With the rapid development of modern Interferometric Synthetic Aperture Radar(InSAR)missions,SAR instruments with wider coverage can be used to monitor the ground surface deformation from regional to global scale.Howe...With the rapid development of modern Interferometric Synthetic Aperture Radar(InSAR)missions,SAR instruments with wider coverage can be used to monitor the ground surface deformation from regional to global scale.However,the ocean tide loading(OTL)displacement is becoming a primary source of errors.It contributes to a long-wavelength signal in InSAR interferograms,leading to errors from millimeter to centimeter-level in InSAR deformation monitoring,especially over coastal areas.Although the state-of-the-art has applied ocean tide models to mitigate the errors,the difference between them and their impact on InSAR measurements are rarely discussed.In this paper,we compare representative ocean tide models and investigate their effects in the correction of OTL errors.We found that(i)the modeled OTL displacements from different models show little difference over interiors far from the ocean,while disagreement becomes larger over coastal areas;(ii)the magnitude of OTL artifacts may be greater than the atmospheric delays in some coastal areas,and the correction using ocean tide models can effectively attenuate the OTL effects for large-scale InSAR measurements;(iii)when correcting the OTL errors for InSAR measurements,the global model TPXO and FES are recommended because of their better overall performance,while the NAO model performs the worst.The local models with high spatial resolution can help improve the capability of coarse global models in complex topographic areas.展开更多
By using 11 global ocean tide models and tidal gauge data obtained in the East China Sea and South China Sea, the influence of the ocean loading on gravity field in China and its neighbor area is calculated in this pa...By using 11 global ocean tide models and tidal gauge data obtained in the East China Sea and South China Sea, the influence of the ocean loading on gravity field in China and its neighbor area is calculated in this paper. Furthermore, the differences between the results from original global models and modified models with local tides are discussed based on above calculation. The comparison shows that the differences at the position near the sea are so large that the local tides must be taken into account in the calculation. When the global ocean tide models of CSR4.0, FES02, GOT00, NAO99 and ORI96 are chosen, the local effect for M2 is less than 0.10 × 10-8 m·s-2 over the area far away from sea. And the local effect for O1 is less than 0.05 × 10-8 m·s-2 over that area when choosing AG95 or CSR3.0 models. This numerical result demonstrates that the choice of model is a complex problem because of the inconsistent accuracy of the models over the areas of East and South China Seas.展开更多
Ocean tide loading (OTL) displacements of eight principal constituents at 12 sites in Hong Kong were determined using more than eight years of continuous GPS observations. Parameters of the OTL displacements were esti...Ocean tide loading (OTL) displacements of eight principal constituents at 12 sites in Hong Kong were determined using more than eight years of continuous GPS observations. Parameters of the OTL displacements were estimated using daily GPS solutions obtained with precise point positioning (PPP) technique. The results were compared with predictions from seven latest global ocean tide models. Gravity measurements of OTL in Hong Kong were also used to validate the GPS results. The study shows that the results from both the GPS and gravity measurements agree best with the GOT4.7 and NAO99b models, when the K1 and K2 constituents are excluded. The agreements between the GPS and the model estimates are generally at sub-millimeter level in both the horizontal and vertical directions, except for S2, K2 and K1 constituents that have relatively larger errors. After removing the systematic biases between the GPS and the model estimates, the misfits of M2, S2, N2, O1, P1 and Q1 at all sites are within 0.5 and 1.0 mm in the horizontal and the vertical directions, respectively, whereas K1 and K2 show relatively larger misfits of up to 2.3 mm. Both the GPS and the gravity S2 estimates have large biases with unknown reasons when compared with the modeled values, which needs to be further investigated. The study demonstrates that GPS is capable of estimating the OTL displacements with the same accuracy as the model predictions, especially for coastal areas.展开更多
This paper describes the ocean loading tides corrections of GPS stations in Antarctica, such as the Great Wall station and Zhongshan station. Based on the theory of ocean loading tides, the displacement corrections of...This paper describes the ocean loading tides corrections of GPS stations in Antarctica, such as the Great Wall station and Zhongshan station. Based on the theory of ocean loading tides, the displacement corrections of ocean loading tides on GPS stations in Antarctica are calculated by using the CRS4.0 ocean loading tides model. These corrections are also applied to GPS data proc-essing. The GPS data are analyzed by the GAMIT software with and without these corrections. We compared and analyzed the GPS baseline components to get the differences. The results show that the ocean tidal displacement corrections have obvious effects upon GPS baseline components. Therefore, we should not ignore the ocean loading tides corrections of GPS stations in Antarctica to obtain precise and reliable results.展开更多
The response of radial inhomogeneous elastic earth under the action of oceanic tides is studied by use of the combination of convolution integral with spherical harmonic expansion. In the meantime, the effect of ocean...The response of radial inhomogeneous elastic earth under the action of oceanic tides is studied by use of the combination of convolution integral with spherical harmonic expansion. In the meantime, the effect of oceanic tides on gravity, tilt and strain in the mainland of China is estimated, and the accuracy of loading correction is also briefly analysed. Results show that the loading effect along the coast of China cannot be neglected, for gravity it is about 5％ of body tides, for tilt it reaches the same magnitude as body tides, for strain about 50％. The result obtained can be used to provide the tidal correction for various precision geodesy. The proposal method may also be applied to the effect of other surface loading except oceanic tides.展开更多
Using tidal potential solar thermal-radiating energy current and the nonlinear effect of the gravity tide as the input function, moreover, considering the ocean tidal species as the input function of the loading effec...Using tidal potential solar thermal-radiating energy current and the nonlinear effect of the gravity tide as the input function, moreover, considering the ocean tidal species as the input function of the loading effect of ocean tide, we make the lumped response analysis of the observational tilt tide in one year. The tilt gravitational tide, the load tide, the radiational tide and the nonlinear tide with the same frequeny are separated off. It is shown that the load tide and the gravitational tide are the same quantity grade, the load tide may spread into inland far away; the solar thermal-radiation has an effect on the tilt tide; there is a little nonlinear tide in the tilt tide, but the nonlinear tide of the ocean tide has the stronger loading effect on the tilt tide than the nonlinear tide brought about by the gravitational tide itself; the lag interval, △τ=41 (h), is the best value in the response analysis. In addition, the harmonic analyses of the tilt tide and the separated tilt tides are made respectively by using j.v model, and their ellipse factors are calculated.展开更多
基金This work was supported by the Natural Science Foundation of China(grant Nos.42074008,41804005,42174018).
文摘With the rapid development of modern Interferometric Synthetic Aperture Radar(InSAR)missions,SAR instruments with wider coverage can be used to monitor the ground surface deformation from regional to global scale.However,the ocean tide loading(OTL)displacement is becoming a primary source of errors.It contributes to a long-wavelength signal in InSAR interferograms,leading to errors from millimeter to centimeter-level in InSAR deformation monitoring,especially over coastal areas.Although the state-of-the-art has applied ocean tide models to mitigate the errors,the difference between them and their impact on InSAR measurements are rarely discussed.In this paper,we compare representative ocean tide models and investigate their effects in the correction of OTL errors.We found that(i)the modeled OTL displacements from different models show little difference over interiors far from the ocean,while disagreement becomes larger over coastal areas;(ii)the magnitude of OTL artifacts may be greater than the atmospheric delays in some coastal areas,and the correction using ocean tide models can effectively attenuate the OTL effects for large-scale InSAR measurements;(iii)when correcting the OTL errors for InSAR measurements,the global model TPXO and FES are recommended because of their better overall performance,while the NAO model performs the worst.The local models with high spatial resolution can help improve the capability of coarse global models in complex topographic areas.
基金The Key Knowledge Innovation Project (KZCX3-SW-131), the Hundred Talents Program of Chinese Academy of Sciences and the National Natural Science Foundation of China (40374029)
文摘By using 11 global ocean tide models and tidal gauge data obtained in the East China Sea and South China Sea, the influence of the ocean loading on gravity field in China and its neighbor area is calculated in this paper. Furthermore, the differences between the results from original global models and modified models with local tides are discussed based on above calculation. The comparison shows that the differences at the position near the sea are so large that the local tides must be taken into account in the calculation. When the global ocean tide models of CSR4.0, FES02, GOT00, NAO99 and ORI96 are chosen, the local effect for M2 is less than 0.10 × 10-8 m·s-2 over the area far away from sea. And the local effect for O1 is less than 0.05 × 10-8 m·s-2 over that area when choosing AG95 or CSR3.0 models. This numerical result demonstrates that the choice of model is a complex problem because of the inconsistent accuracy of the models over the areas of East and South China Seas.
基金supported by the Research Grants Council (RGC) of the Hong Kong Special Administrative Region (Grant Nos. PolyU5157/05E, PolyU5161/06E)the Scientific Research Foundation of The Hong Kong Polytechnic University (Grant No.GY-F81)the Fundamental Research Funds for the Central Universi-ties (Grant Nos. SWJTU09BR029, SWJTU09BR031)
文摘Ocean tide loading (OTL) displacements of eight principal constituents at 12 sites in Hong Kong were determined using more than eight years of continuous GPS observations. Parameters of the OTL displacements were estimated using daily GPS solutions obtained with precise point positioning (PPP) technique. The results were compared with predictions from seven latest global ocean tide models. Gravity measurements of OTL in Hong Kong were also used to validate the GPS results. The study shows that the results from both the GPS and gravity measurements agree best with the GOT4.7 and NAO99b models, when the K1 and K2 constituents are excluded. The agreements between the GPS and the model estimates are generally at sub-millimeter level in both the horizontal and vertical directions, except for S2, K2 and K1 constituents that have relatively larger errors. After removing the systematic biases between the GPS and the model estimates, the misfits of M2, S2, N2, O1, P1 and Q1 at all sites are within 0.5 and 1.0 mm in the horizontal and the vertical directions, respectively, whereas K1 and K2 show relatively larger misfits of up to 2.3 mm. Both the GPS and the gravity S2 estimates have large biases with unknown reasons when compared with the modeled values, which needs to be further investigated. The study demonstrates that GPS is capable of estimating the OTL displacements with the same accuracy as the model predictions, especially for coastal areas.
基金the National 863 Program of China (No.2007AA12Z312)
文摘This paper describes the ocean loading tides corrections of GPS stations in Antarctica, such as the Great Wall station and Zhongshan station. Based on the theory of ocean loading tides, the displacement corrections of ocean loading tides on GPS stations in Antarctica are calculated by using the CRS4.0 ocean loading tides model. These corrections are also applied to GPS data proc-essing. The GPS data are analyzed by the GAMIT software with and without these corrections. We compared and analyzed the GPS baseline components to get the differences. The results show that the ocean tidal displacement corrections have obvious effects upon GPS baseline components. Therefore, we should not ignore the ocean loading tides corrections of GPS stations in Antarctica to obtain precise and reliable results.
文摘The response of radial inhomogeneous elastic earth under the action of oceanic tides is studied by use of the combination of convolution integral with spherical harmonic expansion. In the meantime, the effect of oceanic tides on gravity, tilt and strain in the mainland of China is estimated, and the accuracy of loading correction is also briefly analysed. Results show that the loading effect along the coast of China cannot be neglected, for gravity it is about 5％ of body tides, for tilt it reaches the same magnitude as body tides, for strain about 50％. The result obtained can be used to provide the tidal correction for various precision geodesy. The proposal method may also be applied to the effect of other surface loading except oceanic tides.
基金The paper is funded by the 7.5 Key ScienceTechnology Project(87-02-07)of the National Mapping Bureau
文摘Using tidal potential solar thermal-radiating energy current and the nonlinear effect of the gravity tide as the input function, moreover, considering the ocean tidal species as the input function of the loading effect of ocean tide, we make the lumped response analysis of the observational tilt tide in one year. The tilt gravitational tide, the load tide, the radiational tide and the nonlinear tide with the same frequeny are separated off. It is shown that the load tide and the gravitational tide are the same quantity grade, the load tide may spread into inland far away; the solar thermal-radiation has an effect on the tilt tide; there is a little nonlinear tide in the tilt tide, but the nonlinear tide of the ocean tide has the stronger loading effect on the tilt tide than the nonlinear tide brought about by the gravitational tide itself; the lag interval, △τ=41 (h), is the best value in the response analysis. In addition, the harmonic analyses of the tilt tide and the separated tilt tides are made respectively by using j.v model, and their ellipse factors are calculated.
