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Journal of Geodesy

, Volume 85, Issue 7, pp 377–393 | Cite as

VLBI-derived troposphere parameters during CONT08

  • R. HeinkelmannEmail author
  • J. Böhm
  • S. Bolotin
  • G. Engelhardt
  • R. Haas
  • R. Lanotte
  • D. S. MacMillan
  • M. Negusini
  • E. Skurikhina
  • O. Titov
  • H. Schuh
Original Article

Abstract

Time-series of zenith wet and total troposphere delays as well as north and east gradients are compared, and zenith total delays (ZTD) are combined on the level of parameter estimates. Input data sets are provided by ten Analysis Centers (ACs) of the International VLBI Service for Geodesy and Astrometry (IVS) for the CONT08 campaign (12–26 August 2008). The inconsistent usage of meteorological data and models, such as mapping functions, causes systematics among the ACs, and differing parameterizations and constraints add noise to the troposphere parameter estimates. The empirical standard deviation of ZTD among the ACs with regard to an unweighted mean is 4.6 mm. The ratio of the analysis noise to the observation noise assessed by the operator/software impact (OSI) model is about 2.5. These and other effects have to be accounted for to improve the intra-technique combination of VLBI-derived troposphere parameters. While the largest systematics caused by inconsistent usage of meteorological data can be avoided and the application of different mapping functions can be considered by applying empirical corrections, the noise has to be modeled in the stochastic model of intra-technique combination. The application of different stochastic models shows no significant effects on the combined parameters but results in different mean formal errors: the mean formal errors of the combined ZTD are 2.3 mm (unweighted), 4.4 mm (diagonal), 8.6 mm [variance component (VC) estimation], and 8.6 mm (operator/software impact, OSI). On the one hand, the OSI model, i.e. the inclusion of off-diagonal elements in the cofactor-matrix, considers the reapplication of observations yielding a factor of about two for mean formal errors as compared to the diagonal approach. On the other hand, the combination based on VC estimation shows large differences among the VCs and exhibits a comparable scaling of formal errors. Thus, for the combination of troposphere parameters a combination of the two extensions of the stochastic model is recommended.

Keywords

VLBI Troposphere parameters Intra-technique combination 

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Copyright information

© Springer-Verlag 2011

Authors and Affiliations

  • R. Heinkelmann
    • 1
    Email author
  • J. Böhm
    • 2
  • S. Bolotin
    • 3
  • G. Engelhardt
    • 4
  • R. Haas
    • 5
  • R. Lanotte
    • 6
  • D. S. MacMillan
    • 3
  • M. Negusini
    • 7
  • E. Skurikhina
    • 8
  • O. Titov
    • 9
  • H. Schuh
    • 2
  1. 1.Deutsches Geodätisches Forschungsinstitut (DGFI)MunichGermany
  2. 2.Institute of Geodesy and Geophysics (IGG)Vienna University of TechnologyViennaAustria
  3. 3.NVI Inc. and NASA/Goddard Space Flight Center (GSFC)GreenbeltUSA
  4. 4.Bundesamt für Kartographie und Geodäsie (BKG)LeipzigGermany
  5. 5.Department of Earth and Space ScienceChalmers University of Technology, Onsala Space Observatory (OSO)OnsalaSweden
  6. 6.Centro di Geodesia Spaziale (CGS)MateraItaly
  7. 7.Istituto di Radioastronomia, Istituto Nazionale di Astrofisica (INA)BolognaItaly
  8. 8.Institute of Applied Astronomy (IAA)St. PetersburgRussia
  9. 9.Geoscience Australia (AUS)CanberraAustralia

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