![]() ![]() Schlueter W, Himwich E, Nothnagel A, Vandenberg NR, Whitney A (2002) IVS and its important role in the maintenance of the global reference systems. Scherneck HG (1991) A parameterized solid earth tide model and ocean tide loading effects for global geodetic baseline measurements. Ray R (1999) A global ocean tide model from TOPEX/Poseidon Altimetry/GOT99.2 – NASA/TM-1999-209478, Goddard Space Flight Center/NASA, Greenbelt Petrov L, Boy JP (2004) Study of the atmospheric pressure loading signal in VLBI observations. In: Behrend D, Baver KD (eds) Proceedings of IVS 2006 general meeting, NASA/CP-2006 Niell AE (2006) Interaction of atmosphere modeling and analysis strategy. Institut d’Estudis Espacials de Catalunya, Barcelona Spain, pp 133–136 In: Behrend D, Rius A (eds) Proceedings of the 15th working meeting on European VLBI for geodesy and astrometry. Niell AE (2001) An a priori hydrostatic gradient model for atmospheric delay. Niell AE (1996) Global mapping functions for the atmosphere delay at radio wavelengths. MacMillan DS, Ma C (1997) Atmospheric gradients and the VLBI terrestrial and celestial reference frames. MacMillan DS (1995) Atmospheric gradients from very long baseline interferometry observations. 71, Deutsches Geodätisches Forschungsinstitut (DGFI), Munich, pp 26–29 Haas R, Nothnagel A, Schuh H, Titov O (1999) Explanatory supplement to the section ‘Antenna Deformation’ of the IERS conventions (1996) DGFI report no. Radio Sci 20(6):1593–1607ĭavis JL, Elgered G, Niell AE, Kuehn CE (1993) Ground-based measurements of the gradients in the ‘wet’ radio refractivity of air. J Geophys Res 102(B9):20489–20502ĭavis JL, Herring TA, Shapiro II, Rogers AEE, Elgered G (1985) Geodesy by radio interferometry: effects of atmospheric modelling errors on estimates of baseline length. doi:10.129/2005JB003629Ĭhen G, Herring TA (1997) Effects of atmospheric azimuthal asymmetry on the analysis from space geodetic data. Istituto di Radioastronomia, Noto Italy, pp 64–68īoehm J, Werl B, Schuh H (2006) Troposphere mapping functions for GPS and very long baseline interferometry from European Centre for Medium-Range Weather Forecasts operational analysis data. In: Vennebusch M, Nothnagel A (eds) Proceedings of the 17th working meeting on European VLBI for geodesy and astrometry. Institut d’Estudis Espacials de Catalunya, Barcelona, Spain, pp 143–148īoehm J, Ess M, Schuh H (2005) Asymmetric mapping functions for CONT02 from ECMWF. Proceedings of the 15th working meeting on European VLBI for geodesy and astrometry. Only if 6-h offsets are estimated, the baseline length repeatabilities significantly improve, no matter which a priori gradients are used.īoehm J, Schuh H (2001) Spherical harmonics as a supplement to global tropospheric mapping functions and horizontal gradients. VLBI analysis of the CONT02 and CONT05 campaigns, as well as all IVS-R1 and IVS-R4 sessions in the first half of 2006, shows that fixing these a priori gradients improves the repeatability for 74% (40 out of 54) of the VLBI baseline lengths compared to fixing zero or constant a priori gradients, and improves the repeatability for the majority of baselines compared to estimating 24-h offsets for the gradients. This approach only uses information about the refractivity gradients at the site vertical, but no information from the line-of-sight. In this paper, we present a fast way of extracting both, hydrostatic and wet, linear horizontal gradients for the troposphere from data of the European Centre for Medium-range Weather Forecasts (ECMWF) model, as it is realized at the Vienna University of Technology on a routine basis for all stations of the International GNSS (Global Navigation Satellite Systems) Service (IGS) and International VLBI Service for Geodesy and Astrometry (IVS) stations. Modeling path delays in the neutral atmosphere for the analysis of Very Long Baseline Interferometry (VLBI) observations has been improved significantly in recent years by the use of elevation-dependent mapping functions based on data from numerical weather models. ![]()
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