its mechanism. These sensors complement each other in spatial and temporal resolutions. A leveling network totaling 434 km in length was deployed to derive subsidence at every 1.5 km along the routes, and the result is accurate to few mm and shows a basin-like subsidence pattern centering at Tuku Township. Four multi-level compaction monitoring wells, co-located with GPS pillars, detect compactions at different depths, showing that the aquifer-system compaction (the cause of subsidence) occurs mostly below depths >200 m, where reduction of groundwater pumping is most needed. The vertical displacements from GPS and leveling agree to within 1 cm, and are larger than the cumulative compaction detected by the compaction-monitoring wells, suggesting that compaction also occurs below 300 m (the depth of the wells). The vertical displacements derived using DInSAR and 8 ENVISAT SAR images agree with the leveling result to 1–2 cm. [ABSTRACT FROM AUTHOR]

This study selected five indexes to determine the relationship between data quality and positioning precision. These indexes are multipath on L1, multipath on L2, observations by cycle slips, clock offset, and clock stability. To reduce the number of common errors, six types of global positioning system (GPS) receivers are selected and set up in an Ultra-Short Distance Network at the National Measurement Laboratory, Taiwan, for 3 days. The first three indicators are calculated with the Teqc software, and the last two indicators are computed using the Bernese software. Moreover, the observations from three GPS tracking stations, namely, short baseline (about 25 km), middle baseline (about 150 km), and long baseline (around 2000 km), were downloaded from the Internet and processed using Bernese software. Analytical results indicate that clock stability and observations divided by cycle slips are found to be very important positioning factors. Clock offset and multipath effects do not significantly affect the GPS results. [ABSTRACT FROM AUTHOR]

We use preseismic, coseismic, and postseismic GPS data of the 1999 Chi-Chi earthquake to infer spatio-temporal variation of fault slip and frictional behavior on the Chelungpu fault. The geodetic data shows that coseismic slip during the Chi-Chi earthquake occurred within a patch that was locked in the period preceding the earthquake, and that afterslip occurred dominantly downdip from the ruptured area. To first-order, the observed pattern and the temporal evolution of afterslip is consistent with models of the seismic cycle based on rate-and-state friction. Comparison with the distribution of temperature on the fault derived from thermo-kinematic modeling shows that aseismic slip becomes dominant where temperature is estimated to exceed 200° at depth. This inference is consistent with the temperature induced transition from velocity-weakening to velocity-strengthening friction that is observed in laboratory experiments on quartzo-feldspathic rocks. The time evolution of afterslip is consistent with afterslip being governed by velocity-strengthening frictional sliding. The dependency of friction, μ, on the sliding velocity, V, is estimated to be $${{\partial \mu }/{\partial \, {\rm ln}\, V}} = 8 \times 10^{ - 3}$$. We report an azimuthal difference of about 10–20° between preseismic and postseismic GPS velocities, which we interpret to reflect the very low shear stress on the creeping portion of the décollement beneath the Central Range, of the order of 1–3 MPa, implying a very low friction of about 0.01. This study highlights the importance of temperature and pore pressure in determining fault frictional sliding. [ABSTRACT FROM AUTHOR]

Plum rains and typhoons are important weather systems in the Taiwan region. They can cause huge economic losses, but they are also considered as important water resources as they strike Taiwan annually and fill the reservoirs around the island. There are many meteorological sensors available for investigating the characteristics of weather and climate systems. Recently, the use of GPS as an alternative meteorological sensor has become popular due to the catastrophic impact of global climate change. GPS provides meteorological parameters mainly from the atmosphere. Precise Point Positioning (PPP) is a proven algorithm that has attracted attention in GPS related studies. This study uses GPS measurements collected at more than fifty reference stations of the e-GPS network in Taiwan. The first data set was collected from June 1st 2008 to June 7th 2008, which corresponds to the middle of the plum rain season in Taiwan. The second data set was collected from September 11th to September 17th 2008 during the landfall of typhoon Sinlaku. The data processing strategy is to process the measurements collected at the reference stations of the e-GPS network using the PPP technique to estimate the zenith tropospheric delay (ZTD) values of the sites; thus, the correlations between the ZTD values and the variation of rainfall during the plum rains and typhoon are analyzed. In addition, several characteristics of the meteorological events are identified using spatial and temporal analyses of the ZTD values estimated with the GPS network PPP technique. [ABSTRACT FROM AUTHOR]

The existence of the common mode error (CME) in the continuous global navigation satellite system (GNSS) coordinate time series affects geophysical studies that use GNSS observations. To understand the potential contributors of CME in GNSS networks in Taiwan and their effect on velocity estimations, we used the principal component analysis (PCA) and independent component analysis (ICA) to filter the vertical coordinate time series from 44 high-quality GNSS stations in Taiwan island in China, with a span of 10 years. The filtering effects have been evaluated and the potential causes of the CME are analyzed. The root-mean-square values decreased by approximately 14% and 17% after spatio-temporal filtering using PCA and ICA, respectively. We then discuss the relationship between the CME sources obtained by ICA and the environmental loads. The results reveal that the independent displacements extracted by ICA correlate with the atmospheric mass loading (ATML) and land water storage mass loading (LWS) of Taiwan in terms of both its amplitude and phase. We then use the white noise plus power law noise model to quantitatively estimate the noise characteristics of the pre- and post-filtered coordinate time series based on the maximum likelihood estimation criterion. The results indicate that spatio-temporal filtering reduces the amplitude of the PL and the periodic terms in the GPS time series. [ABSTRACT FROM AUTHOR]

A transition and subduction zone adjacent to the Ryukyu Arc, Ryukyu Trench, and Okinawa Trough, extends between southern Japan and northeastern Taiwan. It is generated during the northwestward subduction of the Philippine Sea Plate, which lies the Eurasian Plate along the Ryukyu Trench. The movement of the Philippine Sea Plate is hindered at the northeastern corner of Taiwan, which causes complicated structure of the Philippine Sea Plate at the western end of the Ryukyu subduction zone. Development of the active subduction and transition boundary near the western Ryukyu Arc is evaluated statistically by using displacements derived from GPS site data. The statistical model shows that the absolute displacement derived from GPS measurements of nearly 8 years indicates a maximum spatial variation of 0.625 m. Three trends are observed for such long-term progress, and use of linear regression also reveals quite good consistency between the data and statistic models. Such rate is also elevated following the trend development. Southeastern and nearly horizontal movement is suggested to the main development of for the site movements, it is likely related to the tensional activity adjacent to this boundary. [ABSTRACT FROM AUTHOR]

GPS observation indicates that the Fujian coastal region of China mainland, the region of Taiwan Strait and northern Taiwan island all show a generally homogenous horizontal motion with weak deformation. Historical earthquake record over more than 800 years and modern instrumental data reveal that there is potential seismic risk in and around Taiwan Strait region. After the National Seismic Zoning Map of China (2001) the expected seismic risk in northern part of the Taiwan Strait is lower than that in middle and southern part. The suggested northern route of the Taiwan Strait passage project seems to be relatively save seismically. [ABSTRACT FROM AUTHOR]