Dependence of Mean Sea Surfaces from Altimeter Data on the Reference Model Used

Rodríguez-Velasco, G.; Sevilla, Miguel J.; Toro, C. De

doi:10.1080/01490410214988

Cited by 3 publications

(2 citation statements)

References 16 publications

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“…Geoid and gravity anomalies may be also used as constraints for ocean circulation modelling (Rodriguez-Velasco et al, 2002;Wunsch and Stammer, 2003;Knudsen et al, 2006) and for subsurface mass distribution determination (Mcadoo, 1981;Camacho et al, 1997;Zhong, 2001;Kuhn, 2003). In effect, geoid and gravity anomalies reflect lateral heterogeneities in the earth's density structure and often correlate with bathymetry, and therefore provide information concerning the subsurface density structure and the style of isostatic compensation of the bathymetric load.…”

Section: Introductionmentioning

confidence: 99%

Sensitivity analysis of the gravity geoid estimation: A case study on the Azores plateau

Catalão¹,

Bos²

2008

Physics of the Earth and Planetary Interiors

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A numerical investigation into the effects of high-resolution heterogeneous data on the estimation of the geoid is presented for the area of the Azores plateau. Gravity data were complemented with highresolution digital terrain models, mass density models from geophysical information, and the most recent geopotential model from the CHAMP mission (GGM02) to derive a high-precision gravity model. Gravity data were reduced from the residual terrain model effects and the GGM02C model, and a grid with 1.5' spatial resolution was generated by least squares collocation. The gravimetric geoid model was computed by the direct evaluation of Stokes' integral with a spherical cap radius of 0.8 degree, with gravity data reduced by Helmert's second condensation method. The geoid model was evaluated over sea by comparison with six years of Topex/Poseidon altimeter data and an absolute agreement of 14 cm RMS was achieved after removing the bias. Over land, the geoid was compared with a total of 223 GPS/levelling points corresponding to five different vertical datums. Locally adjusted solutions were determined for each island with a four-parameter model, and a maximum RMS of 12 cm (on Pico) and a minimum of 2.1 cm (on Faial) were determined. As a result of persistent volcanic and tectonic activity on most of the Azores islands, this geoid residual standard deviation must not be viewed as purely geoid error but containing, in addition, levelling and GPS position errors and vertical displacement. The effect on geoid accuracy of the digital terrain model resolution, of the spatial density of gravity data, and of the mass density was evaluated and two important conclusions were derived. First, the digital terrain model resolution has a clear effect on the geoid accuracy, with a maximum RMS of 3.4 cm on S. Miguel. Second, the mass density model does not affect the accuracy of the geoid. This second result indicates that the effect of variable density Manuscript + tables + figuresPage 2 of 44 A c c e p t e d M a n u s c r i p t 2 models on geoid determination may apply only to extensive areas of high terrain and not to smaller topographic units such as single volcanoes. The high-precision gravity model and gravimetric geoid for Azores (AZGEOD07) generated in this study will allow the conversion of old orthometric heights to ellipsoidal heights at precisions useful for the monitoring of vertical deformation. The geoid will also have application to investigations of ocean circulation modulation and of dynamic processes of Earth's mantle.

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Section: Introductionmentioning

confidence: 99%

Sensitivity analysis of the gravity geoid estimation: A case study on the Azores plateau

Catalão¹,

Bos²

2008

Physics of the Earth and Planetary Interiors

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“…However, this new data from satellite missions is bandwidth limited and marine gravity data or airborne gravity data could be used to recover the high frequencies of the gravity spectrum (Kern et al, 2003). Moreover, its usefulness will be limited in costal areas where altimeter data suffers for large errors that can contaminate the derived gravity anomalies (Deng et al, 2002;Rodriguez-Velasco et al, 2002). By other hand, marine gravity anomalies are irregularly distributed on sea, with sparse tracks crossing the sea, but with a clear densification in coastal areas and near continental margin.…”

Section: Introductionmentioning

confidence: 99%

Iberia-Azores Gravity Model (IAGRM) using multi-source gravity data

Catalão

2006

Earth Planet Sp

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A consistent high precision and high resolution gravity model in the north-east Atlantic off Iberia peninsula using multi-source gravity data, ship-borne and satellite derived gravity anomalies, is presented. A solution strategy based on least squares optimal interpolation was used to assimilate into a coherent gravity model, gravity data with different spectral and spatial resolutions. Satellite derived gravity anomalies from KMS02 model, with an error covariance of 25 mGal 2 , and marine data carefully edited and validated by bias crossover error adjustment, were used in this study. The observation error variance was determined from ship-borne track adjustment and assigned an independent value for each track determined from error variance propagation. Unbiased ship-borne gravity observations were assimilated into the satellite derived gravity KMS02 model by the least squares optimal interpolation algorithm (OI) with bias removed by applying a regional bias to all ship tracks (OI-b) and alternatively by constraining all ship tracks to KMS02 using bias and tilt (OI-t). External error of the model was determined by comparing with recent surveys and it was verified that OI-t approach improved the final gravity model to an accuracy of about 3 mGal. The effect of different merging approaches on geoid solution was also evaluated and it was verified that the merging process can contribute to improve the geoid accuracy up to 4 cm with the OI-t approach.

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Mapping the geoid for Iberia and the Macaronesian Islands using multi-sensor gravity data and the GRACE geopotential model

Catalão

Sevilla²

2009

Journal of Geodynamics

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To cite this version:J. Catalão, M.J. Sevilla. Mapping the geoid for Iberia and the Macaronesian Islands using multisensor gravity data and the GRACE geopotential model. Journal of Geodynamics, Elsevier, 2009, 48 (1) This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Iberia, and the Macaronesian Islands using multi-sensor gravity data and a GRACE derived Earth geopotential model. A high resolution gravity model, determined using least squares optimal interpolation of marine, land, and satellite derived gravity anomalies, was used to resolve the medium and short wavelengths of the geoid. Long wavelengths of the geoid were provided by the GRACE derived Earth geopotential model. The topographic effects were computed in the spectral domain using a high resolution (100 m) digital terrain model derived from SRTM mission data and cartographic charts. The remove-restore technique was used to compute the geoid model on a 1.5 arc minute grid, and the residual geoid height was computed using spherical FFT and a modified Stokes' kernel. The effects of different Earth tide models on the geoid were computed and analyzed.Comparison over the sea with an oceanographic geoid determined from CLS01 MSSH and Rio05MDT yield a relative accuracy of 8 cm, with larger differences close to the shoreline. Over land, comparisons with 1646 GPS/levelling marks indicate an overall precision of 8-10 cm and relative vertical datum offsets of up to 2 m. This new geoid model represents a significant improvement over existing geoid models, with a homogeneous relative accuracy of 8-10 cm over both marine and land areas, and exposes the inaccuracies of local vertical datums as references for studies of vertical deformation.

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Dependence of Mean Sea Surfaces from Altimeter Data on the Reference Model Used

Cited by 3 publications

References 16 publications

Sensitivity analysis of the gravity geoid estimation: A case study on the Azores plateau

Sensitivity analysis of the gravity geoid estimation: A case study on the Azores plateau

Iberia-Azores Gravity Model (IAGRM) using multi-source gravity data

Mapping the geoid for Iberia and the Macaronesian Islands using multi-sensor gravity data and the GRACE geopotential model

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