Pub Date : 2025-12-16DOI: 10.1007/s00190-025-02024-7
Thunendran Periyandy, Michael Bevis
{"title":"The gravitational potential inside, on, and outside of a homogeneous tetrahedron","authors":"Thunendran Periyandy, Michael Bevis","doi":"10.1007/s00190-025-02024-7","DOIUrl":"https://doi.org/10.1007/s00190-025-02024-7","url":null,"abstract":"","PeriodicalId":54822,"journal":{"name":"Journal of Geodesy","volume":"11 1","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145770606","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-28DOI: 10.1007/s00190-025-02021-w
Qiqi Shi, Yonghong Zhou, Jianli Chen, Xueqing Xu
Geophysical sources and processes that excite the Earth’s Chandler wobble (CW) have long been debated. Significant discrepancies remain at times between geophysical fluid models, especially regarding inaccurate hydrological and cryospheric estimates, and observed CW series. Recently, the CW experienced anomalous behavior after 2015, with a disappearance and a re-excitation. Understanding hydrological and cryospheric effects on the CW and their contributions to this anomaly requires urgent investigation. Utilizing the Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow-On (GFO) measurements, we reconstruct the CW series contributed from the hydrology and cryosphere for the GRACE period (April 2002 to December 2015) and GFO period (June 2018 to December 2024), respectively. We find that GRACE/GFO measurements can capture more accurate hydrological and cryospheric forcing CW signals than models. For the first time, our reconstructed results successfully account for the recent observed disappearing and re-excited CW phenomenon. Considering global mass conservation associated with barystatic sea-level changes, the GRACE/GFO-derived hydrological and cryospheric effects agree well with geodetic CW observations. The absence of hydrological and cryospheric contributions on the reconstructed CW would lead to the unmanifested CW re-excitation phenomenon. Additionally, the relative contributions of the hydrology and cryosphere to CW amplitudes exhibit temporal variability, with ratios of approximately 3 to 1 and 2 to 1 during the GRACE and GFO periods, respectively. These findings improve our understanding of the Earth’s rotational dynamics under climate change in relation to the effects of hydrological and cryospheric processes.
{"title":"Recent disappearing and re-excited Earth’s Chandler wobble: contributions from GRACE/GFO hydrological and cryospheric mass changes","authors":"Qiqi Shi, Yonghong Zhou, Jianli Chen, Xueqing Xu","doi":"10.1007/s00190-025-02021-w","DOIUrl":"https://doi.org/10.1007/s00190-025-02021-w","url":null,"abstract":"Geophysical sources and processes that excite the Earth’s Chandler wobble (CW) have long been debated. Significant discrepancies remain at times between geophysical fluid models, especially regarding inaccurate hydrological and cryospheric estimates, and observed CW series. Recently, the CW experienced anomalous behavior after 2015, with a disappearance and a re-excitation. Understanding hydrological and cryospheric effects on the CW and their contributions to this anomaly requires urgent investigation. Utilizing the Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow-On (GFO) measurements, we reconstruct the CW series contributed from the hydrology and cryosphere for the GRACE period (April 2002 to December 2015) and GFO period (June 2018 to December 2024), respectively. We find that GRACE/GFO measurements can capture more accurate hydrological and cryospheric forcing CW signals than models. For the first time, our reconstructed results successfully account for the recent observed disappearing and re-excited CW phenomenon. Considering global mass conservation associated with barystatic sea-level changes, the GRACE/GFO-derived hydrological and cryospheric effects agree well with geodetic CW observations. The absence of hydrological and cryospheric contributions on the reconstructed CW would lead to the unmanifested CW re-excitation phenomenon. Additionally, the relative contributions of the hydrology and cryosphere to CW amplitudes exhibit temporal variability, with ratios of approximately 3 to 1 and 2 to 1 during the GRACE and GFO periods, respectively. These findings improve our understanding of the Earth’s rotational dynamics under climate change in relation to the effects of hydrological and cryospheric processes.","PeriodicalId":54822,"journal":{"name":"Journal of Geodesy","volume":"14 1","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-11-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145611054","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-28DOI: 10.1007/s00190-025-02020-x
Hans Daniel Platz
Traditionally, global navigation satellite system (GNSS) observations in precise point positioning were processed using geometric ionosphere-free (GIF) code and phase linear combinations (LC). With multi-frequency observations of modernized GNSS, the processing of undifferenced and uncombined (UDUC) observations has gained popularity, often attributed to its increased flexibility and generality. Building on the theoretical foundation of UDUC processing, this work derives an equivalent LC-based network processing approach that maintains the full generality of the UDUC approach while offering some practical advantages. The approach makes use of the following types of LCs: (1) geometry-free and ionosphere free (GFIF), (2) geometric ionosphere-free (GIF), and (3) ionospheric geometry-free (IGF). When processing the GFIF LCs, biases and ambiguities can be estimated. The GFIF model enables compact modeling by reducing continuous observation arcs to a single observation and supports (extra-) wide-lane ambiguity resolution. To obtain the ionosphere-free model, i.e., an equivalent reformulation of the UDUC approach where epoch-wise and line of sight specific ionospheric delays are assumed, exactly one GIF LC per line-of-sight and epoch is added to the GFIF LCs. To obtain the geometry-free model, commonly used for ionospheric modeling, exactly one IGF LC is added to the GFIF LCs per line-of-sight and epoch. Adding both the GIF and IGF LCs to the GFIF LCs yields an exact reformulation of the UDUC with no implicit assumptions regarding ionospheric or geometric parameters. Finally, a brief runtime analysis of LC-based models shows case-dependent efficiency gains over UDUC implementations.
{"title":"Generalizing linear combination-based GNSS PPP-RTK network processing: geometry-free, ionosphere-free, and geometry- and ionosphere-free","authors":"Hans Daniel Platz","doi":"10.1007/s00190-025-02020-x","DOIUrl":"https://doi.org/10.1007/s00190-025-02020-x","url":null,"abstract":"Traditionally, global navigation satellite system (GNSS) observations in precise point positioning were processed using geometric ionosphere-free (GIF) code and phase linear combinations (LC). With multi-frequency observations of modernized GNSS, the processing of undifferenced and uncombined (UDUC) observations has gained popularity, often attributed to its increased flexibility and generality. Building on the theoretical foundation of UDUC processing, this work derives an equivalent LC-based network processing approach that maintains the full generality of the UDUC approach while offering some practical advantages. The approach makes use of the following types of LCs: (1) geometry-free and ionosphere free (GFIF), (2) geometric ionosphere-free (GIF), and (3) ionospheric geometry-free (IGF). When processing the GFIF LCs, biases and ambiguities can be estimated. The GFIF model enables compact modeling by reducing continuous observation arcs to a single observation and supports (extra-) wide-lane ambiguity resolution. To obtain the ionosphere-free model, i.e., an equivalent reformulation of the UDUC approach where epoch-wise and line of sight specific ionospheric delays are assumed, exactly one GIF LC per line-of-sight and epoch is added to the GFIF LCs. To obtain the geometry-free model, commonly used for ionospheric modeling, exactly one IGF LC is added to the GFIF LCs per line-of-sight and epoch. Adding both the GIF and IGF LCs to the GFIF LCs yields an exact reformulation of the UDUC with no implicit assumptions regarding ionospheric or geometric parameters. Finally, a brief runtime analysis of LC-based models shows case-dependent efficiency gains over UDUC implementations.","PeriodicalId":54822,"journal":{"name":"Journal of Geodesy","volume":"29 1","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-11-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145611055","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-25DOI: 10.1007/s00190-025-02018-5
Agustín R. Gómez, Claudia N. Tocho, Ezequiel D. Antokoletz, Sergio R. Cimbaro
{"title":"Local quasigeoid modeling at Argentinean stations of the International Height Reference Frame (IHRF)","authors":"Agustín R. Gómez, Claudia N. Tocho, Ezequiel D. Antokoletz, Sergio R. Cimbaro","doi":"10.1007/s00190-025-02018-5","DOIUrl":"https://doi.org/10.1007/s00190-025-02018-5","url":null,"abstract":"","PeriodicalId":54822,"journal":{"name":"Journal of Geodesy","volume":"107 1","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145593536","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-11DOI: 10.1007/s00190-025-02009-6
Janusz Bogusz, Paul Rebischung, Anna Klos
A comparison of the three-dimensional annual motions of the global Navigation satellite system (GNSS) stations in two different solutions – the latest reprocessing campaign of the International GNSS Service (IGS), and the station position time series provided by the Nevada Geodetic Laboratory (NGL) – reveals large-scale differences with amplitudes of about 1 mm in horizontal and 3 mm in vertical. We show that these differences are largely explained, in the vertical component, by differences between the alignment strategies of both solutions to the terrestrial reference frame. Further comparisons with the annual displacements predicted by a global loading deformation model suggest that true annual station motions are less subject to aliasing, hence better preserved with the IGS alignment strategy. Considering these results, we urge providers of GNSS station position time series to take measures to minimize the aliasing of geophysical station motions that occur when aligning their daily station position estimates to the reference frame and propose different such measures.
{"title":"Impact of alignment strategy to the reference frame on the 3D annual station motions from different GNSS solutions","authors":"Janusz Bogusz, Paul Rebischung, Anna Klos","doi":"10.1007/s00190-025-02009-6","DOIUrl":"https://doi.org/10.1007/s00190-025-02009-6","url":null,"abstract":"A comparison of the three-dimensional annual motions of the global Navigation satellite system (GNSS) stations in two different solutions – the latest reprocessing campaign of the International GNSS Service (IGS), and the station position time series provided by the Nevada Geodetic Laboratory (NGL) – reveals large-scale differences with amplitudes of about 1 mm in horizontal and 3 mm in vertical. We show that these differences are largely explained, in the vertical component, by differences between the alignment strategies of both solutions to the terrestrial reference frame. Further comparisons with the annual displacements predicted by a global loading deformation model suggest that true annual station motions are less subject to aliasing, hence better preserved with the IGS alignment strategy. Considering these results, we urge providers of GNSS station position time series to take measures to minimize the aliasing of geophysical station motions that occur when aligning their daily station position estimates to the reference frame and propose different such measures.","PeriodicalId":54822,"journal":{"name":"Journal of Geodesy","volume":"164 1","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145485567","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-06DOI: 10.1007/s00190-025-02014-9
Linshan Zhong, Jiancheng Li, Xiancai Zou
{"title":"Analytical solution of tesseroid gravitational effect with linear approximation I: under spherical polar coordinates","authors":"Linshan Zhong, Jiancheng Li, Xiancai Zou","doi":"10.1007/s00190-025-02014-9","DOIUrl":"https://doi.org/10.1007/s00190-025-02014-9","url":null,"abstract":"","PeriodicalId":54822,"journal":{"name":"Journal of Geodesy","volume":"9 1","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-11-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145448351","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-30DOI: 10.1007/s00190-025-02005-w
Radosław Zajdel, Gustavo Mansur, Pierre Sakic, Paul Rebischung, Andreas Brack, Benjamin Männel, Jan Douša
The International GNSS Service (IGS) requires advanced multi-GNSS orbit combination strategies to replace current GPS/GLONASS-focused operations with consistent products covering GPS, GLONASS, Galileo, and BDS. We developed an enhanced orbit combination methodology using a modified Förstner Variance Component Estimation (VCE) scheme that optimizes weighting strategies through data clustering approaches, including individual satellite weighting, satellite-type grouping, and machine-learning-generated clusters. Our novel approach incorporates a priori knowledge from Satellite Laser Ranging (SLR) orbit validations and sequential weight information from previous combinations to refine Analysis Center (AC) weights. Sequential weight estimation significantly reduces day boundary orbit misclosures and stabilizes temporal AC weight variability. The combined solutions demonstrate exceptional inter-consistency with RMS values below 3–5 mm for GPS and Galileo, while GLONASS and BDS show higher variability (10–15 mm), highlighting the importance of satellite grouping strategies. Intermediate grouping approaches based on IGS metadata or hierarchical clustering provide optimal balance between constellation-level oversimplification and satellite-specific day-to-day variability. SLR-based knowledge incorporation offers targeted improvements, particularly for challenging high and low β angle conditions, demonstrating the effectiveness of external validation in multi-GNSS orbit combination.
{"title":"Advancing multi-GNSS orbit combination in the variance component estimation framework","authors":"Radosław Zajdel, Gustavo Mansur, Pierre Sakic, Paul Rebischung, Andreas Brack, Benjamin Männel, Jan Douša","doi":"10.1007/s00190-025-02005-w","DOIUrl":"https://doi.org/10.1007/s00190-025-02005-w","url":null,"abstract":"The International GNSS Service (IGS) requires advanced multi-GNSS orbit combination strategies to replace current GPS/GLONASS-focused operations with consistent products covering GPS, GLONASS, Galileo, and BDS. We developed an enhanced orbit combination methodology using a modified Förstner Variance Component Estimation (VCE) scheme that optimizes weighting strategies through data clustering approaches, including individual satellite weighting, satellite-type grouping, and machine-learning-generated clusters. Our novel approach incorporates a priori knowledge from Satellite Laser Ranging (SLR) orbit validations and sequential weight information from previous combinations to refine Analysis Center (AC) weights. Sequential weight estimation significantly reduces day boundary orbit misclosures and stabilizes temporal AC weight variability. The combined solutions demonstrate exceptional inter-consistency with RMS values below 3–5 mm for GPS and Galileo, while GLONASS and BDS show higher variability (10–15 mm), highlighting the importance of satellite grouping strategies. Intermediate grouping approaches based on IGS metadata or hierarchical clustering provide optimal balance between constellation-level oversimplification and satellite-specific day-to-day variability. SLR-based knowledge incorporation offers targeted improvements, particularly for challenging high and low β angle conditions, demonstrating the effectiveness of external validation in multi-GNSS orbit combination.","PeriodicalId":54822,"journal":{"name":"Journal of Geodesy","volume":"19 1","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145404170","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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