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Visser, P.N.A.M. (author), Van den IJssel, J. (author)
The computation of high-accuracy orbits is a prerequisite for the success of Low Earth Orbiter (LEO) missions such as CHAMP, GRACE and GOCE. The mission objectives of these satellites cannot be reached without computing orbits with an accuracy at the few cm level. Such a level of accuracy might be achieved with the techniques of reduced-dynamic...
journal article 2003
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Kusche, J. (author), Schrama, E.J.O. (author)
Monitoring hydrological redistributions through their integrated gravitational effect is the primary aim of the Gravity Recovery and Climate Experiment (GRACE) mission. Time?variable gravity data from GRACE can be uniquely inverted to hydrology, since mass transfers located at or near the Earth's surface are much larger on shorter timescales...
journal article 2005
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The upcoming GNSS Galileo, with its new satellite geometry and frequency plan, will not only bring many benefits for navigation and positioning but also help to improve ionosphere delay estimation. This paper investigates ionosphere estimation with Galileo and compares it with the results from GPS-only and combined GPS-Galileo. The standard...
journal article 2006
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Socquet, A. (author), Simons, W.J.F. (author), Vigny, C. (author), McCaffrey, R. (author), Subarya, C. (author), Sarsito, D. (author), Ambrosius, B. (author), Spakman, W. (author)
The island of Sulawesi, eastern Indonesia, is located within the triple junction of the Australian, Philippine, and Sunda plates and accommodates the convergence of continental fragments with the Sunda margin. We quantify the kinematics of Sulawesi by modeling GPS velocities and earthquake slip vectors as a combination of rigid block rotations...
journal article 2006
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Schrama, E.J.O. (author), Visser, P.N.A.M. (author)
journal article 2007
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Bos, M.S. (author), Fernandes, R.M.S. (author), Williams, S.D.P. (author), Bastos, L. (author)
It has been generally accepted that the noise in continuous GPS observations can be well described by a power-law plus white noise model. Using maximum likelihood estimation (MLE) the numerical values of the noise model can be estimated. Current methods require calculating the data covariance matrix and inverting it, which is a significant...
journal article 2007
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Schrama, E.J.O. (author), Wouters, B. (author), Lavallée, D.A. (author)
The Gravity Recovery and Climate Experiment (GRACE) product used for this study consists of 43 monthly potential coefficient sets released by the GRACE science team which are used to generate surface mass thickness grids expressed as equivalent water heights (EQWHs). We optimized both the smoothing radius and the level of approximation by...
journal article 2007
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Odijk, D. (author), Teunissen, P.J.G. (author)
Successful carrier phase ambiguity resolution is the key to high-precision positioning with Global Navigation Satellite Systems (GNSS). The ambiguity dilution of precision (ADOP) is a well-known scalar measure which can be used to infer the strength of the GNSS model for carrier phase ambiguity resolution. In this contribution we present...
journal article 2008
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De Bakker, P.F. (author), Van der Marel, H. (author), Tiberius, C.C.J.M. (author)
This paper demonstrates a geometry-free GNSS measurement analysis approach and presents results of single frequency GPS, EGNOS and GIOVE short and zero baseline measurements. The purpose is to separate the different contributions to the measurement noise of pseudo range code and carrier phase observations at the receiver. The influence of...
journal article 2009
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King, M.A. (author), Altamimi, Z. (author), Boehm, J. (author), Bos, M. (author), Dach, R. (author), Elosegui, P. (author), Fund, F. (author), Hernández-Pajares, M. (author), Lavallee, D. (author), Riva, E.M. (author)
The provision of accurate models of Glacial Isostatic Adjustment (GIA) is presently a priority need in climate studies, largely due to the potential of the Gravity Recovery and Climate Experiment (GRACE) data to be used to determine accurate and continent-wide assessments of ice mass change and hydrology. However, modelled GIA is uncertain due...
journal article 2010
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Lavallée, D.A. (author), Moore, P. (author), Clarke, P.J. (author), Petrie, E.J. (author), Van Dam, T. (author), King, M.A. (author)
Changes in J2, resulting from past and present changes in Earth's climate, are traditionally observed by Satellite Laser ranging (SLR). Assuming an elastic Earth, it is possible to infer changes in J2 from changes in Earth's shape observed by GPS. We compare estimates of non-secular J2 changes from GPS, SLR, GRACE, and a load model. The GPS and...
journal article 2010
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De Bakker, P.F. (author), Tiberius, C.C.J.M. (author), Van der Marel, H. (author), Van Bree, R.J.P. (author)
Stochastic properties of GNSS range measurements can accurately be estimated using a geometry-free short and zero baseline analysis method. This method is now applied to dual-frequency measurements from a new field campaign. Results are presented for the new GPS L5Q and GIOVE E5aQ wideband signals, in addition to the GPS L1 C/A and GIOVE E1B...
journal article 2011
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Bock, H. (author), Jäggi, A. (author), Meyer, U. (author), Visser, P.N.A.M. (author), Van den IJssel, J.A.A. (author), Van Helleputte, T. (author), Heinze, M. (author), Hugentobler, U. (author)
The first ESA (European Space Agency) Earth explorer core mission GOCE (Gravity field and steady-state Ocean Circulation Explorer) was launched on 17 March 2009 into a sun-synchronous dusk–dawn orbit with an exceptionally low initial altitude of about 280 km. The onboard 12-channel dual-frequency GPS (Global Positioning System) receiver delivers...
journal article 2011
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Jie, L. (author), Van Zuylen, H.J. (author), Chunhua, L. (author), Shoufeng, L. (author)
The travel time is an important measure for the quality of traffic. This paper discusses a few methods to measure or estimate the travel time in urban road networks. First of all, it is important to know that urban travel times display a large variation, so that the measurement of a single (average) travel time is not so meaningful. The travel...
journal article 2011
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Lepadatu, L. (author), Tiberius, C.C.J.M. (author)
The Basarab cable-stayed bridge is a newly built structure in Bucharest, Romania, which was inaugurated in June 2011. Before the oficial opening, in order to assure its qualification for trafic, it had to pass several loading tests with convoys of trucks and trams. For this, besides a priori evaluation using the Finite Element Method (FEM),...
journal article 2014
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Bekaert, D.P.S. (author), Hooper, A. (author), Wright, T.J. (author)
In Guerrero, Mexico, slow-slip events have been observed in a seismic gap, where no earthquakes have occurred since 1911. A rupture of the entire gap today could result in a Mw 8.2–8.4 earthquake. However, it remains unclear how slow-slip events change the stress field in the Guerrero seismic region and what their implications are for...
journal article 2015
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Zaminpardaz, Safoora (author), Teunissen, P.J.G. (author), Nadarajah, Nandakumaran (author)
A first assessment of GLONASS CDMA L3 ambiguity resolution and positioning performance is provided. Our analyses are based on GLONASS L3 data from the satellite pair SVNs 755-801, received by two JAVAD receivers at Curtin University, Perth, Australia. In our analyses, four different versions of the two-satellite model are applied: the...
journal article 2016
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Hou, Y. (author), Verhagen, A.A. (author), Wu, J (author)
Ambiguity Resolution (AR) plays a vital role in precise GNSS positioning. Correctly-fixed integer ambiguities can significantly improve the positioning solution, while incorrectly-fixed integer ambiguities can bring large positioning errors and, therefore, should be avoided. The ratio test is an extensively used test to validate the fixed...
journal article 2016
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Mahapatra, P.S. (author), van der Marel, H. (author), van Leijen, F.J. (author), Samiei Esfahany, S. (author), Klees, R. (author), Hanssen, R.F. (author)
Deformation estimates from Interferometric Synthetic
Aperture Radar (InSAR) are relative: they form a ‘free’
network referred to an arbitrary datum, e.g. by assuming a reference
point in the image to be stable. However, some applications
require ‘absolute’ InSAR estimates, i.e. expressed in
a well-defined terrestrial...
journal article 2017
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Peter-Contesse, H. (author), Jäggi, Adrian (author), Fernández, JJ (author), Escobar, D. (author), Ayuga, F. (author), Arnold, D (author), Wermuth, M. (author), Hackel, S. (author), Otten, M. (author), Simons, W.J.F. (author), Visser, P.N.A.M. (author), Hugentobler, U. (author), Féménias, P. (author)
Sentinel-1A is the first satellite of the European Copernicus programme. Equipped with a Synthetic Aperture Radar (SAR) instrument the satellite was launched on April 3, 2014. Operational since October 2014 the satellite delivers valuable data for more than two years. The orbit accuracy requirements are given as 5. cm in 3D. In order to...
journal article 2017
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