Article
Geochemistry & Geophysics
U. Meyer, M. Lasser, C. Dahle, C. Foerste, S. Behzadpour, I Koch, A. Jaeggi
Summary: The Combination Service for Time-variable Gravity fields (COST-G) operationally provides combinations of monthly Earth gravity field models derived from observations of the GRACE Follow-on (GRACE-FO) satellite mission. The combination has been further developed and extended to meet user requirements and achieve optimal signal-to-noise ratio. The quality of the combined gravity fields is assessed by noise content comparison and signal-to-noise ratio comparison with individual time-series.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2023)
Article
Environmental Sciences
Yara Mohajerani, David Shean, Anthony Arendt, Tyler C. Sutterley
Summary: Common mascon solutions provided by processing centers lack user control over placement and inversion assumptions. This study presents an automated approach to non-uniform global mascon solutions focused on user-specified regions, with few global degrees of freedom to minimize noise and leakage. Custom mascon solutions show improved regional trends and different seasonal variations compared to regularized solutions, allowing for optimized global solutions anywhere on Earth.
Article
Environmental Sciences
Lorant Foldvary, Karem Abdelmohsen, Bence Ambrus
Summary: The Gravity Recovery and Climate Experiment (GRACE) and its successor, the GRACE Follow-On (GRACE-FO) gravity satellite missions, have been providing monthly gravity field solutions for almost 20 years, enabling a unique opportunity to monitor large-scale mass variation processes. The method of determining the gravity anomaly time series from GRACE and GRACE-FO monthly solutions has been improved by considering the mass variations of the Caspian Sea. The gravity anomaly time series was then compared to water mass changes determined by considering variations in the salinity and temperature of seawater.
Article
Geochemistry & Geophysics
Bramha Dutt Vishwakarma, Martin Horwath, Andreas Groh, Jonathan L. Bamber
Summary: The Gravity Recovery and Climate Experiment (GRACE) measures gravitational potential anomalies that include the effects of present-day surface mass change (PDSMC) and glacial isostatic adjustment (GIA) on the solid Earth mass redistribution. However, different models for GIA can lead to different estimates for PDSMC in GRACE observations, highlighting the need for consistent treatment of GIA signals in these observations.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2022)
Article
Geochemistry & Geophysics
Qiujie Chen, Yunzhong Shen, Juergen Kusche, Wu Chen, Tianyi Chen, Xingfu Zhang
Summary: By proposing a new regularization method, high-resolution spherical harmonic solutions can be developed from GRACE Level-1B data, which have the potential to improve spatial resolution and signal strength. Through evaluating Tongji-RegGrace2019 and global/regional comparisons, it is found to exhibit high consistency with other GRACE solutions.
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH
(2021)
Article
Astronomy & Astrophysics
Bo Zhong, Xianpao Li, Jianli Chen, Qiong Li
Summary: To suppress correlated noise, a series of constrained monthly gravity field solutions named WHU-GRACE-GPD01s were developed from August 2002 to July 2016 using GRACE-based geopotential differences. The constrained solutions were estimated using Kaula regularization and their performance was validated against official SH solutions and mass concentration solutions. The results showed that the constrained solutions were comparable to the official SH solutions and can be used without postprocessing.
EARTH AND SPACE SCIENCE
(2023)
Article
Geochemistry & Geophysics
Jiashuang Jiao, Yuanjin Pan, Xiaohong Zhang, C. K. Shum, Yu Zhang, Hao Ding
Summary: By analyzing the satellite gravimetry data from GRACE and GRACE Follow-On, this study quantifies the nonlinear and spatially varying mass losses in the Antarctic ice sheet over the past two decades. The research reveals significant nonlinear mass change in seven regions along the coast of Antarctica, with diverse spatial patterns. The overall ice mass loss of the Antarctic ice sheet is estimated to be -101.3 +/- 18.0 Gt yr(-1), accelerating at a rate of -6.4 +/- 1.3 Gt yr(-2) from 2002 to 2021.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2023)
Article
Geochemistry & Geophysics
Khosro Ghobadi-Far, Shin-Chan Han, Christopher M. McCullough, David N. Wiese, Richard D. Ray, Jeanne Sauber, Linus Shihora, Henryk Dobslaw
Summary: This article examines the sensitivity of GRACE-FO LRI measurements to sub-monthly time-variable gravity signals and presents an alternative analysis method for studying short-term mass changes. By combining the LRI observations with other data and models, high-frequency oceanic mass variability and sub-monthly variations in surface water can be detected.
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH
(2022)
Article
Geochemistry & Geophysics
Jiashuang Jiao, Yuanjin Pan, Mirjam Bilker-Koivula, Markku Poutanen, Hao Ding
Summary: In this study, the authors attempt to evaluate the mass changes in Finland using GRACE observation. They propose a hybrid inversion strategy and optimize the parameters of the inversion methods to achieve accurate estimation. Additionally, the authors analyze the seasonal and interannual terrestrial water storage changes in Finland, highlighting the role of snow in the annual cycle and the presence of interannual oscillation.
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH
(2022)
Article
Geochemistry & Geophysics
Biao Yu, Wei You, Dong-Ming Fan, Yong Su, Zemede M. Nigatu
Summary: This paper focuses on analyzing the accuracy of temporal gravity field models derived from GRACE data using the variational equation integration approach. By comparing different data processing methods and models, a new time-series model with improved accuracy was developed. This alternative strategy shows potential for recovering temporal gravity field models from GRACE-type data.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2021)
Article
Geochemistry & Geophysics
O. Goux, J. Pfeffer, A. Blazquez, A. T. Weaver, M. Ablain
Summary: Over the past two decades, the GRACE and GRACE-FO missions have provided measurements of the gravity field, which can be used to infer mass variations on Earth's surface. However, these measurements are affected by correlated errors. In this study, a diffusion-based filter is developed to remove these errors and access the underlying geophysical signals. The diffusion filter allows for spatially variable filtering and preserves global indicators, resulting in better agreement with other estimation methods.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2023)
Article
Geochemistry & Geophysics
Tianyan Shi, Yoichi Fukuda, Koichiro Doi, Jun'ichi Okuno
Summary: In this study, qualitative analysis was performed using independent component analysis on the mass change patterns across Antarctica. The results showed that the continental-scale mass changes can be effectively separated into several spatial patterns, which may be dominated by different processes. The study also found that the time period of the analyzed data set has an impact on the results, with extreme events causing spatial and temporal changes.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2022)
Article
Geochemistry & Geophysics
Khosro Ghobadi-Far, Susanna Werth, Manoochehr Shirzaei, Bryant D. Loomis, Thorben Doehne, Matthias O. Willen, Martin Horwath
Summary: GRACE-D accelerometer data has shown significant bias jumps since one month after the launch of the GRACE Follow-On (GRACE-FO) satellites in May 2018, rendering them unusable for correcting GRACE-FO products. The GRACE-FO Science Data System (SDS) addressed this issue by replacing the problematic GRACE-D data with that of GRACE-C. Recently, an updated transplant method was implemented, which has improved GRACE-FO measurements at various levels, resulting in more accurate time-variable gravity and mass change observations.
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH
(2023)
Article
Geochemistry & Geophysics
Anthony Davila Alvarez, Aaron Knudtson, Unmil Patel, Joseph Gleason, Harold Hollis, Jose Sanjuan, Neil Doughty, Glenn McDaniel, Jennifer Lee, James Leitch, Stephen Bennett, Riccardo Bevilacqua, Guido Mueller, Robert Spero, Brent Ware, Peter Wass, David Wiese, John Ziemer, John W. Conklin
Summary: This article introduces a simplified gravitational reference sensor (S-GRS) for future Earth geodesy missions. The S-GRS is more sensitive than current accelerometers and can be used on microsatellites, reducing costs and improving the temporal resolution of gravity field maps.
JOURNAL OF GEODESY
(2022)
Article
Remote Sensing
Lun Pu, Dongming Fan, Wei You, Zhongshan Jiang, Xinchun Yang, Xiangyu Wan, Zemede M. Nigatu
Summary: This study developed an improved spatial domain filtering (ISDF) approach to extract mass flux variations in the southern Tibetan Plateau from GRACE/GRACE-FO data. Compared with traditional filtering methods, the ISDF method showed higher Nash-Sutcliffe efficiency, lower root mean squared error, and improved signal-to-noise ratio in simulated data. The results calculated using the ISDF method agreed well with the mean-mascon solution.
INTERNATIONAL JOURNAL OF REMOTE SENSING
(2022)
Article
Environmental Sciences
Shengyue Ji, Qianli Zheng, Duojie Weng, Wu Chen, Zhenjie Wang, Kaifei He
Summary: The study focuses on single-epoch ambiguity resolution on a small-scale CORS network, achieving a success rate of more than 90% based on numerical tests with baselines of 49 km and 35 km. The new differencing scheme developed explores the full potential of multi-frequency GNSS, providing benefits such as instant recovery after maintenance or when a new satellite rises for the network RTK service.
Article
Environmental Sciences
Ahmed Mansour, Wu Chen
Summary: This study proposes an enhanced indoor-outdoor environmental awareness service that achieves seamless navigation through automated handover mechanisms, utilizing low-power sensors for continuous detection tasks to ensure accurate and reliable indoor-outdoor detection while reducing power consumption.
Article
Engineering, Electrical & Electronic
Jingxian Wang, Duojie Weng, Xuanyu Qu, Weihao Ding, Wu Chen
Summary: In this study, a smartphone-based positioning method was proposed to continuously improve vehicle positioning performance in GNSS-degraded areas. The DeepOdo network, a combination of a convolutional neural network-gated recurrent unit (CNN-GRU) and deep learning odometry, was used to estimate vehicle velocity using IMU and barometer data. Raw sensor data was utilized to enhance robustness. The proposed method demonstrated significant improvements compared to traditional IMU methods in GNSS-denied areas.
IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT
(2023)
Article
Computer Science, Information Systems
Rui Sun, Linxia Fu, Qi Cheng, Kai-Wei Chiang, Wu Chen
Summary: This article proposes two resilient pseudorange error prediction and correction strategies to improve the GNSS positioning accuracy in complex urban environments. The models, based on random forest, consider factors such as carrier-to-noise density, satellite elevation angle, and local positional information. Experimental results show that the proposed models can significantly enhance the positioning accuracy compared to traditional methods without pseudorange error corrections.
IEEE INTERNET OF THINGS JOURNAL
(2023)
Article
Environmental Sciences
Pengfei Ou, Tao Lai, Shisheng Huang, Wu Chen, Duojie Weng
Summary: This article proposes a clustering partition method based on the normal vector of the atmospheric phase screen (APS), which can partition the complicated APS more reasonably and improve the accuracy of atmospheric phase correction (APC).
Article
Computer Science, Information Systems
Ahmed Mansour, Junhua Ye, Yaxin Li, Huan Luo, Jingxian Wang, Duojie Weng, Wu Chen
Summary: Smartphones have made a significant impact on human life by enabling constant mobility. This study introduces a framework called Everywhere that leverages crowdsourced data to develop a ubiquitous indoor positioning system (IPS). The framework addresses existing challenges in developing a ubiquitous IPS and proposes techniques such as inertial data selection criteria, leveraging GNSS data, deploying anchor nodes, and utilizing cumulative data densification. The framework aims to enhance online fingerprinting and promote the development of a ubiquitous IPS for buildings regardless of their surroundings.
IEEE INTERNET OF THINGS JOURNAL
(2023)
Article
Computer Science, Information Systems
Qihong Dan, Chunrui Yu, Shisheng Huang, Tao Lai, Haifeng Huang, Wu Chen, Duojie Weng
Summary: In this paper, a fast imaging algorithm tailored for ground-based MIMO-SAR data is proposed, which can be applied in both far-field and near-field scenarios. The algorithm uses geometric transformation to convert subaperture imaging results into the full aperture coordinate system, avoiding point-by-point interpolation calculation and reducing computational cost. Simulations and experiments show that the algorithm achieves high-precision focusing imaging and significantly improves operation efficiency compared to interpolation-based algorithms.
Article
Environmental Sciences
Bingbo Cui, Wu Chen, Duojie Weng, Xinhua Wei, Zeyu Sun, Yan Zhao, Yufei Liu
Summary: Integrating global navigation satellite systems (GNSSs) with inertial navigation systems (INSs) is recognized as an ideal solution for autonomous vehicle navigation. However, GNSSs are prone to disturbances and signal blocking, which degrade the performance of GNSS/INSs in the presence of measurement outliers. This paper proposes a robust observability-constrained resampling-free cubature Kalman filter (ROCRCKF) that improves the adaptivity and robustness of the filter by suppressing time-varying measurement outliers. Experimental results show that the ROCRCKF outperforms the existing method, reducing heading error and average root mean square error of position.
Article
Environmental Sciences
San Jiang, Junhuan Liu, Yaxin Li, Duojie Weng, Wu Chen
Summary: This study proposes a reliable feature matching algorithm for spherical images using a combination of local geometric rectification and CNN learned descriptor. Experimental results demonstrate that the algorithm efficiently reduces geometric distortions and provides reliable feature matches for complete reconstruction.
Article
Geochemistry & Geophysics
Zhenyu He, Wu Chen, Yang Yang, Duojie Weng, Ning Cao
Summary: In this article, a two-stage imaging processing method is proposed to obtain the synthetic aperture radar (SAR) image of a moving ship by utilizing the target's translational motion over a long observation time. The first stage confirms the presence of the target by a long-time moving target detection (MTD) processing technique. In the second stage, the target velocity is accurately estimated by analyzing the Doppler history of the target signal in the slow-time domain using a short-time Fourier transform and modified random sample consensus.
IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING
(2023)
Article
Automation & Control Systems
Shengyang Chen, Yurong Feng, Chih-Yung Wen, Yajing Zou, Wu Chen
Summary: In this article, a stereo visual inertial pose estimation method based on feedforward and feedbacks is presented. The proposed method achieves fast processing by storing only the most recent pose and measurements. It introduces gradient decreased feedback, roll-pitch feedforward, and bias estimation feedback to fuse vision and inertial measurements. The system, called FVIS, demonstrates high accuracy and robustness compared to existing visual inertial SLAM approaches. FVIS has been implemented and tested on a UAV platform and the source code is publicly available.
IEEE-ASME TRANSACTIONS ON MECHATRONICS
(2023)
Article
Engineering, Civil
Tianxia Liu, Bofeng Li, Guang'e Chen, Ling Yang, Jing Qiao, Wu Chen
Summary: This paper investigates the localization problem of autonomous vehicles in complex indoor-outdoor environments and proposes a tightly coupled integration algorithm of GNSS RTK, UWB, and VIO. Experimental results show that the proposed algorithm achieves high positioning accuracy and reliability in indoor-outdoor obscured environments.
IEEE TRANSACTIONS ON INTELLIGENT TRANSPORTATION SYSTEMS
(2023)
Article
Geochemistry & Geophysics
Basem Elsaka, Olivier Francis, Jurgen Kusche
Summary: This paper reports a study on the estimation of the calibration factor for a superconducting gravimeter. The results show that tidal analysis can be used to transfer the calibration factor between different gravimeters. Additionally, the study finds specific behavioral patterns in the instrumental drift of the iGrav-043.
PURE AND APPLIED GEOPHYSICS
(2023)
Article
Geochemistry & Geophysics
San Jiang, Qingquan Li, Wanshou Jiang, Wu Chen
Summary: This article proposes an algorithm for extracting the global model for cluster merging in unmanned aerial vehicle (UAV) image orientation. It also presents a parallel ISfM solution to achieve efficient and accurate image orientation. The experimental results demonstrate significant improvements in efficiency and orientation accuracy.
IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING
(2022)
Article
Geochemistry & Geophysics
Zhenyu He, Yang Yang, Wu Chen, Duojie Weng
Summary: This article proposes a joint target detection and range resolution improvement method for GNSS-based passive radar, achieving efficient range resolution enhancement through long-time integration technique and incremental Wiener filter.
IEEE GEOSCIENCE AND REMOTE SENSING LETTERS
(2022)