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  • Data  (27)
  • EARTH SCIENCE 〉 SOLID EARTH 〉 GEODETICS 〉 GEOID CHARACTERISTICS  (27)
  • GFZ Data Services  (27)
  • 2015-2019  (27)
  • 1945-1949
  • 1
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    The KTH geoid based on Least Squares modification of Stokes integral with additive corrections for the Colorado Experiment: ColLSMSA-KTH2019 (2019)
    GFZ Data Services
    Details
    Publication Date: 2021-08-04
    Description: Abstract
    Description: The ColLSMSA-KTH2019 gravimetric geoid model has been computed by the University of Gävle, the Lantmäteriet and the Royal Institute of Technology (KTH) in Sweden. The model has been worked out in the frame of the International Association of Geodesy Joint Working Group 2.2.2 "The 1 cm geoid experiment" and the so called "Colorado experiment". The area covered by the model is 251°E ≤ longitude ≤ 257°E, 36°N ≤ latitude ≤ 39°N with a grid spacing of 1' in both latitude and in longitude. The quasi-geoid is computed using a two-step procedure. First, the terrestrial and de-biased airborne gravity anomalies are gridded using a Remove-Compute-Restore technique and three-dimensional Least Squares Collocation (LSC) with spherical Tscherning and Rapp (1974) type of covariance functions. This step achieves downward continuation of the airborne gravity data and combination with the terrestrial observations. In the second step, the resulting surface gravity anomaly grid is used to compute height anomalies by using Least Squares Modification of Stokes’ formula with Additive corrections (LSMSA or KTH method). The GEOID17RefB global gravity model up to degree 2190 is used in the first gridding step, while the satellite-only GOCO05S model up to degree 240 is used in the second step. Finally, the classical formula by Heiskanen and Moritz (1967) is used for quasi-geoid to geoid conversion. The accuracy of the geoid model, when compared against GSVS17 GPS/leveling, is equal to 2.7 cm. The geoid model is provided in ISG format 2.0 (ISG Format Specifications), while the file in its original data format is available at the model ISG webpage.
    Description: Other
    Description: The International Service for the Geoid (ISG) was founded in 1992 (as International Geoid Service - IGeS) and it is now an official service of the International Association of Geodesy (IAG), under the umbrella of the International Gravity Field Service (IGFS). The main activities of ISG consist in collecting, analysing and redistributing local and regional geoid models, as well as organizing international schools on the geoid determination (Reguzzoni et al., 2021).
    Keywords: Geodesy ; Geoid model ; ISG ; Least Squares modification of Stokes integral with additive corrections ; Colorado experiment ; EARTH SCIENCE 〉 SOLID EARTH 〉 GEODETICS 〉 GEOID CHARACTERISTICS ; EARTH SCIENCE 〉 SOLID EARTH 〉 GRAVITY/GRAVITATIONAL FIELD 〉 GRAVITY
    Type: Dataset , Dataset
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    DATA GFZ
  • 2
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    The KTH quasi-geoid based on Least Squares modification of Stokes integral with additive corrections for the Colorado Experiment: ColLSMSA-KTH2019 (2019)
    GFZ Data Services
    Details
    Publication Date: 2021-08-04
    Description: Abstract
    Description: The ColLSMSA-KTH2019 gravimetric quasi-geoid model has been computed by the University of Gävle, the Lantmäteriet and the Royal Institute of Technology (KTH) in Sweden. The model has been worked out in the frame of the International Association of Geodesy Joint Working Group 2.2.2 "The 1 cm geoid experiment" and the so called "Colorado experiment". The area covered by the model is 251°E ≤ longitude ≤ 257°E, 36°N ≤ latitude ≤ 39°N with a grid spacing of 1' in both latitude and in longitude. The quasi-geoid is computed using a two-step procedure. First, the terrestrial and de-biased airborne gravity anomalies are gridded using a Remove-Compute-Restore technique and three-dimensional Least Squares Collocation (LSC) with spherical Tscherning and Rapp (1974) type of covariance functions. This step achieves downward continuation of the airborne gravity data and combination with the terrestrial observations. In the second step, the resulting surface gravity anomaly grid is used to compute height anomalies by using Least Squares Modification of Stokes’ formula with Additive corrections (LSMSA or KTH method). The GEOID17RefB global gravity model up to degree 2190 is used in the first gridding step, while the satellite-only GOCO05S model up to degree 240 is used in the second step. The accuracy of the quasi-geoid model, when compared against GSVS17 GPS/leveling, is equal to 2.8 cm. The quasi-geoid model is provided in ISG format 2.0 (ISG Format Specifications), while the file in its original data format is available at the model ISG webpage.
    Description: Other
    Description: The International Service for the Geoid (ISG) was founded in 1992 (as International Geoid Service - IGeS) and it is now an official service of the International Association of Geodesy (IAG), under the umbrella of the International Gravity Field Service (IGFS). The main activities of ISG consist in collecting, analysing and redistributing local and regional geoid models, as well as organizing international schools on the geoid determination (Reguzzoni et al., 2021).
    Keywords: Geodesy ; Geoid model ; ISG ; Least Squares modification of Stokes integral with additive corrections ; Colorado experiment ; EARTH SCIENCE 〉 SOLID EARTH 〉 GEODETICS 〉 GEOID CHARACTERISTICS ; EARTH SCIENCE 〉 SOLID EARTH 〉 GRAVITY/GRAVITATIONAL FIELD 〉 GRAVITY
    Type: Dataset , Dataset
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  • 3
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    The experimental gravity field model XGM2019e (2019)
    GFZ Data Services
    Details
    Publication Date: 2021-09-02
    Description: Abstract
    Description: XGM2019e is a combined global gravity field model represented through spheroidal harmonics up to d/o 5399, corresponding to a spatial resolution of 2’ (~4 km). As data sources it includes the satellite model GOCO06s in the longer wavelength area combined with terrestrial measurements for the shorter wavelengths. The terrestrial data itself consists over land and ocean of gravity anomalies provided by courtesy of NGA (identical to XGM2016, having a resolution of 15’) augmented with topographically derived gravity over land (EARTH2014). Over the oceans, gravity anomalies derived from satellite altimetry are used (DTU13, in consistency with the NGA dataset).The combination of the satellite data with the terrestrial observations is performed by using full normal equations up to d/o 719 (15’). Beyond d/o 719, a block-diagonal least-squares solution is calculated for the high-resolution terrestrial data (from topography and altimetry). All calculations are performed in the spheroidal harmonic domain.In the spectral band up to d/o 719 the new model shows over land a slightly improved behavior over preceding models such as XGM2016, EIGEN6c4 or EGM2008 when comparing it to independent GPS leveling data. Over land and in the spectral range above d/o 719 the accuracy of XGM2019e suffers from the sole use of topographic forward modelling; Hence, errors are increased in well-surveyed areas compared to models containing real gravity data, e.g. EIGEN6c4 or EGM2008. However, the performance of XGM2019e can be considered as globally more homogeneous and independent from existing high resolution global models. Over the oceans the model exhibits an improved performance throughout the complete spectrum (equal or better than preceding models).
    Keywords: geodesy ; global gravity field model ; ICGEM ; GOCO ; GOCE ; EARTH SCIENCE 〉 SOLID EARTH 〉 GEODETICS 〉 GEOID CHARACTERISTICS ; EARTH SCIENCE 〉 SOLID EARTH 〉 GRAVITY/GRAVITATIONAL FIELD 〉 GRAVITY
    Language: English
    Type: Dataset , Dataset
    Format: 6 Files
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  • 4
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    The polar extended gravity field model TIM_R6e (2019)
    GFZ Data Services
    Details
    Publication Date: 2021-09-02
    Description: Abstract
    Description: TIM_R6e is an extended version of the satellity-only global gravity field model TIM_R6 (Brockmann et al., 2019) which includes additional terrestrial gravity field observations over GOCE's polar gap areas. The included terrestrial information consists of the PolarGap campaign data (Forsberg et al., 2017) augumented by the AntGG gravity data compilation (Scheinert et al., 2016) over the southern polar gap (〉83°S) and the ArcGP data (Forsberg et al. 2007) over the northern polar gap (〉83°N). The combination is performed on normal equation level, encompassing the terrestrial data as spectrally limited geographic 0.5°x0.5° grids over the polar gaps.
    Description: TechnicalInfo
    Description: Processing procedures: (extending TIM_R6)Gravity from orbits (SST): (identical to TIM_R6)- short-arc integral method applied to kinematic orbits, up to degree/order 150- orbit variance information included as part of the stochastic model, it is refined by empirical covariance functionsGravity from gradients (SGG): (identical to TIM_R6)- parameterization up to degree/order 300- observations used: Vxx, Vyy, Vzz and Vxz in the Gradiometer Reference Frame (GRF)- realistic stochastic modelling by applying digital decorrelation filters to the observation equations; estimated separately for individual data segments applying a robust procedureGravity from terrestrial observations (TER):- collocation of the original terrestrial data sources onto 30'x30' geographic gravity disturbance grids (in the polar gap areas above 83° southern/northern latitude, thus forming a pair of polar caps)- spectral limitation of the data to D/O 300 within the collocation process- the chosen grid is fully compatible with the grid of the zero observation constraints of the original TIM_R6 model. In its function it replaces the original constraints- from the collocated polar caps, a partial normal equation system, up to D/O 300 is derivedCombined solution:- addition of normal equations (SST D/O 150, SGG D/O 300, TER D/O 300)- Constraints: * Kaula-regularization applied to coefficients of degrees/orders 201 - 300 (constrained towards zero, fully compatible with TIM_R6)- weighting of SST and SGG is identical to TIM_R6. All TER observations are weighted with 5 mGal.Specific features of resulting gravity field:- Gravity field solution is (mostly) independent of any other gravity field information (outside the polar gap region)- Constraint towards zero starting from degree/order 201 to improve signal-to-noise ratio- Related variance-covariance information represents very well the true errors of the coefficients (outside the polar gap region)- Solution can be used for independent comparison and combination on normal equation level with other satellite-only models (e.g. GRACE), terrestrial gravity data, and altimetry (outside the polar gap region)- Since in the low degrees the solution is based solely on GOCE orbits, it is not competitive with a GRACE model in this spectral region (outside the polar gap region)- In comparison to TIM_R6, TIM_R6e should deliver more accurate results, especially towards the polar gaps. However, as it uses additional data sources it cannot be seen as totally independent anymore: even outside the polar gap regions correlations (introduced by the holistic nature of spherical harmonics) may be found.
    Keywords: global gravitational model ; ICGEM ; GOCE ; PolarGap ; geodesy ; EARTH SCIENCE 〉 SOLID EARTH 〉 GEODETICS 〉 GEOID CHARACTERISTICS ; EARTH SCIENCE 〉 SOLID EARTH 〉 GRAVITY/GRAVITATIONAL FIELD 〉 GRAVITY
    Language: English
    Type: Dataset , Dataset
    Format: 3 Files
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  • 5
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    The satellite-only gravity field model GOCO06s (2019)
    GFZ Data Services
    Details
    Publication Date: 2021-09-02
    Description: Abstract
    Description: GOCO06s is a satellite-only, global gravity field model up to degree and order 300, with secular and annual variations up to degree and order 120. It was produced by the GOCO Team (Technical University of Munich, University of Bonn, Graz University of Technology, Austrian Academy of Sciences, University of Bern) and is based on 1,160,000,000 observations from 19 satellites. The contributing satellite mission are: GOCE (TIM6 gradiometer observations), GRACE (ITSG-Grace2018s), kinematic orbits from Swarm A+B+C, TerraSAR-X, TanDEM-X, CHAMP, GRACE and GOCE, and SLR observations to LAGEOS, LAGEOS 2, Starlette, Stella, AJISAI, LARES, LARETS, Etalon 1/2 and BLITS. The combination of the individual data sources is performed on the basis of the full systems of normal equations, where the relative weighting between each constituent is determined by variance component estimation. In order to account for the polar gap of GOCE, the solution is Kaula-regularized after degree and order 150.The model is available via the ICGEM Service (Ince et al., 2019)
    Description: TechnicalInfo
    Description: PARAMETERS:modelname GOCO06sproduct_type gravity_fieldearth_gravity_constant 3.9860044150e+14radius 6.3781363000e+06max_degree 300norm fully_normalizedtide_system zero_tideerrors formal
    Keywords: ICGEM ; global gravitational model ; GOCO ; GOCE ; GRACE ; EARTH SCIENCE 〉 SOLID EARTH 〉 GRAVITY/GRAVITATIONAL FIELD 〉 GRAVITATIONAL FIELD ; EARTH SCIENCE 〉 SOLID EARTH 〉 GEODETICS 〉 GEOID CHARACTERISTICS
    Type: Dataset
    Format: 4 Files
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  • 6
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    The DGFI geoid based on spherical radial basis functions for the Colorado Experiment: ColSRBF-DGFI2019 (2019)
    GFZ Data Services
    Details
    Publication Date: 2021-10-27
    Description: Abstract
    Description: The ColSRBF-DGFI2019 gravimetric geoid model has been computed by the Deutsches Geodätisches Forschungsinstitut (DGFI), Technical University of Munich (TUM). It has been worked out in the frame of the International Association of Geodesy Joint Working Group 2.2.2 "The 1 cm geoid experiment" and the so called "Colorado experiment". The area covered by the model is 251°E ≤ longitude ≤ 257°E, 36°N ≤ latitude ≤ 39°N with a grid spacing of 1' in both latitude and in longitude. Input data include terrestrial and airborne gravity observations, both used with their original observation sites. The computation method is based on spherical radial basis functions (SRBFs), using the Shannon function and the Cubic Polynomial (CuP) function for the terrestrial and airborne data, respectively. The computation is performed in the framework of a remove-compute-restore procedure, taking XGM2016 as global gravity model and Earth2014 / ERTM2160 for the topographic gravity effects. The terrestrial and airborne observations are combined within a parameter estimation procedure, and the relative weight between these two types of observations are determined by the method of variance component estimation (VCE). The classical formula by Heiskanen and Moritz (1967) is used for quasi-geoid to geoid conversion. The accuracy of the geoid model, when compared against GSVS17 GPS/leveling, is equal to 3.0 cm. The geoid model is provided in ISG format 2.0 (ISG Format Specifications), while the file in its original data format is available at the model ISG webpage.
    Description: Other
    Description: The International Service for the Geoid (ISG) was founded in 1992 (as International Geoid Service - IGeS) and it is now an official service of the International Association of Geodesy (IAG), under the umbrella of the International Gravity Field Service (IGFS). The main activities of ISG consist in collecting, analysing and redistributing local and regional geoid models, as well as organizing international schools on the geoid determination (Reguzzoni et al., 2021).
    Keywords: Geodesy ; Geoid model ; ISG ; Spherical radial basis functions ; Colorado experiment ; EARTH SCIENCE 〉 SOLID EARTH 〉 GEODETICS 〉 GEOID CHARACTERISTICS ; EARTH SCIENCE 〉 SOLID EARTH 〉 GRAVITY/GRAVITATIONAL FIELD 〉 GRAVITY
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  • 7
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    The CASM geoid based on spectral combination approach for the Colorado Experiment: ColSCA-CASM2019 (2019)
    GFZ Data Services
    Details
    Publication Date: 2021-11-05
    Description: Abstract
    Description: The ColSCA-CASM2019 gravimetric geoid model has been computed by the Chinese Academy of Surveying and Mapping (CASM). It has been worked out in the frame of the International Association of Geodesy Joint Working Group 2.2.2 "The 1 cm geoid experiment" and the so called "Colorado experiment". The area covered by the model is 109.5°W ≤ longitude ≤ 102.5°W, 35.5°N ≤ latitude ≤ 39.5°N with a grid spacing of 1' in both latitude and in longitude. The height anomaly computation from the satellite gravity model GOCO05S, terrestrial and airborne gravity data is based on the spectral combination approach. Spectral weights of each dataset are determined by using the KTH error degree variance estimation method. A remove-compute-restore procedure, based on the EGM2008 global gravity model, is applied to account for the contribution outside local gravity data coverage. A residual terrain correction is computed from the SRTM model to consider the short wavelength components of gravity field generated by the high frequency part of topography. Height anomalies are converted to geoid undulations by using the refined Bouguer anomalies and the gradient of the gravitational potential (Flury and Rummel, 2009). The accuracy of the geoid model, when compared against GSVS17 GPS/leveling, is equal to 3.5 cm. The geoid model is provided in ISG format 2.0 (ISG Format Specifications), while the file in its original data format is available at the model ISG webpage.
    Description: Other
    Description: The International Service for the Geoid (ISG) was founded in 1992 (as International Geoid Service - IGeS) and it is now an official service of the International Association of Geodesy (IAG), under the umbrella of the International Gravity Field Service (IGFS). The main activities of ISG consist in collecting, analysing and redistributing local and regional geoid models, as well as organizing international schools on the geoid determination (Reguzzoni et al., 2021).
    Keywords: Geodesy ; Geoid model ; ISG ; Spectral combination approach ; Colorado experiment ; EARTH SCIENCE 〉 SOLID EARTH 〉 GEODETICS 〉 GEOID CHARACTERISTICS ; EARTH SCIENCE 〉 SOLID EARTH 〉 GRAVITY/GRAVITATIONAL FIELD 〉 GRAVITY
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  • 8
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    The CASM quasi-geoid based on spectral combination approach for the Colorado Experiment: ColSCA-CASM2019 (2019)
    GFZ Data Services
    Details
    Publication Date: 2021-11-05
    Description: Abstract
    Description: The ColSCA-CASM2019 gravimetric quasi-geoid model has been computed by the Chinese Academy of Surveying and Mapping (CASM). It has been worked out in the frame of the International Association of Geodesy Joint Working Group 2.2.2 "The 1 cm geoid experiment" and the so called "Colorado experiment". The area covered by the model is 109.5°W ≤ longitude ≤ 102.5°W, 35.5°N ≤ latitude ≤ 39.5°N with a grid spacing of 1' in both latitude and in longitude. The height anomaly computation from the satellite gravity model GOCO05S, terrestrial and airborne gravity data is based on the spectral combination approach. Spectral weights of each dataset are determined by using the KTH error degree variance estimation method. A remove-compute-restore procedure, based on the EGM2008 global gravity model, is applied to account for the contribution outside local gravity data coverage. A residual terrain correction is computed from the SRTM model to consider the short wavelength components of gravity field generated by the high frequency part of topography. The accuracy of the quasi-geoid model, when compared against GSVS17 GPS/leveling, is equal to 3.1 cm. The geoid model is provided in ISG format 2.0 (ISG Format Specifications), while the file in its original data format is available at the model ISG webpage.
    Description: Other
    Description: The International Service for the Geoid (ISG) was founded in 1992 (as International Geoid Service - IGeS) and it is now an official service of the International Association of Geodesy (IAG), under the umbrella of the International Gravity Field Service (IGFS). The main activities of ISG consist in collecting, analysing and redistributing local and regional geoid models, as well as organizing international schools on the geoid determination (Reguzzoni et al., 2021).
    Keywords: Geodesy ; Geoid model ; ISG ; Spectral combination approach ; Colorado experiment ; EARTH SCIENCE 〉 SOLID EARTH 〉 GEODETICS 〉 GEOID CHARACTERISTICS ; EARTH SCIENCE 〉 SOLID EARTH 〉 GRAVITY/GRAVITATIONAL FIELD 〉 GRAVITY
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  • 9
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    The Belgian hybrid quasi-geoid: hBG18 (2018)
    GFZ Data Services
    Details
    Publication Date: 2021-11-26
    Description: Abstract
    Description: hBG2018 is the hybrid quasi-geoid model for Belgium, including both the Belgian mainland and the Exclusive Economic Zone. The hBG18 quasi-geoid heights are referred to the ETRS89/GRS80 ellipsoid. It is computed using radar altimetry data, terrestrial gravity anomalies, airborne gravity disturbances, and shipboard gravity anomalies. The quasi-geoid computation is based on the remove-compute-restore procedure. The long-wavelength signal content in the data is reduced by removing the contribution of the GOCO05S global gravity field model complete to degree 280. At the very short wavelengths, residual terrain modelling (RTM) is applied to the shipboard, terrestrial and airborne gravity datasets using EuroDEM as input data. The residual disturbing potential is parameterized over the target area using Spherical Radial Basis Functions (SRBF). The SRBF coefficients and bias parameters for the sets of gravity anomalies and disturbances are estimated using weighted least-squares with regularization, assuming white noise. To support the exploitation of the hBG2018 gravimetric quasi-geoid for the conversion of GNSS derived heights to the TAW/DNG height system, several post-processing steps were applied. First, as the TAW/DNG height system is a mean-tide height system (i.e., mean-tide crust = zero crust over mean-tide geoid) the quasi-geoid was transformed from the zero-tide to the mean tide system. Thereafter, a corrector surface (also called 'innovation function') has been estimated from the differences between the geometric quasi-geoid at 3707 GNSS/leveling points and the gravimetric quasi-geoid. This surface also accounts for the difference between the fictitious datum point of the gravimetric hBG18 and the datum point of the TAW/DNG. Finally, the transformation from the tide-free permanent tide system adopted in the GNSS community and the mean-tide system adopted in TAW/DNG, has been applied. hBG18 replaces hBG03 as the official Belgian model since August 1, 2018. The geoid model is provided in ISG format 2.0 (ISG Format Specifications), while the file in its original data format is available at the model ISG webpage.
    Description: Other
    Description: The International Service for the Geoid (ISG) was founded in 1992 (as International Geoid Service - IGeS) and it is now an official service of the International Association of Geodesy (IAG), under the umbrella of the International Gravity Field Service (IGFS). The main activities of ISG consist in collecting, analysing and redistributing local and regional geoid models, as well as organizing international schools on the geoid determination (Reguzzoni et al., 2021).
    Keywords: Geodesy ; Geoid model ; ISG ; Spherical Radial Basis Functions ; Belgium ; EARTH SCIENCE 〉 SOLID EARTH 〉 GEODETICS 〉 GEOID CHARACTERISTICS ; EARTH SCIENCE 〉 SOLID EARTH 〉 GRAVITY/GRAVITATIONAL FIELD 〉 GRAVITY
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  • 10
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    The GSI-DTU geoid based on the UNB Stokes-Helmert scheme for the Colorado Experiment: ColUNBSH-GSI2019 (2019)
    GFZ Data Services
    Details
    Publication Date: 2021-11-29
    Description: Abstract
    Description: The ColUNBSH-GSI2019 gravimetric geoid model has been computed by the Geospatial Information Authority of Japan (GSI) in cooperation with the Technical University of Denmark (DTU). It has been worked out in the frame of the International Association of Geodesy Joint Working Group 2.2.2 "The 1 cm geoid experiment" and the so called "Colorado experiment". The area covered by the model is 109°W ≤ longitude ≤ 103°W, 36°N ≤ latitude ≤ 39°N with a grid spacing of 1' in both latitude and in longitude. Terrestrial and airborne gravity data are combined and gridded by least-squares collocation with the planar logarithmic covariance model. The resulting grid of free-air gravity anomalies is converted into Helmert gravity anomalies by applying the spherical topographic reduction and the analytical downward continuation with Helmert's second method of condensation. The computation method is based on the remove-compute-restore technique, using XGM2016 up to degree and order 719 as the reference global gravity model. In particular, the geoid model is computed by Stokes integration of residual Helmert gravity anomalies with the hybrid Meissl-Molodensky modified spheroidal Stokes kernel (UNB Stokes-Helmert scheme). The accuracy of the geoid model, when compared against GSVS17 GPS/leveling, is equal to 2.9 cm. The geoid model is provided in ISG format 2.0 (ISG Format Specifications), while the file in its original data format is available at the model ISG webpage.
    Description: Other
    Description: The International Service for the Geoid (ISG) was founded in 1992 (as International Geoid Service - IGeS) and it is now an official service of the International Association of Geodesy (IAG), under the umbrella of the International Gravity Field Service (IGFS). The main activities of ISG consist in collecting, analysing and redistributing local and regional geoid models, as well as organizing international schools on the geoid determination (Reguzzoni et al., 2021).
    Keywords: Geodesy ; Geoid model ; ISG ; UNB Stokes-Helmert scheme ; Colorado experiment ; EARTH SCIENCE 〉 SOLID EARTH 〉 GEODETICS 〉 GEOID CHARACTERISTICS ; EARTH SCIENCE 〉 SOLID EARTH 〉 GRAVITY/GRAVITATIONAL FIELD 〉 GRAVITY
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  • 11
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    The DGFI quasi-geoid based on spherical radial basis functions for the Colorado Experiment: ColSRBF-DGFI2019 (2019)
    GFZ Data Services
    Details
    Publication Date: 2021-12-08
    Description: Abstract
    Description: The ColSRBF-DGFI2019 gravimetric quasi-geoid model has been computed by the Deutsches Geodätisches Forschungsinstitut (DGFI), Technical University of Munich (TUM). It has been worked out in the frame of the International Association of Geodesy Joint Working Group 2.2.2 "The 1 cm geoid experiment" and the so called "Colorado experiment". The area covered by the model is 251°E ≤ longitude ≤ 257°E, 36°N ≤ latitude ≤ 39°N with a grid spacing of 1' in both latitude and in longitude. Input data include terrestrial and airborne gravity observations, both used with their original observation sites. The computation method is based on spherical radial basis functions (SRBFs), using the Shannon function and the Cubic Polynomial (CuP) function for the terrestrial and airborne data, respectively. The computation is performed in the framework of a remove-compute-restore procedure, taking XGM2016 as global gravity model and Earth2014 / ERTM2160 for the topographic gravity effects. The terrestrial and airborne observations are combined within a parameter estimation procedure, and the relative weight between these two types of observations are determined by the method of variance component estimation (VCE). The accuracy of the quasi-geoid model, when compared against GSVS17 GPS/leveling, is equal to 2.9 cm. The geoid model is provided in ISG format 2.0 (ISG Format Specifications), while the file in its original data format is available at the model ISG webpage.
    Description: Other
    Description: The International Service for the Geoid (ISG) was founded in 1992 (as International Geoid Service - IGeS) and it is now an official service of the International Association of Geodesy (IAG), under the umbrella of the International Gravity Field Service (IGFS). The main activities of ISG consist in collecting, analysing and redistributing local and regional geoid models, as well as organizing international schools on the geoid determination (Reguzzoni et al., 2021).
    Keywords: Geodesy ; Geoid model ; ISG ; Spherical radial basis functions ; Colorado experiment ; EARTH SCIENCE 〉 SOLID EARTH 〉 GEODETICS 〉 GEOID CHARACTERISTICS ; EARTH SCIENCE 〉 SOLID EARTH 〉 GRAVITY/GRAVITATIONAL FIELD 〉 GRAVITY
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  • 12
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    The Curtin University geoid based on 1D FFT with Wong-Gore modification of the Stokes kernel for the Colorado Experiment: ColFFTWG-Curtin2019 (2019)
    GFZ Data Services
    Details
    Publication Date: 2021-12-20
    Description: Abstract
    Description: The ColFFTWG-Curtin2019 gravimetric geoid model has been computed by the Curtin University, Perth, Australia. It has been worked out in the frame of the International Association of Geodesy Joint Working Group 2.2.2 "The 1 cm geoid experiment" and the so called "Colorado experiment". The area covered by the model is 250°E ≤ longitude ≤ 258°E, 35°N ≤ latitude ≤ 40°N with a grid spacing of 1' in both latitude and in longitude. Terrestrial and airborne free-air gravity anomalies were reduced by subtraction of gravity anomalies from the GO_CONS_GCF_2_DIR_R6 global gravity model (for pre-processing of the gravity data only) and a topographic correction based on the SRTM 3″ v4.1 model. These reduced data were simultaneously gridded by application of 3D least-squares collocation (LSC) with planar logarithmic covariance function, and then converted to Faye anomalies. The quasi-geoid computation was then computed with a remove-compute-restore technique, for which the xGEOID17RefB global gravity model was used. The 1D-FFT integration with Wong-Gore modified Stokes kernel was applied, where optimal modification parameters were determined from comparison to GPS-levelling data. The classical formula by Heiskanen and Moritz (1967) was used for the geoid/quasi-geoid separation. The accuracy of the geoid model, when compared against GSVS17 GPS/leveling, is equal to 4.1 cm. The geoid model is provided in ISG format 2.0 (ISG Format Specifications), while the file in its original data format is available at the model ISG webpage.
    Description: Other
    Description: The International Service for the Geoid (ISG) was founded in 1992 (as International Geoid Service - IGeS) and it is now an official service of the International Association of Geodesy (IAG), under the umbrella of the International Gravity Field Service (IGFS). The main activities of ISG consist in collecting, analysing and redistributing local and regional geoid models, as well as organizing international schools on the geoid determination (Reguzzoni et al., 2021).
    Keywords: Geodesy ; Geoid model ; ISG ; Fast Fourier Transform ; Wong-Gore Stokes kernel modification ; Colorado experiment ; EARTH SCIENCE 〉 SOLID EARTH 〉 GEODETICS 〉 GEOID CHARACTERISTICS ; EARTH SCIENCE 〉 SOLID EARTH 〉 GRAVITY/GRAVITATIONAL FIELD 〉 GRAVITY
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  • 13
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    The Curtin University quasi-geoid based on 1D FFT with Wong-Gore modification of the Stokes kernel for the Colorado Experiment: ColFFTWG-Curtin2019 (2019)
    GFZ Data Services
    Details
    Publication Date: 2021-12-20
    Description: Abstract
    Description: The ColFFTWG-Curtin2019 gravimetric quasi-geoid model has been computed by the Curtin University, Perth, Australia. It has been worked out in the frame of the International Association of Geodesy Joint Working Group 2.2.2 "The 1 cm geoid experiment" and the so called "Colorado experiment". The area covered by the model is 250°E ≤ longitude ≤ 258°E, 35°N ≤ latitude ≤ 40°N with a grid spacing of 1' in both latitude and in longitude. Terrestrial and airborne free-air gravity anomalies were reduced by subtraction of gravity anomalies from the GO_CONS_GCF_2_DIR_R6 global gravity model (for pre-processing of the gravity data only) and a topographic correction based on the SRTM 3″ v4.1 model. These reduced data were simultaneously gridded by application of 3D least-squares collocation (LSC) with planar logarithmic covariance function, and then converted to Faye anomalies. The quasi-geoid computation was then computed with a remove-compute-restore technique, for which the xGEOID17RefB global gravity model was used. The 1D-FFT integration with Wong-Gore modified Stokes kernel was applied, where optimal modification parameters were determined from comparison to GPS-levelling data. The accuracy of the quasi-geoid model, when compared against GSVS17 GPS/leveling, is equal to 3.2 cm. The geoid model is provided in ISG format 2.0 (ISG Format Specifications), while the file in its original data format is available at the model ISG webpage.
    Description: Other
    Description: The International Service for the Geoid (ISG) was founded in 1992 (as International Geoid Service - IGeS) and it is now an official service of the International Association of Geodesy (IAG), under the umbrella of the International Gravity Field Service (IGFS). The main activities of ISG consist in collecting, analysing and redistributing local and regional geoid models, as well as organizing international schools on the geoid determination (Reguzzoni et al., 2021).
    Keywords: Geodesy ; Geoid model ; ISG ; Fast Fourier Transform ; Wong-Gore Stokes kernel modification ; Colorado experiment ; EARTH SCIENCE 〉 SOLID EARTH 〉 GEODETICS 〉 GEOID CHARACTERISTICS ; EARTH SCIENCE 〉 SOLID EARTH 〉 GRAVITY/GRAVITATIONAL FIELD 〉 GRAVITY
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  • 14
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    The DTU quasi-geoid based on spherical FFT with Wong-Gore modification of the Stokes kernel for the Colorado Experiment: ColFFTWG-DTU2019 (2019)
    GFZ Data Services
    Details
    Publication Date: 2022-03-25
    Description: Abstract
    Description: The ColFFTWG-DTU2019 gravimetric quasi-geoid model has been computed by the Technical University of Denmark (DTU), Copenhagen. It has been worked out in the frame of the International Association of Geodesy Joint Working Group 2.2.2 "The 1 cm geoid experiment" and the so called "Colorado experiment". The area covered by the model is 250°E ≤ longitude ≤ 258°E, 35°N ≤ latitude ≤ 40°N with a grid spacing of 1' in both latitude and in longitude. The computation was performed by the GRAVSOFT package in the framework of a remove-compute-restore procedure. XGM2016 was used up to degree and order 360 as global gravity model, and SRTM v4.1 was used for the residual terrain reductions at 3″ resolution for both airborne and terrestrial data, computed from a 9″ mean model. The linear Prey term approximation was applied for the harmonic correction of surface gravity points below the mean elevation surface (Forsberg and Tscherning, 1981). The reduced airborne gravity data were downward continued and gridded, together with surface gravimetry, at the terrain surface using 3D Least-Squares Collocation with planar logarithmic covariance function (Forsberg, 1987). The resulting 1'x1' grid was converted to a residual quasi-geoid by spherical FFT, using a Wong-Gore modified Stokes kernel, with a low-wavelength cut-off transition band at harmonic degrees 180-190, to keep the GOCE information unchanged up to this degree. Residual terrain effects and the XGM2016 contribution were restored to obtain the final gravimetric quasi-geoid. The accuracy of the quasi-geoid model, when compared against GSVS17 GPS/leveling, is equal to 3.1 cm. The geoid model is provided in ISG format 2.0 (ISG Format Specifications), while the file in its original data format is available at the model ISG webpage.
    Description: Other
    Description: The International Service for the Geoid (ISG) was founded in 1992 (as International Geoid Service - IGeS) and it is now an official service of the International Association of Geodesy (IAG), under the umbrella of the International Gravity Field Service (IGFS). The main activities of ISG consist in collecting, analysing and redistributing local and regional geoid models, as well as organizing international schools on the geoid determination (Reguzzoni et al., 2021).
    Keywords: Geodesy ; Geoid model ; ISG ; Fast Fourier Transform ; Wong-Gore Stokes kernel modification ; Colorado experiment ; EARTH SCIENCE 〉 SOLID EARTH 〉 GEODETICS 〉 GEOID CHARACTERISTICS ; EARTH SCIENCE 〉 SOLID EARTH 〉 GRAVITY/GRAVITATIONAL FIELD 〉 GRAVITY
    Type: Dataset , Dataset
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  • 15
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    The DTU geoid based on spherical FFT with Wong-Gore modification of the Stokes kernel for the Colorado Experiment: ColFFTWG-DTU2019 (2019)
    GFZ Data Services
    Details
    Publication Date: 2022-03-25
    Description: Abstract
    Description: The ColFFTWG-DTU2019 gravimetric geoid model has been computed by the Technical University of Denmark (DTU), Copenhagen. It has been worked out in the frame of the International Association of Geodesy Joint Working Group 2.2.2 "The 1 cm geoid experiment" and the so called "Colorado experiment". The area covered by the model is 250°E ≤ longitude ≤ 258°E, 35°N ≤ latitude ≤ 40°N with a grid spacing of 1' in both latitude and in longitude. The computation was performed by the GRAVSOFT package in the framework of a remove-compute-restore procedure. XGM2016 was used up to degree and order 360 as global gravity model, and SRTM v4.1 was used for the residual terrain reductions at 3″ resolution for both airborne and terrestrial data, computed from a 9″ mean model. The linear Prey term approximation was applied for the harmonic correction of surface gravity points below the mean elevation surface (Forsberg and Tscherning, 1981). The reduced airborne gravity data were downward continued and gridded, together with surface gravimetry, at the terrain surface using 3D Least-Squares Collocation with planar logarithmic covariance function (Forsberg, 1987). The resulting 1'x1' grid was converted to a residual quasi-geoid by spherical FFT, using a Wong-Gore modified Stokes kernel, with a low-wavelength cut-off transition band at harmonic degrees 180-190, to keep the GOCE information unchanged up to this degree. Residual terrain effects and the XGM2016 contribution were restored to obtain the final gravimetric quasi-geoid, and the geoid was obtained by adding the classical separation term (Heiskanen and Moritz, 1967). The accuracy of the geoid model, when compared against GSVS17 GPS/leveling, is equal to 2.7 cm. The geoid model is provided in ISG format 2.0 (ISG Format Specifications), while the file in its original data format is available at the model ISG webpage.
    Description: Other
    Description: The International Service for the Geoid (ISG) was founded in 1992 (as International Geoid Service - IGeS) and it is now an official service of the International Association of Geodesy (IAG), under the umbrella of the International Gravity Field Service (IGFS). The main activities of ISG consist in collecting, analysing and redistributing local and regional geoid models, as well as organizing international schools on the geoid determination (Reguzzoni et al., 2021).
    Keywords: Geodesy ; Geoid model ; ISG ; Fast Fourier Transform ; Wong-Gore Stokes kernel modification ; Colorado experiment ; EARTH SCIENCE 〉 SOLID EARTH 〉 GEODETICS 〉 GEOID CHARACTERISTICS ; EARTH SCIENCE 〉 SOLID EARTH 〉 GRAVITY/GRAVITATIONAL FIELD 〉 GRAVITY
    Type: Dataset , Dataset
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  • 16
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    The GSI-DTU quasi-geoid based on the UNB Stokes-Helmert scheme for the Colorado Experiment: ColUNBSH-GSI2019 (2019)
    GFZ Data Services
    Details
    Publication Date: 2022-03-27
    Description: Abstract
    Description: The ColUNBSH-GSI2019 gravimetric quasi-geoid model has been computed by the Geospatial Information Authority of Japan (GSI) in cooperation with the Technical University of Denmark (DTU). It has been worked out in the frame of the International Association of Geodesy Joint Working Group 2.2.2 "The 1 cm geoid experiment" and the so called "Colorado experiment". The area covered by the model is 109°W ≤ longitude ≤ 103°W, 36°N ≤ latitude ≤ 39°N with a grid spacing of 1' in both latitude and in longitude. Terrestrial and airborne gravity data are combined and gridded by least-squares collocation with the planar logarithmic covariance model. The resulting grid of free-air gravity anomalies is converted into Helmert gravity anomalies by applying the spherical topographic reduction and the analytical downward continuation with Helmert's second method of condensation. The computation method is based on the remove-compute-restore technique, using XGM2016 up to degree and order 719 as the reference global gravity model. In particular, the geoid model is computed by Stokes integration of residual Helmert gravity anomalies with the hybrid Meissl-Molodensky modified spheroidal Stokes kernel (UNB Stokes-Helmert scheme). Finally, the quasi-geoid model is obtained by subtracting the classical geoid/quasi-geoid separation term from the geoid model. The accuracy of the quasi-geoid model, when compared against GSVS17 GPS/leveling, is equal to 2.9 cm. The geoid model is provided in ISG format 2.0 (ISG Format Specifications), while the file in its original data format is available at the model ISG webpage.
    Description: Other
    Description: The International Service for the Geoid (ISG) was founded in 1992 (as International Geoid Service - IGeS) and it is now an official service of the International Association of Geodesy (IAG), under the umbrella of the International Gravity Field Service (IGFS). The main activities of ISG consist in collecting, analysing and redistributing local and regional geoid models, as well as organizing international schools on the geoid determination (Reguzzoni et al., 2021).
    Keywords: Geodesy ; Geoid model ; ISG ; UNB Stokes-Helmert scheme ; Colorado experiment ; EARTH SCIENCE 〉 SOLID EARTH 〉 GEODETICS 〉 GEOID CHARACTERISTICS ; EARTH SCIENCE 〉 SOLID EARTH 〉 GRAVITY/GRAVITATIONAL FIELD 〉 GRAVITY
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  • 17
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    The NGS geoid based on the spherical harmonic analysis scheme with Wong-Gore modification of the Stokes kernel for the Colorado Experiment: ColSHAWG-NGS2019 (2019)
    GFZ Data Services
    Details
    Publication Date: 2022-04-08
    Description: Abstract
    Description: The ColSHAWG-NGS2019 gravimetric geoid model has been computed by the US National Geodetic Survey (NGS). It has been worked out in the frame of the International Association of Geodesy Joint Working Group 2.2.2 "The 1 cm geoid experiment" and the so called "Colorado experiment". The area covered by the model is 251°E ≤ longitude ≤ 257°E, 36°N ≤ latitude ≤ 39°N with a grid spacing of 1' in both latitude and in longitude. The computation method is based on the spherical harmonic analysis scheme. The airborne gravity data are combined with the reference model xGEOID17RefB to produce an enhanced reference spherical harmonic model. This model is then used in a remove-compute-restore procedure, computing residual height anomalies from terrestrial gravity data by using the Wong-Gore modification of the Stokes kernel (truncation degree equal to 980), also including the g1 term because of rugged mountains. Finally, the geoid undulations are obtained by adding the geoid/quasi-geoid separation term (based on the simple Bouguer anomalies) to the computed height anomalies. The accuracy of the geoid model, when compared against GSVS17 GPS/leveling, is equal to 2.3 cm. The geoid model is provided in ISG format 2.0 (ISG Format Specifications), while the file in its original data format is available at the model ISG webpage.
    Description: Other
    Description: The International Service for the Geoid (ISG) was founded in 1992 (as International Geoid Service - IGeS) and it is now an official service of the International Association of Geodesy (IAG), under the umbrella of the International Gravity Field Service (IGFS). The main activities of ISG consist in collecting, analysing and redistributing local and regional geoid models, as well as organizing international schools on the geoid determination (Reguzzoni et al., 2021).
    Keywords: Geodesy ; Geoid model ; ISG ; Spherical harmonic analysis scheme ; Wong-Gore Stokes kernel modification ; Colorado experiment ; EARTH SCIENCE 〉 SOLID EARTH 〉 GEODETICS 〉 GEOID CHARACTERISTICS ; EARTH SCIENCE 〉 SOLID EARTH 〉 GRAVITY/GRAVITATIONAL FIELD 〉 GRAVITY
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  • 18
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    The NGS quasi-geoid based on the spherical harmonic analysis scheme with Wong-Gore modification of the Stokes kernel for the Colorado Experiment: ColSHAWG-NGS2019 (2019)
    GFZ Data Services
    Details
    Publication Date: 2022-04-08
    Description: Abstract
    Description: The ColSHAWG-NGS2019 gravimetric quasi-geoid model has been computed by the US National Geodetic Survey (NGS). It has been worked out in the frame of the International Association of Geodesy Joint Working Group 2.2.2 "The 1 cm geoid experiment" and the so called "Colorado experiment". The area covered by the model is 251°E ≤ longitude ≤ 257°E, 36°N ≤ latitude ≤ 39°N with a grid spacing of 1' in both latitude and in longitude. The computation method is based on the spherical harmonic analysis scheme. The airborne gravity data are combined with the reference model xGEOID17RefB to produce an enhanced reference spherical harmonic model. This model is then used in a remove-compute-restore procedure, computing residual height anomalies from terrestrial gravity data by using the Wong-Gore modification of the Stokes kernel (truncation degree equal to 980), also including the g1 term because of rugged mountains. The accuracy of the quasi-geoid model, when compared against GSVS17 GPS/leveling, is equal to 2.3 cm. The geoid model is provided in ISG format 2.0 (ISG Format Specifications), while the file in its original data format is available at the model ISG webpage.
    Description: Other
    Description: The International Service for the Geoid (ISG) was founded in 1992 (as International Geoid Service - IGeS) and it is now an official service of the International Association of Geodesy (IAG), under the umbrella of the International Gravity Field Service (IGFS). The main activities of ISG consist in collecting, analysing and redistributing local and regional geoid models, as well as organizing international schools on the geoid determination (Reguzzoni et al., 2021).
    Keywords: Geodesy ; Geoid model ; ISG ; Spherical harmonic analysis scheme ; Wong-Gore Stokes kernel modification ; Colorado experiment ; EARTH SCIENCE 〉 SOLID EARTH 〉 GEODETICS 〉 GEOID CHARACTERISTICS ; EARTH SCIENCE 〉 SOLID EARTH 〉 GRAVITY/GRAVITATIONAL FIELD 〉 GRAVITY
    Type: Dataset , Dataset
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  • 19
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    The geometric geoid of Guayaquil Canton: GEOID-GUAYAQUIL2019 (2019)
    GFZ Data Services
    Details
    Publication Date: 2022-04-08
    Description: Abstract
    Description: The GEOID-GUAYAQUIL2021 model for the rural area of the Guayaquil Canton in Ecuador was calculated by the Universidad de las Fuerzas Armadas ESPE, Sangolquí, Ecuador. It is based on a non-conventional technique, such as Cokriging (Goovaerts, 1997), through the combination of GPS data/differential leveling and a densely sampled auxiliary variable. The GPS satellite positioning was performed using the Static Differential method through dual-frequency receivers in each point; regarding the level heights they were obtained by second-level differential leveling. The geoid undulation from the EGM2008 model with spatial resolutions of 1 arc min was proposed as an auxiliary variable for the interpolation of geodetic undulation in combination with dispersed GPS data (Odera and Fukuda, 2015). Ordinary, Residual and Universal Cokriging and Kriging techniques were used and their results were compared to select the best for achieving accuracy. In particular, a “split-off” validation was performed by excluding a subset of data, repeating the processing, and then comparing the results with the one obtained with the full dataset. This validation yielded that the solution based on Universal Cokriging was the most accurate with an RMSE of 8 cm and RSR of 0.0282, obtained just with 66 samples (20% of the dataset). This model is presented as a practical alternative for obtaining level heights for various geoscience applications. The geoid model is provided in ISG format 2.0 (ISG Format Specifications), while the file in its original data format is available at the model ISG webpage.
    Description: Other
    Description: The International Service for the Geoid (ISG) was founded in 1992 (as International Geoid Service - IGeS) and it is now an official service of the International Association of Geodesy (IAG), under the umbrella of the International Gravity Field Service (IGFS). The main activities of ISG consist in collecting, analysing and redistributing local and regional geoid models, as well as organizing international schools on the geoid determination (Reguzzoni et al., 2021).
    Keywords: Geodesy ; Geoid model ; ISG ; Universal Cokriging ; Guayaquil Canton ; Ecuador ; EARTH SCIENCE 〉 SOLID EARTH 〉 GEODETICS 〉 GEOID CHARACTERISTICS ; EARTH SCIENCE 〉 SOLID EARTH 〉 GRAVITY/GRAVITATIONAL FIELD 〉 GRAVITY
    Type: Dataset , Dataset
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  • 20
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    The CGS geoid based on FFT with degree-banded modification of the Stokes kernel for the Colorado Experiment: ColFFTDB-CGS2019 (2019)
    GFZ Data Services
    Details
    Publication Date: 2022-06-09
    Description: Abstract
    Description: The ColFFTDB-CGS2019 gravimetric geoid model has been computed by the Canadian Geodetic Survey (CGS), Natural Resources Canada. It has been worked out in the frame of the International Association of Geodesy Joint Working Group 2.2.2 "The 1 cm geoid experiment" and the so called "Colorado experiment". The area covered by the model is 110°W ≤ longitude ≤ 102°W, 35°N ≤ latitude ≤ 40°N with a grid spacing of 1' in both latitude and in longitude. The solution is based on the Stokes-Helmert method, which is used with the degree-banded Stokes kernel modification (Huang and Véronneau, 2013). A band-wise spectral scheme is developed to combine the global model, airborne and surface gravity data, contributing to low-, medium- and high-degree bands of the geoid, respectively. In particular, the global gravity model provides entirely the low-degree band up to degree 150 from where it goes into transition with the surface gravity data up to degree 210. The surface gravity data complete the geoid frequencies up to degree 10800 with complement information from SRTM 3″ digital terrain model. As for the GRAV-D airborne gravity data, they provide corrective values directly to the geoid model, contributing between degrees 210 and 790 with smooth transition at each end. The geoid computation is performed by Fast Fourier Transform (FFT) numerical integration. The accuracy of the geoid model, when compared against GSVS17 GPS/leveling, is equal to 2.0 cm. The geoid model is provided in ISG format 2.0 (ISG Format Specifications), while the file in its original data format is available at the model ISG webpage.
    Description: Other
    Description: The International Service for the Geoid (ISG) was founded in 1992 (as International Geoid Service - IGeS) and it is now an official service of the International Association of Geodesy (IAG), under the umbrella of the International Gravity Field Service (IGFS). The main activities of ISG consist in collecting, analysing and redistributing local and regional geoid models, as well as organizing international schools on the geoid determination (Reguzzoni et al., 2021).
    Keywords: Geodesy ; Geoid model ; ISG ; Fast Fourier Transform ; Degree-banded Stokes kernel modification ; Colorado experiment ; EARTH SCIENCE 〉 SOLID EARTH 〉 GEODETICS 〉 GEOID CHARACTERISTICS ; EARTH SCIENCE 〉 SOLID EARTH 〉 GRAVITY/GRAVITATIONAL FIELD 〉 GRAVITY
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  • 21
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    The CGS quasi-geoid based on FFT with degree-banded modification of the Stokes kernel for the Colorado Experiment: ColFFTDB-CGS2019 (2019)
    GFZ Data Services
    Details
    Publication Date: 2022-06-09
    Description: Abstract
    Description: The ColFFTDB-CGS2019 gravimetric quasi-geoid model has been computed by the Canadian Geodetic Survey (CGS), Natural Resources Canada. It has been worked out in the frame of the International Association of Geodesy Joint Working Group 2.2.2 "The 1 cm geoid experiment" and the so called "Colorado experiment". The area covered by the model is 110°W ≤ longitude ≤ 102°W, 35°N ≤ latitude ≤ 40°N with a grid spacing of 1' in both latitude and in longitude. The solution is based on the Stokes-Helmert method, which is used with the degree-banded Stokes kernel modification (Huang and Véronneau, 2013). A band-wise spectral scheme is developed to combine the global model, airborne and surface gravity data, contributing to low-, medium- and high-degree bands of the geoid, respectively. In particular, the global gravity model provides entirely the low-degree band up to degree 150 from where it goes into transition with the surface gravity data up to degree 210. The surface gravity data complete the geoid frequencies up to degree 10800 with complement information from SRTM 3″ digital terrain model. As for the GRAV-D airborne gravity data, they provide corrective values directly to the geoid model, contributing between degrees 210 and 790 with smooth transition at each end. The geoid computation is performed by Fast Fourier Transform (FFT) numerical integration and then the quasi-geoid model is obtained by adding a classic geoid to quasi-geoid correction grid. The accuracy of the quasi-geoid model, when compared against GSVS17 GPS/leveling, is equal to 1.8 cm. The geoid model is provided in ISG format 2.0 (ISG Format Specifications), while the file in its original data format is available at the model ISG webpage.
    Description: Other
    Description: The International Service for the Geoid (ISG) was founded in 1992 (as International Geoid Service - IGeS) and it is now an official service of the International Association of Geodesy (IAG), under the umbrella of the International Gravity Field Service (IGFS). The main activities of ISG consist in collecting, analysing and redistributing local and regional geoid models, as well as organizing international schools on the geoid determination (Reguzzoni et al., 2021).
    Keywords: Geodesy ; Geoid model ; ISG ; Fast Fourier Transform ; Degree-banded Stokes kernel modification ; Colorado experiment ; EARTH SCIENCE 〉 SOLID EARTH 〉 GEODETICS 〉 GEOID CHARACTERISTICS ; EARTH SCIENCE 〉 SOLID EARTH 〉 GRAVITY/GRAVITATIONAL FIELD 〉 GRAVITY
    Type: Dataset , Dataset
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  • 22
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    The Ghanaian gravimetric geoid: GGG2017 (2017)
    GFZ Data Services
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    Publication Date: 2022-07-20
    Description: Abstract
    Description: The Ghanaian Gravimetric Geoid 2017 (GGG2017) covers the area between 4°N to 12°N and 4°W to 2°E. It is referred to the WGS84 reference ellipsoid and was computed using Heck and Grüninger’s modification of Stokes’ kernel in the framework of a remove-compute-restore approach. EGM2008 was used up to degree and order 222 to calculate the long-wavelength component of the geoid. A total of 499 surface gravity (from the Ghana Geological Survey Authority) and 29,249 marine gravity (from the Bureau Gravimétrique International) data were used to compute the GGG2017 model. Its validation was based on 11 GPS/trigonometric measurements, leading to the choice of the optimal maximum degree of EGM2008 and resulting in an overall accuracy of 45.7 cm. This means that the GGG2017 model can be used to replace second-order class II levelling, with an expected error of 6.8 mm/km for baselines ranging from 20 to 225 km. The geoid model is provided in ISG format 2.0 (ISG Format Specifications), while the file in its original data format is available at the model ISG webpage.
    Description: Other
    Description: The International Service for the Geoid (ISG) was founded in 1992 (as International Geoid Service - IGeS) and it is now an official service of the International Association of Geodesy (IAG), under the umbrella of the International Gravity Field Service (IGFS). The main activities of ISG consist in collecting, analysing and redistributing local and regional geoid models, as well as organizing international schools on the geoid determination (Reguzzoni et al., 2021).
    Keywords: Geodesy ; Geoid model ; ISG ; Heck and Grüninger’s modification of Stokes’ kernel ; Ghana ; EARTH SCIENCE 〉 SOLID EARTH 〉 GEODETICS 〉 GEOID CHARACTERISTICS ; EARTH SCIENCE 〉 SOLID EARTH 〉 GRAVITY/GRAVITATIONAL FIELD 〉 GRAVITY
    Type: Dataset , Dataset
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  • 23
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    The Slovenian hybrid quasi-geoid: SLO-VRP2016/Koper (2016)
    GFZ Data Services
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    Publication Date: 2022-12-06
    Description: Abstract
    Description: The SLO-VRP2016/Koper quasi-geoid model is the latest height reference surface for Slovenia, referred to the GRS80 ellipsoid. The acronym means SLOvenska Višinska Referenčna Ploskev iz leta 2016, datum Koper (translated in English, Slovenian Height Reference Surface from the year 2016, datum Koper). It was computed by the Surveying and Mapping Authority of the Republic of Slovenia, in cooperation with the Norwegian Mapping Authority (Kartverket). The model is based on a set of old terrestrial gravity data (origin from Yugoslavia, from 1956-75), a set of new Slovenian gravity data (along levelling lines and regional gravimetric survey, from 2000 to 2015) and sets from neighboring countries (Italy, Austria, Hungary and Croatia), altogether 16.400 points in the mean-tide system. Stokes/Molodensky equations and the Fast Fourier transform technique have been applied with use of global geopotential model EGM2008. The computed quasi-geoid surface was adapted (fitted) to 66 high quality GNSS/levelling points, which were fairly distributed throughout the territory of Slovenia. Therefore, the resulting quasi geoid model can be used to perform the conversion between ellipsoidal heights (Slovenian realization of ETRS89 - D96, GRS80 ellipsoid) and normal heights (Slovenian Height System 2010 - SVS2010 with Koper tide gauge). The SLO_VRP2016/Koper model is given in the form of a regular grid, with resolution of 30” × 45”, within the limits of 13° 〈 λ 〈 17° (east of Greenwich) and 45° 〈 φ 〈 47° (north of the equator). In this area geoid heights range between 42.157 m and 50.608 m, with an average of 46.162 m. The inner accuracy of the calculated geoid heights is 2.6 cm, the outer accuracy (based on 871 control GNSS/levelling measurements along levelling lines) is up to 10 cm. The geoid model is provided in ISG format 2.0 (ISG Format Specifications), while the file in its original data format is available at the model ISG webpage.
    Description: Other
    Description: The International Service for the Geoid (ISG) was founded in 1992 (as International Geoid Service - IGeS) and it is now an official service of the International Association of Geodesy (IAG), under the umbrella of the International Gravity Field Service (IGFS). The main activities of ISG consist in collecting, analysing and redistributing local and regional geoid models, as well as organizing international schools on the geoid determination (Reguzzoni et al., 2021).
    Keywords: Geodesy ; Geoid model ; ISG ; Fast Fourier Transform ; Slovenia ; EARTH SCIENCE 〉 SOLID EARTH 〉 GEODETICS 〉 GEOID CHARACTERISTICS ; EARTH SCIENCE 〉 SOLID EARTH 〉 GRAVITY/GRAVITATIONAL FIELD 〉 GRAVITY
    Type: Dataset , Dataset
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  • 24
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    The Argentinian gravimetric geoid: GEOIDE-Ar16 (2016)
    GFZ Data Services
    Details
    Publication Date: 2023-05-23
    Description: Abstract
    Description: The GEOIDE-Ar16 Argentinian gravimetric geoid model covers the area from 57° S to 20° S in latitude and from 76° W to 52° W in longitude, with a grid resolution of 1' × 1'. It was developed using the remove-compute-restore technique and incorporating the GOCO05S satellite-only global geopotential model up to degree and order 280, together with about 650,000 land and marine gravity measurements. Terrain corrections were calculated for all gravity observations using a combination of the SRTM_v4.1 and SRTM30_Plus_v10 digital elevation models. For the regions that lacked of gravity observations, the DTU13 gravity model was utilised. The residual gravity anomalies were gridded using the tensioned spline algorithm. The resultant gravity anomaly grid was applied in the Stokes' integral using the spherical multi-band FFT approach and the deterministic kernel modification proposed by Wong and Gore. The accuracy of GEOIDE-Ar16 was assessed by comparing it with GPS-levelling derived geoid undulations at 1,904 locations and the EGM2008 model. Results show that the GEOIDE-Ar16 geoid model has an accuracy of less than 10 centimetres. The geoid model is provided in ISG format 2.0 (ISG Format Specifications), while the file in its original data format is available at the model ISG webpage.
    Description: Other
    Description: The International Service for the Geoid (ISG) was founded in 1992 (as International Geoid Service - IGeS) and it is now an official service of the International Association of Geodesy (IAG), under the umbrella of the International Gravity Field Service (IGFS). The main activities of ISG consist in collecting, analysing and redistributing local and regional geoid models, as well as organizing international schools on the geoid determination (Reguzzoni et al., 2021).
    Keywords: Geodesy ; Geoid model ; ISG ; Spherical multi-band Fast Fourier Transform ; Wong-Gore Stokes kernel modification ; Argentina ; EARTH SCIENCE 〉 SOLID EARTH 〉 GEODETICS 〉 GEOID CHARACTERISTICS ; EARTH SCIENCE 〉 SOLID EARTH 〉 GRAVITY/GRAVITATIONAL FIELD 〉 GRAVITY
    Type: Dataset , Dataset
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  • 25
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    EIGEN-6S4 A time-variable satellite-only gravity field model to d/o 300 based on LAGEOS, GRACE and GOCE data from the collaboration of GFZ Potsdam and GRGS Toulouse (2016)
    GFZ Data Services
    Details
    Publication Date: 2023-10-04
    Description: Abstract
    Description: EIGEN-6S4 (Version 2) is a satellite-only global gravity field model from the combination of LAGEOS, GRACE and GOCE data. All spherical harmonic coefficients up to degree/order 80 are time variable. Their time variable parameters consist of drifts as well as annual and semi-annual variations per year. The time series of the time variable spherical harmonic coefficients are based on the LAGEOS-1/2 solution (1985 to 2003) and the GRACE-LAGEOS monthly gravity fields RL03-v2 (August 2002 to July 2014) from GRGS/Toulouse (Bruinsma et al. 2009).The herein included GRACE/LAGEOS data were combined with all GOCE data which have been processed via the direct numerical approach (Pail et al. 2011). The polar gap instabilty has been overcome using the Sperical Cap Regularization (Metzler and Pail 2005). That means this model is a combination of LAGEOS/GACE with GO_CONS_GCF_2_DIR_R5 (Bruinsma et al. 2013).Version History: This data set is an updated version of Foerste et al. (2016, http://doi.org/10.5880/icgem.2016.004) Compared to the first version, EIGEN-6S4v2 contains an improved modelling of the time variable part, in particular for C20.
    Keywords: ICGEM ; Global Gravitational Model ; GRACE ; GOCE ; LAGEOS ; EARTH SCIENCE 〉 SOLID EARTH 〉 GEODETICS 〉 GEOID CHARACTERISTICS ; EARTH SCIENCE 〉 SOLID EARTH 〉 GRAVITY/GRAVITATIONAL FIELD 〉 GRAVITATIONAL FIELD
    Type: Dataset
    Format: 8651697 Bytes
    Format: 3 Files
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  • 26
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    Multi-approach Gravity Field Models from Swarm GPS data (2019)
    GFZ Data Services
    Details
    Publication Date: 2023-12-01
    Description: Abstract
    Description: Although the knowledge of the gravity of the Earth has improved considerably with CHAMP, GRACE and GOCE satellite missions, the geophysical community has identified the need for the continued monitoring of its time-variable component with the purpose of estimating the hydrological and glaciological yearly cycles and long-term trends. Currently, the GRACE-FO satellites are the sole provider of this data, while previously the GRACE mission collected these data for 15 years. Between the GRACE and GRACE-FO data periods lies a gap spanning from July 2017 to May 2018, while the Swarm satellites have collected gravimetric data with its GPS receivers since December 2013. This project aims at providing high-quality gravity field models from Swarm data that constitute an alternative and independent source of gravimetric data, which could help alleviate the consequences of the 10-month gap between GRACE and GRACE-FO, as well as the short gaps in the existing GRACE and GRACE-FO monthly time series. The geodetic community has realized that the combination of the different gravity field solutions is superior to any individual model. This project exploits this fact and delivers to the highest quality monthly-independent gravity field models, resulting from the combination of 4 different gravity field estimation approaches. All solutions are unconstrained and estimated independently from month to month. Preliminary comparison with GRACE data has demonstrated that the signal in the Swarm gravity field models is restricted to degrees 12-15 and below, while the temporal correlations decrease considerably above degree 10. The 750km smoothed models are suitable to retrieve the global annual temporal variations of Earth's gravity field and the agreement with GRACE over large basins (e.g. Amazon, Congo-Zambezi, Ganges-Brahmaputra) is within 1cm RMS in terms of Equivalent Water Height. The global RMS relative to a bias, trend, an annual and semi-annual model derived from GRACE over deep ocean areas (those roughly 1000km from shorelines) is under 1mm geoid height during periods of low ionospheric activity. More information about this project can be found at https://www.researchgate.net/project/Multi-approach-gravity-field-models-from-Swarm-GPS-data and ESA's Swarm DISC (the Data, Innovation and Science Cluster) Website (https://earth.esa.int/web/guest/missions/esa-eo-missions/swarm/activities/scientific-projects/disc#MAGF). This project is funded by ESA via the Swarm DISC, Sub-Contract No. SW-CO-DTU-GS-111.
    Keywords: Swarm Satellites ; Gravity Field ; Mass Transport Processes ; GPS ; Kinematic orbit ; ICGEM ; COST-G ; International Combination Service for Time-variable Gravity Field Solutions ; EARTH SCIENCE 〉 TERRESTRIAL HYDROSPHERE ; EARTH SCIENCE 〉 SOLID EARTH 〉 GRAVITY/GRAVITATIONAL FIELD 〉 GRAVITY ; EARTH SCIENCE 〉 ATMOSPHERE 〉 ALTITUDE 〉 GEOPOTENTIAL HEIGHT ; EARTH SCIENCE 〉 SOLID EARTH 〉 GEODETICS 〉 GEOID CHARACTERISTICS ; science 〉 geography 〉 geodesy
    Type: Dataset
    Format: 2 Files
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  • 27
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    The Minia University geoid based on window remove-restore technique for the Colorado Experiment: ColWRRT-Minia2019 (2019)
    GFZ Data Services
    Details
    Publication Date: 2024-02-09
    Description: Abstract
    Description: The ColWRRT-Minia2019 gravimetric geoid model has been computed by the Civil Engineering Department of Minia University. It has been worked out in the frame of the International Association of Geodesy Joint Working Group 2.2.2 "The 1 cm geoid experiment" and the so called "Colorado experiment". The area covered by the models is 110°W ≤ longitude ≤ 102°W, 35°N ≤ latitude ≤ 40°N with a grid spacing of 1' in both latitude and in longitude. The computation is performed by the Window Remove-Restore Technique (WRRT), subtracting the effect of the topographic-isostatic masses of the data window from the reference model to obtain an adapted reference model to be used in the traditional remove-compute-restore procedure. The chosen reference model is xGEOID17RefB, complete to degree and order 2190. The window-reduced gravity anomalies are used to compute the geoid undulations by employing Stokes formula with Meissl modified kernel (with a cap size of 0.5°). The window restore step yields the final geoid. The accuracy of the ColWRRT-Minia2019 model, when compared against GSVS17 GPS/leveling, is equal to 3.0 cm. The geoid model is provided in ISG format 2.0 (ISG Format Specifications), while the file in its original data format is available at the model ISG webpage.
    Description: Other
    Description: The International Service for the Geoid (ISG) was founded in 1992 (as International Geoid Service - IGeS) and it is now an official service of the International Association of Geodesy (IAG), under the umbrella of the International Gravity Field Service (IGFS). The main activities of ISG consist in collecting, analysing and redistributing local and regional geoid models, as well as organizing international schools on the geoid determination (Reguzzoni et al., 2021).
    Keywords: Geodesy ; Geoid model ; ISG ; Window remove-restore technique ; Colorado experiment ; EARTH SCIENCE 〉 SOLID EARTH 〉 GEODETICS 〉 GEOID CHARACTERISTICS ; EARTH SCIENCE 〉 SOLID EARTH 〉 GRAVITY/GRAVITATIONAL FIELD 〉 GRAVITY
    Type: Dataset , Dataset
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