Abstract Digital Elevation Models (DEMs) are real-world geographical databases that are important in studying many Earth related topics. Because the vertical accuracy of global DEMs differs across regions due to various reasons, acquiring reliable heights for a region using global height models is crucial. The objective of this study is to compare and assess the most reliable global height model for Sri Lanka. The official height system in Sri Lanka is the Mean Sea Level (MSL) based orthometric height system. In this study, the quality of ASTER, SRTM, NASADEM, MERIT, and DEMs compiled from digitized contour data of Sri Lanka was evaluated using the known heights of the Fundamental Benchmarks (FBMs) of Sri Lanka. In addition, recently published high-resolution Global Geopotential Models (GGMs) were used for the accuracy assessments of gravity related quantities computed using DEMs. The SGG-UGM-2 GGM, which showed the minimum STD and RMSE of geoid undulation difference was found as the best fit GGM over Sri Lanka. It was found that the NASADEM at its highest resolution, which gave the lowest RMSE of 2.954 m was the best global DEM for Sri Lanka.
{"title":"Comparison of different global DTMs and GGMs over Sri Lanka","authors":"Weeramuni Javana Praboni De Silva, H. Prasanna","doi":"10.1515/jag-2022-0026","DOIUrl":"https://doi.org/10.1515/jag-2022-0026","url":null,"abstract":"Abstract Digital Elevation Models (DEMs) are real-world geographical databases that are important in studying many Earth related topics. Because the vertical accuracy of global DEMs differs across regions due to various reasons, acquiring reliable heights for a region using global height models is crucial. The objective of this study is to compare and assess the most reliable global height model for Sri Lanka. The official height system in Sri Lanka is the Mean Sea Level (MSL) based orthometric height system. In this study, the quality of ASTER, SRTM, NASADEM, MERIT, and DEMs compiled from digitized contour data of Sri Lanka was evaluated using the known heights of the Fundamental Benchmarks (FBMs) of Sri Lanka. In addition, recently published high-resolution Global Geopotential Models (GGMs) were used for the accuracy assessments of gravity related quantities computed using DEMs. The SGG-UGM-2 GGM, which showed the minimum STD and RMSE of geoid undulation difference was found as the best fit GGM over Sri Lanka. It was found that the NASADEM at its highest resolution, which gave the lowest RMSE of 2.954 m was the best global DEM for Sri Lanka.","PeriodicalId":45494,"journal":{"name":"Journal of Applied Geodesy","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2022-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42787965","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Chuandong Zhu, Liuqing Pang, Didi Sheng, Jialiang Huang, Jinwu Li
Abstract The gravitational effects of ocean tide loading, which are one of the main factors affecting gravity measurements, consist of three components: (1) direct attraction from the tidal water masses, (2) radial displacement of the observing station due to the tidal load, and (3) internal redistribution of masses due to crustal deformation. In this study, software for gravitational effects of ocean tide loading was developed by evaluating a convolution integral between the ocean tide model and Green’s functions that describe the response of the Earth to tide loading. The effects of three-dimensional station coordinates, computational grid patterns, ocean tide models, Green’s functions, coastline, and local tide gauge were comprehensively considered in the programming process. Using a larger number of high-precision coastlines, ocean tide models, and Green’s functions, the reliability and applicability of the software were analyzed at coastal stations in the China Earthquake Gravity Network. The software can provide the amplitude and phase for ocean tide loading and produce a predicted gravity time series. The results can effectively reveal the variation characteristics of ocean tide loading in space and time. The computational gravitational effects of ocean tide loading were compared and analyzed for different ocean tide models and Green’s functions. The results show that different ocean tide models and Green’s functions have certain effects on the calculated values of loading gravity effects. Furthermore, a higher-precision local ocean tide model, digital elevation model, and local tidal gauge record can be further imported into our software to improve the accuracy of loading gravity effects in the global and local zones. The software is easy to operate and can provide a comprehensive platform for correcting the gravitational effects of ocean tide loading at stations in the China Earthquake Gravity Network.
{"title":"Modeling the gravitational effects of ocean tide loading at coastal stations in the China earthquake gravity network based on GOTL software","authors":"Chuandong Zhu, Liuqing Pang, Didi Sheng, Jialiang Huang, Jinwu Li","doi":"10.1515/jag-2022-0023","DOIUrl":"https://doi.org/10.1515/jag-2022-0023","url":null,"abstract":"Abstract The gravitational effects of ocean tide loading, which are one of the main factors affecting gravity measurements, consist of three components: (1) direct attraction from the tidal water masses, (2) radial displacement of the observing station due to the tidal load, and (3) internal redistribution of masses due to crustal deformation. In this study, software for gravitational effects of ocean tide loading was developed by evaluating a convolution integral between the ocean tide model and Green’s functions that describe the response of the Earth to tide loading. The effects of three-dimensional station coordinates, computational grid patterns, ocean tide models, Green’s functions, coastline, and local tide gauge were comprehensively considered in the programming process. Using a larger number of high-precision coastlines, ocean tide models, and Green’s functions, the reliability and applicability of the software were analyzed at coastal stations in the China Earthquake Gravity Network. The software can provide the amplitude and phase for ocean tide loading and produce a predicted gravity time series. The results can effectively reveal the variation characteristics of ocean tide loading in space and time. The computational gravitational effects of ocean tide loading were compared and analyzed for different ocean tide models and Green’s functions. The results show that different ocean tide models and Green’s functions have certain effects on the calculated values of loading gravity effects. Furthermore, a higher-precision local ocean tide model, digital elevation model, and local tidal gauge record can be further imported into our software to improve the accuracy of loading gravity effects in the global and local zones. The software is easy to operate and can provide a comprehensive platform for correcting the gravitational effects of ocean tide loading at stations in the China Earthquake Gravity Network.","PeriodicalId":45494,"journal":{"name":"Journal of Applied Geodesy","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2022-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41695527","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract Logistic processes of construction sites are transferred into virtual and full 3D environments to increase the interoperability for all project partners. These digital twins are emerging for the construction process of modern building processes and are already designed to be used for the operation of the building afterwards. In structural health monitoring (SHM) the sensor installations are also designed to monitor the structure over its whole lifespan. Therefore, the embedding process and the operation of the sensor systems and the Building Information Modelling (BIM) have overlapping long-term goals. Beside these 3D software advances in civil engineering, the working environments in the field of geodesy still follow more established approaches. In many cases using only 2D CAD plans and on-site visits at the existing structure are best practice for the design of geodetic monitoring installations. This paper describes the improvement of the concept creation of permanent monitoring systems with geodetic total stations in an interactive virtual 3D environment. The simulated instruments are behaving according to their specification data and are linked with a physics engine to automatically detect common problems in a network design like obstructed line of sights, disadvantageous incidence angles at the targets or automatic aiming issues due to multiple targets in the field of view. Furthermore, the Virtual Reality (VR) technology is introduced as a user interface for a virtual 3D planning environment. The functionality of the developed VR application is tested in a real-life use case for the feasibility study of the automatic monitoring of a railway tunnel.
{"title":"3D concept creation of permanent geodetic monitoring installations and the a priori assessment of systematic effects using Virtual Reality","authors":"P. Bauer, W. Lienhart","doi":"10.1515/jag-2022-0020","DOIUrl":"https://doi.org/10.1515/jag-2022-0020","url":null,"abstract":"Abstract Logistic processes of construction sites are transferred into virtual and full 3D environments to increase the interoperability for all project partners. These digital twins are emerging for the construction process of modern building processes and are already designed to be used for the operation of the building afterwards. In structural health monitoring (SHM) the sensor installations are also designed to monitor the structure over its whole lifespan. Therefore, the embedding process and the operation of the sensor systems and the Building Information Modelling (BIM) have overlapping long-term goals. Beside these 3D software advances in civil engineering, the working environments in the field of geodesy still follow more established approaches. In many cases using only 2D CAD plans and on-site visits at the existing structure are best practice for the design of geodetic monitoring installations. This paper describes the improvement of the concept creation of permanent monitoring systems with geodetic total stations in an interactive virtual 3D environment. The simulated instruments are behaving according to their specification data and are linked with a physics engine to automatically detect common problems in a network design like obstructed line of sights, disadvantageous incidence angles at the targets or automatic aiming issues due to multiple targets in the field of view. Furthermore, the Virtual Reality (VR) technology is introduced as a user interface for a virtual 3D planning environment. The functionality of the developed VR application is tested in a real-life use case for the feasibility study of the automatic monitoring of a railway tunnel.","PeriodicalId":45494,"journal":{"name":"Journal of Applied Geodesy","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2022-08-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41662550","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract The Hong Kong Principal Datum (HKPD) is the currently adopted official geodetic vertical datum at the Hong Kong territories. The HKPD is practically realized by heights of levelling benchmarks. The HKPD heights are, however, neither normal nor orthometric. The reason is that heights of levelling benchmarks were determined from precise levelling measurements, but without involving gravity observations along levelling lines. To reduce systematic errors due to disregarding the gravity information along levelling lines, we used terrestrial and marine gravity data to interpolate gravity values at levelling benchmarks in order to compute and apply the orthometric correction to measured levelling height differences. Our results demonstrate the importance of incorporating the gravity information even for a relatively small region but characterized by a rough topography with heights of levelling benchmarks exceeding several hundreds of meters. According to our estimates, the orthometric correction reaches (and even slightly exceeds) ±2 cm, with maxima along levelling lines crossing mountain chains.
{"title":"The use of gravity data to determine orthometric heights at the Hong Kong territories","authors":"Albertini Nsiah Ababio, R. Tenzer","doi":"10.1515/jag-2022-0012","DOIUrl":"https://doi.org/10.1515/jag-2022-0012","url":null,"abstract":"Abstract The Hong Kong Principal Datum (HKPD) is the currently adopted official geodetic vertical datum at the Hong Kong territories. The HKPD is practically realized by heights of levelling benchmarks. The HKPD heights are, however, neither normal nor orthometric. The reason is that heights of levelling benchmarks were determined from precise levelling measurements, but without involving gravity observations along levelling lines. To reduce systematic errors due to disregarding the gravity information along levelling lines, we used terrestrial and marine gravity data to interpolate gravity values at levelling benchmarks in order to compute and apply the orthometric correction to measured levelling height differences. Our results demonstrate the importance of incorporating the gravity information even for a relatively small region but characterized by a rough topography with heights of levelling benchmarks exceeding several hundreds of meters. According to our estimates, the orthometric correction reaches (and even slightly exceeds) ±2 cm, with maxima along levelling lines crossing mountain chains.","PeriodicalId":45494,"journal":{"name":"Journal of Applied Geodesy","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2022-08-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47970844","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. Zaki, Yasmeen Elberry, Hamad Al-Ajami, M. Rabah, Rasha Abd El Ghany
Abstract Determining a precise local geoid is particularly important for converting the Global Navigation Satellite System (GNSS) heights to orthometric heights. The geometric method for computing the geoid has been extensively used for a comparatively small region, which, in some points, interpolates geoid heights based on GNSS-derived heights and levelling heights. Several considerations should be considered when using the geometric method to increase the accuracy of a local geoid. Kuwait is used as a test area in this paper to investigate several features of the geometric method. The achievable precision is one of these aspects, the role of the interpolation method, global geopotential models, and the influence of the topographic effect. The accuracy of the local geoid can be substantially enhanced by integrating a geopotential model with a digital terrain model of the research region. It is possible to get a precision of 2–3 cm.
{"title":"Determination of local geometric geoid model for Kuwait","authors":"A. Zaki, Yasmeen Elberry, Hamad Al-Ajami, M. Rabah, Rasha Abd El Ghany","doi":"10.1515/jag-2022-0017","DOIUrl":"https://doi.org/10.1515/jag-2022-0017","url":null,"abstract":"Abstract Determining a precise local geoid is particularly important for converting the Global Navigation Satellite System (GNSS) heights to orthometric heights. The geometric method for computing the geoid has been extensively used for a comparatively small region, which, in some points, interpolates geoid heights based on GNSS-derived heights and levelling heights. Several considerations should be considered when using the geometric method to increase the accuracy of a local geoid. Kuwait is used as a test area in this paper to investigate several features of the geometric method. The achievable precision is one of these aspects, the role of the interpolation method, global geopotential models, and the influence of the topographic effect. The accuracy of the local geoid can be substantially enhanced by integrating a geopotential model with a digital terrain model of the research region. It is possible to get a precision of 2–3 cm.","PeriodicalId":45494,"journal":{"name":"Journal of Applied Geodesy","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2022-07-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46105895","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract It is well-known that the solution domain has a discrete character in precise satellite positioning because of the integer nature of ambiguities. Therefore, in addition to the classic least squares estimation, the search procedure has to be employed in the computation process to obtain the so-called ‘fixed solution.’ The article’s subject is to improve the search procedure conducted in the coordinate domain. The reduction process is to transform the original math model into an equivalent one in the sense of obtaining the same solution. The reduction aims to increase the efficiency of searching for some parameters, i. e., integer ambiguities. The article presents the concept of employing the reduction procedure to the computation process of precise positioning based on the ambiguity function. The transformation matrix for the reduction is based on the well-known integer decorrelation procedure. Numerical experiment results display a positive impact of the reduction process on the search procedure efficiency. This positive impact is manifested by a dramatic decrease in the number of candidates needed to test all admissible solutions inside the search region. The percentage decrease in that magnitude is at least 50 % for all session lengths and achieves a maximum value of over 75 % for the 10-minute session. Computational time decreases by over 40 % while short sessions are processed. There is no improvement for sessions longer than 15 minutes, but, as explained in the paper, there is no need to improve that magnitude in such cases.
{"title":"Reduction as an improvement of a precise satellite positioning based on an ambiguity function","authors":"S. Cellmer, K. Nowel, Artur Fischer","doi":"10.1515/jag-2022-0005","DOIUrl":"https://doi.org/10.1515/jag-2022-0005","url":null,"abstract":"Abstract It is well-known that the solution domain has a discrete character in precise satellite positioning because of the integer nature of ambiguities. Therefore, in addition to the classic least squares estimation, the search procedure has to be employed in the computation process to obtain the so-called ‘fixed solution.’ The article’s subject is to improve the search procedure conducted in the coordinate domain. The reduction process is to transform the original math model into an equivalent one in the sense of obtaining the same solution. The reduction aims to increase the efficiency of searching for some parameters, i. e., integer ambiguities. The article presents the concept of employing the reduction procedure to the computation process of precise positioning based on the ambiguity function. The transformation matrix for the reduction is based on the well-known integer decorrelation procedure. Numerical experiment results display a positive impact of the reduction process on the search procedure efficiency. This positive impact is manifested by a dramatic decrease in the number of candidates needed to test all admissible solutions inside the search region. The percentage decrease in that magnitude is at least 50 % for all session lengths and achieves a maximum value of over 75 % for the 10-minute session. Computational time decreases by over 40 % while short sessions are processed. There is no improvement for sessions longer than 15 minutes, but, as explained in the paper, there is no need to improve that magnitude in such cases.","PeriodicalId":45494,"journal":{"name":"Journal of Applied Geodesy","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2022-06-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42426165","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. Zaki, Ebtehal Younes, Osama El Ghrabawy, Islam Azab, M. Rabah
Abstract In the current study, the accuracy of airborne gravity data is evaluated based on the most recent Global Geopotential Models (GGM) and terrestrial gravity data to find out to what extent these data are acceptable to be used in multi-applications (e. g., geodesy and geophysics). To achieve this goal, the remove-compute-restore (RCR) scheme, upward, and downward continuation operational methods (least square collocation and fast Fourier transform procedures) are applied. The airborne gravity data had been acquired by the Egyptian Nuclear Material Authority (ENMA) in the central-western desert for geological applications. Firstly, three GGMs models (EGM2008, EIGEN-6C4 and XGM2019e up to various degrees) are used to compare with the free-air airborne gravity anomaly, The EGM2008 model up to degree 720 produces the smallest mean and STD difference values with 2.59 and 3.07 mGal, respectively. The terrestrial gravity data are compared with the airborne gravity anomaly at both flight and ground levels. In-flight level, the terrestrial gravity data are upward continued to the flight level and compared with the airborne gravity anomaly. The statistical results show that the mean and STD differences are about 4.2 and 0.75 mGal, respectively. While in-ground level evaluation, two operational techniques are used to downward continue the airborne gravity data (Fast Fourier Transform (FFT) and Least Squares Collocation (LSC)). The combined Satellite model EGM2008 up to degree 720 and SRTM 30 m are used to remove and restore the long and short-wavelength information. It is observed that the collocation gives better statistical results than FFT with mean and STD difference values are about 3.13 and 1.13 and mGal, respectively.
{"title":"Accuracy assessment of available airborne gravity data in the central western desert of Egypt","authors":"A. Zaki, Ebtehal Younes, Osama El Ghrabawy, Islam Azab, M. Rabah","doi":"10.1515/jag-2021-0066","DOIUrl":"https://doi.org/10.1515/jag-2021-0066","url":null,"abstract":"Abstract In the current study, the accuracy of airborne gravity data is evaluated based on the most recent Global Geopotential Models (GGM) and terrestrial gravity data to find out to what extent these data are acceptable to be used in multi-applications (e. g., geodesy and geophysics). To achieve this goal, the remove-compute-restore (RCR) scheme, upward, and downward continuation operational methods (least square collocation and fast Fourier transform procedures) are applied. The airborne gravity data had been acquired by the Egyptian Nuclear Material Authority (ENMA) in the central-western desert for geological applications. Firstly, three GGMs models (EGM2008, EIGEN-6C4 and XGM2019e up to various degrees) are used to compare with the free-air airborne gravity anomaly, The EGM2008 model up to degree 720 produces the smallest mean and STD difference values with 2.59 and 3.07 mGal, respectively. The terrestrial gravity data are compared with the airborne gravity anomaly at both flight and ground levels. In-flight level, the terrestrial gravity data are upward continued to the flight level and compared with the airborne gravity anomaly. The statistical results show that the mean and STD differences are about 4.2 and 0.75 mGal, respectively. While in-ground level evaluation, two operational techniques are used to downward continue the airborne gravity data (Fast Fourier Transform (FFT) and Least Squares Collocation (LSC)). The combined Satellite model EGM2008 up to degree 720 and SRTM 30 m are used to remove and restore the long and short-wavelength information. It is observed that the collocation gives better statistical results than FFT with mean and STD difference values are about 3.13 and 1.13 and mGal, respectively.","PeriodicalId":45494,"journal":{"name":"Journal of Applied Geodesy","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2022-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48259582","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract Based on multidimensional equivalent water height (EWH) time series in the Qinghai-Tibetan Plateau recovered from GRACE data, rotated multi-channel singular spectrum analysis (RMSSA) was employed to separate and reconstruct its more accurate local mode of inter-annual oscillations of terrestrial water storage (TWS). The results show that RMSSA could effectively suppress the mode mixture of MSSA, and improve the physical interpretation of the inter-annual oscillations of TWS. Three significant inter-annual oscillations with periods of 6.1a, 3.4a, and 2.5a have been found in the multidimensional EWH series in the Qinghai-Tibetan Plateau (QTP), which account for 38.5 %, 23.5 %, and 16.7 % of the total variance, respectively (after the seasonal and long term have been deducted). The spatial patterns and propagation paths of these three inter-annual oscillations are different and exhibit their own independent local characteristics. Based on the analysis of multi-source GRACE GSM data, the results show that the data solution errors have little influence on the extraction of inter-annual oscillations of TWS. The significant 6.4a, 3.5a, and 2.5a inter-annual oscillations are also found in CPC hydrologic model in the QTP using RMSSA, which account for 22.9, 29.9, and 19.3 % of the total variance, respectively. Three inter-annual oscillations separated from GRACE and CPC show similar spatial patterns and significant cross-correlations, respectively. The maximum cross-correlation coefficients are above 0.5 at the 95 % confidence level over 42, 71, and 75 % of the grids in the QTP, respectively. The results indicate that the soil moisture and terrestrial water storage from GRACE have common inter-annual oscillations and corresponding driving factors in the QTP. We conclude that these three inter-annual oscillations of TWS can be explained by the influence of the Arctic oscillation, oceanic Niña, and Indian Ocean dipole.
{"title":"Inter-annual oscillations of terrestrial water storage in Qinghai-Tibetan plateau from GRACE data","authors":"Chuandong Zhu, Wei Zhan","doi":"10.1515/jag-2022-0002","DOIUrl":"https://doi.org/10.1515/jag-2022-0002","url":null,"abstract":"Abstract Based on multidimensional equivalent water height (EWH) time series in the Qinghai-Tibetan Plateau recovered from GRACE data, rotated multi-channel singular spectrum analysis (RMSSA) was employed to separate and reconstruct its more accurate local mode of inter-annual oscillations of terrestrial water storage (TWS). The results show that RMSSA could effectively suppress the mode mixture of MSSA, and improve the physical interpretation of the inter-annual oscillations of TWS. Three significant inter-annual oscillations with periods of 6.1a, 3.4a, and 2.5a have been found in the multidimensional EWH series in the Qinghai-Tibetan Plateau (QTP), which account for 38.5 %, 23.5 %, and 16.7 % of the total variance, respectively (after the seasonal and long term have been deducted). The spatial patterns and propagation paths of these three inter-annual oscillations are different and exhibit their own independent local characteristics. Based on the analysis of multi-source GRACE GSM data, the results show that the data solution errors have little influence on the extraction of inter-annual oscillations of TWS. The significant 6.4a, 3.5a, and 2.5a inter-annual oscillations are also found in CPC hydrologic model in the QTP using RMSSA, which account for 22.9, 29.9, and 19.3 % of the total variance, respectively. Three inter-annual oscillations separated from GRACE and CPC show similar spatial patterns and significant cross-correlations, respectively. The maximum cross-correlation coefficients are above 0.5 at the 95 % confidence level over 42, 71, and 75 % of the grids in the QTP, respectively. The results indicate that the soil moisture and terrestrial water storage from GRACE have common inter-annual oscillations and corresponding driving factors in the QTP. We conclude that these three inter-annual oscillations of TWS can be explained by the influence of the Arctic oscillation, oceanic Niña, and Indian Ocean dipole.","PeriodicalId":45494,"journal":{"name":"Journal of Applied Geodesy","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2022-05-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46710561","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. Vivat, K. Tretyak, I. Savchyn, M. Navodych, O. Lano
Abstract The study of determining the accuracy of spatial vectors by the global navigation satellite system (GNSS) in real time (RTK) was conducted. The possibility of construction of precision geodetic networks by the combined method of static and RTK GNSS measurements which correspond to the set accuracy and reach the maximum economic efficiency is investigated. A technique providing the densification of GNSS network and the use of two simultaneously operating GNSS receivers (Rover) is proposed. The research was carried out at the points of the GNSS network of Dnister Pumped Storage Power Plant (PSPP) (Ukraine). As a result of comparison of reference and measured elements of vectors, it was found that the average absolute error in determining the spatial distance of 14 vectors was 5.3 mm. Rejection of vectors with a closed horizon reduced the error to 2.1 mm. The vectors are most accurately determined from two satellite systems (GPS, GLONASS) and from a single base station. The recommended distance to the base station is within one kilometer. Increasing the accuracy by 75 % in determining the vector by the proposed method in RTK mode is also shown. As a result of a posteriori optimization of combined GNSS networks, high accuracy on the reliability of vectors determined by the method in RTK mode was confirmed. The technique can be used to construct precision networks, to carry out repeated measurements for the monitoring of large engineering structures with an open horizon.
{"title":"Investigation of determining the accuracy of spatial vectors by the satellite method in a real time mode","authors":"A. Vivat, K. Tretyak, I. Savchyn, M. Navodych, O. Lano","doi":"10.1515/jag-2022-0003","DOIUrl":"https://doi.org/10.1515/jag-2022-0003","url":null,"abstract":"Abstract The study of determining the accuracy of spatial vectors by the global navigation satellite system (GNSS) in real time (RTK) was conducted. The possibility of construction of precision geodetic networks by the combined method of static and RTK GNSS measurements which correspond to the set accuracy and reach the maximum economic efficiency is investigated. A technique providing the densification of GNSS network and the use of two simultaneously operating GNSS receivers (Rover) is proposed. The research was carried out at the points of the GNSS network of Dnister Pumped Storage Power Plant (PSPP) (Ukraine). As a result of comparison of reference and measured elements of vectors, it was found that the average absolute error in determining the spatial distance of 14 vectors was 5.3 mm. Rejection of vectors with a closed horizon reduced the error to 2.1 mm. The vectors are most accurately determined from two satellite systems (GPS, GLONASS) and from a single base station. The recommended distance to the base station is within one kilometer. Increasing the accuracy by 75 % in determining the vector by the proposed method in RTK mode is also shown. As a result of a posteriori optimization of combined GNSS networks, high accuracy on the reliability of vectors determined by the method in RTK mode was confirmed. The technique can be used to construct precision networks, to carry out repeated measurements for the monitoring of large engineering structures with an open horizon.","PeriodicalId":45494,"journal":{"name":"Journal of Applied Geodesy","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2022-05-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46337284","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract When starting any GNSS measurements, there is a need to establish a survey plan with the required optimal baselines. The optimal GNSS baselines can be chosen by solving the geodetic second-order design (SOD). The particle swarm optimization PSO is used widely to solve geodetic design issues. This work employed the particle swarm optimization (PSO) algorithm, a stochastic global optimization method, to select the optimal GNSS baselines. The optimal baselines satisfy the set criterion matrix at a reasonable cost. The fundamentals of the algorithm are presented. The effectiveness and usefulness of the technique are then demonstrated using a Nile Delta GNSS network as an example. In some cases, we have to observe many GNSS benchmarks with limited instrumentations. PSO represents a powerful tool for optimizing baseline to get the required accuracy with limited capabilities (like limited receivers). The PSO algorithm, a stochastic global optimization approach, was used in this paper to find the best observation weights to measure in the field that will match the predetermined criterion matrix with a fair degree of precision. The method’s fundamentals are presented with an actual geodetic network over the Nile delta in Egypt. In the current work, two survey strategies were applied. One represents a case with 9 GNSS receivers (high capability), and another one represents the tested survey plan with limited GNSS receivers (3 receivers, low capability) after applying PSO. By comparing two survey strategies, applying the PSO algorithm to a real Nile delta geodetic network shows its effectiveness on the obtained coordinate accuracy. This obtained accuracy ranged from 2 mm to 3 mm in X, Y, Z, and 3 mm in height. Also, the linear closure error between known and estimated coordinates improved to be 1.4 cm after applying PSO.
在开始任何GNSS测量时，都需要建立具有所需最佳基线的测量计划。通过求解大地测量二阶设计(SOD)，选择最优GNSS基线。粒子群算法在大地测量设计中得到了广泛的应用。本文采用随机全局优化方法粒子群优化(PSO)算法选择最优GNSS基线。最优基线以合理的代价满足所设置的准则矩阵。介绍了该算法的基本原理。然后以尼罗河三角洲GNSS网络为例演示了该技术的有效性和实用性。在某些情况下，我们必须用有限的仪器观察许多GNSS基准。PSO是一个强大的工具，可以在有限的能力(如有限的接收器)下优化基线以获得所需的精度。本文采用随机全局优化算法——粒子群算法(PSO)，寻找与预定准则矩阵匹配精度较高的最佳观测权值。该方法的基本原理与埃及尼罗河三角洲的实际大地测量网相结合。在目前的工作中，采用了两种调查策略。其中一幅代表有9个GNSS接收机(高容量)的情况，另一幅代表应用PSO后的有限GNSS接收机(3个接收机，低容量)的测试测量方案。通过对两种测量策略的比较，将PSO算法应用于实际的尼罗河三角洲大地测量网，验证了该算法对得到的坐标精度的有效性。这获得的精度范围从2毫米到3毫米在X, Y, Z和3毫米的高度。应用粒子群算法后，已知坐标与估计坐标之间的线性闭合误差提高到1.4 cm。
{"title":"Optimization of baseline configuration in a GNSS network (Nile Delta network, Egypt) – A case study","authors":"M. Farhan, M. Gomaa, A. Sedeek","doi":"10.1515/jag-2022-0010","DOIUrl":"https://doi.org/10.1515/jag-2022-0010","url":null,"abstract":"Abstract When starting any GNSS measurements, there is a need to establish a survey plan with the required optimal baselines. The optimal GNSS baselines can be chosen by solving the geodetic second-order design (SOD). The particle swarm optimization PSO is used widely to solve geodetic design issues. This work employed the particle swarm optimization (PSO) algorithm, a stochastic global optimization method, to select the optimal GNSS baselines. The optimal baselines satisfy the set criterion matrix at a reasonable cost. The fundamentals of the algorithm are presented. The effectiveness and usefulness of the technique are then demonstrated using a Nile Delta GNSS network as an example. In some cases, we have to observe many GNSS benchmarks with limited instrumentations. PSO represents a powerful tool for optimizing baseline to get the required accuracy with limited capabilities (like limited receivers). The PSO algorithm, a stochastic global optimization approach, was used in this paper to find the best observation weights to measure in the field that will match the predetermined criterion matrix with a fair degree of precision. The method’s fundamentals are presented with an actual geodetic network over the Nile delta in Egypt. In the current work, two survey strategies were applied. One represents a case with 9 GNSS receivers (high capability), and another one represents the tested survey plan with limited GNSS receivers (3 receivers, low capability) after applying PSO. By comparing two survey strategies, applying the PSO algorithm to a real Nile delta geodetic network shows its effectiveness on the obtained coordinate accuracy. This obtained accuracy ranged from 2 mm to 3 mm in X, Y, Z, and 3 mm in height. Also, the linear closure error between known and estimated coordinates improved to be 1.4 cm after applying PSO.","PeriodicalId":45494,"journal":{"name":"Journal of Applied Geodesy","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2022-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42721221","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：