A Priori Gradients in the Analysis of Space Geodetic Observations

  • J. Böhm
  • L. Urquhart
  • P. Steigenberger
  • R. Heinkelmann
  • V. Nafisi
  • H. SchuhEmail author
Conference paper
Part of the International Association of Geodesy Symposia book series (IAG SYMPOSIA, volume 138)


We introduce a static a priori gradient model (APG) based on a spherical harmonic expansion up to degree and order nine to describe the azimuthal asymmetry of tropospheric delays. APG is determined from climatology data of the European Centre for Medium-Range Weather Forecasts (ECMWF), and the refined model can be used in the analysis of observations from Global Navigation Satellite Systems (GNSS) and Very Long Baseline Interferometry (VLBI). Comparisons reveal that gradients estimated in GNSS analysis are mostly smaller than those provided by APG. This difference is also confirmed by station and source coordinate changes if APG is used in GNSS and VLBI analysis.


Tropospheric delay Tropospheric gradients VLBI GNSS APG 



J. Böhm and V. Nafisi are grateful to the Austrian Science Fund (FWF) for supporting this research under project P20902-N10 (GGOS Atmosphere). V. Nafisi would also like to acknowledge Iran Ministry of Science, Research and Technology (MSRT) for funding part of his research at the Vienna University of Technology. L. Urquhart would like to thank the Natural Sciences and Engineering Research Council (NSERC) of Canada for providing funding. We like to acknowledge the International VLBI Service for Geodesy and Astrometry (IVS; Schlüter and Behrend 2007) and the International GNSS Service (IGS; Dow et al. 2009) for providing their data and products.


  1. Böhm J, Schuh H (2007) Troposphere gradients from the ECMWF in VLBI analysis. J Geodesy 81(6–8):403–408. doi: 10.1007/s00190-007-0144-2 CrossRefGoogle Scholar
  2. Böhm 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. J Geophys Res 111:B02406CrossRefGoogle Scholar
  3. Chen G, Herring TA (1997) Effects of atmospheric azimuthal asymmetry on the analysis of space geodetic data. J Geophys Res 102(B9):20489–20502. doi: 10.1029/97JB01739 CrossRefGoogle Scholar
  4. Dach R, Hugentobler U, Fridez P, Meindl M (eds) (2007) Bernese GPS software version 5.0. Astronomical Institute, University of Bern, BerneGoogle Scholar
  5. Davis JL, Elgered G, Niell AE, Kuehn CE (1993) Ground-based measurement of gradients in the “wet” radio refractivity of air. Radio Sci 28(6):1003–1018. doi: 10.1029/93RS01917 CrossRefGoogle Scholar
  6. Dow JM, Neilan RE, Rizos C (2009) The international GNSS service in a changing landscape of global navigation satellite systems. J Geodesy 83(3–4):191–198. doi: 10.1007/s00190-008-0300-3 CrossRefGoogle Scholar
  7. Hobiger T, Ichikawa R, Kondo T, Koyama Y (2008) Fast and accurate ray-tracing algorithms for real-time space geodetic applications using numerical weather models. J Geophys Res 113:D20302. doi: 10.1029/2008JD010503 CrossRefGoogle Scholar
  8. MacMillan DS (1995) Atmospheric gradients from very long baseline interferometry observations. Geoph Res Lett 22(9):1041–1044. doi: 10.1029/95GL00887 CrossRefGoogle Scholar
  9. MacMillan DS, Ma C (1997) Atmospheric gradients and the VLBI terrestrial and celestial reference frames. Geoph Res Lett 24(4):453–456. doi: 10.1029/97GL00143 CrossRefGoogle Scholar
  10. Petit G, Luzum B (eds) (2010) IERS Conventions (2010) IERS Technical Note 36, Frankfurt am Main: Verlag des Bundesamts für Kartographie und GeodäsieGoogle Scholar
  11. Schlüter W, Behrend D (2007) The international VLBI service for Geodesy and Astrometry (IVS): current capabilities and future prospects. J Geodesy 81(6–8):379–387. doi: 10.1007/s00190-006-0131-z CrossRefGoogle Scholar
  12. Schubert SD, Rood R, Pfaendtner J (1993) An assimilated data set for Earth science applications. Bull Am Meteorol Soc 74(12):2331–2342CrossRefGoogle Scholar
  13. Titov O, Tesmer V, Böhm J (2004) OCCAM v. 6.0 software for VLBI data analysis. In: Vandenberg NR, Baver KD (eds) International VLBI service for Geodesy and Astrometry 2004 general meeting proceedings. NASA/CP-2004-212255, pp 267–271Google Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 2013

Authors and Affiliations

  • J. Böhm
    • 1
  • L. Urquhart
    • 2
  • P. Steigenberger
    • 3
  • R. Heinkelmann
    • 4
  • V. Nafisi
    • 1
    • 5
    • 6
  • H. Schuh
    • 1
    Email author
  1. 1.Vienna University of TechnologyViennaAustria
  2. 2.University of New BrunswickFrederictonCanada
  3. 3.Technische Universität MünchenMunichGermany
  4. 4.Deutsches Geodätisches ForschungsinstitutMunichGermany
  5. 5.University of TehranTehranIran
  6. 6.University of IsfahanIsfahanIran

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