A Wavelet-Based Assessment of Topographic-Isostatic Reductions for GOCE Gravity Gradients

Grombein, Thomas; Luo, Xiao; Seitz, Kurt; Heck, Bernhard

doi:10.1007/s10712-014-9283-1

Cited by 37 publications

(20 citation statements)

References 40 publications

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“…As already done for creating the RWI_TOPO_2012 model (Grombein et al 2014a), a spherical grid with radius R ¼ a GRS80 þ 20 km is selected, which ensures that all grid points are safely outside the topographic masses. However, toward the poles, the radial distance between these spherical grid points and the ellipsoidal arranged topography rises up to 40 km.…”

Section: Processingmentioning

confidence: 99%

“…4). Such a procedure is frequently used for the harmonic downward continuation of airborne and satellite-based measurements (Novák et al 2003;Janák et al 2014;Grombein et al 2014a) or gravimetric (quasi-)geoid determination (Omang and Forsberg 2000).…”

Section: Introductionmentioning

confidence: 99%

“…In the second step, global gridded topographic potential values are transformed to the frequency domain by using SHA (e.g., Sneeuw 1994;. By applying this RWI approach to the 5 0 Â 5 0 global topographic database DTM2006.0 , the topographic gravity field model RWI_TOPO_2012 up to degree and order (d/o) 1800 has been generated by Grombein et al (2014a). Moreover, taking into account deeper lying compensation masses, a modified Airy-Heiskanen concept has been applied to calculate the consistent isostatic gravity field model, RWI_ISOS_2012, as well as a combined topographic-isostatic gravity field model, RWI_TOIS_2012.…”

Section: Introductionmentioning

confidence: 99%

“…4 provides detailed information on the processing, in Sect. 5 the main characteristics of the new RWI_TOPO_2015 model The RWI approach as proposed by Grombein et al (2014a) is based on a three-layer decomposition of the Earth's topography with respect to its rock, water, and ice masses. The basic idea is that the masses of each terrain type, e.g., land topography, oceans, lakes, ice sheets and shelves can consistently be described by a vertically arranged (1) rock, (2) water, and (3) ice proportion.…”

Section: Introductionmentioning

confidence: 99%

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The Rock–Water–Ice Topographic Gravity Field Model RWI_TOPO_2015 and Its Comparison to a Conventional Rock-Equivalent Version

2016

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RWI_TOPO_2015 is a new high-resolution spherical harmonic representation of the Earth's topographic gravitational potential that is based on a refined Rock-Water-Ice (RWI) approach. This method is characterized by a three-layer decomposition of the Earth's topography with respect to its rock, water, and ice masses. To allow a rigorous separate modeling of these masses with variable density values, gravity forward modeling is performed in the space domain using tesseroid mass bodies arranged on an ellipsoidal reference surface. While the predecessor model RWI_TOPO_2012 was based on the 5 0 Â 5 0 global topographic database DTM2006.0 (Digital Topographic Model 2006.0), the new RWI model uses updated height information of the 1 0 Â 1 0 Earth2014 topography suite. Moreover, in the case of RWI_TOPO_2015, the representation in spherical harmonics is extended to degree and order 2190 (formerly 1800). Beside a presentation of the used formalism, the processing for RWI_TOPO_2015 is described in detail, and the characteristics of the resulting spherical harmonic coefficients are analyzed in the space and frequency domain. Furthermore, this paper focuses on a comparison of the RWI approach to the conventionally used rockequivalent method. For this purpose, a consistent rock-equivalent version REQ_TOPO_2015 is generated, in which the heights of water and ice masses are condensed to the constant rock density. When evaluated on the surface of the GRS80 ellipsoid (Geodetic Reference System 1980), the differences of RWI_TOPO_2015 and REQ_TOPO_2015 reach maximum amplitudes of about 1 m, 50 mGal, and 20 mE in terms of height anomaly, gravity disturbance, and the radial-radial gravity gradient, respectively. Although these differences are attenuated with increasing height above the ellipsoid, significant magnitudes can even be detected in the case of the satellite altitudes of current gravity field missions. In order to assess their performance, RWI_TOPO_2015, REQ_TOPO_2015, and RWI_TOPO_2012 are validated against independent gravity information of current global geopotential models, clearly demonstrating the attained improvements in the case of the new RWI model.

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Section: Processingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The Rock–Water–Ice Topographic Gravity Field Model RWI_TOPO_2015 and Its Comparison to a Conventional Rock-Equivalent Version

2016

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“…We are aware that on modern computers topographic effects can be computed globally, either by integration in the space domain (e.g. Grombein et al 2014) or in terms of spherical harmonics (e.g. Hirt 2013).…”

Section: Practical Implementation Of the Topographic Effectsmentioning

confidence: 99%

The evaluation of the geoid–quasigeoid separation and consequences for its implementation

2015

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The realization of precise height systems demands to assess the effect and necessity of approximations made to the pure theory. In this context, the formulas for the geoid-quasigeoid separation as presented by Flury and Rummel (J Geod 83:829-847, 2009) and further discussed by Sjöberg (J Geod 84:699-702, 2010) are reinterpreted. Starting from the fully topographically reduced gravity disturbance, a modification of the strict formulation of the downward continuation and the indirect effect according to Sjö-berg (2010) is given. In practice any implementation of the formula requires approximations in order to realize the downward continuation of gravity along the plumbline with the help of density assumptions and a topography model. The significance of the individual contributors to a refined approximation, taking into account the indirect effect and the firstorder gravity gradient, is elaborated in a numerical simulation for the example of the Himalaya region. Special focus is given on the sensitivity and convergency of the topography-induced terms with respect to the integration radius.

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GOCE's view below the ice of Antarctica: Satellite gravimetry confirms improvements in Bedmap2 bedrock knowledge

Hirt

2014

Geophysical Research Letters

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Accurate knowledge of Antarctica's topography, bedrock, and ice sheet thickness is pivotal for climate change and geoscience research. Building on recent significant progress made in satellite gravity mapping with European Space Agency's Gravity field and Ocean Circulation Explorer (GOCE) mission, we here reverse the widely used approach of validating satellite gravity with topography and instead utilize the new GOCE gravity maps for novel evaluation of Bedmap1/2. Space-collected GOCE gravity reveals clear improvements in the Bedmap2 ice and bedrock data over Bedmap1 via forward modeled topographic mass and gravity effects at spatial scales of 400 to 80 km. Our study demonstrates GOCE's sensitivity for the subsurface mass distribution in the lithosphere and delivers independent evidence for Bedmap2's improved quality, reflecting new radar-derived ice thickness data. GOCE and Bedmap2 are combined to produce improved Bouguer gravity maps over Antarctica. We recommend incorporation of Bedmap2 in future high-resolution global topography and geopotential models and its use for detailed geoid modeling over Antarctica.

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A Wavelet-Based Assessment of Topographic-Isostatic Reductions for GOCE Gravity Gradients

Cited by 37 publications

References 40 publications

The Rock–Water–Ice Topographic Gravity Field Model RWI_TOPO_2015 and Its Comparison to a Conventional Rock-Equivalent Version

The Rock–Water–Ice Topographic Gravity Field Model RWI_TOPO_2015 and Its Comparison to a Conventional Rock-Equivalent Version

The evaluation of the geoid–quasigeoid separation and consequences for its implementation

GOCE's view below the ice of Antarctica: Satellite gravimetry confirms improvements in Bedmap2 bedrock knowledge

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