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- Klees, R. (author) public lecture 1996
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- Klees, R. (author) book 1998
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- Klees, R. (author) book 1998
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- Usai, S. (author), Klees, R. (author) journal article 1999
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- Ditmar, P. (author), Visser, P. (author), Klees, R. (author) journal article 2003
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Klees, R. (author), Ditmar, P. (author), Broersen, P. (author)An approach to handling colored observation noise in large least-squares (LS) problems is presented. The handling of colored noise is reduced to the problem of solving a Toeplitz system of linear equations. The colored noise is represented as an auto regressive moving-average (ARMA) process. Stability and invertability of the ARMA model allows...journal article 2003
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Ditmar, P.G. (author), Kuznetsov, V. (author), Van Eck van der Sluis, A.A. (author), Schrama, E. (author), Klees, R. (author)Performance of a recently proposed technique for gravity field modeling has been assessed with data from the CHAMP satellite. The modeling technique is a variant of the acceleration approach. It makes use of the satellite accelerations that are derived from the kinematic orbit with the 3-point numerical differentiation scheme. A 322-day data set...journal article 2005
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- Winsemius, H.C. (author), Savenije, H.H.G. (author), Gerrits, A.M.J. (author), Zapreeva, E.A. (author), Klees, R. (author) journal article 2006
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Winsemius, H.C. (author), Savenije, H.H.G. (author), Van de Giesen, N.C. (author), Van den Hurk, B.J.J.M. (author), Zapreeva, E.A. (author), Klees, R. (author)The temporal signature of terrestrial storage changes inferred from the Gravity Recovery and Climate Experiment (GRACE) has been assessed by comparison with outputs from a calibrated hydrological model (lumped elementary watershed (LEW)) of the upper Zambezi and surroundings and an inspection of the within?month ground track coverage of GRACE...journal article 2006
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- Klees, R. (author), Zapreeva, E.A. (author), Winsemius, H.C. (author), Savenije, H.H.G. (author) journal article 2007
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- Ditmar, P. (author), Klees, R. (author), Liu, X. (author) journal article 2007
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Prutkin, I. (author), Klees, R. (author)We consider the problem of local (quasi-)geoid modelling from terrestrial gravity anomalies. Whereas this problem is uniquely solvable (up to spherical harmonic degree one) if gravity anomalies are globally available, the problem is non-unique if gravity anomalies are only available within a local area, which is the typical situation in local...journal article 2007
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Wittwer, T. (author), Klees, R. (author), Seitz, K. (author), Heck, B. (author)We present software for spherical harmonic analysis (SHA) and spherical harmonic synthesis (SHS), which can be used for essentially arbitrary degrees and all co-latitudes in the interval (0°, 180°). The routines use extended-range floating-point arithmetic, in particular for the computation of the associated Legendre functions. The price to be...journal article 2007
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Klees, R. (author), Tenzer, R. (author), Prutkin, I. (author), Wittwer, T. (author)We propose a methodology for local gravity field modelling from gravity data using spherical radial basis functions. The methodology comprises two steps: in step 1, gravity data (gravity anomalies and/or gravity disturbances) are used to estimate the disturbing potential using least-squares techniques. The latter is represented as a linear...journal article 2008
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Tenzer, R. (author), Klees, R. (author)The choice of the optimal spherical radial basis function (SRBF) in local gravity field modelling from terrestrial gravity data is investigated. Various types of SRBFs are considered: the point-mass kernel, radial multipoles, Poisson wavelets, and the Poisson kernel. The analytical expressions for the Poisson kernel, the point-mass kernel and...journal article 2008
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Klees, R. (author), Liu, X. (author), Wittwe, T. (author), Gunter, B.C. (author), Revtova, E.A. (author), Tenzer, R. (author), Ditmar, P. (author), Winsemius, H.C. (author), Savenije, H.H.G. (author)When using GRACE as a tool for hydrology, many different gravity field model products are now available to the end user. The traditional spherical harmonics solutions produced from GRACE are typically obtained through an optimization of the gravity field data at the global scale, and are generated by a number of processing centers around the...journal article 2008
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- Klees, R. (author), Revtova, E. (author), Gunter, B.C. (author), Ditmar, P.G. (author), Oudman, R.J. (author), Winsemius, H.C. (author), Savenije, H.H.G. (author) journal article 2008
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Gunter, B.C. (author), Wittwer, T. (author), Stolk, W. (author), Klees, R. (author), Ditmar, P. (author)In this study we address the question of whether regional gravity field modeling techniques of GRACE data can offer improved resolution over traditional global spherical harmonic solutions. Earlier studies into large, equatorial river basins such as the Amazon, Zambezi and others showed no obvious distinction between regional and global...conference paper 2009
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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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- Liu, X.L. (author), Ditmar, P.G. (author), Siemes, C. (author), Slobbe, D.C. (author), Revtova, E. (author), Klees, R. (author), Riva, R. (author), Zhao, Q. (author) journal article 2010