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Klees, R. (author), Seitz, Kurt (author), Slobbe, D.C. (author)We present exact, closed-form expressions for the complete RTM correction and the harmonic correction to disturbing potential, gravity disturbance, gravity anomaly, and height anomaly. They need to be applied in quasi-geoid modelling whenever data points are buried inside the masses after residual terrain model (RTM) reduction and...journal article 2023
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Klees, R. (author), Slobbe, D.C. (author)This paper investigates the full variance–covariance (VC) matrix of two high-resolution regional quasi-geoid models, utilizing a spherical radial basis function parameterization. Model parameters were estimated using weighted least-squares techniques and variance component estimation (VCE) for data weighting. The first model, known as the ...journal article 2023
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Li, X. (author), Huang, J. (author), Klees, R. (author), Forsberg, R. (author), Willberg, M. (author), Slobbe, D.C. (author), Hwang, C. (author), Pail, R. (author)In this study, we compare six commonly used methods for the downward continuation of airborne gravity data. We consider exact and noisy simulated data on grids and along flight trajectories and real data from the GRAV-D airborne campaign. We use simulated and real surface gravity data for validation. The methods comprise spherical harmonic...journal article 2022
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Hosseini-Asl, M. (author), Amiri Simkooei, A. (author), Safari, A. (author)The performance of the gravimetric geoid models is usually evaluated by comparison of geoid heights with the GNSS/levelling derived geoid. But the GNSS/levelling network can be infected by significant systematic biases and random errors, especially in large and uneven areas. This contribution addresses the challenging problem of the corrector...journal article 2022
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Klees, R. (author), Seitz, K. (author), Slobbe, D.C. (author)In this paper, we derive improved expressions for the harmonic correction to gravity and, for the first time, expressions for the harmonic correction to potential and height anomaly. They need to be applied at stations buried inside the masses to transform internal values into harmonically downward continued values, which are then input to...journal article 2022
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Cob, Sanusi (author), Kadir, Majid (author), Forsberg, Rene (author), Simons, W.J.F. (author), Naeije, M.C. (author), Din, Ami Hassan (author), Yacob, Husaini (author), Amat, Asyran (author), Mahdzur, Daud (author)The Peninsular Malaysia Geodetic Vertical Datum 2000 (PMGVD2000) inherited several deficiencies due to offsets between local datums used, levelling error propagations, land subsidence, sea level rise, and sea level slopes along the southern half of the Malacca Strait on the west coast and the South China Sea in the east coast of the...journal article 2022
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Hosseini-Asl, Mahin (author), Amiri Simkooei, A. (author), Safari, Abdolreza (author)High precision geoid determination is a challenging task at the national scale. Many efforts have been conducted to determine precise geoid, locally or globally. Geoid models have different precision depending on the type of information and the strategy employed when calculating the models. This contribution addresses the challenging problem...journal article 2021
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Sun, Y. (author), Riva, R.E.M. (author), Ditmar, P.G. (author), Rietbroek, Roelof (author)We present a new approach to estimate time variations in J2. Those variations are represented as the sum of contributions from individual sources. This approach uses solely Gravity Recovery And Climate Experiment (GRACE) data and the geoid fingerprints of mass redistributions that take place both at the surface and in the interior of the solid...journal article 2019
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Slobbe, D.C. (author), Klees, R. (author), Farahani, H. (author), Huisman, L. (author), Alberts, Bas (author), Voet, Pierre (author), Doncker, Filip De (author)We present a local quasi-geoid (QG) model which combines a satellite-only global gravity model with local data sets using weighted least squares. The QG is computed for an area comprising the Netherlands, Belgium, and the southern North Sea. It uses a two-scale spherical radial basis function model complemented by bias parameters to account...journal article 2019
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Klees, R. (author), Slobbe, D.C. (author), Farahani, H. (author)The posed question arises for instance in regional gravity field modelling using weighted least-squares techniques if the gravity field functionals are synthesised from the spherical harmonic coefficients of a satellite-only global gravity model (GGM), and are used as one of the noisy datasets. The associated noise covariance matrix, appeared...journal article 2018
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Klees, R. (author), Slobbe, D.C. (author), Farahani, H. (author)The paper is about a methodology to combine a noisy satellite-only global gravity field model (GGM) with other noisy datasets to estimate a local quasi-geoid model using weighted least-squares techniques. In this way, we attempt to improve the quality of the estimated quasi-geoid model and to complement it with a full noise covariance matrix...journal article 2018
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Slobbe, D.C. (author), Sumihar, JH (author), Frederikse, T. (author), Verlaan, M. (author), Klees, R. (author), Zijl, F (author), Hashemi Farahani, H. (author), Broekman, R (author)In this paper, we present a novel Kalman filter approach to combine a hydrodynamic model-derived lowest astronomical tide (LAT) surface with tide gauge record-derived LAT values. In the approach, tidal water levels are assimilated into the model. As such, the combination is guided by the model physics. When validating the obtained “Kalman...journal article 2017
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Farahani, H. (author), Klees, R. (author), Slobbe, D.C. (author)We assess the surface gravity data requirements for a 5-mm quasi-geoid model for the Netherlands mainland and continental shelf in terms of omission and commission errors. The omission error critically depends on the roughness of the topography and bathymetry. For the Netherlands continental shelf, Central and Northern Netherlands, the...journal article 2017
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Farahani, H. (author), Slobbe, D.C. (author), Klees, R. (author), Seitz, Kurt (author)We study the impact of an accurate computation and incorporation of coloured noise in radar altimeter data when computing a regional quasi-geoid model using least-squares techniques. Our test area comprises the Southern North Sea including the Netherlands, Belgium, and parts of France, Germany, and the UK. We perform the study by modelling...journal article 2017
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Slobbe, D.C. (author)This thesis presents a combined approach for the realization of the (quasi-)geoid as a height reference surface and the vertical reference surface at sea (chart datum). This approach, specifically designed for shallow seas and coastal waters, provides the relation between the two vertical reference surfaces without gaps down to the coast. It...doctoral thesis 2013
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Slobbe, D.C. (author), Simons, F.J. (author), Klees, R. (author)The mean dynamic topography (MDT) can be computed as the difference between the mean sea level (MSL) and a gravimetric geoid. This requires that both data sets are spectrally consistent. In practice, it is quite common that the resolution of the geoid data is less than the resolution of the MSL data, hence, the latter need to be low-pass...journal article 2012
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Gruber, T. (author), Visser, P.N.A.M. (author), Ackermann, C. (author), Hosse, M. (author)Three GOCE-based gravity field solutions have been computed by ESA’s high-level processing facility and were released to the user community. All models are accompanied by variance-covariance information resulting either from the least squares procedure or a Monte-Carlo approach. In order to obtain independent external quality parameters and to...journal article 2011
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Broerse, D.B.T. (author), Vermeersen, L.L.A. (author), Riva, R.E.M. (author), Van der Wal, W. (author)Large earthquakes do not only heavily deform the crust in the vicinity of the fault, they also change the gravity field of the area affected by the earthquake due to mass redistribution in the upper layers of the Earth. Besides that, for sub-oceanic earthquakes deformation of the ocean floor causes relative sea level changes and mass...journal article 2011
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Klees, R. (author), Prutkin, I. (author)We propose a methodology for the combination of a gravimetric (quasi-) geoid with GNSS-levelling data in the presence of noise with correlations and/or spatially varying noise variances. It comprises two steps: first, a gravimetric (quasi-) geoid is computed using the available gravity data, which, in a second step, is improved using ellipsoidal...journal article 2010
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Tenzer, R. (author), Novak, P. (author), Prutkin, I. (author), Ellmann, A. (author), Vajda, P. (author)To reduce the numerical complexity of inverse solutions to large systems of discretised integral equations in gravimetric geoid/quasigeoid modelling, the surface domain of Green’s integrals is subdivided into the near-zone and far-zone integration sub-domains. The inversion is performed for the near zone using regional detailed gravity data. The...journal article 2009
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